Scientific basis for Lot/Barrell compatibility

[Elmas]

From what we read on here , certain barrels prefer certain .22LR ammo ... not just the make , but the manufacture LOT . This is universally accepted as a given by the pro's on here and we believe what they say .

If we take Eley Tenex ammo as a popular expample , why is it that a certain gun will 'prefer' a particular lot and not just any ammo produced by the manufacturer to Tenex specs . My question is ; is there a scientific explanation for this idiosyncracy ? can anyone explain ? Doesn't Tenex imply that it has been produced under the most exacting standards to turn out 'identical cartridges' .
Surely the standards for Tenex are different to those of the less expensive Eley Club where one can expect some almost insignificant variations in the latter but not the former ?

[Tim S]

Because there are variations between batches of the same brand of ammunition. The quality control for Tenex is higher than for Club, but still not every batch is identical. Each Tenex lot uses bullets made from a single billet of lead. The next batch is made from a different billet. The propellant powder too can be different: Eley buy in large quantities, far larger than the small pots bought by home handloaders. Look at different boxes of Tenex and you will see each is marked with an average muzzle velocity. This varies from batch to batch. Speed and acceleration in the barrel differ, which affects the barrel vibration, where the muzzle is pointing when the bullet exits.

Eley grade Tenex as Tenex because it meets a certain standard when test fired. They use four barrels. Batches that do not meet Tenex standard are sold as Match. You can just buy Tenex, but you may find that some batches shoot no better than Match in your barrel. It's why Eley have customer test ranges. It's not just Eley, Lapua and RWS also offer testing too.

[kevinweiho]

why is it that a certain gun will 'prefer' a particular lot and not just any ammo produced by the manufacturer?

There have been numerous cases where two guns of the exact same model liked two different particular brands of ammo.

I think it has to do with the mandrel that imparts the rifling in the bore, no two barrels are exactly the same, just like fingerprints. I believe manufacturers cherry pick the best lots of barrels for more expensive guns which command a premium, the rest are sold for regular production guns.

[SlartyBartFast]

Not a shooting or gun manufacturing expert, but I'll chime in anyways...

Everything in manufacturing has tolerances. And functionality and performance is the result of the addition of all the tolerances.
For you consider the simple case of hole and pin. To ensure all parts go together, the largest pin produced needs to fit in the smallest hole produced.

If a tighter fit results in better performanceof the assembly as a whole, the random occurrence of smallest hole and largest pin being assembled for batches of each will result in a product that performs far better than average.

Thus, matching barrels to bullets.

There will still be deviations and variations within a batch, but they'll be statistically closers together than the variations between mixed batches.

In the car racing world, there's the works cars. Fully production parts. With nothing custom, and very tightly enforced limitations on how parts can be polished or changed. So, to get the best performance engineers spend huge amounts of time measuring and classifying parts from the standard production lines and build one or more perfect engines and cars. Each ring matched to each piston, each bearing matched to each shafts and housing.

[GOVTMODEL]

I once took three (3) Hammerli pistols to the Eley Customer Range, and tested seventeen (17) batches of TENEX. I was able to identify a batch of ammunition that clearly grouped better than the rest in each pistol. Three pistols, three batches of TENEX. No correlation batch to batch or pistol to pistol.

For each pistol the best batch grouped under an inch at fifty meters, and the worst batch grouped around two inches. Obviously, all would fit easily into the 10 ring of the NRA 50 Yard pistol target.

[Pat McCoy]

[*]Each Tenex lot uses bullets made from a single billet of lead. The next batch is made from a different billet. The propellant powder too can be different[*]

Not to mention the cases are made from different sheets of brass, which can include slight differences in thickness, or hardening. Both of which can affect bullet "pull".

When Federal came out with UM1, I was told that "pull" was one of the most difficult things to get consistent, and they "wasted much of the brass sheeting they started with.

[Mike Carter]

Go here and collect a random sample of Tenex Lot numbers from Zanders current inventory.
http://www.gzanders.com/sites/default/f ... nexinv.pdf

Then go here and plug the lot numbers in and see what kind of deviation you see between the test barrels at Eley.
http://www.myeley.com/lot-analyser

One might never find a pattern or consistency from barrel to barrel in a controlled test environment. Seeing the differences from barrel to barrel at Eley is enough to reinforce the notion there is no method aside from testing to determine what will shoot well in your rifle. And then you have to consider the variations on the day you tested it. Temperature, humidity, barometric pressure, angle of the sun, phase of the moon, etc.
I'm sure the armorers from the Army Marksmanship Unit could write volumes on the subject if they were permitted. Hank Gray told me the army has probably a million rounds of .22 match ammo that, at one point, met there specification, but now no longer does.
Mike Carter

[mbradley]

Whew, boy - "scientific basis..." Very few people have any experience with scientific quantitative testing, and from what I have seen, ammo testing is about on the same level as the "science" that passes for testing in the social sciences: Not much.

Without delving too deep in the weeds, to start with, what makes you think 50 rounds of a particular lot is representative of the 50,000 produced? I could go on for hours, but twirl that single question in your mind for a bit.

[SlartyBartFast]

Without delving too deep in the weeds, to start with, what makes you think 50 rounds of a particular lot is representative of the 50,000 produced? I could go on for hours, but twirl that single question in your mind for a bit.

Statistics. All manufacturing quality control is based on statistical analysis, random sampling, and testing.

[dronning]

Without delving too deep in the weeds, to start with, what makes you think 50 rounds of a particular lot is representative of the 50,000 produced? I could go on for hours, but twirl that single question in your mind for a bit.

Statistics. All manufacturing quality control is based on statistical analysis, random sampling, and testing.

+1 on the stats, all rimfire ammo must 1st be produced to the ANSI/SAMMI spec which is pretty wide. How little variation (width of their bell curve) or where a specific manufacturer falls within the spec is up them. Ever wonder why some US ammo have feeding issues in Euro guns. Remember there are both dimensional specs and performance specs.

Here is some good reading for you stat guys if you want:
http://www.saami.org/specifications_and ... imfire.pdf

- Dave

[GOVTMODEL]

Without delving too deep in the weeds, to start with, what makes you think 50 rounds of a particular lot is representative of the 50,000 produced? I could go on for hours, but twirl that single question in your mind for a bit.

IIRC, Eley shoots ~500 rounds from each batch in QA testing. Then they decide what label goes on that batch of ammunition.

[redschietti]

As much variation as eley red has from lot to lot i suspect that the variation is intentional.

[jhmartin]

Then go here and plug the lot numbers in and see what kind of deviation you see between the test barrels at Eley.
http://www.myeley.com/lot-analyser

Has anyone used the lot-tester to correlate the deviations and compatibility with their own barrels?