Piercing Primers

[Lief]

I was testing some loads in my M&P10 yesterday and near the end of my session I noticed a fired case with no primer.

I looked in the receiver because that is where I had heard of loose primers causing problems but there was nothing and the gun worked fine.

I shot my last group of loads over the chrono and at the paper and then decided to expend a few at my steel. I had fired 45 rounds by now of varying powder and bullet weights.

The rounds I had left were some of the ones I had made for fouling rounds with 50.8gr CFE under a 150 BTFMJ Hornady bulk projectile. All the loads had Winchester WLR for primers. All primers inserted with the Lee tool.

I started the session with ten of these rounds and they ran great.

At the end however after about 5 rounds the gun locked up tight, not in battery because I pressed the trigger, got a click but no bang.

I got up and looked at the cases on the ground and found a pierced primer.

I butt-stroked the gun to eject the stuck round and tried again, thinking I had done a bad job sizing. No, stuck again.

I removed the mag and round, disassembled the gun wiped everything, saw a very little piece of brass (or primer) put it back together and tried again.

2 rounds fired and the gun locked again. Two more pierced primers. This time I had to use a range rod to force the bolt back but it went fairly easily for all that.

More little pieces.

I stopped for the day and when I got home I disassembled everything and cleaned everything. Found a little more chips but not many. No marks of dings on the firing pin. Firing pin hole looks good to me.

Does any of this sound afmilar to anyone?
Does anyone have an idea of what I should do before firing it again?

TIA, Lief

 

[ole-cowboy]

no experiance with CFE223 but Hodgden's website calls 50.1 to be max for 150gr .308 my research leads me to believe that semi's have a max a bit lower than bolt guns

 

[Lief]

no experiance with CFE223 but Hodgden's website calls 50.1 to be max for 105gr .308 my research leads me to believe that semi's have a max a bit lower than bolt guns

Thanks for your reply ole-cowboy; the stats are a little different than you suggest;

I am shooting the 150gr BTFMJ with 50.8 CFE223.

The 51.1 is max for the Nosler e-tip and if you click the + you get the Nosler BT which is 51.5 max.

I loaded 50.8 (and I measured every load before putting it in the case) so I should have been at the least 3 tenths under and more likely 6 tenths under the max.

My first thought was that it was still too hot, but then why did they work so well in the beginning of my session. They were the first rounds fired.

The primers were all flattened but not smeared and the edges of the primers still had a little radius to them.

Some of the primer strikes that did not pierce left a little rim (like a drop of water brings up a little side around the hole it makes). It is not much but you can feel it with your fingernail and see it when you are looking for an oddity.

I am going to take the left overs apart and use a lighter charge. It will still serve as a fouling round and I have chrono'd these already. They were running at 2771 btw.

 

[ole-cowboy]

I edited my post because I typed 105gr but I meant was 150gr

I don't really do "load development" I just use long established loads for my .308 as well as various pistol calibers, so I will leave that up to those more experienced.

With that being said I use these guys alot:
Practical Riflery Forums... techniques and equipment of the practical rifleman... Forums

they are pros and from my reading it seems as though most folk push their cartridges, (and rifles) harder than is really need to, to get the desired performance.
good luck in troubleshooting this issue

 

[Lief]

I edited my post because I typed 105gr but I meant was 150gr

I don't really do "load development" I just use long established loads for my .308 as well as various pistol calibers, so I will leave that up to those more experienced.

With that being said I use these guys alot:
Practical Riflery Forums... techniques and equipment of the practical rifleman... Forums

they are pros and from my reading it seems as though most folk push their cartridges, (and rifles) harder than is really need to, to get the desired performance.
good luck in troubleshooting this issue

Thanks for the link. I went out there and I will spend a few hours looking the posts over. I notice already there is not much use of 8208XBR, which is a powder I am going to be using for a while.

In 10 minutes I got some good info on .308 loads ... fun place.

 

[Lief]

I took the remaining fouling rounds apart and during that I was reminded that there were some primer pockets that were pretty easy to stuff the primer in. I am using range brass.

I had already decapped the pierced ones so I couldn't pay special attention but after recovering the parts I picked up a random federal case (FC) and inserted a primer, very easily, maybe too easy for the fairly hot load of the CFE.

I am wondering if the pierced primers were because the primer was being moved back against the firing pin vigorously, before the gas started the carrier back and the pin spring began to retract.

There would be a couple thousandths of space between the primer and the bolt face normally so if the primer was blown back because of a loose pocket it could hit the firing pin and get pierced.

Maybe a smarter guy than me can comment on the rightness of this theory.

In the meantime I am going to toss the cases that are easy and make mouse loads for the ones that are just kind of easy for fouling rounds.

The LC I have are lightly used because I had to swage them. They are a great example of how the primer should feel so I have a baseline.

 

[BlueOvalBandit]

The movement of primers didn't cause it. Primers will move whether they slip in easy or not.

Now, you can say these are established loads, but rifles are a bit different and all chambers are different. Bullet jump matters, a lot. What's your bullet jump specs? Too long an OAL for a given chamber results in high pressure and stuck rounds like you described as the bullet jams into the rifle lands upon chambering.

 

[Lief]

The movement of primers didn't cause it. Primers will move whether they slip in easy or not.

Now, you can say these are established loads, but rifles are a bit different and all chambers are different. Bullet jump matters, a lot. What's your bullet jump specs? Too long an OAL for a given chamber results in high pressure and stuck rounds like you described as the bullet jams into the rifle lands upon chambering.

Thanks for chiming in BlueOvalBandit;

I think the stuck part of the equation was parts of the disintegrated primer floating around jamming the bolt in the carrier. I did find little pieces in there.

What made it start piercing primers?

My M&P10 was new in December and the loads I was shooting are new. I have not made them before. To be clear I have been reloading since 1994 but the .308 is new to me.

Unless you are going to single load you are limited to the OAL that will fit in your magazine, which results in a nice big gap before the lands in an AR. Nothing you can do about it.

I would bet a $1 that the ogive was nowhere near the lands in my rifle (but I haven't measured it). I remember the base to ogive was 2.105 I believe and the max oal was 2.800 to fit in the mag. Of course the nose of the bullets vary so the oal on the rounds was probably around 2.750 give or take a bit.

Does your base idea say that there was over-pressure in the case?

Given that the projectile was not lodged against the lands, what would cause that?

I have a factory crimp die but these rounds were not crimped. others that I was testing were but not the fouling rounds.

It is true that 50.8 of CFE filled the case almost to the bottom of the neck. I don't know how the max of 51.5 was arrived at but that would be a compressed load for sure.

 

[BlueOvalBandit]

If you haven't decapped them all yet pictures would help rule out over pressure. If it for sure not related to pressure, a second theory could be to firing pin protrusion be too long for a certain primer stretching the cup to thin on strike.

This is an issue with only these loads or does it occur with others?

Sent from behind enemy lines using TapaTalk

 

[Lief]

Unfortunately I got busy and decapped all of the cases. All of the fired primers were flat with a light radius at the edge. Most had a nice pin strike divot. Some had a little raised ridge around the strike hole. The pierced ones had a black hole in them.

I took pictures of the bolt face with the firing pin protruding. It looks like I got a little flame cut out of the deal too. Drat.

This is the first time I have had pierced primers.

 

[gm272gs]

I am shooting the 150gr BTFMJ with 50.8 CFE223.

The 51.1 is max for the Nosler e-tip and if you click the + you get the Nosler BT which is 51.5 max.

I loaded 50.8 (and I measured every load before putting it in the case) so I should have been at the least 3 tenths under and more likely 6 tenths under the max.

Since you originally stated that you were shooting Hornady's bullet, I looked in my latest (9th edition) Hornady manual, which shows their 150gr. FMJ-BT on page 416.
COL is 2.700".
MAX LOAD with CFE 223 is 49.6 gr. (2,800 fps)

 

[MichiganScott]

I took the remaining fouling rounds apart and during that I was reminded that there were some primer pockets that were pretty easy to stuff the primer in. I am using range brass.

I stopped using range brass when I had similar issues. My guns are worth too much to chance it.

If you are blowing primers out with a safe charge the chances are the pockets have been enlarged by high pressure sometime in their past. It will also cause the piercing and is more likely than a gun issue. Flattened primers with a safe load indicate that there is excess headspace caused by oversizing the cases.

The flame cutting doesn't look bad enough to be an issue. The time to stop and look for a cause of the problems you had was when you blew or pierced your first primer.

 

[gm272gs]

It really clicked in my head when I read 50.8, because I can't remember putting any more than 42.0 (Varget) in a .308 case, ever.

I think the moral of the story here is that if you're going to load at max pressure (or within 0.3 grains of it) you need to use data for that particular manufacturer's bullet. Using data from the powder manufacturer for a Nosler bullet, when you're using a Hornady bullet - is more often than not - going to give you the wrong data.

In the Hornady manual (for instance) there is no load for any of their bullet designs of any profile or weight (using CFE 223) that allows for more than 49.6 gr. of powder.

Being a full 1.2 grains over that maximum, is quite a lot.
I'm glad you pulled the bullets.

 

[Lief]

gm272gs, MichiganScott; Thanks for replying.

Wow, you guys have opened my eyes quite a bit. It did not occur to me to go to the bullet manufacturers website for load data (dumb in retrospect), I kind of assumed a 150 BTFMJ was pretty much the same across manufacturers (again with the dumb).

I have always assumed the manufacturer of the powder would be the last word. Again with proof of the meaning of 'assume'.

Overloading that much was an accident waiting to happen and I am very lucky to not have had a much more serious problem.

I will cull my brass and stick with LC I have to swage and pay attention to the primer insert. When it gets easier than it used to be I will toss it.

I figure if I have to swage it the brass is probably once fired. Is that a bad assumption?

Of course you are right, the first blown or pierced primer was the warning sign. I did stop but did not know what to look for so it took a couple more before I got the hint that I had more of a problem than I could solve on my own.

Little did I know.

On the 'safe load' flattened primers; I am using the Lee die set in a single stage press. I am full length resizing because everywhere I read the opinion was that for a semi-auto you must full length resize. I did try neck size but had feed problems. By 'oversize' do you mean the die is set too far down? The shoulder looks normal to me.

What else would cause 'excess headspace'?

Even when I use mil-surp or Fiocchi rounds the primers are flattened with the slight radius around the edge.

Thanks again for the info. You have likely saved my gun.

 

[Lief]

I should have mentioned BlueOvalBandit too because his instinct was overpressure and that was surely the problem.

Thanks.

 

[MichiganScott]

If the primer has been crimped in place and you need to swage the crimp out to reload, the brass is once fired.

You need to full length size cases for a semi-auto. The easiest way to to tell if you have just kissed the shoulder and set it back about 0.003" is with the Hornady Lock n Load headspace gauge set.

If you don't, the same thing can be done with smoking the neck and shoulder of a case with a candle. You start with your die a couple of turns out from contacting the shell holder and resize a case. Depending on how much of the neck was sized, you turn in your die in small amounts and re-smoke and resize the case until it become obvious that you are just kissing the shoulder. Lock the die in place and resize another couple of cases.

If you were shooting a bolt gun, you would wipe the sizing lube off and see if the case goes easily into the chamber. Since you are shooting a gas gun, load a bullet without powder in the additional two cases you sized and see if they hand feed through the mag, eject, and the hammer falls normally. If they don't, continue turning in your sizer until they do. If everything seems to work well, load maybe 5 cases and try them out at the range.

By the way, the process you use to unstick the fired cases mentioned in the original post is "mortaring". Butt stroking is a totally different process.

 

[Lief]

More great data. Thanks MichiganScott.

I visited Brownells.

BTW, thanks for the terminology tune-up ... I guess I wasn't actually breaking someones nose with the rifle...

 

[Lief]

MichiganScott,
Trying not to be needy and a pain but here is another question;

I added a couple of pictures of the way my die is set right now. I smoked an LC case and a GGG case since they both had to be swaged.

It looks to me like the neck is sized very close to the shoulder but the shoulder is not touched.

Would you consider this suitable? It does cycle perfectly in the gun (when I don't over charge it).

Thanks

 

[Lief]

Sorry, forgot the pictures.

 

[MichiganScott]

If those were fired in your rifle, you need to actually touch the shoulder. The GGG case is close, but the LC is quite a ways off. If this is range brass, all bets are off because the chamber will not be the same as yours.

If they are range brass, continue sizing until you kiss the shoulder and hope for the best. Just plan on resetting your resizing die next time after the brass has been shot in your chamber. With a semi-auto it is always best to size a hair too much instead of a hair too little. Undersized reloads will stick in your chamber forcing you to practice your mortaring again.