Suppressor POI Migration

[Dubbya]

I shoot a .308 Rock River LAR BT3 with an 18” barrel. I attached a Yankee Hill Machine Resonator R2. Noticed accuracy issues. Took it to a gunsmith for advice and was told to run 5 rounds through it cold, then 5 rounds warming up the can and then 5 more with the can hot all at 100yrd. The first 5 rounds had 4 inside an inch with 1 flyer. Each shot about 5-10 minutes apart with enough time for the can to become cool to the touch.
The next 5 for warm up produced a 5 inch group.
Then a reload
The 5 rounds hot ended up inside an inch with another round slightly outside the 1 inch group. but the grouping migrated up from the cold rounds about 1-1.5 mils.
Is this normal suppressor behavior?

 

[Evintos]

You ever test the barrel for for heat induced vertical stringing without the suppressor on?

 

[Dubbya]

You ever test the barrel for for heat induced vertical stringing without the suppressor on?

What would you suggest as the best method to test that? If it is diagnosed, is a new barrel the answer?

 

[Evintos]

Same method as you used with the suppressor making sure you use ammo that is known to be temperature insensitive.

If heat induced vertical stringing is diagnosed, assuming it isn't temperature sensitive ammo related and you wanted to keep the barrel, then you either keep track of the heat of the barrel by controlling rate of fire or you memorize the impact shifts as it is likely repeatable. If it is ammo related then change the ammo or handload consistently.

If you wanted to replace the barrel and not have to deal with it, choose a barrel that is properly stress relieved.

All this also assumes your shooting was good such as no shooter induced point of aim shifts due to suppressor mirage (if it is shooter error from suppressor mirage, solution is suppressor cover) and nothing mechanically wrong such as physically touching the barrel or gas block whether it's a rest or the handguard (adequate clearance).

 

[Dubbya]

Ok I’ll give that a try. Thanks.