OzFclass

Just a quick question, After somewhat of a poor performance at the longs 2 weeks back due to lack of MV(2750) in my 26" tube, I've decided to barrel it to at least a 30" and will make up a new load from there. Now before anyone says up the powder load i'm using the best accuracy load tested and only gain an extra 25fps before i start to get pressure signs. so therefore I,m after some advice on the best twist rate for the bjd 155grs.

cheers stuart

What is your load? I run a 26" barrel and have gotten the dyers to 2950fps with 2208.

12 twist will be your best bet. On the chance that you cant get them to shoot in your new barrel you will be fine for any of the 155's. 13 twist used to be good for the old 2155 sierras I heard but might not cut the mustard with some of the newer bullets around.

Hi Shaun, I'm using 45gr of 2208 inside lapua cases with CCI primers for my Omark with the original 26" black mountain barrel, which since I've owned it has shot in excess of 4000 rounds, no idea how many before i got it.
The load has an proved to be accurate at the short to mid ranges and only has a MV variation of only 4-8fps and the CTC group size at 100 meters is only 0.104MOA
The rifle still shoots great out to the 700 mark but the rounds are getting blown around a lot after that.

Mate, I think you will find another accuracy node around the 46gr mark. Try upping it but if your barrel has done that much, I would rebarrel for sure. I think a 308 for F-Class accuracy is good for around 2500-3000rds. That is with one Rechamber around the 1250-1500 mark.

Most FS rifles around my part of the world are running loads around the 46gr mark of 2208 with 155gr.

this is test results from when i originally dropped my load from 46.3gr i did have seperate target for a 47 and 47.3 which it definitely didn't like.



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Stu,

If you look at the 46gr load, you will find its actually the better load is it is very flat vertically. Yes it has two rounds low but that could have been you, not the load. I would try that in your rifle at long range and see how it performs.

Your Black Mountain barrel has done it's job, time to retire it. You don't mention the twist but I'm guessing it's slow, hence the problems your having at the longs. Dyers are good projectiles if you batch them. After doing a lot of testing I don't go past Bergers now. 1-11 twist will stabilise both 155.5's and the Hybrid Bergers. 1-11 twist gives you more options and you may be able to drop the powder load a tad due to the faster twist. The suggested load of 46gns of 2208 approx. is spot on, I use 2206H @3050f/s and it shoots very well all in Lapua brass. Your groups with 2208 -46gns indicates to me the Dyers are ok but wrong twist with a short barrel and your pushing "it" up hill.
cheers
Geoff

Thanks for the replies guys, I believe the original black mountain barrels had a 1-13 twist but don't quote me on that, but either way as Geoff said it is time for an upgrade so i think i'll be doing some overtime to pay for it

cheers stuart

I'm getting much the same velocity with the old BJD bullets, same brass, powder and barrel as you ! Except my barrel only has 450 rounds fired. I vaguely recall seeing comment in the past somewhere that the Black Mountain barrels can be hard to get the desired velocity from. I've been meaning to try some Win brass which has more capacity. My Lapua brass is full to the neck around 45.5 gns of 2208, and didn't get any real gain in velocity going up from 45gns.

Sam, It would interesting to learn the position of the projectile in the case?

Nearly everyone I know use around 46gns + of 2208 in a Lapua .308 case and definately not full. Maybe the chamber throat needs some work to move the projectile out into the case neck only. Just an idea.
Geoff

Krakey - been a while since I loaded any but a bit of the boat tail is below the neck/shoulder junction. I'll come back with some proper details eventually