Group Problem

[RLA]

I am shooting a 300 RUM 26" 1:10 twist 230g Berger OTM 88g H1000

5 Shots @ 100

3 Shots @ 200

I shot good groups at 100 yards. At 2 and 300 yards the groups open up!

Any suggestions

 

[WildRose]

Hard to say.

Without knowing you or your rig here's where I'd start in order of most likely.

1) Bedding/floating issues.

2) Shooter error.

With the groups being inconsistently all over the place those are the most likely causes.

3) Inconsistency in loading. Have you chrony'd these loads to see what your ES is?

4) Not pushing them quite fast enough to stabilize; but if indeed you have a 10 twist this shouldn't be a problem since that's the recommended twist rate for these bullets.

 

[WildRose]

Question for you. On the top target. Where did your first round strike relative to the rest?

 

[RLA]

WildRose, The first shot was the low one..... Its a custom gun, bedded shilen match grade barrel with Jewel trigger. I have the same basic gun in 300 wsm that shoots lights out!

 

[Jordan Smith]

Do all your groups look like that? Have you tried another powder, bullet, primer, etc?

 

[RLA]

I have tried 200 AB's and they would not group at all.

 

[WildRose]

WildRose, The first shot was the low one..... Its a custom gun, bedded shilen match grade barrel with Jewel trigger. I have the same basic gun in 300 wsm that shoots lights out!

Well it sounds to me like a float/bedding issue with the first shot being so low and the rest fairly tight if this is a well seasoned barrel.

Do you generally get something similar where the first shot is well separated from the rest?

Was it completely cleaned prior to the first shot in that group?

After a good cleaning do you typically see the first shot separation from the rest of the group?

How many total rounds down the tube so far and what sort of barrel break in did you do?

 

[WildRose]

I have tried 200 AB's and they would not group at all.

Take a cleaning rod with a tight fitting patch.

Insert it a couple of inches. Mark a dot on the rod, and the end of the muzzle as an index point. Put additional dots on the rod at 1" intervals.

Slowly insert it, and count the inches to a full rotation.

Make sure it's a 1:10 vs a 1"11-1:12.

 

[backwoods83]

Sounds like a seating depth and extreme spread problem.

 

[RLA]

WildRose, the barrel has about 250 round through it. It was a clean barrel. The fouling shot is usually not that far out of the group at 100 yards.

I do have the bullet way out there at 3.875 10 thou off the lands. I will start messing with seating depth.

 

[backwoods83]

If it was mine i'd start with them .010" in the lands and switch to retumbo, and check the whole thing over and make sure everything is tight.

 

[Jordan Smith]

The scope is known to be good and hold zero?

Try seating the bullet a little farther out, kissing the lands.

If that doesn't work, try a different powder.

It's not likely to be a bedding problem, but the barrel is floated, I assume?

How is the trigger? If it's too heavy, that could be causing problems.

What kind of shooting rest are you using? A hard front rest, or an inconsistent rest will cause problems.

How's the muzzle crown?

 

[WildRose]

WildRose, the barrel has about 250 round through it. It was a clean barrel. The fouling shot is usually not that far out of the group at 100 yards.

I do have the bullet way out there at 3.875 10 thou off the lands. I will start messing with seating depth.

Seating the bullet out a little farther might tighten things up for you but be careful to watch for pressure signs.

Also like BW suggested check the torque on your actions bolts/screws and be sure it's tight and even. Also double check on your rings/scope mount.

If you have a load that has been shooting better for you in the past, run a few of them through it and compare.