SMLE Excessive firing pin penetration?


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brass shower
October 18, 2004, 12:17 AM
While at the range I took my Savage built SMLE out with some PMP ammunition and did not notice anything unusual while shooting, however in collecting the brass I noticed a couple pierced primers. I'm not planning on firing it again until I get that resolved. I'm assuming the firing pin is protruding too much, possibly due to dry firing? Or perhaps the PHP primers are just too soft. Would replacing the bolt face with a different sized one affect the protrusion of the firing pin? Any suggestions on what To check replace/measure?

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SMLE
October 18, 2004, 01:05 AM
According to the Armourer's Handbook, the firing pin protrusion sould be about .045" . .050" being the max and .040" being the minimum. A wartime measure allowed .055", but .050" is as much as you should need for commercial ammo.

Take the bolt out of your rifle. The tip of the pin should NOT be protruding from the bolt face.

Unscrew the bolt head about 1 turn and then back in. It should make contact with the firing pin and push it back slightly. The bolt head should not turn past the long rib on the bolt more than 15 degrees.

Turn the cocking piece counter-clockwise(like it would be turning when you close the bolt). This will let the cocking into the long cam groove on the bolt, you can then measure the protrusion of the firing pin.

If the pin is too long, then remedy is to adjust or replace it. If it's too short(not likely here) it should be replaced.

Springfield sporters at http://ssporters.com should have the parts. Sarco had firing pin tools.

Arrowmark tools in Australia has gauges and tools http://www.arrowmark.com.au/

I have shot several boxes of PMP in .303 and had no problems with it. It is made by the same factory that made all that 7.7x56 mil-surp in the 50 round boxes. The only differance I can find is that PMP commercial uses Boxer primners and is thus re-loadable.

mete
October 18, 2004, 01:07 AM
The variables are hardness and thickness of the primer, pressure of the round, strength of firing pin, protrusion [ ~.060" ] firing pin radius, firing pin hole diameter. A large , smooth radius, proper protrusion, hole not much bigger than the pin is what to look for .If that's ok try a new spring.

SMLE
October 18, 2004, 01:17 AM
The spring shouldn't have any bearing on this problem, at least not in a Lee Enfield. If the hole in the bolt face is too large, that could be allowing primer material to flow back around the tip of the pin.

Replacing the bolt head will alter headspace, but not pin protrusion.

brass shower
October 18, 2004, 11:48 PM
Thanks, my protrusion seems to be too long, I measured it at .06". I saw a firing pin tool at brownells, how do you adjust the pin for protrusion depth?

SMLE
October 18, 2004, 11:58 PM
Since it's too long, you can just take it down a little with a fine file. Remember to keep the very tip somewhat rounded and smooth. You'll probably want to finish up with a stone. In this case, you probably won't even need to remove the pin from the bolt, but the tool is a good thing to have in your kit anyway.

brass shower
October 19, 2004, 12:19 AM
That occured to be earlier but I figured there could be some case hardening to deal with. I take it that's not the case and I can just dremmel away until it's the proper length?

SMLE
October 19, 2004, 12:38 AM
I would avoid the Dremel tool because of the heat it can generate. You're only going to remove .010" to .015" of material, so a file followed by a hand stone should do just fine.

As far as I know, the firing pins are not surface case hardened but rather heat treated and tempered.

benEzra
October 19, 2004, 12:44 PM
Be aware that a small burr on the end of the firing pin can also cause pierced primers. You might want to feel the end of the pin to ensure the end is smooth before trying anything more drastic.

brass shower
October 19, 2004, 03:19 PM
Well I shortened the firing pin and it's now a respectable 0.049", I'll see if that makes a difference, but now I seem to have run into another problem. The dang thing doesnt want to eject consistently. I've tried it slow, I've tried it fast, and I've turned the ejector screw as far as it will go before it starts interfering with bolt movement but I cant seem to find a way to get it to consistantly eject. This has been tried with loaded rounds only, I'm wondering if spent cases will behave differently. Are there any tricks to improving the ejection? I had an idea to machine a shallow channel maybe .02" wide and .01" deep along the lengh of the bolt where the ejector screw is rubbing against it all the way up tp the bolt face, then install a longer ejector screw to fit into that channel. I'm pretty sure that would kick out the empties with authority. Seems like a lot of work to do on a gun that I didnt spend much money on though. Anyone got any ideas I can try or input on my proposed solution?

SMLE
October 19, 2004, 04:00 PM
Empties will indeed behave differently. Grooving the bolt would be a BAD idea.

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