Shoulder Bump Question

Here’s some feedback on my question about shoulder bump, overpressure and primers falling out. I checked the headspace on my rifle, gauged hundreds of loaded cartridges and I’ve disassembled, re-weighed, re-measured and checked approx. 25% of all different shells in batches of different types and weights of bullets. Being satisfied that all is well with my gun and reloads I went back to the range today. Shot a couple with no problems and then another primer fell out. I switched to a different reload and no problems for three shots. Then shot yet another load and the primer fell out on the first round. I switched guns and continued shooting and while switching the suppressor I began wondering if the suppressor could be the cause. All of my loads were developed before I got a suppressor and are 0.8-1.3 gr below max and were developed by starting at the minimum and working up. So, I shot the rifle again without the suppressor and didn’t have any more primers fall out. I didn’t risk putting the suppressor on and blowing primers again. In the end, the only variable is the suppressor and the primers didn’t fall out until I started using it and I don’t have this problem with other guns which host the suppressor. I don’t have any explanations but these are my observations.
 
I have no suppressor experience so I will leave that alone.

I have seen the results of excessive head clearance, Some semi-automatic rifles MAY present residual pressure after unlocking.A suppressor might aggravate the situation by being a pressure reservoir.

If its a bolt gun,with excessive head clearance,the primer will get pushed out by the amount of head clearance. This happens while the case head is off the bolt face in response to the firing pin strike. Initially, pressure will obturate the case and it will grab the chamber walls as the primer is. forced to the bolt face.
As the case is still gripping the chamber forward,at the chamber mouth there is nothing to grip. As pressure blows the case head back to the bolt face,two things happen.The primer will get re-seated.It may look very flattened by the process.
And the case will stretch. This stretch will be localized near the chamber mouth.
It will cause the brass to thin. If things are as you suspect,your brass will have a good start on a stretch ring,. It will look like an internal O-ring groove just ahead of the case head. Its easy to see if you section a case. It can be felt if you make a probe hook with a paper clip. Look up "Stretch ring"

That scraps your brass.

You may notice another problem. Its remarkable how fast hot gas leakage past a primer can cut an erosion ring on the bolt face.

I would not fire any more of that brass.IMO,its dangerous. See if Remington will give you a return authorization. If they can find the brass defective I'd think they'd replace it.

If its a semi-automatic other folks know more.You may need an adj gas block or a heavier buffer,but I;m not a suppressor guy.
 
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That's like saying changing the muffler caused spark plug failures on a pickup truck.

I think hibc is right.

I also think your primer pockets are loose and the cartridge cases should be retired, and that it's possible your brass and go- no go gauges may be headspaced on the extractor.
 
and that it's possible your brass and go- no go gauges may be headspaced on the extractor.
Click to expand...

If that is the case, you're either doing something wrong, or you've got the wrong kind of gauge. Some designs require removal of the extractor (and perhaps the ejector, others have relief cuts in the gauge so neither of those touches the gauge.
 
Murphy's law says "If it can go wrong,it will" I suppose its possible some combination of dies and shellholder could result in excessive head clearance.
That said,the ,manufacturers of reloading tools generally make dies and shellholders compatible.
We SHOULD be able to use a Lee or RCBS shellholder with Redding or Forster dies without sizing the brass out of SAAMI spec. In other words"Sizing brass too short " for a SAAMI chamber "shouldn't" happen.
But I believe in Murphy's law. IMO, it may be best to buy "same brand" shellholders with your dies and keep that shellholder in the die box. I cannot say I'm that meticulous.

What I DO is buy a Wilson type bushing "Cartridge Headspace Gauge" and verify my tools are sizing brass to SAAMI limits. I can also use it as a case comparator (with a mic or calipers or height gauge) to tailor cartridge head clearance to a particular rifle. Note these are NOT an ammo checking "plunk gauge".

I cannot imagine how commercial dies and shellholders wou;d create a problem such as you describe unless they were modified.

There are only so many ways primers fall out.

Among them,

1) Gross and dangerous overpressure (Getting your powder charge weight out of an old PO Ackley book for a 30-06. The H-4895 changed "Why does this thing kick so hard? And the primers fall out. Yeah, Dads old hunting buddy reloaded them the same as in the 1960's) )
2) Defective or improperly annealed brass. Soft cases or oversize pockets(Fire Sale Brass?)
3) Handloader created issues. Processes gone wrong, such as "uniforming pockets,reaming pockets,decrimping pockets annealing brass,etc. I'm not saying these processes are wrong. They can be messed up.
4) Brass is just ready to retire. Sometimes after 3 or 4 loadings, sometimes 20+.
5) Somerging else.
 
I had a batch of Winchester .223 brass that did the same thing. The primers would Jam my AR because they would fall down into the trigger group.

They were brand new , Tossed them… to this day I no longer buy .223 brass from Winchester .

But in general loose primer pockets usually indicate its time to retire the case or as other say over pressure due to several factors etc etc

If you notice it again.. lets say you loaded 50 and the first couple fall out. You need to stop, and just pull them get different brass.

If you need some be gladly to mail you some too keep ya safe
 
I don't know if it was mentioned anywhere here, but I still have a couple of sleeves of Winchester brand large rifle primers that in some types of new brass fit extremely loose. I was told it was due to a manufacturing change in going from plated primers to unplated. When I first noticed these, if I did not absolutely know the brass to be brand new, I would assume that the primer pockets had loosened up. I went to CCI primers with this same brass, to good effect. Just a possible consideration, especially now when we are being forced to use what we can find, not what we prefer.
 
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