308 Grouping Advice

[pavlovaw]

Hello, after some information and advice from the members in here about the groups from my 308 F-standard rifle. Is a Barnard P action with a 12 twist Bartlein barrel with 250 rounds on the counter. I'm using no neck turn Lapua large primer brass, 210M Federal Gold Medal Match primers, 44 grains of 2206H with a Sierra 155 (2156B) seated on top with 13 thou jump, which has chronographed at 3015FPS, ES of 15. The powder charge showed the most consistent groups at 100 yards and the setting depth the tightest groupings. I fired 4, 5 shot groups and in every group there is always one flyer. I tried jamming from 5 thou to 15 but the groups were terrible. I was going to attach a picture of one of the groups but did not end up having a photo of it like I thought I did. In all groups, there are 4 shots grouping in under quarter inch, and the flyer is between a half inch to an inch out from the group. I'm sure it isn't me pulling the shot, as I can then shoot my other 308 right after these groups and shoot a group consistently under .5 inch. The flyer isn't a consistent shot number fired during the group shoots either. Do I need to keep increasing the jump to see if the flyer is minimised, or change to 2208 and redo the load development?

[KentLC]

These things are tough to nail down and frustrating at times. I have a rifle that is doing the same thing.
Are your flyers always out in the same direction or vary?
If anyone out there or club member has a recommended jump for the sierra's find that, then stick with it until you can get a reasonable group, then start adjusting your jump. Otherwise you are just chasing your tail. do you know if the throat was setup for the Sierra?
I assume you've been through all the fittings, scope mounts, action screws ensure nothing's loose? Haven't got any oil or cleaning fluid in the action bedding or v block?
I've always run 2208 in my 308\155 combos with good success. So I can't help with 2206H sorry. A very experienced shooter recently also informed me that powder may be my problem. I am yet to test that.
neck tension and\or incosistent seating depth\OAL can also cause this.
Also only change one thing at at time or you will go round in circles.. been there.
lastly, take it to a smith, check\inspect your barrel\crown etc. Crown damage can do weird things.

[AD5010]

In my experience with sierra 2156 you need to be jumping them alot more, I found 45 to 50 off touch
And the speed to be around 2980fps, that should help a bit

Pushing the sierras to hard will cause all sort of issues

[Rich4]

Have you checked your bag arrangements?
Can you check your rest combination with a similar rifle to check?
I had a similar situation which I nailed down to a sloppy rest shaft.

[Brett.44]

Do you ogive batch your projectiles? I find that has helped my constancy with Sierra 155g. I was surprised with the variance in ogive length in a 1200 box.

[phillh]

I found if they were going too fast the groups opened up. Try slowing them down to 2950-2975fps. 46.0gr of 2208 in Lapua cases worked for me.

Cheers

[pavlovaw]

Hi guys, thanks for all the responses. I shoot my other 308 with Lilja barrel off the same rear bag and biped, my setup is more an F-tr style. The Lilja barrel at 300 yards will group 10 in under an inch consistently on the bag and bipod setup I'm using on this rifle. Only difference is the Lilja is a heavy varmint profile and this is a heavy palma profile. I tried weight batching, then batching the same weight by over all length, and then the same length batching by base to olive to try and eliminate everything that can be different. The reamer used was setup for the Sierra's but I have also had good success with the 155.5 FB Bergers with about half the neck used to hold the projectile. The Sierra's are seated in using almost most of the neck. I think I need to slow the speed down a bit more and try longer jumps. Have done some loads with 2208 from 45 up to 46.4 to see if that may be better suited.

[AlanF]

[MattyG]

Sierras need jump. As mentioned above, try 0.040" and keep moving back until you find a sweet spot. 2206H is just a tad hotter than 2208, it is made for .308 so no need to change it. I keep hearing so many people keep saying "I can't get Sierras to shoot" but refuse to increase the seating depth.
Just FYI, I have found that a COAL of 2.770" to 2.780" works well in my Lothar Walther 32" 1:12 barrel (M852 chamber).
Furthermore, the ADI factory Sierra 2155 ammo shoots very well in it as well, it has a COAL of 2.750"

[DingoDeerHunter]

[pavlovaw]