308 . . . 10 twist vs 11 twist

[DennisH]

I decided to rebarrel one of my 308's. I put a 28" 11 twist bull barrel on it.

My other 308 is the same, but a 10 twist.

I used some of my proven loads from my 10 twist in my new 11 twist, and the closest group I could get was around 2"! These loads will drill nails in my 10 twist.

I can't believe there is this much difference with a 11 twist barrel.

Any comments/help?

 

[fr3db3ar]

What weight bullet? Every gun (barrel) is unique and may like a totally different load. this is not new news.

 

[DennisH]

185 Hybrids, . . .

 

[Larryh128]

You could be on the edge with that bullet, you might try a 168 to get a comparison.

 

[memilanuk]

So you took loads from one barrel, and shot them from another barrel, and are somehow surprised that they don't shoot as well as they did in the barrel they were developed for/in...?

I doubt the twist rate is the problem here

 

[DennisH]

I should have worded my OP different. I wouldn't dare take any of my proven Lapua's and test on a new barrel.

I used new Federal brass with the same load, primer, powder, bullet, COAL, etc.

Thanks,

 

[fr3db3ar]

New barrel = new gun = start from scratch. JMO

 

[FroggyOne2]

Yeah, had a friend that tried that, using someone elses load and wondered why it didn't shoot in his rifle.. it took a lot of explaining to get him to understand that every rifle is different and you have to start from scratch to find a load.

 

[DennisH]

it took a lot of explaining to get him to understand that every rifle is different and you have to start from scratch to find a load.

I totally agree, and I have many rifles inc 5 308's. Just this one is "way" off and shocked me.

My other rifles were pretty close with my fav load and just required tweaking...

Something else, I dropped my charge to 42.5 which is the lowest charge I have used with any of my 308's. I am showing pressure signs!

Scratching my head!

 

[FroggyOne2]

You may want to switch to a 155 bullet and see if you still get those pressure signs.. esp up near proven competition loads.. most palma rifles use between 46-47 grs of Varget. With 46.5 usually being the norm with 155 bullets.

 

[spclark]

Did the same 'smith chamber the 1:11 as did your othet barrels? Is the new one from the same barrel maker? Same reamer used, or at least on made to the same print / specs?

I seriously doubt the slower twist is what's causing unusual pressure signs with moderate loads. Try comparing fired case dimensions or make a Cerrocasting of a couple of your chambers and the new one to compare. Either will give you info you can then factor in.

If you have a barrel that shoots great with less powder once you get around to working up safe, accurate loads for it, why worry?

 

[DennisH]

Did the same 'smith chamber the 1:11 as did your other barrels

NO, this barrel was chambered with a person's personal reamer. I just thought of this as well.

I am going to work with it to see what it actually likes. I am going to load up more and pull the chrono out!

This will be the best thing to do.

Dennis

 

[spclark]

Let us know what you learn please.