WHY (c3) do barrels with the same specs ‘prefer’ different ammo? - Page 2


Firearm & Gun Forum - FireArmsTalk.com > Long Guns > .22 Rifle/Rimfire Discussion > WHY (c3) do barrels with the same specs ‘prefer’ different ammo?

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Old 03-31-2013, 07:15 PM   #11
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Originally Posted by Vincine View Post
Okay, this is getting to it. But it makes my point. Being off by a hundredth of an inch, or thousandth of a psi, or whatever, on a rifle is a much lower variation than the same variation on a 22lr round and that different lots of 22lr, and even different rounds of the same lot, are more variable than different barrels. So that to say a rifle 'likes' Elmer Fudd brand ammo in their wabbit wifle the best is naive.
No... It's not naive. Elmers rabbit rifle WILL like a particular ammo... but it won't like it forever. How's that for another wrinkle. Not only do we get to deal with finding the right match. We must also recognize that once found... barrel wear with each round fired means it will only go downhill from there.

The best term I've found to explain ^^THIS^^ is "harmonics".

Stick you index finger straight out... Now rotate it as though your drawing a small circle in the air. This is what your barrel is doing while each round travels down it's length. Accuracy is factor of consistently getting your round to exit the barrel at the exact same point of rotation.

^^THIS^^ is why many match grade bench rifles sport "heavy" barrels. While a barrels rifling is emparting "spin" on the projectile, the projectile "and the force of gas pressure behind it" are imparting torque on the barrel causing this rotation and heavier barrels rotate less than light weight barrels.

It's also why serious centerfire competitors use handloads and why rim fire competitors individually weigh each cartridge. Consistency of load determines consistant "rotational" point of exit.

As to why different barrels from the same builder and model prefer different loads, this is a factor of tooling and raw materials. Each time a barrel is "cut" the act of cutting imparts a degree of wear on the tooling, which means no two barrels are ever the same... and different "runs" may come from different batches of steel which effects "harmonics" and the resulting effects of "rotation" and "point of exit.

Tack


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Old 03-31-2013, 08:53 PM   #12
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And we haven't even touched on the metaphsyical and genetic aspects...



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Old 03-31-2013, 09:57 PM   #13
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There are a number of "Intangibles" that cannot be accounted for. "Why" one brand, or weight, or velocity, or powder, or etc, works and another does not? Your guess is as good as mine.

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Old 03-31-2013, 11:59 PM   #14
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Stress points in the metal as the bore in made, then rifled. Then stress relieving the barrel. Also each barrel bore may not be cut with the exact same tools on each line. The tools do wear which causes other variations. A lot of the final trying is actually done by hand. Then rimfires, especially semi autos, rely a lot on rim thickness and chamber rim dimensions for consistent accuracy. So bolt face and extractor cuts play into it.

I found I got best accuracy by measuring ammo for rim thickness and brands that had similar rim thicknesses performed similarly. So finding a rim thickness that a .22 likes seemed pretty important to accuracy.

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Old 04-01-2013, 12:46 AM   #15
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Originally Posted by SSGN_Doc View Post
Stress points in the metal as the bore in made, then rifled. Then stress relieving the barrel. Also each barrel bore may not be cut with the exact same tools on each line. The tools do wear which causes other variations. A lot of the final trying is actually done by hand. Then rimfires, especially semi autos, rely a lot on rim thickness and chamber rim dimensions for consistent accuracy. So bolt face and extractor cuts play into it.

I found I got best accuracy by measuring ammo for rim thickness and brands that had similar rim thicknesses performed similarly. So finding a rim thickness that a .22 likes seemed pretty important to accuracy.
they also make a measuring device for checking rim thickness on rimfire ammo for consitency.
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Old 04-01-2013, 02:25 AM   #16
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You have to remember:

A measurement is an estimate.

Estimates have ranges no matter how fine your resolution is.

Even with the finest resolution is production - one piece will differ from another - at a very small amount.

Just like a 1.00 meter piece of 12g copper might will resonate differently than a 1.01 meter piece of 12g copper wire with a frequency range shift in the 10ths of Hertz.

Perhaps one barrel is longer than the other by .01mm. Perhaps one barrel's rifling start left in chamber and end right on end, while the other starts up in chamber and ends down at the end. Perhaps the diameter of one barrel is .2201 while the other is .2202 allowing a little more premature gas escape. Perhaps the first barrel's rifling was done with a fresh "bit" while the second barrel's rifling was done with a "bit" that had already done 20 or 30 barrels resulting in rifling that is .001 in. less in depth.

When your teacher in college give you a 97% on a chapter exam. That's not your real score. You real "estimate" was likely 97% with a SEM of +/- 2.5 with an alpha coefficient of .97.

That means on a good day you might have gotten 99.5% and a bad day 94.5%. In either case, the score would have been considered a reliable statement about the test itself and your performance.

All you can do is observe the behavior - and adjust to it.

=8-)

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Old 04-08-2013, 02:53 PM   #17
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As .22 LR ammo is so hard to find in southern Alabama I ordered what I could find online. I bought 1,000 rds of this fancy match grade German stuff, figuring most of what comes out of that country is of good quality. It was Randfeuerpatronen Kal .22 made by SK
I used this in my new Ruger Single Six Convertible. It shot like a pig trying ballet for the first time. I "borrowed" some of my brother's el cheapo and very old CCI ammo and my groups really tightened up. Later, I tried the uber German rounds in my Henry Golden Boy and they really shined. Go figure.

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Old 04-08-2013, 04:12 PM   #18
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Quote:
Originally Posted by Hawg View Post
Remington rimfire ammo is crap.
Quote:
Originally Posted by 7point62 View Post
I'll drink to that.
Am I the only person on earth that likes these??!!
Whats the big problem with them? Im starting to think its your guys crappy guns not the ammo...

The Golden Rems are what both of my .22 like best..
My .22's are ancient too, one is a Winchester from 1933 and the other is a 1964 Weatherby

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Old 04-12-2013, 06:32 PM   #19
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There is a certain amount of variation from one barrel to the next, even in ones that came off the assembly line one after the other.

The major reason for different rifles preferring different ammo is barrel harmonics. When a rifle is fired, the muzzle vibrates back and forth, not a lot but enough to influence where the bullet lands 100 yards away.

Ammunition that has the bullet exiting the muzzle just as it's changing direction (i.e. standing still for an instant while it does it) will be more accurate than than ammunition that has the bullet exiting while the muzzle is still moving.

Since how the barrel vibrates is dependent on how the gun is bedded, there is plenty of room for variation between to seemingly identical rifles.

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Old 04-12-2013, 07:09 PM   #20
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Quote:
Originally Posted by Trez

Am I the only person on earth that likes these??!!
Whats the big problem with them? Im starting to think its your guys crappy guns not the ammo...

The Golden Rems are what both of my .22 like best..
My .22's are ancient too, one is a Winchester from 1933 and the other is a 1964 Weatherby

I like em too they shoot out of my marlin great


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