5 or 3 shot group when determining ES/SD???

[Bart B]

When considering barrel life one should keep testing within limits otherwise there would be no chance to shoot a buck. Look at the following table on barrel life.

http://www.longrangehunting.com/forums/f19/ultra-mag-powders-barrel-life-48760/

That's an interesting table. Too bad it doesn't show how much powder's used for each caliber range. The more one burns for a given bore diameter the shorter the barrel life will be.

The best thing about it is the results for very slow powders. All the rest is misleading. And one post in that thread claims a barrel with 20,000 rounds through it still shoots 1/2 MOA. The author doesn't mention if that's the largest or smallest groups it now shoots. I doubt either is reality unless it's a .22 rimfire match barrel which these days will go 30,000 rounds of sub 3/4 MOA accuracy through 100 yards; maybe his is an old McMillan one using pre-1983 Eley Tenex match ammo.

 

[J E Custom]

Now we've gotten to the meat and potatoes. My title for this thread was mis leading. I understand the more info the more accurate the hypothesis. I was just wondering if there was a consistent number of shots that everyone uses to determine ES/SD. Now I know that there is not but I also learned how to conduct proper testing while developing loads for long range hunting. I like the way you summed it up sleepyeddie but all of the info in this thread has been quite informative. Thankyou for sharing your knowledge guys!

I think you have it now.

There is always a progression to any problem and In my opinion using a chronograph is the best
way to start working up a load.

The number of shots used is determined by the results of each load tested.

I have seen great SDs and poor accuracy. And great accuracy and poor SDs (At shorter ranges)

Using the chronograph saves time and barrel life because you can narrow a potential load down
without excessive /Wasted shots.

I like to load 5 rounds of each load to be tested, Start with a clean barrel with each load, shoot
2 rounds through the chronograph and check the SDs. If the spread is to high for the intended
use (Long rang or short range) I abandon the load and move on to the next load.

If the SDs are what I consider good on one of the test loads I continue shooting all 5 or until
one round is excessive. I keep "ALL" information even the bad loads so that I don't duplicate
them in later testing.

After finding several good SD loads I then start shooting at the intended range to see if it is
accurate at the range desired or needed.

Good SDs Tells you that you have a good powder,primer,bullet weight combination. (It does
not tell you that you have an accurate load only range testing will tell you that.

Some times a barrel just does not like a particular bullet and you have to change to a different
style or make. As long as you keep the weight the same the SDs should remain close to what
they were (There is exceptions to everything).

The main reason for finding low SDs is for long range shooting where 10 to 15 ft/sec velocity
difference will cause virtical stringing. for shooting 4 to 500 yards or less accuracy and consistency
is more important because 15 ft/sec does noe change the POI that much.

If you test accuracy only and find a good load for all distance or the longest distance to be shot
you will find it has a good SD. So which came first, the chicken or the egg.

I tried the accuracy route first and spent lots of time and money on a hit and miss method and
when I started using the chronograph it reduced the number of test firings 75% in order to find
the best load for a particular rifle and use.

So I guess my answer would be 2 to 10 because if you haven't found an accurate load after 10
shots you are wasting your time and Barrel.

Just My Opinion

J E CUSTOM

 

[rscott5028]

JE made some great points. I never load 100 rounds for load development.

I always start with small batches looking for something with potential.

Based on the most information I have after shooting, I decide what direction to proceed in. And, I begin to load larger batches as I zero in on a load.

Sometimes, loads that showed promise with an initial 3 shot group don't pan out.

And if the first 2 shots are 2 MOA (notwithstanding a truly explained/called flier), you can keep shooting, but it won't shrink your group size.

Ultimately, I will probably have shot 50 or more of a given load before I feel comfortable that it's the one. You can say that it's wasting barrel life. But, I call it practice. And, you can declare your load superior after 3 shots. But, if you keep shooting and the groups or ES/SD get worse, I would hope that you'd back up and fix something.

-- richard

 

[Bart B]

The main reason for finding low SDs is for long range shooting where 10 to 15 ft/sec velocity difference will cause virtical stringing. for shooting 4 to 500 yards or less accuracy and consistency is more important because 15 ft/sec does not change the POI that much.

I've had some barrels and ammo tested at 1000 yards to check vertical shot stringing with a chronograph 10 feet in front. Even with a 25 to 30 fps spread, a third of the shots struck high for a low velocity and another third low for a high velocity. About a third struck even in elevation. Such is life when your barrel whips to enable positive compensation; slower bullets leave sooner, faster ones later in the upward whip of the bore at the muzzle. SMLE Enfield .303's are well known to do this with huge muzzle velocity spreads of their arsenal match grade ammo with even greater velocity spreads. Same ammo shot in rifles built on Mauser 98 front locking actions didn't compensate very much at the longer ranges but did better at short ranges compared to the SMLE.

Ballistic tables show 30 caliber magnums will have about 15 inches vertical shot stringing at 1000 yards with a 50 fps velocity spread. With a .308 Win., it's about 20 inches.

 

[shortpants]

Thanks for the great detail JE, sounds like you found what works best for you. I don't believe there is one right way and all others are wrong. I do believe when you find what works best for yourself it is a good feeling. I'll have to experiment with different ways and try to find what works for me. Those who have shared the details of how you test sure make it easier for those of us starting out so once again thankyou!!!

 

[shortpants]

Hey Bart B, wouldn't what you just said explain why it is so important to find your node and keep your velocities as close to the node as possible (low SD/ES). Earlier I thought you were saying ES was not as important as some make it out to be. I guess if you haven't found your node ES would not be all that important but if you have it seems it would be critical.

 

[Bart B]

Hey Bart B, wouldn't what you just said explain why it is so important to find your node and keep your velocities as close to the node as possible (low SD/ES). Earlier I thought you were saying ES was not as important as some make it out to be. I guess if you haven't found your node ES would not be all that important but if you have it seems it would be critical.

I guess I don't know what my "node" is. Never did a lot of chronographing to get sub .6 MOA accuracy with 30 caliber magnums at 1000 yards. I just used the same charge weight for IMR4350 I always did, maybe dropping it a grain if pressure signs (more primer cup extruded into bolt face hole around the firing pin) appeard. Only had to do that with my last barrel; the previous 3 shot the same with 66 grains under a Sierra 190. Only did velocity tests with one barrel, none with the other three barrels. They all shot just fantastic. Shot 200 gr. HPMK's in one barrel and just dropped the charge 1 grain; same accuracy but they printed about 1/2 MOA lower requiring a small sight change for zero.

 

[shortpants]

From what I have gathered from talking with guys on this site it seems that finding the node first and then tuning for low ES would be the most accurate way to load for precision long range hunting. You referred to barrel whip earlier so with that in mind finding your node means finding the charge weight/velocity that causes the bullet to leave the barrel when the barrel is at top-dead-center or TDC. If you can find your node and then load consistent rounds with a low ES ( below 20fps hopefully lower) you will find the true potential of you and your rifle. I know that you already know this but thought I would sum it up for others that might read this thread. Thanks again for helping me try to wrap my head around this stuff!

 

[rscott5028]

[...]
If you can find your node and then load consistent rounds with a low ES ( below 20fps hopefully lower) you will find the true potential of you and your rifle. [...]

Someone in another thread stated or implied they consistently get 3-4 ES with their hunting loads.

Sometimes I don't know whether to feel completely inept or call BS.

-- richard

 

[Bart B]

You referred to barrel whip earlier so with that in mind finding your node means finding the charge weight/velocity that causes the bullet to leave the barrel when the barrel is at top-dead-center or TDC.

I don't know that my bullets leave at the top of their whip cycle, or TDC. I nor anybody else I know of has the test equipment to show where in the barrel whip cycle a bullet leaves. It's all theory by those who promote it and none of them can prove it.

Bullets leaving at TDC (or thereabouts) is not best for accuracy. I want them to leave while the barrel's bore axis at the muzzle is still swinging up so the slower ones start out at a greater angle and those faster at a lower one. As most barrels don't reach TDC before the bullets leave, trying to do so is difficult. Barrels whip mostly such that they go through one cycle in .010 seconds or less; that's 100 cycles per second or a very low frequency. Barrel time for most centerfire bullets is .0010 to .0015 seconds; they're long gone before the barrel completes one cycle of whip and they leave while the barrel's bore axis is moving upward.

 

[shortpants]

THUD, THUD, THUD! That's the sound of my head beating against the wall. Bart you are supposed to be making this stuff easier for me. Just when I think I'm understanding this stuff somebody has to put another fork in the road. Like I said before when you find something that works for you it's a great feeling. I hope to get there. You have pointed out several instances where the way some conduct load testing will be inconsistent. I don't believe you have shared the details of how you conduct load testing. Would you mind sharing that? I hope you can sense there was some sarcasm in this post and realize that I really do appreciate the fact that you are taking the time to help others learn through your experience.

 

[Bart B]

THUD, THUD, THUD! I don't believe you have shared the details of how you conduct load testing. Would you mind sharing that?

In three decades of shooting high power rifle matches, I never developed a single load, except one. All I did was use the same components as the winners and record setters use and put the same charge weight in the cases as they do. All my .308 Win. and .30 caliber magnum barrels have shot my handloads inside 1/2 MOA through 600 yards and inside 3/4ths MOA at 1000.

The only one I developed was when part of a group of top classified long range competitors working up a load for Sierra's new Palma bullet in 1991. We all just happened to get best accuracy with 45.5 grains (metered to 3/10ths grain spread) of IMR4895 with a Fed. 210M match primer igniting it in brand new Winchester cases. 20 rounds picked at random from the production lot of a couple hundred thousand rounds tested 2.7 inches at 600 yards. Later that year when several top long range shooters from around the world in a 5-day long range match shot that ammo in all sorts of rifle barrels, they all said it was definitely half MOA ammo at 600 yards. Not too shabby for ammo with 3 thousandths bullet runout and new, unprepped virgin brass.

PS: Oops, there was one other load I developed from scratchg. Sierra Bullets said I should use about 72 grains of H870 in a .264 Win. Mag. long range match rifle shooting Norma match bullets. I tried 71, 72 and 73 grains for 10 shots each at 1000. 72 grains did it.

 

[sleepyeddie]

Someone in another thread stated or implied they consistently get 3-4 ES with their hunting loads.

Sometimes I don't know whether to feel completely inept or call BS.

-- richard

LOL, pretty much agree with this!

 

[Michael Eichele]

I have only read a few posts so please excuse me if I offer redundant ideas.

I run dozens of my loads over the chrony. Not all at once of course. Unless I am in the field shooting prone and am just at the range dialing in, testing, experiemnting etc....all of my loads get fired over my chrony. This gives me a very clear and accurate picture of my real ES/SD is as well as temperature swings. Some groups are 4-5 FPS apart and others are 20+. The bottom line is that I can see what the general average is. My 'single digit' ES loads typically are single digits most of the time with some groups showing 10-20 FPS difference. I don't think there is ever a TRUE single digit ES load all the time. Even in the BR crowd. I don't know how important single digit ES's are anyway. I have had multiple loads that had 20-30 FPS ES and they grouped very well even at long range. There is more to vertical separation than just an extreme velocity spread. That said, there comes a point in every bullet's life when high extreme spreads rear their ugly heads. 15-25 will still offer a decent group at 1K provided it is a good load to begin with. For my 1K loads, I strive for 0-15 FPS ES with an occasional 20 FPS spread, even though 0 is not possible at this point in time, its just a reference.

Find a load that offers good accuracy and consistency and be happy. Good velocities are #2 and low ES are #3. A load that offers the best harmonics possible is worth more than low ES (IMHO). Find good harmonics and you will be a successfull longrange marksman.