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Thread: Lot Testing Theory

  1. #1
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    Lot Testing Theory

    Hi everyone,

    I would like to start by divulging the fact that by discipline I am a smallbore position and prone shooter. I do not compete in benchrest competition, but I try to stay on top of the current developments in benchrest.

    Anyway, whether it be in position shooting or benchrest shooting, everyone I know tests different lots of ammo to find which one shoots better. I have done, my fair share of ammo testing over the years, from the bench, in position etc and fully understand that certain ammo shoots better in my rifle then others. Accepting this as fact, the question arises, what makes that particular ammo shoot better in my rifle than others? Often times the obvious answer lies in the grade of ammo being used. Certainly I would not expect SK Standard plus to shoot better than my Eley Tenex, simply from a tolerance in manufacturing standpoint. Now when you take the manufacturing tolerance differences out of the equation what is it really that makes two different lots of the same grade ammo shoot differently?

    Personally, I believe that if you are shooting a quality grade ammo, like Eley EPS, there is no superior difference in lots. This goes on the assumption that the ammo has been made to the same exacting tolerances. Basically you aren't going to have two lots of Eley EPS with one shooting 0.265" groups and the other shooting 1.5" groups. If you do then you are just extremely unlucky or something is broken. Now you might have two different lots with one shooting 0.265" groups and another shooting 0.305" groups. Since the one lot had groups 0.040" larger than the other, does that mean the ammo is crap? Personally, I don't think so. With quality ammo, I think the only difference seen in lots is that one lot by chance more closely matches the ideal harmonics of your rifle than another. With tuners and torque settings, however, the harmonics of the rifle can altered. So by changing the torque around on my bedding screws or my tuner settings, I can completely reverse the above test making the lot that shot bad the first time shoot the best out of the two. With this in mind what is the point in testing lots? If you are using quality ammo, with a little bit of experimentation and tweaking, you can change the way the ammo shoots in your rifle to better suit your needs.

    Maybe this doesn't apply to benchrest the same as it does position shooting, but I have never had a quality ammo that I could not at least get groups out of, which I could stuff inside the 10 ring. I don't know how big of a 10 ring ya'll have, but in international smallbore rifle at 50 meters it is 10mm.

    I probably made to many assumptions, so tell me what ya'll think.

    Brian

  2. #2
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    prepare for incoming rounds.
    we just lot test for something to do and to have
    something to complain about. thanks for setting
    us straight.

  3. #3
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    Brian,
    Iíll think youíll find that BR shooters test lots for the same reason that the better smallbore shooters go to the ammo factories and test lots. Same lots are better than others and you need to find the lot that works in your barrel. I take it youíve never seen a printout of a smallbore rifle tested at the Eley factory, if you had you wouldnít think all tenex is the same.

    As for SK, you can find good lots in that too but you do need to test, in July I was at the Lapua factory in Germany (I live in Australia) and I found a lot of SK match that shot on par with all the X-Act I tested there.

    Peter

  4. #4
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    Brian,

    Watch out! Here is a round incoming.

    First, I would like to say that I have to tip my hat to a position shooter. Most of us rimfire benchrest shooters could not come close to your skill and we know it.

    That being said, we rimfire benchrest shooters are reaching for the ultimate in accuracy. Our game is even more a test of equipment and ammo than your game. With our great one piece rests and 36 power scopes and four to six wind-flags we can out shoot your discipline. (It 's not braggin' if you can do it.)

    In 50/50 our ten ring is about 6 mm compared to your 10 mm. We could shoot a lot more 250s if our 10 ring were 66% larger but it would not be as challenging . In our game the best shooters do lot test. It makes a difference. I really don't know if it would be worth the effort in your game to lot test. It would not help me very much.

    Concho Bill

  5. #5
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    Well most I know in BR test ammo which boils down to the fact that barrels have distinct preferences, and I swap lots of ammo and info with a nationally ranked prone shooter who does the exact same thing.

  6. #6
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    Sault Ste. Marie, Michigan
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    Incoming rounds ain't much fun when it's artillery or mortars!

    Finding a lot of ammo your rifle likes is real FUN! But the fun can depend on the temperature.

    UP here on the Canadian Border, many of our club matches are shot at temperatures below 55 degrees. When that happens, we shoot the faster speeds of Eley Black Box and Biathlon. I still have some Federal 1000A (1140 FPS) I use when it's below freezing UP here. A few of our shooters test by lot number, but tuner setting, temperature and ammo speed are more popular at our club.

    I was a prone/position shooter before I got OLD, fat and lazy. Benchrest is a good option for anyone who lives long enough to experience 2 out of 3 of those symptoms.

    Joe Haller (Mr. Frosty)

  7. #7
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    On RF Tuning:

    Could you please explain what you are saying about making ammo shoot in a rifle by adjusting bedding screws? Does this apply to BR rifles that are Pillar Bedded?

    Thanks,

    Pete
    Last edited by Pete Wass; 10-04-2010 at 10:16 PM.

  8. #8
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    Quote Originally Posted by Pete Wass View Post
    Could you please explain what you are saying about making ammo shoot in a rifle by adjusting bedding screws? Does this apply to BR rifles that are Pillar Bedded?

    Thanks,

    Pete
    By changing the torque on the action screws, you can change the performance of a rifle. Essentially, you are changing the harmonics of the action.

    Every rifle is different, and the change varies from one rifle to the next. In some, the change is significant while others it is marginal at best.

  9. #9
    Join Date
    Feb 2005
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    I think what BAJ somewhat may be trying to say is that good ammo is VERY VERY good. The variation within a lot and the variation between lots is so small that it's just kinda hard to believe a shooter might accurately be able to measure this difference. Maybe if he carefully fires enough rounds he could find it but by this time the lot is probably all shot up! Most shooters want to believe their rifles are capable of reacting in some way to the little variation but again, it's so hard to accurately measure the very small difference, I think the normal shooter will, after a lot of shots, come to some point at which he believes he's found the best lot and he'll just go from there. Or.....what is more likely to happen, he will only shoot a few shots and simply take the results to indicate one, or the other, lot is better and thus go with it. Bottom line is....the very good ammo is so good you will get good results no matter which lot you shoot!

  10. #10
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    Quote Originally Posted by Peter Armstrong View Post
    Brian,
    Iíll think youíll find that BR shooters test lots for the same reason that the better smallbore shooters go to the ammo factories and test lots. Same lots are better than others and you need to find the lot that works in your barrel. I take it youíve never seen a printout of a smallbore rifle tested at the Eley factory, if you had you wouldnít think all tenex is the same.

    As for SK, you can find good lots in that too but you do need to test, in July I was at the Lapua factory in Germany (I live in Australia) and I found a lot of SK match that shot on par with all the X-Act I tested there.

    Peter
    what is gained testing sending a rifle to eley or lapua, shooting at 54.68 yards. coming home and shooting lots that were tested by the manufacturers at 54.68 yards tested in a rifle at 54.68 yards that was tuned at 42 yards and the goal all along is shooting 50 yards. I don't get it.

  11. #11
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    Quote Originally Posted by martin hammond View Post
    what is gained testing sending a rifle to eley or lapua, shooting at 54.68 yards. coming home and shooting lots that were tested by the manufacturers at 54.68 yards tested in a rifle at 54.68 yards that was tuned at 42 yards and the goal all along is shooting 50 yards. I don't get it.
    Martin,
    It might be hard to understand, but international rimfire BR matches are shoot at 50m not 50 yards.

    Peter

  12. #12
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    Peter, thank you. that's exactly my point. other than getting tenex before the chinese get it, what is the point or advantage of an american testing in any eruopean facility?
    Last edited by martin hammond; 10-22-2010 at 08:28 AM.

  13. #13
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    Peter, let me phrase this differently. as a international bench shooter what advantage is it to: purchase a rifle shot and tuned at 38.4 meters then, purchase ammo shot and tested at 50 meters, compete at 50 meters return to the states and shoot at 50 yards? or is their no advantage of any of this? thank you. martin hammond

  14. #14
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    Quote Originally Posted by martin hammond View Post
    Peter, thank you. that's exactly my point. other than getting tenex before the chinese get it, what is the point or advantage of an american testing in any eruopean facility?
    Martin, I'll take a shot at your question. If it don't shoot in your rifle at the factory, no matter where that might be, it probably won't shoot here. But if it does, you at least have a chance it will shoot here. I would love to be able to test all the ammo available in my rifles before commiting funds.

  15. #15
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    Iíll take a shot (pun intended) at this also.

    Earlier this year over about a 3 month time frame, I fired approximately 1,000 shots in my tunnel across dual calibrated chronographs with four different Bench rifles and 25 various lots of Lapua/Eley ammo. The rifles were fired both with and without muzzle weighting, but no attempt was made to find an exact tuner setting.

    Every shot fired was plotted to a location on target accurate to about 0.005Ē with its matching velocity. Iíve provided an example taken at random of a 25 shot group that visually illustrates what some of that data looks like with the color coded data points having a minimum of 40 ft/sec in ES:



    Donít try to read anything special into this sample specific testing result or draw any conclusions about velocity/vertical dispersion because it didnít always repeat and this particular ammo is some of the most inaccurate Iíve ever tested. But, it was useful for some of my testing because it also has the most variation in speed Iíve ever encountered with match ammunition. I had to acquire the data from several hundred shots before I thought I could see some trends I had much confidence in.

    The point Iím trying to make is that there will be both vertical and horizontal dispersion not attributable to velocity variation or muzzle weighting and lot testing a large enough sample is effective for picking the best ammo regardless of distance or tuning. Even if you totally disagree with the tuning aspect for dispersion in the y plane and whether itís distance specific....the x-axis dispersion is equally important and just might be the best indicator of ammo quality.

    Landy

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