Groups gone bad!!

[Thumper580]

My LR308 was shooting consistent 1/2" groups.... Decided to get fancy and bought a nickel boron BCG. I have changed nothing else and now groups opened up to about and inch or 1.25"???? Of course I sold the original BCG so I can't recheck it. Headspacing changed???

 

[High Binder]

My LR308 was shooting consistent 1/2" groups.

If it aint broke...

P.S. try the AR or gunsmithing forum.

 

[Thumper580]

Yes....no good deed goes unpunished!

 

[Temp9]

Did you keep the original bolt?

 

[turbo54]

Did you keep the original bolt?

Ugh.

 

[Thumper580]

Original BCG sold..... To dense to wait and see if anything bad might happen.

 

[Temp9]

I was wondering if you had swapped out the bolt carrier, cam pin, etc., but kept the original bolt. I suppose "BCG" would imply you changed the entire assembly, including the bolt, which is where your problem is likely coming from. The headspace is determined by the bolt face depth and locking lug dimensions on the bolt. Changing the bolt carrier shouldn't change much, but changing the bolt itself will most definitely change the headspace. This very well may be the reason for the change in accuracy.