Tag Archives: long-range rifle

RELOADERS CORNER: SD Pt. 2

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Here’s how Standard Deviation calculations can figure in ammo decisions (or not…) READ MORE…

Glen Zediker

Seems like the last couple of articles on load testing and velocity data got some pretty good responses and attention, and so that means there’s more! Of course there is…

As said, Standard Deviation (SD) plotted out forms a bell curve. A bell curve indicates the “probability density” of the normal distribution, or range, for something like velocity consistencies. For our purposes that’s the likely speed of the next shot.

Chances are outstanding that running all the numbers gotten from a chronograph session will plot into what’s called a “normal curve.” Like any normal bell curve, it gets divided into three segments and values, and these divisions are the “standard deviations.” And remember it is “a” standard deviation.

(I’ve said many a time that I’m sho no mathematician, and I am aware that there’s more and different ways to apply and model a curve, and to manipulate standard deviation results for different applications, but I’m trying to keep it more simple and use this “normal curve” for examples, it’s also called “population standard deviation.”)

We’ve been working with the right-respectable SD example of 12.

standard deviation curve
Here’s the same old curve I’ve been using, but at least in a different color!

Assuming that normal curve, the distribution of “some number” of shots is forecasted like so: some 68 percent will lie within 1 standard deviation of the mean, about 95 percent lie within 2, and over 99 percent lie within 3 standard deviations. Again, since our SD is 12, then about 68 percent (approx. 2 out of 3) of all “next shots” will be +/- 12 feet per second. Since, though, the curve is in threes, that means that a scant number of the shots pose a chance for +/- 24 and some much (much) smaller chance remains for some shots to go to +/- 36. SD estimates how likely it is for those “head-scratchers” to show up, and also what might be the most realistic extreme any shot can deviate.

Data is a record of numbers and I do know that there’s 100-percent chance that the highest and lowest velocities collected for an SD calculation did, in fact, happen. To me, that’s what matters. No matter what the collected shot results calculated into for an SD, those were the two that represent the highest and lowest prints on the target.

It’s mathematically not possible for an SD to be higher than the greatest single measured deviant, and an SD can sho be lower than any single “bad” shot. Given how it’s calculated, along with how many samples contributed to the calculation, it’s plain that the nearer the majority are to themselves the less impact a bad one or more has. The more input the better.

ppc
Cartridge choice has a whopping lot to do with it! Some cartridges are seemingly destined (designed really) to produce better velocity consistency. Many magnums, for instance, are notoriously sporadic, while others, like the 6XC or one of the PPC cartridges (shown), seem to deliver constant velocities without a lot of special effort. It all has to do with internal ballistics and “efficiency,” and architectural analysis I don’t claim to understand, but I do know that’s one of the reasons 6XC holds the NRA High Power Rifle Long Range record, at the hands of David Tubb.

Many of us have heard or read the frequently-sung “…seen good accuracy with high SDs…” And we’ve probably also all decided that can’t be taken at literal value. Well, it can’t. Three things: what is “good accuracy” to this fellow, at which distance were the groups printed, and what’s he say is “high,” because without knowing these things there’s no accounting for the accuracy, believability, or interpretative definitiveness of what’s being said. So I say it’s 12. A 12 should not be responsible for a points loss, also considering the edge limits of usual group size. Getting into more and more numbers derived from more and more “what if’s” plotting out bullet trajectories and wind drift amounts, and, always assuming a consistent bullet ballistic coefficient demonstration (also not likely) running “12” through all these mathematical-hypothetical scenarios will show that 12 doesn’t lose many, if any, points.

One last that isn’t really a strong point, but is a point… If we’re shooting something like a .223 Rem. then a half-grain is about 40 feet per second. If that 12 SD shows its worst and pops one out +36 feet per second, to me that represents something akin to a pressure spike (logic dictates that more velocity had something to do with more pressure). I know my loads are running a tad amount edgy, and seeing a small velocity variation is likewise a tad amount more reassuring that a primer won’t go over the edge.

tubb 1000 yard clean
Here’s the ultimate result of low velocity deviations. It’s up to the shooter to apply the left and right, but it’s up to the ammo to keep vertical stringing to a minimum. David Tubb does a stellar job on both. 1000 yards, fired prone with a scope. 6XC.

TESTING TIP
If you’re testing much beyond 200 yards, and especially beyond 300, pay no mind to the left and right, but keep a close watch on the up and down. In ideal conditions, groups are supposed to be round (I’m convinced they’re actually square, but there’s no need to go into that). If there’s any wind, don’t even try to correct for it (as long as impacts are on the target). I honestly don’t need a chronograph to confirm load consistency if I’m seeing small vertical dispersions. I’ll already have speed-checked the load I’m down on the mat with, and, again, I’m just wanting to see how level I get my perforations. If I come out with a 600-yard group that’s a foot wide but only three inches tall, I’m happy.

6 TIPS FOR LOWER SDs
Aside from finding the perfect and magical load combination, ha, there are a few things that do seem to help tighten shot-to-shot velocity deviations. They’ve all be talked all the way through and back again in this space in other articles, but, considered ultimately that this is the overall effect they have, here they are again:

One. Primer seating: fully seated onto a flat pocket bottom.

Two. Consistent propellant charge: weigh the charges if metering isn’t dead-on.

Three. Ignition efficiency: consider trying that inside flash hole deburring routine…

Four. Consistent case neck sizing, and, believe it or not, about 0.003 worth of “tension.” Don’t go too light…

Five. Temperature insensitivity: choose propellants that exhibit stability under extremes.

Six. Balance: strive to find a propellant that fills the case, but “loosely” (no compressed charges); even more, avoid an overage of air space. These both allow too much variance in ignition pattern.

inside deburring tool

This article is adapted from Glen’s books, Handloading For Competition and Top-Grade Ammo, available at Midsouth HERE. For more information about other books by Glen, visit ZedikerPublishing.com

RELOADERS CORNER: Standard Deviation

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Improving longer-range accuracy has a lot to with consistent bullet velocities. First comes understanding it! Here’s a start on it… KEEP READING

chronograph

Glen Zediker

It’s springtime (finally) and one of the things on your list might be working up a load for a new rifle, or new bullet. I’ve talked about testing processes and procedures, and also some about those bullets, and especially those with higher ballistic coefficients. The more aerodynamic bullet, by itself, is no guarantee of a smaller group (and whether you’re shooting one shot or 20 shots, you’re always shooting a group…).

To make the “magic” of a high-BC bullet come to life, they all need to be arriving at the destination at really close to the same speed. On target, that’s all about elevation consistency. It’s pretty commonly accepted among long-range competitive shooters that points losses come more from errant high and low impacts than from missed wind calls. High-BC bullets traveling at more consistent speeds reduces dispersions in all directions. But only if they’re traveling at consistent velocities!

The first step to improving velocity consistency is getting a good way to measure it. That there would be a chronograph. Nowadays especially, there are a number of simple-to-use and inexpensive chronographs available, that are accurate. Some have more features, which mostly revolve around providing printouts, digital records, and calculations, but what matters most (to me at least) is one that lets me easily read the velocity of each shot.

Check Misdouth offerings HERE

MagnetoSpeed
The newer barrel-mounted electro-magnetic chronographs make it really easy. I like the idea of being able to chronograph from shooting position, not just from a benchrest. This is a MagnetoSpeed.

So. What’s next is understanding the terms associated with this area of data-gathering.

“Standard deviation” (SD) is the most common measure of shot-to-shot consistency. It reflects on the SD reflects on the anticipated consistency of bullet velocities (some number of recorded velocities). The “standard” part reflects on a sort of an average of the rounds tested.

[Phrases like “sort of” upset mathematically-oriented folks, so here’s the actual definition: SD is the square root of the mean of the squares of the deviations. More in a bit.]

I pay less attention than many to standard deviation because: I don’t think standard deviation is near as important as is the “range,” which is the lowest and highest speeds recorded. Another that matters is “extreme spread,” which, by definition, is the difference between this shot and the next shot. I watch the speed on each shot. I compare this one to the next one and to the last one, and, as said, find the highest and the lowest.

Why? Well because that’s how I shoot tournament rounds. This one, then another, and another. A low velocity difference means that the accuracy of my judgment of my own wind call has some support.

standard deviation
Standard deviation calculation forms a bell curve. The steeper and narrower the apex of the bell, the narrower the fluctuations were. But there’s always a bell to a bell curve and the greatest deviations from desired standard are reflected in this portion of the plot. Depending on the number of shots that went into the SD calculation, these deviations may be more or less notable than the SD figure suggests. So? Watch each shot. That’s the way to know how a load performs with respect to velocity consistency. SD allows you to estimate how likely it is for “outliers” to show up.

A load that exhibits a low SD is not automatically going to group small, just because a low SD. I’ve had Benchrest competitors tell me that sometimes their best groups don’t come with a low-SD load, but do not apply that to greater distance! At 100 yards a bullet’s time of flight and speed loss are both so relatively small that even what some might call a big variation in bullet velocities (+/-25 fps or so) isn’t going to harm a group, not even the tiny groups it takes to be competitive in that sport. On downrange, though, it really starts to matter. (And keep in mind that “it” is a reference to velocity consistency, whether denoted by SD or otherwise.)

For an example from my notes: Sierra 190gr .308 MatchKing. Its 2600 fps muzzle velocity becomes 2450 at 100 yards and 1750 at 600 yards. (These numbers are rounded but serve for a example.)

If we’re working with a just awful 100 fps muzzle velocity change, that means one bullet goes out at 2550 and the next leaves at 2650, in the worst-case. The first drifts about 28 inches (let’s make it a constant full-value 10-mph wind to keep it simple) and the next slides 26 inches. But! Drop… That is THE factor, and here’s where inconsistent velocities really hurt. With this 190, drop amounts over a 100 fps range are about three times as great as drift amounts. This bullet at 2600 muzzle velocity hits 5-6 inches higher or lower for each 50 fps muzzle velocity difference. That’s going to cost on target, big time. And it gets way, way (way) worse at 1000 yards. Velocity-caused errors compound on top of “normal” group dispersion (which would be group size given perfect velocity consistency). Now, it’s unusual for a wind to be full-value and dead constant, so on-target left and right displacement is even relatively less — but elevation displacement is consistent regardless.

So, my 100 fps example is extreme, but half of that, or a quarter of that, still blows up a score, or an important hit on a target.

propellant charge consistency
This is probably the most influential factor in improving SD: consistent propellant charge. It’s not only that each case has an identical powder load, though, because primer factors, and finding the right combination ultimately is why we do all the testing…

So what’s a tolerable SD? 12. There have been, rest assured, much calculation to lead  up to that answer. That’s the SD that “doesn’t matter” to accuracy, meaning it’s not going to be the leading factor in a miss. It’s more than I’ll accept for a tournament load, but for those I’m looking for an extreme spread never more than 10 fps (the range might be higher, but now we’re just mincing terms). More later…

The information in this article is from Glen’s newest book, Top-Grade Ammo, available HERE at Midsouth. Also check HERE for more information about this and other publications from Zediker Publishing.

REVIEW: Ruger Precision Rifle .223/5.56 NATO

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Following the success of its bigger brothers, this new package from Ruger is sure to find a host of fans. Read alll about it HERE

RPR review
The V2 Ruger Precision Rifles now include a lower profile handguard and a few extras.

by Major Pandemic

Ruger shocked and stunned everyone when they introduced the Ruger Precision Rifle dubbed RPR for short. It was a rifle that featured loaded top end upgrades all in a rifle that can actually print tiny groups and retails for around $1500 on the street…and now they offer this great gun in .223/5.56 NATO.

The Ruger Precision Rifle is competition killer in the factory precision rifle market from a number of perspectives. It includes everything you could possibly want on a custom target rifle and if you do want to upgrade the design the grip, buttstock, forend, and selector are all AR15-compatible items. Swapping out triggers is easy as well and rebarreling to one of the many aftermarket options only requires a barrel block and some leverage.

It is all included — billet precision chassis, fully adjustable buttstock, folding stock adapter, outstanding factory trigger, tri-lug style bolt, free floated AR15-compatible forend, and AICS compatible box-fed magazine. Ruger offered the RPR in .308 and .243 (now discontinued), but they have also kept up with the competitive precision shooting markets demand for 6.5mm Creedmore and 6mm Creedmore. Now of course Ruger has the RPR in the insanely cheap to shoot .223/5.56 NATO chambering.

RPR stock
A folding fully adjustbable stock make this one of the most comfortable out-of-the box rifles.

FINALLY… ALL THE RPR OWNERS SAID
Sure the .308, .243, and Creedmore rounds are fun to shoot, but there are a lot of us who want a “trainer” gun that feels and shoots like our precision gun, but does it at greatly reduced per round price. Maybe there are even a few of us that just want a really accurate .223 bolt action that still feels like a full sized rifle. Now we have the .223/5.56 NATO Ruger Precision Rifle which is a delightful duplicate of the other models that you can shoot all day long without a sore shoulder or emptying your wallet.

RPR mounts
Included in the box are a QD and picatinny mount.

Without question, varmint hunters are going to love the exceptionally accurate .223 RPR, however I believe this is going to become a hit with two other types of customers — customers who want a trainer for their larger bore guns, and customers who want a precision rifle that “feels” like their AR15 and shoots the same caliber.

RPR feel
Just like the big brother, the .223 has the same size and feel.

As a trainer, even if the Ruger .223 Precision Rifle is only used to practice trigger pull, grip, shooting position, general marksmanship tactics, and perhaps hammer a few critters in the process, the gun would pay for itself in ammo savings in only a few thousand rounds. Really, I have to tell you those insanely accurate Hornady 6.5 Creedmore ELD Match rounds are not cheap. The Hornady .223 equivalent are half the price of 6.5CM and a good reload recipe could deliver further savings. This is the category I fall into: wanting a training gun that will allow me to fiddle around with shots and shooting positions to find my sweet spot all without blasting $2 rounds down range.

I have a lot of friends in the other category of potential .223 RPR owner who do not want to add managing yet another caliber to their firearm inventory. For them the huge selection of .223 ammo for match, plinking, hogs, and other game is enough. The price point, precision, and user friendly nature of the .223 RPR makes it a perfect fit for these shooters.

RPR brake
The Included brake on the .223 is extremely effective in negating any recoil of the little round.

FEATURES OF NOTE
Most would expect that the .223/5.56 NATO Ruger Precision Rifle would duplicate the larger calibers in size, length and weight and it does. In fact this rifle is exactly the same weight as the .308 model. Ruger did go with a .223/5.56 NATO chambering presumably some type of .223 Wylde chamber which Ruger notes is completely cross compatible between the calibers. Ruger has really set up this smaller caliber RPR to extend the precision range with a 5 gove 1:7 rifling to stabilize heavy longer bullets better. One feature which I really liked on the original larger caliber rifles was that they were cross compatible between Magpul LR20 and AICS magazines.

The .223 is not, and is only compatible with Remington Short Action .223 AICS size magazines. Personally this is disappointing that I cannot run any of the hundreds of GI spec AR 15 magazines on this gun. There would be some real cross compatibility advantages to that in the field, but alas the Ruger only feeds from AICS mags. The reason Ruger went with the much more expensive AICS sized magazines was to allow round with 77gr or heavier .223 bullets to fit, function and feed. If you are going to create a precision rifle, then I suppose the compromise you should be able to shoot the best heavy bullet you want.

The trigger on this unit was not as good as previous RPR triggers I have tested. Our primary tester jokingly noted that the trigger felt like Ruger’s three stage trigger. There was a noticeable second stage before the third stage break. In this case, I would say a Timney trigger upgrade is in order.

Bushnell Elite
A Bushnell Elite helped deliver crystal clear images downrange.

ACCURACY TEST
As with all the other Ruger Precision Rifles, the .223 model is also a tack driving 1/2-MOA gun with the right match ammo. We tested a number of .223 Hornady and Federal rounds including Hornady 68gr, 75gr, and TAP 55gr, PMC Bronze 55gr, Federal Match 68gr Sierra Match King, and standard M855 steel core penetrator rounds. The Ruger Precision Rifle performs its best with high-grade match ammo. The best two 100-yard groups were Federal SMK 68gr .383-in., and Hornady Match 75gr. at .375-in.. Notable the Federal SMK 68gr round was the clear accuracy favorite in our test averaging .453-in. across all three of the three-round groups.

Sure were were able to punch some plinking grade groups with PMC Bronze and the M855 Steel Core rounds were about the same, but feed the RPR the right high grade match ammo and suddenly you are greeted with considerably better than 1/2-in. groups at 100-yards. The Federal 69gr Sierra Match King rounds consistently delivered the best groups. Unfortunately we did not have any 77gr rounds to test with.

RPR TARGET

RPR TARGET

RPR TARGET

RPR accuracy test

FINAL THOUGHTS
In my reviews of the first RPR, I asked where my .223 version was and Ruger delivered. The total Ruger Precision Rifle package adds up to a gun which shoots extremely well, is stunningly accurate for the price and is loaded with pretty much everything you could want in a precision rifle for far less than any other offering on the market. Ruger…simply amazing gun for the price…now where is my rimfire variant?

RPR specs

LEARN MORE HERE

Check out ammo HERE

Major Pandemic

[Major Pandemic is an editor at large who loves everything about shooting, hunting, the outdoors, and all those lifesaving little survival related products. His goal is simple, tell a good story in the form of a truthful review all while having fun. He contributes content to a wide variety of print and digital magazines and newsletters for companies and manufacturers throughout the industry with content exposure to over 2M readers monthly. Click HERE to learn more.]

RELOADERS CORNER: SD Pt. 2

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Here’s how to use (or not use) Standard Deviation calculations in ammo decisions, what they are, and aren’t… Keep reading…

Glen Zediker

A standard deviation plotted out is a bell curve. Chances are outstanding that a range session calculation will plot into what they call a “normal curve.” Like any normal bell curve, it can get divided into three segments and given values, and, technically, these are the “standard deviations.” It’s “a” standard deviation rather than “the” standard deviation.

SD bell curve plot

Assuming a normal curve, the values are that about 68 percent of forecasted results will lie within one standard deviation of the mean, about 95 percent lie within two, and over 99 percent lie within three standard deviations. If we have an SD calculated to be 12, that means that applying one standard deviation means that about 68 percent of all “next shots” will be +/- 12 feet per second. Since, though, the curve is in threes, in effect if not in fact, that means that a scant number of the shots pose a chance for +/- 24 and some teeny chance remains for shots to go to +/- 36. That, however, is extrapolating or predicting with data and that’s not really wise and doubtlessly uncalled for. Data collection is a record of numbers and I do know that there’s 100 percent chance that the highest and lowest velocities collected for an SD calculation did, in fact, happen. That’s what matters. No matter what the shot results calculated into for an SD, those were the two that represent the highest and lowest prints on the target.

It’s mathematically not possible for an SD to be higher than the greatest single raw deviant, but I do for a fact know that an SD can easily be far lower than the worst shot. Given how it’s calculated, along with how many samples contributed, it’s plain that the nearer the majority are to themselves the less impact a bad one or more has.

I said in a very open-ended way last article that a tolerable SD is 12. Anything more than that is not good; anything less than that probably won’t perform noticeably any, if at all, better than a 12. However! It is at this number, so I say, where the often-uttered tune of “…SD doesn’t matter…” and its refrain of “…seen good accuracy with high SDs…” starts and stops. Twelve. That’s it. Now we have an SD that “doesn’t matter.” The reason this is stuck out here is that everyone has heard this chorus but hopefully figured that it couldn’t be taken universally at literal value. Well it can’t.  So now you know! It’s 12. 12 should not be responsible for a points loss, even accounting for or including coincidence of any one shot hitting the edge limit of usual group size.

(Yes, 13 or 14 or 16 or even 20, which is often given as a “limit,” might well be a realistic ceiling but I drew a line to have one. Since there’s a line, now we can cross it and commence argument. I won’t use any load in competition that wouldn’t calculate to a single-digit SD. My 600-yard .223 Rem. load tested to an SD of 3.18 with a Range of 8 fps.)

So after all this has been said, I don’t give SD as much weight in my load decisions as some do. The reason for my focus on it here, as said in the first article, is because that’s the usual “standard” measure of consistency. I look at the speeds as they come up on the chronograph display and write them down. I weigh range and extreme spread more heavily, and I want to see really small variations over the number of test rounds I fire. It’s a matter of waning patience and waxing time. If I see a variance that could cost a point, that load is abandoned.

TESTING TIP
If you don’t have a chronograph or don’t want to burden a testing session with using one, watch for a correlation between the elevation dispersion and the wind dispersion of test groups. At 600 yards I always test from position (prone, “suited up”). No chronograph (muzzle-mounted chronographs now make this a non-issue). I’ll already have speed-checked the load I’m now down on the mat with. When I shoot my groups, I honestly don’t pay much attention at all to anything but measuring how level I got my perforations. Attempting shot-to-shot wind corrections when testing for ammunition accuracy throws another variable into it that might be most misleading. If I come up with a group that’s a foot wide but only three inches tall, I’m happy.

5 TIPS FOR LOWER SDs
Aside from finding the perfect and magical load combination, ha, there are a few things that do seem to help tighten shot-to-shot velocity deviations. They’ve all be talked all the way through and back again in this space in other articles, but, considered ultimately that this is the overall effect they have, here they are again:

One. Primer seating: fully seated onto a flat pocket bottom.

Two. Consistent propellant charge: weigh the charges if metering isn’t dead-on perfect.

Three. Ignition efficiency: consider that inside flash hole deburring routine…

Four. Temperature insensitivity: choose propellants that exhibit stability under extremes.

Five. Balance: strive to find a propellant that fills the case, but “loosely” (no compressed charges); even more, avoid an overage of air space. These both allow too much variance in ignition pattern.

Propellant level.

Addition
I learn things all the time. A most knowledgeable and helpful reader pointed out a detail in SD calculation that is better adapted to calculations for ballistics, and it helps because of the usually relatively small size sample involved. We’re not going to chronograph 100s of rounds, usually 10-20. So, instead of dividing the average square of the deviations by the number of samples, but the average square of the values, less one (n-1). That helps any distortion of results toward a number that calculates too small. Keep in mind always that SD is an estimate, in one way of looking at it.

This article is adapted from Glen’s book, Handloading For Competition, available at Midsouth HERE. For more information on that and other books by Glen, visit ZedikerPublishing.com

RELOADERS CORNER: SD — what it matters and why

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Getting a handle on improving long-range accuracy has a lot of to do with understanding the importance of consistent bullet velocities. Here’s a start toward that…

Glen Zediker

There’s one more thing (seemingly, there’s always one more thing…) that’s important to accuracy at extended distance. I’ll say “extended distance” is anything over 300 yards. That is bullet velocity consistency.

I’ve said in these pages before that a good shooter will lose more points to elevation than to wind. This next explains that a might more.

First, and the first step, is getting and using a chronograph. It doesn’t have to be a zoot-capri model, and nowadays that’s a fortunate bonus because there are a number of inexpensive chronographs available that are entirely accurate.

PACT chronograph.
A chronograph is essential, well, at least for all this here. There are a lot of good ones. I’m partial to PACT.

Check Misdouth offerings HERE

magnetospeed chronograph
The newer barrel-mounted electro-magnetic chronographs make it really easy. I like the idea of being able to chronograph from shooting position, not just from a benchrest. This is a MagnetoSpeed.

“Standard deviation” (SD) is probably the most commonly used measure of bullet velocity consistency. SD reflects on the consistency of velocity readings taken over a number of shots. “Standard” reflects on a sort of an average of the rounds tested.

[Math folks don’t use phrases like “sort of” when describing numbers and can provide tickier definitions of SD and the means to calculate it. Here it is: it’s the square root of the mean of the squares of the deviations. Actually harder to say than it is to calculate.]

Steady Wins the Race
Standard deviation is not the only measure, and I don’t even think it’s the right one, let alone the most important, but it’s no doubt the most popular way to talk about ballistically consistent bullet performance. I don’t think standard deviation is near as important as is the “range,” which is the lowest and highest speeds recorded. Some who write and talk about it call that “extreme spread,” but if we want to get picky over terms (and ballisticians, card-carrying and self-styled, tend to get right touchy over such formalities) extreme spread is the difference between this shot and the next shot.

I watch the speed on every shot. I compare this one to the next one and to the last one, and, as said, find the highest and the lowest.

There is no saying that a load that exhibits low standard deviation is going to group small, just because of that. Any Benchrest competitor will tell of experiences whereby “screamer” groups came with high SDs and hideous groups with low SDs (“high” and “hideous” by their standards, still pretty small for the most of us). But, at 100 yards the bullet’s time of flight and speed loss are both so relatively small that variation in bullet velocities isn’t going to harm a group, and, yes, not even the tiny groups it takes to be competitive in that sport. On downrange, though, there is going to be a relatively greater effect on shot placement, right? Yes and no. Drift and drop are influenced. There is a relatively greater effect in ultimate displacement of elevation, more next. Based on drift allowance it probably does not.

To put an example on it, let’s say we’re shooting a Sierra® 190gr .308 MatchKing. Its 2600 fps muzzle velocity becomes 2450 at 100 yards and 1750 at 600 yards. (All these numbers are rounded examples, and examples only.)

If we’re working with a truly hideous inconsistency of 100 fps, say, that means one bullet goes out at 2550 and the next leaves at 2650 in a worst-case event. The first bullet tracks across about 28 inches (constant full-value 10-mph wind to keep it simple) and the next moves sideways 26 inches. Figuring drift on 2600 fps means it’s two inches off, one inch per shot.

Drop, which means elevation, is a (the) factor, and here’s where poor SDs bite. With this Sierra® 190, drop amounts over a 100 fps range are about three times as great as drift amounts. A vertically-centered bullet at 2600 fps hits about 5-6 inches higher or lower at each 50 fps muzzle velocity difference. That’s enough to blow up a score to elevation. And it gets way, way on worse at 1000. Keep always in mind that velocity-induced errors are compounding “normal” group dispersion. And, in reality and as discussed before, it’s unusual in a competitive shooting venue for a wind to be full-value, so the on-target lateral displacement is even relatively less — but the elevation displacement is consistent.

The next-to-the-bottom line, then, is that poor SDs don’t hurt in the wind as much as they do on the elevation. The bottom-line, then, is back to the start: don’t shoot a load with inconsistent speeds. It’s flat not (ever) necessary.

So what’s a tolerable SD? 12. That’s the SD that “doesn’t matter” to accuracy. More later…

SD bell curve
Standard deviation calculation forms a bell curve. The steeper and narrower the apex of the bell, the more level and narrower the fluctuations were. But there’s always a bell to a bell curve and the greatest deviations from desired standard are reflected in this portion of the plot. Depending on the number of shots that went into the SD calculation, these deviations may be more or less notable than the SD figure suggests. So? Watch each shot. That’s the way to know how a load performs with respect to velocity consistency. Each and every speed collected for each and every shot fired in a test. More next time…

MATH: For Them That Wants It
If you have no electronic gadgetry to help, calculate SD like so: add all the velocities recorded together and divide them by however many there were to get a mean. Subtract that mean number from each single velocity recorded to get a deviation from the mean. Square each of those (eliminates the negative numbers that ultimately would cancel out and return a “0”). Add the squares together and find the mean of the squares by dividing again by the number of numbers. Then find the square root of that and that’s the standard deviation figure, which is “a” standard deviation, by the way.

This article is adapted from Glen’s book, Handloading For Competition, available at Midsouth HERE. For more information on that and other books by Glen, visit ZedikerPublishing.com

 

 

REVIEW: Savage Arms BA10 Stealth 6.5 Creedmoor

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If you’re in need of an out-of-the-box long-range tack driver, and don’t want to pay thousands, this Savage proved a great choice in this test. Read more…

by Patrick E. Kelley

Savage Stealth BA10

The Savage Arms BA10 “Stealth” is anything but stealthy! This rifle shows up “in your face” ready to put bullets in little groups up close, or where the real test is — way out there!

CUTTING TO THE CHASE…
Lets start at about “half way” to way out there. This AICS (Accuracy International Chassis System) compatible box magazine-fed turn-bolt is accurate! While many may claim half-minute accuracy, this stick actually is that precise, and it can do it right out of the box. Take a look…

Savage Stealth 450 yard groups

Now I would love to take credit for those groups, but knowing my longer-range skill set was less than what I expected the rifle could shoot, I enlisted the help of my shooting buddy Bill. As an F-Class competitor, he knows his way around long range shooting. It took a few shots to get him settled in behind this rather lightweight (9.2 pounds) long range bullet placement tool, but settle in he did. Yes, I included ALL 5 groups! We got to take the good with the bad, but I would ask you to really look at those groups…this rifle wants to shoot 1/2 MOA or better! Thanks Bill!

benchrest setup
This was Bill’s set up. A good shooting rest setup is very important to good groups.

SET-UP
With the Savage carrying a MSRP of $1207 I thought it would be a good idea to marry this rifle up with a comparable scope. I chose one that, like the Stealth itself, has value well beyond its modest price: the Burris XTRII 5×25. I tell people, “Don’t buy cheap scopes!” Buy good glass and then put them in the best mounts. You will break a scope someday, but a good mount will last though several scopes! The scope base is part of the Savage BA10 package and is made by the good guys at EGW, and the scope rings I supplied are 34mm units from Xtreme Hardcore Gear. “On right stays tight” — use a proper inch-pound torque wrench!

Savage Stealth, Burris scope

HITS
This bolt gun’s “chassis system” is made by MTD and is a solid, well-made unit. I popped the barreled action out of the stock before the first rounds went downrange and looked it over. It is very nice and beautifully machined. I mentioned using an inch-pound torque wrench for scope mounting, well it is a good practice to use one when installing the barreled action back into the chassis. I did 60 inch-pounds.

Savage Accutrigger
Savage has really put their AccuTrigger front and center as a high quality unit and this one did not disappoint! It broke clean and crisp at a factory-set 22 ounces! In keeping with the “practical/tactical” nature of this bolt gun you’ll find an appropriately over-sized bolt handle, a comfortable Hogue pistol grip from which to trip that excellent trigger, and quick access to the magazine release latch. The excellent ergos on this rifle were no accident.
AICS magazines
Above are the 3 magazines I tested…all worked perfectly. The tall one on the left came with the gun as is an MDT 10-rounder. The other two are 5-round mags from MagPul, and are AICS compatible.
threaded muzzle cap
The muzzle is threaded 5/8x24tpi and finished with an 11-degree target crown and thread protector: a handy addition to accommodate a suppressor or muzzle brake.

I could not just watch my friend Bill shoot so after he completed his session with the Hornady factory ammunition at 450 yards I tried my hand at 300 yards with some Federal American Eagle 140 grain OTM (Open Top Match). Even with me behind the incredibly nice 22-ounce Savage AccuTrigger, sub-minute of angle groups were the norm. Norm…that is not normal! Sub-MOA groups from a factory-fresh rifle without any tuning or tweaking or even barrel break-in with off-the-shelf factory ammo! I think I am going to like this long-range game! Thanks Savage!

300 yard groups

MISSES
We covered most of this, but let me point out a nit-pick or two. You knew I would have at least one… The EGW scope rail appears to be a “flat” rail, not a 20 or 30 MOA rail that is common in long-range circles. If you have enough elevation adjustment within your optic you might be okay, but give me a 20 MOA base any day.

Then there’s the buttstock… I don’t like it. It is okay for an AR but this one lacks two elements that I want (need): first, the cheek rest sits too far back to get proper eye relief, and second, for use with a rear bag the bottom of the buttstock ought to be flat. Small nits to pick, and both are easily remedied through the aftermarket.

LAST WORD
The BA10 Stealth has proven itself to be accurate and reliable with a trigger that has me wishing every rifle I own were so equipped! It does this “right out of the box” and it does it within the wallet of a “working man.” Ultimately, Savage Arms has assembled an excellent long-range tool that in capable hands shouldn’t have any problem running right along side guns with price tags several times the Stealth price. Stealthy?…not a chance. This one screams “I am a winner!”

Savage Stealth Specifications
So as to not leave anything out, Savage literature states: Factory Blue Printed Savage Action, Monolithic Aluminum Chassis Machined from Solid Billet, M-LOK forend, One-Piece EGW Scope Rail, Fab Defense GLR-SHOCK Six-Position Buttstock with Adjustable Cheek Piece, 5/8×24 Threaded Muzzle with Protector. Nice!

Click here for MORE information on the Savage Stealth series

About the author: Patrick E. Kelley is a competition shooter, instructor, gunwriter, photographer, and videographer. After four years as a featured competitor on 3-Gun Nation he was hired as the Expert Analyst and commentator for the show. He started to compete actively in 3-Gun in 1999, placing Top Tyro in his first championship, the Soldier of Fortune 3 gun match. Patrick has earned numerous first-place finishes at major matches in 12 U.S. states and Canadian provinces. He has mastered several shooting disciplines, from NRA Bullseye and Metallic Silhouette to the world of Practical Shooting. Patrick is also a member of the NRA 2600 Club and was ranked in the USPSA’s top twenty early in his shooting career. Patrick’s articles on shooting and firearms, as well as his photography, can be found within the pages of Shooting Illustrated, Outdoor Life, and 3 Gun Nation Magazine. His YouTube channel includes instructional and exhibition shooting videos, including the series “Patrick’s Tac Tricks” produced in concert with the NRA. Check one out HERE