can heat change group size in a pistol


July 2, 2004, 08:01 AM
after shooting for a while maybe 200 or 300 rounds in a row.i started missing more than i should.i thought ok i just changed from the turret to the pro 2000 press and my crimp must be to strong.that will screw up your accuracy.i also have a few 40 barrels so i went home and tried them they shot ok .so i then tried the barrel in ? it had cooled off by then and it shot ok as must be the barrel heat plus i was shoot a 180 at 1100 fps.i have never seen this with a 357 SIG it is accurate right off the bat and stays that way.the barrel does have a thicker wall in the barrel in that the hole in the slide is the same but the barrel bore is smaller.have i been out in the sun to long or what do you think ? i was getting 6 inch to 8 inch groups at 25 yards even at 10 yards it was 2.5 inch groups after the barrel cooled i was shooting 2.25 inch groups at 15 yards.still not great but better than it was.the gun has night sites on it they suck for group shooting.i think it was the makes me love the 357 SIG even more it has never done this and it will shoot great even at 50 yards i will put 4 or 5 in the ten ring on a man size target out of 6 rounds,thanks,keith

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July 2, 2004, 12:12 PM
I guess thoeretically you could say yes.
I think in practical terms, nobody would be able to tell.

In rifles you are dealing with a much longer barrel, and usually much longer distances. Any small changes due to heat are magnified by those factors.

Jim K
July 2, 2004, 04:45 PM
Hi, kidcolt,

You don't say what kind of pistol, but yes, heat can affect group size or even cause malfunctions. In a 1911 type pistol with a very tight barrel bushing, heat can cause the barrel to expand and bind, which in turn can cause the barrel to "spring" or the slide to slow down or hang up. Few pistols ever get that hot, since even changing magazines will usually let the gun cool some. But if one is determined to create a problem and has plenty of loaded magazines, it can happen.


July 3, 2004, 02:43 AM
i going to try and make it happen again casue i don't belive it either with a p229 that was hot and my glasses were fogging up .another thing the load was very hot and the heat would have made it even hotter.a 180 at 1100 plus from a 3.9 inch barrel,thanks,keith

July 4, 2004, 12:22 PM
I'm not an expert, but I believe the heat factor is one of the reasons that my two pistols with bull barrels continue to shoot so accurately, even after 150 rounds ( a Kimber Ultra 10 II, and an SVI Infinity). This is perhaps more evident in rifles, the "mountain" variety with thinner barrels are less accurate on second and third shots. All that said, it shouldn't make much of a difference.

Black Snowman
July 4, 2004, 03:16 PM
Might also consider with that many rounds fatuge to be a factor. I don't know what kind of shape your in but the short breaks of tinkering with the guns might have let your muscles recover. Just something to consider so you don't waste a lot of time and money trying to fix what could be a human factor.

July 4, 2004, 11:33 PM
and the more i shoot the 40 smith and wesson the more i like my 357 SIG.the 40 has the edge in penetration my hot load will shot through 3 treated 2x6's and .5 in to the is a 180 at over 1100 fps.the 357 SIG only shot through one and into the other maybe .5 of an this to hard of a test shooting through treated 2x6's or not ?? in accuracy there is a clear winner the 357 SIG.the 40 barrel looks good but i wonder if it is or not the feed ramp has no blueing at all.the 357 SIG has most of it's blueing and has over 3,000 rounds through it.the 40 is a police trade in gun.the gun shoots good with a 357 sig barrel on it but not with the 40 barrel.i shot 9 5 shot groups the average was 2.2 inches at 25 yards.i shoot with my back against the car and the gun between my knees.i did do a first today off hand i shot 4 shots at 25 yards into an inch i did not fire the 5 lost my nerve lol.thanks,keith

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