Blown primer = unlock???

[DSMcG]

 
Had a bit of a scary moment today. Thinking a self inflicted injury;
Rifle:
308 Survivor, barrel cut to 16.5" and threaded.
AAC Cyclone suppressor
3x reloaded federal brass, 43.5gr RL-15, Fed 210M primer, 168gr Sierra MK

Fired round and felt sharp strike over right eye just above brow - had safety glasses on. Felt rifle recoil strangly and jump up (unlocked violently)
Looked into chamber and it was empty. Deduct it was the case that cracked me on the forehead. Found case on the ground and the primer was gone.
Normal non-suppressor load takes 45gr RL-15 with same components.

The 43.5gr load has never shown over pressure when used w/ suppressor. Perhaps a loose primer pocket caused it to back out and blow-by possibly pushed the latch out of the way? I'm pretty religous about shutting the action with gusto.

Now the lug on the barrel has a rounded edge and bur on the underside. It still locks up good and tight with no slop. I removed the suppressor and fired three more rounds (with caution!) with no sign of unlocking. This rifle has NEVER unlocked before. None of my NEF's do.

Needless to say I'm very suspicious and now am somewhat "gun shy." Very bummed. As strange as this sounds I do hope I am at fault trying to push too many reloads out of this Federal brass. Not an issue with my Rem mdl 700 308. I think the suppressor pushed the pressure over the top.

Any thought would be welcome.

DSMcG

[bikerbeans]

Does the case looked bulged?  Will it rechamber in the gun?  IF the case looks bad then maybe a powder overload or wrong powder?  Also, could have loaded a heavier bullet by accident, as Quick would say "don't ask me how I know this", or OAL too long and bullet in the rifling.  Did you have the suppressor off the gun since the last time you shot it?  Maybe some type of obstruction in the suppressor or bore?

I've read here that the gun can't open up fast enough for the case to eject before the bullet leaves the barrel and relieves the pressure.  My guess is the ejector got you with the case after the pop open.

The senior H&R experts should chime in soon and will help you alot more in the determination of the cause.  $5.00 shooting glasses are actually worth a lot more than that.

Be safe.

BB

[Rustyinfla]

  It could have been a loose primer pocket. Try and reprime the case and see what happens. That's the main reason I like the hand priming tools rather than the ones mounted on a loading press. I like to feel the primer go into the pocket.

[bud1]

  I would check the lenght of the case.  I have found that if my cases get to long, my NEF fire arms will not lock up or will lock up very hard.  I have never found a load that will unlock a properly locked NEF and I have 5 of them.  Again, I would check the lenght of the case or check for a swollen base, but I WOULD find the cause.  My cause has always been one of the above or a OAL, over all lenght.

[gcrank1]

For 'high pressure loads' for anything, if, when priming, you can feel the primer seating 'abnormally' easy, discard that case by crushing the neck with pliers. That 'just one more shot' might get you.

[bikerbeans]

Lyman #49 it lists 44.8 grain of reloder 7 as maximum for a Sierra 168 HPBT, with a pressure around 61,000.  Might to back off the powder just a tad.

BB

[necchi]

Lyman #49 it lists 44.8 grain of reloder 7 as maximum for a Sierra 168 HPBT, with a pressure around 61,000.  Might to back off the powder just a tad.

Sierra book V, lists 44.6 as Max for RL-15,,, so .1 lower than max might be just a tad hot for accuracy. I usually find my best groups a full grain or more lower than max. Hope you can find what it was an share,, Keep it safe man. 

[PawPaw]

Lyman #49 it lists 44.8 grain of reloder 7 as maximum for a Sierra 168 HPBT, with a pressure around 61,000.  Might to back off the powder just a tad.

Sierra book V, lists 44.6 as Max for RL-15,,, so .1 lower than max might be just a tad hot for accuracy. I usually find my best groups a full grain or more lower than max. Hope you can find what it was an share,, Keep it safe man. 

I agree.  Reloder 15 is a fine powder for the .308 Winchester.  I use a load of 43.0 with a 165 GameKing and the load is well under the max.  That load just happens to be what shoots best in my Savage bolt and I haven't done any specific load development for the .308 Ultra.  Still, I get about a 1.5 group at 100 yards, so I haven't found any reason to tinker with the load.  I'm getting 2800 fps out of this load. 

I don't think that the load is the problem.  I'd suspect lock-up problems.  Make sure your shelf is dry and close the action with authority.

[SHOOTALL]

The gun may have failed to lock up when closed ? The primer would flow back into fireing pin hole with an over load MAYBE . A bit of trash or dirt may have fallen in the action ? When you consider the safety built into modern rifles you may want to check out the lock up .

[NFG]

A blown primer usually means a VERY high pressure load...some causes could be...

1.   Bullet jammed into the lands...
2.   Case neck too long jamming into lands and crimping bullet...or a combination of 1 and 2.
3.   Wrong powder.
4.   Wrong powder amount.
5.   Primer pocket already expanded from previous HOT loads and this shot was the final straw.
6.   Obstruction in the barrel...usually accompanied by damage to the barrel.
7.   Some conflict with the pressure waves and the suppressor.  Very likely if you fired 3 more without any other misshap.
8.   Thick case necks holding the bullet...not all cases are uniform in neck thickness and necks get thicker the more times they are shot.
9.   A combination of any/all the above.
10.  A fluke...has happened to me several times over 50 years and I can't explain why.

The case whacking you in the head is a result of a combination of the action unlocking then opening, recoil forces lifting and pushing/pulling you and your hands gripping different parts of the rifle during the instant of firing, snapping the action open and the ejector popping out the case.

My reloading proceedure EVERY TIME, EVERY CASE, EVERY CALIBER, includes visual inspection prior to and throught out reloasing, trimming cases to minimum length or slightly shorter, turning necks to about 90% average wall thickness(one firing will even it up usually), weight sorting, uniforming primer pocket and flash holes,  checking the OD and ID on a fired case to be sure there is enough gap to release the bullet without problems...I like 0.003"-0.004" for hunting or factory chamber and you usually get much more. 0.001"-0.002" on varminters.

ANY breakopen shooter, and ESPECIALLY the NEF aren't rifles to push ANY envelope in.  Keeping WELL below any pressure limits is the safest bet.