Weird Pressure and Velocity Today

[tallbuchholz]

I have a tikka 6.5 prc that I have about 100 rounds through. It’s been very consistent so far until yesterday. My velocity was dramatically lower than it had been and I got ejector marks and heavy bolt lift. This was consistent with 2 different loads that I’ve used before with no problems - factory 147s and the UM 147s. I don’t have a chrono so I don’t know the specifics but at 400 yards the groups with each load were about 6” lower than they had been the week before. Still shot decently tight groups so it wasn’t like one bullet was off. Also have never had the heavy bolt lift on this gun or ejector marks on the brass. Checked zero afterwards and it was actually shooting an inch high at 100. I’m willing to accept scope/rings/action screws failure but none of my witness marks have moved and it doesn’t explain the bolt lift and ejector marks.

Anyone seen this or have suggestions for things to try to fix?

Gun is a 18” tikka 6.5 prc, factory stock, UM rings, RS1.2, Hyperion K.

 

[Q_Sertorius]

What were the environmental factors? Temperature? Precipitation?


____________________
“Keep on keepin’ on…”

 

[tallbuchholz]

What were the environmental factors? Temperature? Precipitation?


____________________
“Keep on keepin’ on…”

Normal day. 88 degrees, no rain, 60% humidity. North Texas.

 

[Q_Sertorius]

Normal day. 88 degrees, no rain, 60% humidity. North Texas.

Had you recently cleaned the rifle?

Are these hand loads? Or the same lot of factory ammo?


____________________
“Keep on keepin’ on…”

 

[WhatToHunt]

Had something similar just this past week, Tikka 6.5 PRC shooting factory 147 ELDMs. Rifle had about 100 rounds through it and I had cleaned it about a week ago. When I shot it next, the heavy bolt lift was evident and not something I'd noticed before. And I had ejector marks on these rounds, but not on those prior to cleaning (see pic). After this event I made sure to wipe things out again in case there was excess solvent or oil from my cleaning. I took apart the bolt, degreased it well, and only wiped it lightly with a little oil. I've since shot it two days this week, 3 rounds one day and 6 rounds yesterday. No heavy bolt lift and no ejector marks.
Similar, but I didn't notice erratic groups like you mentioned.