short barreled rifle question - barrel too short for powder to burn ?

Gatehouse said:
What it actually shows is that the pistol they used got higher velocity with Varget and the rifle got higher velocity with the H4350. They didn't use the same firearm and shorten the barrel when they did their load testing.

The only way to do an apples to apples comparison is to shoot the rifle (24" barrel) and then chop it down to 15" and shoot again.

Looking at the data you posted, all the 15" and 24" velocities are within 50fps of each other, and it could probably go some other way with different firearms.
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That may be true. I wonder if they just use a test action and swap barrels.
 
Gatehouse said:
I predict you will lose about 150fps in both. Maybe a bit less, but probably not much more..But it's just a guess as I've never shot a 20" WSM, although I do have a 20" 300RUM sitting in my shop right now.:D
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So you figure it will make no difference that in the first instance the WSM needs significantly less powder to attain a similar velocity? Maybe there would be no real difference. Hhhmph.:confused:


I would have thought that in in the second case they might have a similar loss. I guess there really is only one way to find out for sure!
 
1899 said:
So you figure it will make no difference that in the first instance the WSM needs significantly less powder to attain a similar velocity? Maybe there would be no real difference. Hhhmph.:confused:


I would have thought that in in the second case they might have a similar loss. I guess there really is only one way to find out for sure!
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As far as can tell, nobody can give a precise number of fps lost until the barrel is chopped!:)

20-30fps loss per inch seems to be about as good a guess as any. There may be some difference with the WSM using less powder but once again I think it's one of those issues that is more theory than practical. Like the ballistic advantage of one 300 magnum over another:p
 
It is far more important to match the powder burn rate to the bullet weight than it is to the barrel length. A light bullet can be driven faster with a moderate burn rate, but go too quick and you will have pressure issues before you have hit your target velocity. A heavy bullet does better with slower powders, but go too slow and you will run out of capacity before your reach the desired velocity. None of this changes with barrel length, but there are sweet spots where one powder proves significantly better than one other. Side by side comparisons of two different barrels are of little help as there are many dimensional issues that can effect velocity. The real test is to start with a long barrel and lop off an inch at a time then measure velocity and record the results.
 
The Light magnum is made with a very slow powder ball powder that has been heavily compacted with a ram, before the case is necked.

If you pull a bullet in 7-08, I expect you will find 55 to 60 gr of powder. If you shoot it over snow in a short barrel you will find a lot of unburnt powder.

It would be intersting to see if a conventional factory load with same weight bullet is any faster or slower.
 
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