Pierced primer!!

[lngstrt]

I just fired 14 rounds out of my 1950 Faz Mk2. 13 of them were fine. The 14th has a pierced primer. Tiny, tiny hole all the way through. Didn't sound different. Didn't feel different. Didn't shoot the bolt backward 'cross the room imbedding itself in a passing range master.

What should I worry about?
What should I look for to solve the 'problem'?

The ammo was factory fresh Sellier & Bellot. 150 grain soft points.

Thanks

Information

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[John Sukey (Deceased)]

Probably the ammunition.

[lngstrt]

Soft primers??

[Parashooter]

Every pierced primer event erodes some little pits in the tip of the firing pin. Most pierced primers are caused by a rough or angular firing pin tip. (Think of the difference between poking a toy balloon with your elbow or with your fingernail.) The best way to reduce primer piercing is to put a highly-polished, hemispherical tip on the firing pin, examining your work with a good magnifier. Fine hard stones and 600-grit or finer abrasive cloth/paper are the right tools for the job. Unless the pin was badly chewed, very little material will have to be removed and pin protrusion will be virtually unchanged.

Pay no attention to false internet prophets who want to convince us that common and usually benign events like pierced primers and head separations spell certain doom - but do wear safety glasses just in case something unusual does happen.

[lngstrt]

Round and smooth as a bowling ball. 10x magnification.

[Edward Horton]

Commercially loaded ammunition does not have staked or crimped primers as military ammunition does. Because the primer is free to move backwards and out of the primer pocket as the internal cartridge pressure builds up two things happen.

1. The firing pin hits the primer starting the ignition process.

2. As pressure builds up and the primer is forced out of the primer pocket, and the primer is forced back over the firing pin. This action of the primer being forced over the firing pin as it moves to the rear acts like a cookie cutter or donut hole cutter and punches the already dented primer indentation into the inside of the primer.

The cause is non-crimped primers and military headspace, or the distance the primer can move to the rear and the firing pin acting like a hole punch.

Below an un-crimped primer can move backwards equal to the distance from the bolt face to the rear of the case (head gap clearance)



Below are images from Parashooters “Headspace 101” showing how the primer backs out under pressure and meets the bolt face.







And proof from the Speer reloading manual about the firing pin “hole cutter”.




In closing your problem has to do with that old guy named Newton, apples falling out of trees, action and reactions (contact interactions) and military and civilian headspace settings colliding with each other.

There is also the possibility of the opposite reaction, short headspace and a long firing pin which could be turning Newtons apples into crushed applesauce. (Firing pin protrusion .040 to .050)

[lngstrt]

Thanks for the input Mr. Ed.

Well ...... The bolt does not close on a SAAMI Field gauge (.070). Not even close. #2 bolt head (which I confess I haven't actually measured yet). All matching numbers on bolt, barrel, and receiver. Very nice bore.

I'll have to measure the tip of the striker as it pokes out the bolt head hole.

More later.

[John Sukey (Deceased)]

Good explanation Ed.
Never had a pierced primer with milsurp.

[ireload2]

>>>What should I look for to solve the 'problem'?<<<

Try to isolate the variable.

Shoot the remaining offending ammo in other rifles.

Shoot other ammo in the rifle with the pierced primer.


If you had a single bad primer forget it and go on.

If the ammo is systematically bad it will pierce in other rifles.

If your rifle pierces other primers The rifle needs attention.


(If you were using reloads and pierce a primer you have an entirely different problem)

[Edward Horton]

Another thing to do is check to see if the primer strike is off center and also if the firing pin spring is weak which any of the two could also could cause the pierced primer.

Last but not least if it only happened once it could have been the primers fault and not the rifle.

97% of all errors are human errors and only 3% are mechanical failures, meaning if you inspect the rifle and everything is set according to the specifications in the manual you can blame the primer.

Do not be afraid to replace the firing pin spring, a weak or light hit on the primer followed by the “full and harder hit” by 46,000 CUP of chamber pressure is a definite cookie cutter – hole punch situation.

While your at it go ahead and replace both the extractor spring and firing pin spring, the two most used and abused springs on your Enfield Rifle.

One last check and thing to eliminate. (It could soften the firing pin hit)