Barrel Heat


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Jayhawker
September 1, 2004, 11:29 AM
Hello:

I'm relatively new to shooting a Marlin 1894SS .44Mag having been a avid pistol shooter until I got pistol caliber carbine fever. One thing I've noticed about this gun is when I start shooting with a cold, clean gun it will plant 5 shots in a 2 inch group at 100 yds through a scope off the bench. After that, the groups get bigger and bigger. The barrel does not lead so I don't think that's it. Barring something wrong with the scope, I was wondering if this is about par for the course. In 10 or 20 shots that barrel is too hot to touch. Does barrel heat affect grouping that much?

Thanks for any help.

Pete

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DevilDog
September 1, 2004, 11:37 AM
Hey Pete,

It probably is due to heat. If it was a scope problem, I think once you saw the groups open up, they would stay opened up.

Lever actions are great, but one thing with their design is the barrel probably touches the forearm in a number of places and it probably has a barrel band around the barrel and the forearm.

I think as the barrel heats up, it puts more pressure on those contact points, and then its overall shape changes a bit, and therefore affects its accuracy.

I am not all that knowledgeable on lead bullet issues, but it is possible that a hotter barrel will suffer accuracy more with lead bullets. Maybe someone else can expand on that.

perry1963
September 1, 2004, 06:27 PM
yes, barrel heat will cause groups to open up, a factory barrel is drilled, chambered and has the rifleing cut before it's heat treated, which causes the barrel to warp, it is then put through a straighting prosses, when the barrel heats up from shooting it will retun to it warped state and, like devildog said, contact the forend and forend band, another cause is fouling from shooting it.

moredes
September 3, 2004, 04:49 AM
There's an "old wives' tale" that says that one shouldn't fire a rifle too hot to hold.

The 'common wisdom is that barrel life is shortened when the barrel is "misused" in this manner.

Art Eatman
September 3, 2004, 10:44 AM
As it heats up, the steel expands much faster and more than does the wood. This changes the pressure on the barrel at the points of contact, changing the vibrations and thus making minor changes in the alignment of the bore. "Minor" is enough to widen the groups.

But, hunting rifles aren't meant to be shot more than once or twice at a time, really. After all, if you don't hit Bambi or whomever by the second shot, odds are you're done for a while. By and large, all hunting rifles will give excellent three-shot groups, and many do great for five shots.

No rifle in "firefight" usage of many rapid-fire shots will give tight groups. That just doesn't happen, nor is it necessary. "Minute of enemy" at fifty to one hundred or so yards doesn't require tight-group accuracy.

The ultimate-accuracy rifles used in benchrest competition are a whole different story, but they don't sell for $400, either...

:), Art

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