pressure and primer issues

newer rifle savage stealth evolution in 6 creedmoor with short freebore , when I first received this rifle in noticed freebore was to short for factory hornady ammo which didn't present a big problem as I planned to handload , which I did.
I found VERY GOOD LOAD at the top pressure wise 40gr h 4350 lapua brass small primer pocket neck turned to .014 and a .269 neck bushing , rem 7.5 under berger 105 hybrid .
this load shot .26 moa at 3007 fps es 14 sd 7
I also worked up a load using hornady brass and 80gr noslers 43gr h 4350 cci br2 , this load shot .313 moa at 3200 fps which was also up there in pressure.
so I decided to rework these loads to find a lower velocity node for the berger 105's and started at 38.3 with the twice lapua brass with all components being from same lot numbers through out testing the results are as follows 5 shot group avg velocity
38.3gr 3118 fps es 80 sd 32
38.5gr 3134 fps es 82 sd31
38.8gr 3149 fps es 67 sd 27
39.1gr 3160 fps es 45 sd 20
39.4gr 3162 fps es 22 sd 9
39.7gr 3244 fps es 48 sd 19
40.0gr 3195 fps es 38 sd 14
now my real problem..... I have blown 1 primer and pierced 4 or 5
now I understand barrels can get faster after so many rnds ( i'm at 400) but I cant wrap my head around that much velocity increase along with the primer issues and the heavier bolt lift
oh and by the way I reset the factory hornady 108 eld depth to .005 off lands and the produced the best group of the day at an avg of 3033 fps
also tried some hornady brass with the 105's and started at 40gr cause of increased case capacity over the lapua and they procceded to blow 3 primers .
END OF TESTING .
my first thought was my scale was off so I pulled bullets from remaining test loads and found charge weight to be correct
rifle was clean prior to testing with no obstuctions
I am at a loss as to my next step other than reducing loads another 2gr and starting again

I don't have a 6mm Creed but your velocity is fairly high for the charge weight used. Please correct me if I'm wrong.

But in this kinda scenario just forget reloading data and go with what your rifle tells you. Reduce and stay withing acceptable pressures.

Too much pressure will always give high ES and SD.

I wonder if H-4831sc might be worth a try for you.

Polish the chamber if you can. I've had a Savage rifle that was over pressure with even FGMM factory ammo (which is not knows for being hot), until I polished the chamber. And I've heard of others solving their pressure issues with chamber polish jobs.

I'm not surprised about the short freebore, but it could be also that the freebore diameter is a little tight.
You can get a thoater from PTG and extend the freebore yourself with out a lathe and without taking the barrel of off the action.

Well for sure one thing you can wrap your head around is that blown primers and heavy bolt lifts are sure signs of high pressure.
Id personally be listening to the gun, and looking at the targets, and not much else.

Don't shoot it anymore. I'm surprised you got as many rounds thru it as you did. You are living dangerously. Send it back and have the problem corrected.

Well no real answers as to why but it is what it is , dropping charge weight 3gr and starting over , if problems still persist back to savage it goes

Read the post below, it appears these rifles are short throated

Topic: savage stealth evolution 6mm creedmoor

http://www.65creedmoor.com/index.php?topic=8509.0

savage stealth evolution 6mm creedmoor

http://www.savageshooters.com/showth...-6mm-creedmoor

Well aware of that , 6mm post is mine