Primer cratering - Ruger American

[waitforit]

6.5CM Ruger American predator. 22" barrel.
H4350 powder, 147 eld-m bullets. Seated 0.20" off lands as measured w comparator.
Lapua small rifle primer brass
CCI #450 small rifle mag primers

What do you think? The 10 rounds on the left side of the pic are a ladder from 40.4 - 43.1

Velocities are 2531 - 2696. No heavy bolt lift (well to be honest the ruger has heavy lift all the time...)

The 5 on the right are a reduced charge for the kids. 36.6-37.4, velocities 2317-2342.

Is this a pressure sign or a firing pin hole problem? Scratches on the brass are from my hornady shellholder when seating - it is a tight squeeze. This is first-fired brass.

 

[sndmn11]

I had the same thing occuring with Federal small brass. I switched to Hornady large brass and it does not occur. I tried different primers and different powder and couldn't get the Federal brass to not do what your picture shows.

I'd grab a few pieces of a different brass and try, or just live with it.

 

[waitforit]

Also, this barrel seems a little slow but its also brand new.

 

[Wrench]

Looks like a bushed bolt face would be in order.

 

[MThuntr]

Slopping firing pin?

 

[Pickettpuncher]

Oversized firing pin hole. It can be fixed with the bushing method mentioned above. But the primers are still rounded at the edge. I wouldn’t be concerned.

 

[waitforit]

Top left case was the 43.1 charge. This was substantially over book range but I didnt feel it was overpressure. My 7mm08 will definitely flatten primers and sticky bolt if the charges are getting too hot.

Can anyone share where they have seen pressure with this combo?

 

[Mulyhuntr]

Pretty common with small rifle primers. Looks like ejector swipe on top left case as well? 2700fps with h4350, 147s, and a 22" barrel seems a tad warm.

43 grains was too much for my tikka.

I load 41.5 with 147s and h4350.

 

[waitforit]

Agree. I usually run up the ladder until i hit flattened primers or sticky bolt lift. The 450s are a harder cup and the ruger already has a heavy bolt so Im going to be a bit more cautious. Im going to try a node I found in the 42s..

42.2: 2670
42.5: 2664
42.8: 2673

Plan to try 42.5 at 20,30,40, and 50 thou off lands. Hope one of them is the winner.

 

[35WhelenAI]

What about the firing pin tip being small in diameter, effectively the same thing as a large firing pin hole. JAT.

 

[parshal]

You've got some ejector swipes on the cases on the left. You're nearing pressure. I don't personally pay much attention to primer cratering since some cups are softer than others. I use bolt lift and/or ejector swipes. Soft brass can show some swipes or marks earlier than other cases but Lapua is not soft brass.

Personally, I'd back off that load. If you want to know for sure, spritz a little water on the case with spray bottle and shoot it. If you have bolt lift you have too much pressure.

 

[waitforit]

I shot a few groups and the 0.040" (first) and 0.050" (second) look promising.