Whats the problem?

[SamuraiTrapper]

OK guys, here's the scoop. we've been working a load up for my buddies 300WSM. We got a load that grouped 1/2 MOA. I loaded up 50 more rounds, and he headed back to the range to sight in, and run through the chrono. Sent me this pic message last night, and it didn't look good. Getting different groups within the group. What could be causing this?

Rifle has been glass bedded, trigger done, and he is running a Bushnell Elite, honed rings. He was shooting off a bench. What coupd be causing this?

 

[SamuraiTrapper]

I forgot to mension that this group measures 2", and was shot at 200 yards. I am thinking inconsistant cheek welding. Would you agree?

 

[406pat]

I'd check things in this order;

Clean barrel?
Barrel floated? (did something get under the barrel in the channel?)
Action screws tight/too tight?
Scope rings and bases tight?
Scope rings and bases tight 2nd time?
Trade scopes to see if that's the problem?

Best of luck and keep us posted.

-PJS

Edit

Sorry I was typing at the same time.

Cheek weld could definitely do that. A trick I've found for that is to turn up the scope so you get a small amount of "tunneling", then make sure to check that the tunnel is centered in the scope. Simple thing but I've caught myself forgetting on more than one occasion and blamed equipment for poor groups then re-shot for groups paying more attention and found that I owed the equipment an apology

 

[royinidaho]

Shoulder pressure on butt + resulting cheek weld differences are considerations.

If the "bench" isn't metal and concrete with a solid seat "butt weld" variations will also influence the group.

If the bench is portable with some flex ya have to "load" it similar to loading a Harris bipod.

Also ensure parallax is adjusted out of the scope. This coupled with varying cheek weld seems the most likely problem?

 

[21buck]

SamuraiTrapper,
All of the previous potential problems should be considered. This is not questioning your cleaning abilities. Possibly a part of the problem might be copper deposits coupled with some of the forgoing angles. Hot barrel? Want to know what kind of problem you have, then consider all of the above assists.

Good Luck

 

[bkondeff]

How many times did the load go .5 moa before you loaded up 50. If once, then maybe you got a lucky group and what you are seeing is what you got. Also did it go multiple .5 moa groups at 200 yards before? If you have gun shooting in the .5 moa at 100 yards and now it's 2" at 200 yards that may not be as big a difference as you think. Certainly a million things can make things go hinkey, including using a different lot of reloading components which could affect your velocity.

 

[boomtube]

Ditto.

ONE tight 3 shot group does not establish a pattern that can be depended on.

 

[SamuraiTrapper]

Multiple groups were shot with this load, it was consistently good. This ended up being shooter error. He was not getting a consistant cheek weld.

 

[Boss Hoss]

Ditto.

ONE tight 3 shot group does not establish a pattern that can be depended on.

Honest to God I know people who only shoot a 3 shot group Once just so they say they have a small group and have the target to prove it lol!! About 90% of the time people could not repeat that feat ever. Luck is a big player in the 3 shot group crowd esp with factory rifles. When I am developing a load for a competition rifle I shoot five shot groups then narrow those down to 2 five shot groups then the final gets 3 five shot groups. More than once the 2 five shot groups did not continue down the same path as the first 5 shot group.

Sporters only get the first 5 shot group then the 2 five shot groups to confirm --- call it a day after that.

 

[boomtube]

"This ended up being shooter error. He was not getting a consistant cheek weld. "

Okay, so you have your answer.



"I know people who only shoot a 3 shot group Once just so they say they have a small group and have the target to prove it lol!!"

True. I smile and "Wow" a bit and go on. No point in saying it's a wallet group simply because it's so unusual!