Help-Group Analysis

[Festus]

My 7mm STW frequently puts 2 bullets touching at 100 yds. but the third sometimes 1 1/2" from the others. It's not always the third shot that's out. I know the bedding is good. Does this sound like a seating depth problem or something else?
Thanks, Festus

 

[BountyHunter]

Check the "head spacing". /ubbthreads/images/graemlins/smile.gif

does not really sound like seating depth issue.

Is this old problem or new problem. Was is just rebarreled, bedded etc. this helps you know where to look.

really, could be your form in how you are shooting or lastly mechanical in the gun, brass or scope.

if you are not doing something, ie inconsistent pressure on stock, rear bags, shoulder somewhere when shooting or lastly the bedding, scope or brass could be the issue.

so eliminate each in order.

Let someone else shoot it so see if they "throw" a shot each time. that will confirm the headspacing.

Check the torque on action screws first to make sure they are tight. Check the bases and rings to make sure that they are tight.

Reshoot groups. Still issue, change scopes to a scope that is a "known' shooter and reshoot. Good scopes can suddenly go bad.

Lastly shoot 6-8 rounds and keep cases that group together and reload those cases only and shoot again. If those cases shoot good, then measure the bad case base for trueness compared to the good cases. Highly unlikely unless really out of true bad.

Check runout of your loaded rounds before firing.

You have to assume that it is one of the three major things I mentioned above normally, but not always.

could also be 5 yr old glass bedding that is now loose and needs to be redone, possible but not probable.

Look at lugs, if not lapped are the wear marks close to even or only wearing on one lug and then a porting.

BH

 

[Buffalobob]

A couple more

Make sure the sling swivel studs aren't hitting the bags.
Take a look at the primers after firing- are the fliers different.

 

[Festus]

You guys are good!! I knew most of this stuff but hadn't thought of some of it. Next time out I will pay more attention to detail and mark the cases that resulted in fliers. Thanks for the help.
Festus

 

[Bart B]

I'd shoot a couple of 10-shot groups as 3-shot groups aren't statistically significant; evidenced by your mention that the wide shot in a 3-shot group isn't always the same place in sequence. If you want to cull cases that shoot wide shots, fine. Then reload all those culled cases and see what they do for a 10 shot group. You may well find out they shoot just as good as the keepers did.

 

[Festus]

The brass in question is R-P. I am preping some WW brass I purchased recently and have sorted by weight. I'll try some groups with the new WW brass next and see if the results are the same and go from there. I can still go back to the R-P brass and try some 10-shot groups later but will have to shoot slowly as the barrel heats up rather quickly.
Festus