I spent the morning shooting and all of a sudden the bolt shroud goes flying. I guess I'll be ordering the aluminum replacement and maybe reduce my load a little. I did have two pierced primers but I've probably shot 150 or so of this same load with zero issues.

Yea might want to throttle back a little. Warm temps tend show the hot loads that are too hot..... no matter the powder

How's the boltface look? Man that sucks.

Bolt face looks fine . I shot about 20-30 rounds after it popped off. I didn't think 36 grains of varget pushing the 143 eld x was hot but I guess it is.

Bolt shroud is an easy fix. I've got one from glades armory and one from coretac. Wouldn't be a bad idea to have Tony give it a once over though.

6.5x47 Lapua?

Yes sir.

Flush your trigger good.

Also how many rounds since the last cleaning? Could have formed a carbon ring that will cause a pressure spike.

The rifle has only 170 rounds total fired.

I would invest in a new bolt while I was at it.

Nonsense.

OK.

I did go ahead and pull everything apart and clean it . I don't think the load was too hot but I'm going to try dropping down to 35.8 grains since I'm using a different lot of powder maybe it's hotter than the last lot. I didn't have anymore pierced primers after the shroud blew off. I contacted the gunsmith with some pics and he said everything looked fine and probably was just don't shoot anymore of that ammo. I did however finish what I had loaded up with no problem.

Standard procedure, when moving to a new lot of powder, is to re-tweak the load. Go to the old powder charge, on a short action,-.6 gr, -.4 gr, -.2 gr, even with the old load, +.2 gr, +.4 gr, +.6 gr. Stop when you see pressure.

And your incident is why, as well as making sure your rifle keeps shooting to its' potential.

This goes back to my small rifle primer issue in a large rifle firing pin action. If the action has a small firing pin, the impact or dent from the firing pin is much smaller, and keeps the primer stronger. I have this same issue with my 6.5 Lapua. I run a #450 primer, which is a small rifle magnum primer with a thick primer cup. But the Surgeon action I run has a large firing pin (LFP). This LFP makes a much larger dent into the primer, creating a weak spot. When you load up a 60K psi round, the pressure finds the weakest link to go, which is where the LFP made a large dent into the small primer. The surface area of the LFP dent in comparison to the small rifle primer is very large.

The solution is to have your bolt face bushed to fire a small firing pin. If you keep shooting it with a LFP, the gasses from several pierced primers will foul up the trigger. I have 1 Jewell trigger that still has issues from one match that this happened to me, and it was already repaired by them.

Well I think I might have figured out why I had a spike in pressure. I was checking some brass and my sizing die and somehow I guess screwed something up because I bumped the shoulder back on the last batch .010 give or take a little. I thought I had my die set and locked down so I just assumed I was bumping the shoulder.002 like always. I can't believe I did that . Brass won't last long doing that .

Hornady lock rings.

If I'm bumping the shoulder a certain amount, I always check the sizing each time. I've had the sizing be off or different from the the last time with the lock ring set.

If you have more than one shell holder for that die there can be some difference there. If you set the die up with one shell holder and use a different shell holder the next time it can mess things up.

Your load was over maximum for your rifle. Hot weather has a way of amplifying that. To be safe on your next batch I would double check the overall length of the ogive to the lands against what you are loading. If you are loading them close and accidentally poke one in the lands you can get a spike. If that checked out, I would drop the powder charge and work my way back up, looking for pressure signs and chrono the velocities. Sometimes pressure signs don't show themselves till you go well past where you should be. Sometimes a chrono will make what is happening clearer. The picture of your brass was blurry but, sticky bolt on extraction, pierced primers, or a blown off bolt shroud in any combinaition is enough to determine that atleast sometimes you are getting pressures well over maximum. When loading right up against maximum pressure you should be very diligent with your measurements. There is not much room for variation in either technique or components. I have been down the road of trying to squeeze every foot per second out of a cartridge. Ultimately I decided there was too much downside for me to load right at the hairy edge. Now days I look for the most accurate and reliable 12 month load. If I want more speed than a cartridge offers, the best way to get it is to bump up cartridges.
In my experience varget is about as good as it gets where temperature stability is concerned. A quick look at hogdon data shows 34.9 gr for a 140 as their max, so my guess is powder charge was the culprit.

Good luck and be careful

Tikka???

Yeah, I'd like to know more about this failure also.

I am trying to imagine how you blow the shroud off the bolt, unless the gas handling scheme actually caused it...but due to a pierced primer? I'm not familiar enough with Tikka to even begin to guess BUT I would never expect a pierced primer to cause that.

WTH?

Plastic shroud, that merely locks a tongue into a groove. There's not much holding it on, and it's a light weight part, at that.

Well...thanks for that info. I don't think that would suit me at all.