I had a load worked up for this rifle, remington 700 rebarreled with 26" Bartlein, which was 42.9gr H4350 in Hornady brass, CCI BR2 primer, seated 2.810" @ 2850ish.  Zero pressure signs of any kind.  Primers all looked great.

I got my Lapua small primer brass in, so started over.  I want a target velocity on the higher side, so I started at 41.5gr, in .3gr increments.   I do understand that Lapua is a smaller case capacity, so 1.4gr under my previous load seemed sensible.  I was using the same powder from the same keg, same 140ELD-M, change to Wolf Small Rifle Magnum primer (I stocked up a few years ago when I saw how these primers were giving people the best SD numbers)

I was checking my brass, and didn't notice anything out of the ordinary.  However, when I got to 42.4gr, I pierced a primer.  Upon inspection, no other pressure signed observed, so I continued.  Each subsequent round showed a cratering primer (see pics) and I stopped at this load.

Here are the results:

41.5  AVG2772  ES10  SD4.3
41.8  AVG2793  ES17 SD7.0
42.1  AVG2806  ES12 SD5.2
42.4  AVG2828  ES8 SD3.2

The question -

Why are my primers cratering at a lower velocity, than I had with large primer hornady brass?

I can change primers, but I haven't seen this reported by anyone else with Wolf primers.  I also have a stockpile of CCI #41 and regular old WSR.

I know that SOME people say when shooting 6.5CR or other higher pressure loads, you should get a factory Remington bolt bushed and the firing pin turned down.  I am not opposed to this, but I question why I didn't see any issues at a MUCH higher load in LR Hornady brass?

42.4gr load showing cratering primer.  It is raised and you can distinctly feel it.



41.5gr load.  You can see some primer flow around the pin strike, but all my loads look like this and always have:



Here is some of my Hornady brass for comparison:

its not an overpressure sign, its the firingpin hole on the Remington bolt. get it bushed and it will go away.

What you need to do is to get the bolt firing pin bushed.
As it is there is a lot of clearance between the firing pin and the edge of the bolt bushing.
A new machined bushing pressed in will eliminate the excess clearance and suppress this anomalous pressure sign.

Yep as said you need your bolt bushed.  Greg Tannel at Gre Tan would be the guy to contact for it.  I have a feeling this is something we are going to see a lot of with the Lapua brass and any other small primers offerings that may hit the market.

If that FP hole looks large, I would also say to have Greg bush the hole. He has done excellent work for me.

Also, take a look at your FP under magnification to see if the tip is damaged.

I am in agreement on the firing pin.

My 6x47L, which uses small primers, was built on a former Remington 7mm-08 action and I get lots of primer flow with Wolf or CCI magnum primers.  I just keep the loads turned down a little until I put a barrel on my Defiance action which I ordered with a small firing pin.

You can mail your bolt to Gre-Tan Rifles and they'll do a first class job bushing the firing pin hole. Problem solved.

I had the issue with my RPR and LRI barrel until I switched from CCI400s to 450s. Like others have said though sounds like you need to have your firing pin bushed.