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Old March 14, 2013, 07:12 AM   #1
Pond, James Pond
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Match Vs Standard: Barrel performance.

I've understood for some time that a fat match barrel will be more accurate than a standard barrel.

I also think that I understand why. If I've got it straight, this is because the fatter match barrel will not heat up as readily as a thinner walled barrel and thus not be subjected to the small degree of warping you might get after a number of shots in quick succession.

Assuming this is correct thinking can anyone tell me the following:

With a normal barrel, what would be the greatest rate of fire per minute that you could acheive before accuracy started being adversely affected?

Secondly, does this mean that military sharp-shooters have to lug around a monstrous match-barrel if they are to keep plugging away at the enemy with any consistency of shot placement?

Aside from the military theory question, you can take my question in the contest of target shooting at various ranges.

If you need two models to compare, the take the CZ Varmint 550 (24" barrel) and the CZ American 550 (20" barrel, threaded).
In this context: What can the 25" Varmint do that the 20" American cannot?

Thanks
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Old March 14, 2013, 07:43 AM   #2
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Obviously, it depends on the cartridge being used. A .223 Rem will shoot more rounds than, say a 300 Win Mag before the barrel is too hot to touch, which signals the start of being too hot and increased barrel erosion. It doesn't mean that it won't shoot to nearly the same POI, but it's likely to have wandered somewhat.

Accuracy of sporter weight barrels can be equal to heavy barrels, but probably not for longer strings, as in combat. A lot depends on the characteristics of the particular barrel, including internal stresses.

I have a sporter-weight, super match barrel on my pillar-bedded, Rem 700, .243 Win that shoots 5/8 MOA, but it's no more accurate than my box-stock, Tikka T3 Lite, in the same chambering. (It cost me the same to buy the Tikka as it did to have the Remington re-barreled, which took more than 3 months.)

This may not fully answer your question, but it's the best I can offer.
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Old March 14, 2013, 08:07 AM   #3
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A match barrel's improved accuracy comes from:
1) bore machining precision and finish- this allows the bore to keep cleaner
2) stiffness - reduces touch points and makes vibrations more consistent shot to shot
3) mating- A match barrel will have threads and mating surfaces indexed to the bore
4) weight - key to holding steady
5) concentric crown
6) perfect chamber

These things make a match barrel. Reducing weight or not truing the action eliminates some benefit, but not all...
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Old March 14, 2013, 08:13 AM   #4
Bart B.
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In my opinion, there's no difference in accuracy between two match grade barrels with the same bore and chamber dimensions but one thicker than the other. While each one will have a different resonant frequency it whips at when fired, it'll always be the same frequency and amount for every shot fired. It doesn't matter how much or how fast it wiggles; it's the most repeatable thing from shot to shot in a rifle-ammo system. I've not observed any difference in accuracy between my own stiff and whippy barrels. The basic reason why match barrels are thicker and heavier is they make the rifle hold more steadily in shooting positions. More mass held by us shooters moves around less while we're aiming.

Nor have I and others observed any change in accuracy in match barrels properly fitted to receivers as they go from ambient temperature to way too hot to touch. Barrel heat does not change the resonant frequency they whip at. At least not until they get soft and rupture when fired. Folks shooting prone match rifle matches have 22 minutes to shoot unlimited sighting shots and 20 record shots at 600 yards. At 1000 yards, they have 30 minutes to do the same thing. Some of them will put 5 or 6 sighters down range before their 20 record shots and only make sight changes to correct for changing cross winds. Accuracy does not suffer and impact doesn't move around.

Starting with a cold barrel, I've put 30 rounds down range to a 1000 yard target testing a 30 caliber magnum in 20 seconds; all 30 went inside 5 inches. I forgot to bring my IR temperature gauge to measure barrel temperature, but I'd had a bad 2nd degree burn had I laid that barrel against my neck.

A friend had his .308 Win. match rifle clamped in a machine rest and fired 40 shots about 20 seconds apart at the 600 yard target. The barrel was cool at the start, but all bullets went inside 2 inches down range. That barrel was really, really hot when the last round was fired.

Lake City Army Ammo Plant tested 7.62 NATO match ammo shooting a couple hundred shots 20 seconds apart in their test barrels. With good lots of National Match ammo, all of the bullet holes would fit well inside a 6 inch circle. Pretty darned good for new cases, metered powder charges, and MIL SPEC chambers.

Virtually all factory barrels are fit to receivers such that they bear hard at one point around their tenon shoulder; that flat part that touches the face of the receiver. That happens 'cause the receiver face ain't square with its threads for the barrel. As the barrel heats up and expands, it bears harder at that point and it wiggles differently with more pressure at that point than all the others around it. Squaring up the receiver typically fixes that. Match rifles properly built have receivers faced square with the barrel threads and chamber so they won't change point of impact when they bend from getting hot.

The only difference between a match and standard barrel is typically the tolerances of their chamber, bore, and groove dimensions and twist. This has no effect on how their accuracy changes as they heat up.

Here's a link to barrel temperature tests on an M16 rifle that's interesting:

http://www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA019649
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Old March 14, 2013, 08:22 AM   #5
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I've shoot a heck of a lot of matches, with thin & heavy barrels, match and standard.

So as not to be repetitive, I'll just say I concur with Bart, he pretty much covered it.

Bart mentioned squaring the receiver with the treads. Regardless of what type of barrel you use, this is ONE OF the quickest ways to make a so so rifle accurate.

To see this, Brownell sells a Action Facing Mandrel. This is nothing more the a rod with a section in the middle that is treaded for what ever action you're using.

The action is slide onto the rod, and screwed on the threaded section. The rod is then put in a lathe between centers. Use a dial indicator to make sure the tail stock is lined up with the head stock.

Now take some layout ink or something else to paint the front of the action. Take a very light cut ( lets say .001) on the front of the action.

Chances are, you'll see bear metal on one side of the action face and on the other side you'll see the layout ink hasn't been touched.

I've re-barreled a heck of a lot of actions and believe me, few are square.

As Bart said, if the face of the action isn't square, its not gonna shoot the same if its hot as it did when its cold.

Talk about cold bore, the is the best way I know to get the cold bore shot the same as when its warm.
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Old March 14, 2013, 08:50 AM   #6
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Military rifles don't need to perform to the same degree of accuracy as target rifles. Rather than shoot a tight group on a known range, the idea is to hit a rather large target at unknown distances. Two or three MOA is sufficient for most military engagements.
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Old March 14, 2013, 09:11 AM   #7
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To add to Art's comment:

Regarding target shooting, the X-10 ring on the 1000 yard servce rifle target is 20 inches in diameter.

A 2 MOA Military Rifle is capable of cleaning that target.

Problem is, there are few cleaned 1000 yard targets.................but its not the gun that's the limiting factor.
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Old March 14, 2013, 03:09 PM   #8
Pond, James Pond
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Hmmm... as I've read through these great responses, it dawns on me that I may have made a mistake in my initial post:
the CZ 550 Varmint that I used as one comparator in the OP may have a heavy walled barrel, but is probably not an actual match barrel.

Am I right?

Is the CZ 550 Varmint no different in construction to a 550 American or Lux or any other model, other than a having a fatter barrel?

I started this as a theoretical question, but there is a practical reason for my question. It all this boils down to trying to make a choice. A choice based on understanding.

My existing .308 is heavily used (muzzle bore gauge read at possibly just under 7.63mm) and I want to replace it with a new one now as I will soon no longer be able to buy anything new due to up and coming commitments...

I like the shorter 20" CZ American, but I also like th beefy 25" CZ 550 Varmint. But the Varmint is almost €200 more.

Is that worth getting match barrel performance? Yes.

Is it worth just the look of a match barrel? Not so sure.

Based on the responses, it seems that a heavy barrel may not really offer me many more accurate shots than the standard if the barrel was not set against a square action face.

And so it follows that the only advantages other than the look of the Varmint, would be greater weight for stability and recoil. The extra 5 inches of barrel amy afford me some extra fps and hence range, but how much more and will I ever reach a stage where I can shoot that far?!
I don't anticipate needing any kind of rapid fire and don't yet have the necessary skill set, but nor do I want the option arbitrarily unavailable to me right from the get-go...

So final question taking range, accuracy, resilience to warming barrels, recoil and anything I've overlooked:
Realistically, in the hands of your average shooter (I'm no Zaitzev nor Bob Lee Swagger ) what can the 25" Varmint do that the 20" American cannot?
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Old March 14, 2013, 03:48 PM   #9
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Rainbow, if the muzzle's bore diameter is a bit under 7.63mm, that's a bit under 0.30034". Many fine match grade 30 caliber barrels are right at .300000" which that one may well be at. It's the groove diameter that matters most. Push a .310" (7.874mm) diameter round ball from breech to muzzle, then use a good micrometer to measure it's diameter. That's the groove diameter. Good 30 caliber match barrels have groove diameters about .0005" (0.0127mm) smaller than bullet diameters used in them.

Barrel wear is best measured at the origin of the rifling at the back end of the barrel. Very little wear happens at the muzzle. If that barrel's got more than 4000 rounds through it, it's accuracy has degraded about 40%.

I've seen some very ugly match barrels win matches and set records; they're just a tool to shoot bullets into paper, not something to win beauty contests with.

Extra velocity with a longer barrel gains very little in useful range for hunting purposes, but it helps as bullets drift less in cross winds and keeps some bullets supersonic all the way out to far distant targets.

A 25 inch barrel will shoot the same bullet out about 100 to 125 feet per second faster than a 20 inch one will. That's the only difference ballistically. The longer barrel is easier to hold on target as it's heavier and swings around less when you're aiming it.

And "match" barrels are usually those with very uniform bore, groove and twist dimensions. Bore and groove diameters held to 0.000254mm (.0001") tolerances and less than 1% change in twist rate from breech to muzzle. They can be any length or diameter. And they're very well stress relieved, too.
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Old March 14, 2013, 06:46 PM   #10
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My understanding is that MW is a far bigger factor than throat wear in accuracy reduction (that assumes the barrel was accurate to start with, a good MW reading does not guarantee accuracy).

On the other hand a bad one ensures poor accuracy.

You can have the muzzle cut and re-crowned or tapered back and restore MW as long as the rifling is not worn out which is a result of 4-8000 round through it.

Obviously throat erosion at some point will factor in but usually its a rare case of that before MW.

Shooting hand loads of as low a velocity as you can maintain your desired accuracy with (and above the minimum powder loads) adds a lot of life to a barrel.
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Old March 14, 2013, 06:53 PM   #11
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RC20, "MW" is an abbreviation I'm not familiar with.

Does it mean "muzzle weight?"
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Old March 14, 2013, 09:48 PM   #12
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Looking back over many a year of testing rifles and loads from a bench, I guess I would shoot a five-shot group in probably a minute between rounds, but no more than two minutes. Guessing.

I've seen a bunch of sub-MOA groups from one heavy-barrel Swift and several medium-weight sporters. .223, .243, .270, 7mm08 and '06.

I shot up a bunch of '06 ammo getting sighted in at my 500-yard range one day. Finally got dialed in, but was running low on ammo. So, two four-shot groups of 4" and then a no-dilly-dally ten-shot string. I had two called fliers before I even looked; eight shots in six inches. #2 profile barrel. Not sure what it proves, other than a medium-weight barrel didn't walk around on me very much.

I guess I figure that the advantage of a heavy barrel for target shooting is for long and fairly rapid strings of fire. But, I'm mostly a hunter and not a target shooter.
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Old March 15, 2013, 01:32 AM   #13
Pond, James Pond
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Quote:
"MW" is an abbreviation I'm not familiar with.
My guess is it stands for "muzzle wear".
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Old March 15, 2013, 06:32 AM   #14
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James, you asked: with a normal barrel, what would be the greatest rate of fire per minute that you could acheive before accuracy started being adversely affected?

Probably 30 or 40. But the barrel would have a shorter overall life.

In the USA, there's a service rifle match wherein competitors shoot about 24 rounds in 50 seconds at 600 yards and again at 500 yards in the first two of four stages of fire. Their super accurate match grade 7.62 NATO semiauto. There's not one bit of accuracy drop off shooting strings of fire that fast.

And I agree that MW must mean muzzle wear. Rifle barrels do not wear any significant amount whatsoever at their muzzle. Pressure's lowest there and by the time a bullets an inch full into the rifling, its perfectly sized to the bore and groove diameters and shapes ther and all the way to the muzzle anyway. Too many folks have set barrels back an inch or two and accuracy was as good as before. All they did was get rid of the bore erosion at the origin of the rifling. Bore gauges measuring barrel wear do so at the origin of the rifling; the only place that they wear out at.
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Old March 15, 2013, 10:29 AM   #15
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Bart B:

Thanks for the further input on my odd question!!

At least that means that I could be shooting as fast as I can and still be nowhere near a point at which that rifle would start throughing them left, right and not so centre!!

A feel another blundering "What rifle" thread coming on.... no doubt much to the groans of the initiated and experienced!!
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Old March 15, 2013, 11:14 AM   #16
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Odds are that if you think it through about your intended purpose, we can give better answers to well-thought-out questions concerning that purpose.
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Old March 15, 2013, 11:38 AM   #17
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Tim Mullin said his custom 7.5 lb .308 was not enough less accurate than a 15 lb name brand military sniper rifle to bother him. Give up a small fraction of a MOA for half the weight to hump? You bet. I do not understand why military sniper rifles are so heavy.

I think the heavy FACTORY barrel might be a better shooter than a light profile, because the added metal MIGHT counteract some of its mass production dimensions, hasty stress relief (if any) and quick fit to action.
E200 better? I don't know.
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Old March 15, 2013, 01:42 PM   #18
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I'd be willing to bet money (a reasonable sum) that with factory barrels from the mass manufacturers, the heavy barrels will shoot consistently better than the thinner barrels. I would not make that bet on custom barrels, though some little voice in my head says that if I had to build a rifle to make just the perfect shot, it would have a heavy barrel.

My cousin was in blackpowder unlimited at the national class level, and his unlimited barrel must be 4 inches across at the muzzle. I never asked him why he needed a heavy barrel and not some thin whippy barrel, but I suspect that I know the reason.
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Old March 16, 2013, 06:36 PM   #19
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Heavy rifles are more forgiving of less than perfect shooting form and are easier to shoot accurately. Heavy barrels help make for heavy rifles. In my opinion this is the main advantage of heavy barrels. A quality lightweight barrel has the potential to be just as accurate with one exception. Shorter barrels tend to be more stiff. In order to get a longish 26-30" barrel as stiff as a standard 20-24" barrel it must be thicker.

If you are talking about long strings fired rapidly a heavy barrel will mantain accuracy a little longer before it overheats, but the inside of the barrel, where the rifiling is, will be just as hot. A heavy barrel also takes longer to cool down than a lighter barrel and could be a disadvantage under certain circumstances.

A very lightweight barrel can be amazingly accurate if the shooter does his part, at least for 3 shots, or if enough time is allowed between shots. I used to own a couple of heavy barreled target/tactical rifles, but sold them because the accuracy differnce between my lighter sporter weight rifles was just not that much greater. I never used them except at the range.

These are typical of a Remington Mt rifle with a pencil thin barrel. By taking about 1 minute between shots this is a pretty normal group. 5 shots, or rapid fire, would result in groups at least 2X that large.

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Old March 16, 2013, 07:42 PM   #20
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Quote:
Originally Posted by 603Country
I'd be willing to bet money (a reasonable sum) that with factory barrels from the mass manufacturers, the heavy barrels will shoot consistently better than the thinner barrels. I would not make that bet on custom barrels, though some little voice in my head says that if I had to build a rifle to make just the perfect shot, it would have a heavy barrel.

My cousin was in blackpowder unlimited at the national class level, and his unlimited barrel must be 4 inches across at the muzzle. I never asked him why he needed a heavy barrel and not some thin whippy barrel, but I suspect that I know the reason.
You would loose your bet. Not to very long ago I would have made the same bet though.

Top target; Custom built Remington 700 .308 heavy barrel. Bottom target: Remington 700 30-06 factory action and sporter barrel. Both rifles have Timney triggers. .308 is in a fully adjustable Bell & Carson Medalist 5 stock. Rifle weights close to 25 Lbs. The 30-06 is in a Bell & Carson Medalist 4. Rifle weights around 7 Lbs.

Both are 5 shot groups. I pulled one with the 06 (bottom target) it wasn't the rifle. Both strings were fired 5 shot in succession only taking long enough to eject the spent case and toss a new round in the chamber. Both rifles started cold.



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Old March 16, 2013, 10:32 PM   #21
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Those standard weight skinny Garand barrels on 7.62 NATO match grade conversions would put 10 shots inside 2 inches at 300 yards in 50 seconds. Wanna lick one of them with your toungue after doing that to cool one down?
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Old March 17, 2013, 08:37 AM   #22
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jmr and Jerry, your evidence that thin barrels are equal to heavy barrels for accuracy is tempting, and I can see that in some cases that would be true. However, I still believe that if you took 100 heavy barreled rifles from an assortment of gun manufacturers and 100 light barreled rifles from those same makers, the averaged accuracy from the heavy barreled rifles would be better. Right or wrong, that is what I do believe.
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Old March 17, 2013, 09:58 AM   #23
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The OP has an allied thread now underway, so this one is of declining use to him.
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