Does this twist hinder velocity and reach max pressure too quick?

S

sambubba1

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I have a .284 with a 1:11 twist that is rechambered from a 7BR. My question is can this slower twist hinder this rifle from
achieving normal .284 velocities? My loads cannot begin to approach the loads in several of the manuals without excess
pressure signs. Just wondering?
 
I seriously doubt it. Other factors, such as a tight bore, short throat, short barrel, or flimsy action are more likely to limit pressure and/or velocity. All else being equal, the slower twist may tend to reduce pressure and allow slightly higher velocity. Can you give more specifics; barrel, length, throat length, bullet, and powder?
 
Twist doesn't effect pressure as much as people think it might.

Total surface are of the bore or maybe I should say changing the bore and groove sizes especially the groove size will have more of an effect on the pressures than anything else.

Who made the barrel?

Have you had the bore and groove size measured/checked?

I've seen even factory barrels that were grossly undersize. One of the guys had a factory rifle here in 7mm-08. The bore and the groove especially the groove was so undersize that the gun wouldn't even handle box ammo. He had to hand load it with reduced loads in order to shoot it.

Also what type of chamber reamer was used to chamber the barrel? Different throat specs. can make a difference as well.

Later, Frank
Bartlein Barrels
 
This is a Shilen select match 22.5" long and I'm using RL15,17 and H4350 primarily. All brass is match prepped. It is set up on a
700 LA and the chamber and bore have not been miked. The reamer was either a Kiff or Clymer.
 
Last edited by a moderator:
sambubba1 said:
I have a .284 with a 1:11 twist that is rechambered from a 7BR. My question is can this slower twist hinder this rifle from
achieving normal .284 velocities? My loads cannot begin to approach the loads in several of the manuals without excess
pressure signs. Just wondering?
Click to expand...

No
 
sambubba1 said:
This is a Shilen select match 22.5" long and I'm using RL15,17 and H4350 primarily. All brass is match prepped. It is set up on a
700 LA and the chamber and bore have not been miked. The reamer was either a Kiff or Clymer.
Click to expand...

I haven't come across a Shilen that was much tighter than usual, not to say it's not possible. RL 17 and H4350 are the burn rate I would use with 120 gr bullets. With heavier projectiles, you might squeeze out a little more velocity with powder in the RL22 or 4831 range.

For myself, I would just use the combination that gives the best groups and not worry one bit if my velocity is a little slower than what the books suggest. With a 22.5"barrel if your throat is fairly short, That would be about normal any way.
 
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