Primer Piercing / Blanking

[gzig5]

Nice rifle. Can't say I've ever seen a Springfield setup to feed .223. That looks like a looooong barrel. The primer brand is a good point, and may save having to do work on the rifle. The Rem 7 1/2 are tough as are the CCI BR primers. Winchester is soft in my experience, Federal are so-so from a hardness aspect. If you can get your hands on them, the Wolf SRM primers are very tough and consistent. They are the only thing I will run in my AR15's. For bolt parts, they are on ebay or gunbroker all the time or Numerich Arms should have some.

[GrocMax]

.070" pin protrusion is on the long side. You can get reliable strikes at .040" +/- .005". Making the tip shape a flatter bowl shaped semi-hemisphere instead of a full hemisphere shape will remove a large portion of the space the brass can flow into. A light or weak spring will also allow the same symptoms.

There is one new problem you can introduce on a 223 or other shallow shoulder angle case by using hard thick cup primers (BR4, 450, 7 1/2) and a large protrusion and that is either increased misfires/FTF or center body case head separations in subsequent loadings, the pin strike will shove the entire case forward and neck it down just like a die, making for large headspace when there isn't any outward sign of it. If you don't believe me, record your pin protrusion, put a primed but otherwise empty properly sized case in and fire it, then try to explain why the primer indent is .020" deep and not .070" deep, and the neck is longer. Sometimes headspace isn't headspace. The above scenario will become very evident when you try to fireform AI such as 223AI or 6TCU using 450's or 7 1/2's and have a very high rate of FTF's even though everything is in spec and fine, and changing nothing but going back to 400's or 6 1/2's its 100% reliable again.

[TinMan]

Harold M, you might try Sarco, Inc. or Numrich for M1903 strikers (firing pins), if you need one. They should be <$10.

[Kevin Gullette]

What is the firing pin diameter, as is passes through the boltface?

Kevin

[georgeld]

Am happy for you finding such ? "fair" shipping!

I placed a $20 order for small replacement parts on a Lee press.
weighed 9 oz's, Lee charged $13 for shipping in a 6" sq box. That
could have been sent in a book sized box Flat Rate for $7.
Gotta bitch about it to them!

[Kevin Gullette]

An easier method might be to measure the boltface FP hole.

To keep from disassembling the bolt......I use a variety of small drill bit shanks, to slip-fit into the hole, and then caliper measure the shank.

Hope this helps.

Kevin

[Kevin Gullette]

Wow......that's one BIG firing pin.

It ain't gonna work.....on a small rifle primered cartridge that's .224 caliber or smaller.

A little Jerry Stiller math.....

A 0.082" firing pin probably has an 0.084" boltface hole. The hole is 0.005412 square inches. At 50,000psi, this results in a total shearing force of 277.1 pounds.

Now use a 0.060" firing pin, with a 0.062" boltface hole. The hole is 0.003019 square inches. At 50,000psi, this gives a total shearing force of 151.0 pounds.

So.....for a 0.022" reduction in the boltface hole diameter, there is a 45.5 percent reduction in the shearing force.

As would be expected, a stronger firing pin spring has little effect.........been there, tried that.

Why these things only seem to happen with small rifle primers AND small calibers????.....I do not know, or can prove........but I strongly suspect that as the sectional density is lowered, a more "focused" pressure spike through the flash hole is created.....and the firing pin is pushed rearward. BUT.......that's just me.

BTW.....my old 20BR had about the same situation as above. Quite an eye-opening experience. Greg Tannel reduced the firing pin diameter, and bushed the boltface to a smaller firing pin hole size. The result.........with 40gr bullets blanking at 3400fps.........to NO cratering whatsoever at 4150fps.

Hope this helps.

Kevin

[georgeld]

Kevin:

Good thing you were dealing with Harold as no one else on here
I'm aware of could stay with you on that figuring!

Does look like a big FP hole.

I'm shooting two barrels: one marked 1918, other 1919. '17 Enfields
Inch 3 shots at 200yds. Not enough reason to replace the barrel yet.

[17tbs]

Bushing the firing pin hole sounds like an easy task, does he handle TC frames with the same problems ?

[Kevin Gullette]

Is the primer pocket still tight......during primer seating?

Did the case web "over" expand/swell?

Even if they did.......the excessively large boltface hole, is still the weak link.

Kevin