Author Topic: how does barrel length affect load recipes? (Read 649 times)

gasr55 · « **on:** September 30, 2003, 10:17:14 PM »

I have noticed that some load recipes list a barrel length that was used to test that load. What happens if the barrel length of my gun is longer than the barrel length of the test gun? for instance a load i want to use was tested with a 4" barrel and the gun i will be loading for has a 6" barrel will this pose a significant problem such as an increase in pressure or is it something i should not worry about? I just dont know why they would list barrel length if it was not important however if it is important why dont all load recipes give you the length of the test barrel ? Thanks to all that reply i appreciate your time and trouble to help with my question.

Ullr · « **Reply #1 on:** October 01, 2003, 02:42:43 AM »

The barrel lengths are given as a reference for the velocity. With your barrel being slightly longer you should see a little higher velocity for the same load in the book. Some also list the actual gun model that was used. Once again as a reference, some guns are more accurate with one powder then another.

gasr55 · « **Reply #2 on:** October 01, 2003, 06:49:41 AM »

Thanks for the info that really makes a lot of sense.

KN · « **Reply #3 on:** October 01, 2003, 12:07:21 PM »

A couple of inches won't make much difference, but if your load was based on a rifle and your shooting it from a contender pistol then the powder selection may be more important to you. You may wan't a faster powder for a shorter barrel. Or vise versa. KN

Questor · « **Reply #4 on:** October 01, 2003, 12:25:29 PM »

It also seems to depend on the lab that does the testing. I don't trust the velocity figures in any of Lyman's data. They use special test barrels that must not be anything like real barrels.

Speer has what I consider the best data because they use real factory guns of popular make and configuration for their testing. Velocity from my guns is pretty close to velocity published by Speer.

Nosler seems a bit optimistic in their velocity figures, but I haven't tried a lot of loads from their books.

Rick Teal · « **Reply #5 on:** October 01, 2003, 07:44:20 PM »

I think the differential between velocities in different barrel lengths is more pronounced with slower burning powders than the faster ones.

When I load for my 30-06 carbine, I can't get anywhere near the "book" velocities with IMR 4831, however, I'm much closer when I use a medium burn-rate powder like IMR 4320.

Kragman71 · « **Reply #6 on:** October 04, 2003, 08:37:33 AM »

gasr55,
The only thing that I know,that would effect the load makeup is the shorter barrel requires a faster burning powder to complete the burn while still in the barrel.
If you have a pronounced muzzle flash,I would suggest that you try a faster powder.
If you have access to a chronograph,it will show you te difference.
Frank

savageT · « **Reply #7 on:** October 04, 2003, 09:27:29 AM »

Quote from: Questor

It also seems to depend on the lab that does the testing. I don't trust the velocity figures in any of Lyman's data. They use special test barrels that must not be anything like real barrels.

Speer has what I consider the best data because they use real factory guns of popular make and configuration for their testing. Velocity from my guns is pretty close to velocity published by Speer.

Nosler seems a bit optimistic in their velocity figures, but I haven't tried a lot of loads from their books.

According to my 47th Lyman Manual, the actual rifle used is listed in the Test Specifications: 6.5x55mm Swedish Mauser uses a Swedish Military Carbine (M38) 18", 23 1/2" HVA.

Test Specifications: 300 Savage uses a Savage Model 99 AND Universal Receiver. Savage 22" bbl., Universal Receiver 25".

Test Specifications: 30-06 NOTE: Universal Receiver w/ 24" bbl.

CONCLUSION: Yes you are correct in some cases, but not every time.

Jim