Firing pin hole is SHAVING primers!

[fulloflead]

Well, HERE'S a strange malfunction...

When firing +P loads in my Browning Hi-Power - ya know the little 'volcano' made by the firing pin in the primer - my firing pin hole is shaving off the raised portion of that volcano and it's clogging up my firing pin hole and causing a failure-to-fire.

The hotter the load, the worse it gets.
With CorBon 125gr+P it takes several rounds for the firing pin hole to shave off enough bits for it to fill up the firing pin hole and prevent the firing pin from passing through. I usually get a couple light hits that require pulling back the hammer for a second strike, then after those it won't fire at all.

On some hot loads I'd worked up myself, it happened really fast. It would only take one or two rounds for it to happen AND you could look into the chamber and see a little gold dot where the firing pin hole used to be. I can shake the gun or hit it with my palm with the action open and no mag present and the little disk would pop free, and fall down the mag well and onto the bench. After a magazine full, I'd have a little collection of tiny gold disks on the bench.

And if THAT'S not strange enough...
you should see the spent brass! On the hotter loads the primers look unfired and if you look closely you can see that there's a wipe mark on the primer. It's like the firing pin indent flowed back into the firing pin hole, got shaved off and left what looks like an unused primer.
On the Corbon+P loads there's still an indentation from the pin in the primer; you can just see where the pin hole shaved a portion from the side of the indentation which sometimes leaves a little edge peeled up.

So, what's my problem? DO I have a problem? (because I'm just kinda planning on not shooting +P ammo now)

Do I have a headspace problem? It's a GOOD gun! It's a 1988 Belgium Hi-Power and has only had about 1000 rounds through it. It looks up great and will routinely shoot one ragged hole at 50 feet - even while it's shaving primers.

I've considered chamfering the firing pin hole to remove the sharp edge, but I don't know if removing material from that area is a smart idea; it could make things worse.

Comments?

 

[Jim K]

Have you done anything to the hammer spring (mainspring) or the firing pin or firing pin spring?

That problem has one cause - the firing pin does not have enough momentum to block the back pressure of the primer, so the primer metal tries to back up into the firing pin hole. It is common when the mainspring has been lightened or a light metal firing pin used.

Jim

 

[fulloflead]

Wow! Somebody knows! (This is actually a common thing?)

Thanks for the reply!

"Have you done anything to the hammer spring (mainspring) or the firing pin or firing pin spring?"

All of the above!
Cylinder and Slide "Target" spring kit. It has it's original firing pin, however.

I can:
A.) Tighten up the nut at the bottom of the hammer stud to tighen up the main spring.
B.) Put back the original main spring.
C.) Replace the original firing pin return spring. (I can't imagine what the difference is.)
D.) All of the above.

What shall I do?
.

 

[Jim K]

Put both original springs back in and let us know what happens.

Jim

 

[fulloflead]

Crap. Gotta buy more Corbon now or work up more hot loads!

I had SUUUUUUCHH a nice trigger pull too!

Maybe I'll leave it. It is my "fun" gun.
My Glock is for the important stuff.

At least I know what's causing it so I can fix it anytime I wanna sacrafice that nice 3.5lb. trigger for better reliability.

Thanks for the education. I did NOT know that.

.

 

[DT Guy]

When you put the C&S kit in, did you put an increased rate recoil spring in? With the reduced mainspring tension, you've effectively reduced the strength of the recoil/mainspring combination, and that could be letting the barrel unlock too early.


Just a thought, but might be worth a shot.


Larry

 

[Jim Watson]

My Springfield UC 9mm would do that even with standard loads until I ditched the titanium firing pin.

I would quit pounding a BHP with overloads. You could go back to stock springs and maybe quit shaving off primer cups but the pressure is still there.

 

[fulloflead]

That's interesting about the recoil spring. It doesn't seem like a reduced hammer spring would matter THAT much as far as lockup time, but it might be worth a try. It's probably time to replace it anyway.

I don't make a practise of shooting a lot of high-pressure rounds out of my guns, but I do like to have them as an option. In this case, I was testing how various "Defense" rounds ran through my 9mms. It's nice to know what runs 100% when I choose that option and keep a few boxes on hand.

By the way, the Corbon 125gr JHP is too short and caused stoppages in my BHP a couple times and was hard to clear. But the SAME bullet loaded by me to max length according to Sierra data ran great in everything.

.

 

[HSMITH]

Back down a little and switch to small rifle primers, then work back up. They are much harder cups and won't flow as much as pistol primers will. A firing pin bushing or a larger firing pin would also go a long way toward preventing so much primer flow.

For the condition you are having the firing pin hole is too big or the firing pin is too small, couple that with added pressure and problems will show.

 

[Jim K]

Lockup time is not really the problem in those cases, nor is the size of the firing pin hole, within reason. Besides, an enlarged firing pin hole in an almost new gun would be unlikely.

The condition described is the same condition that causes "pierced" primers, which are almost never "pierced", but actually are blown out because the firing pin does not have enough resistance to the backward pressure. In almost every case, the firing pin spring tension or firing pin weight has been reduced in an effort to improve trigger pull, although high pressure beyond the design limitation can also cause primer blowout. The condition has been seen in 1911 type pistols which have had light firing pins installed to meet the California drop tests.

With an inertia firing pin, the firing pin will usually back up in its hole until it is stopped by the hammer. Since that point is normally about where the tip of the firing pin is even with the breech face, the primer will not be blown completely out ("pierced"), but will shear as Fulloflead described.

The use of small rifle primers might reduce primer blowout, but I suspect it would result in misfires.

Jim

 

[HSMITH]

Jim, I have seen exactly the symptoms you describe and the results. I have also seen quite a few new guns with oversized firing pin holes. Taurus autos are notorious for this. IIRC the HP has a spring to retract the firing pin back against the hammer like the 1911, but I have never seen one that was able to move the hammer back and make room for primer flow. Maybe the firing pin is a tad short? Something I hadn't thought of, but it would do the same thing. If the firing pin was too pointed that would also make room for flow. Just some random thoughts..........

9mm and small rifle primers work well, even in striker fired guns. It is a lot more common combination than you would think. Ignition is about the same as a small pistol magnum primer or a touch hotter, so loading data is not a 1 for 1 cross. You must reduce charges and work back up watching for pressure signs on the case, the rifle primer won't tell you anything until you are WAAAYYYYY past normal 9mm pressures.

 

[Jim Watson]

I thot BHP had an inertial firing pin like 1911. Primer flow wouldn't have to move it back against the hammer, the spring takes it back from the hole.

Use of rifle primers to prevent primer extrusion is a bandaid for a symptom. The high pressures are still there. OK in a strongly built racegun but I would not do it to a nice light service pistol like BHP.

I did considerable chronographing with different primers as I came into many more small rifle primers than I expect to need in rifles. They do not give as high velocity as a small pistol magnum of the same brand.

 

[Jim K]

I have seen internal pressure move the hammer back. It is pretty common on revolvers when the mainspring is lightened too much and/or the hammer mass reduced (as in "bobbing" the hammer). The result is a hung up gun, as the cylinder won't turn.

I didn't say that an enlarged firing pin hole could not cause a problem; I said that I doubted that an almost new BHP would have that problem.

As to small rifle primers, my feeling was that if the mainspring in the gun in question had been reduced to the point where there was primer flow, it would probably not be strong enough to fire small rifle primers. While I know many folks (I included) have used small rifle primers in pistols, the reason for pistol primers is that in general pistols have a lighter striker blow than rifles, and less pressure. The whole issue is a matter of "push in here and it pops out there," as a friend says.

Pistols have less firing pin force than rifles, so pistol primers are softer. This is OK when pistol pressure is low, as is usually the case. But when pistol cartridges are loaded to rifle pressures, the soft pistol primers try to flow. If the firing pin blow is light, that pressure will push back the firing pin and the primer metal will flow into the firing pin hole if it can. But, if we go to harder primers (rifle primers), the lighter firing pin blow may not ignite the harder primers so we have misfires. (This is all aside from the need for rifle primers to be harder to prevent other problems that can occur with higher rifle pressures.)

I have "been there, done that" with most of those tricks and run a fair number of experiments, so what I am saying is not out of a book. In fact, that primer flow business contradicts most of the gunzine writers and web experts, who almost always attribute "pierced" primers to a heavy firing pin spring, a sharp firing pin, or too great firing pin protrusion.

Jim

 

[fulloflead]

Fascinating thread this turned out to be. I'm enjoying everyone's posts and getting something out of them.


Back when I was testing some hot (too hot) 9mm loads I was getting primers that would come COMPLETELY out of the primer pockets on occasion as well, but no pierced ones. At the time, I was interpreting ALL these symptoms as too-high-pressure signs.

Of course, I DID have too high pressure. I know this because I got a KABOOM (sort of) when I fired these from my Glock 17. One of the cases ruptured out the side near the head and blew a flame out the side of the gun and down the mag well... and the Glock cycled the round and kept right on running without a hint of damage.

(I don't do that anymore.)

Stupid question...
If I need a HARDER whack on the firing pin and need it to have MORE inertia and to stay forward LONGER, why not LIGHTEN the firing pin return spring?


.

 

[Jim K]

"Push it in here and it comes out there." Lightening the firing pin spring can result in firing pin drag which may not be a big problem but isn't right.

Jim

 

[saltydog452]

Misters Keenan and Watson,

If I understand both of you correctly, it appears that you are implying that XtraPower Firing Pin return springs as supplied by Wolff would cause the firing pin to retract back into its 'tunnel' a bit quicker and would likely help prevent the situtation that fulloflead is experiencing. Is that the case?

I have a Colt Officers Model that was having timing problems and was leaving firing pin 'drag marks' across the face of the primer. That was a timing issue and was corrected by 1911Tuner.

I remember years ago when I was fooling around with plastic and wax bullets that were powered by the primer only. Those rounds would consistently 'lock-up' my Smith&Wesson revolvers. There wasn't enough power to obituate (sp?) the cylinder. Don't know if thats relevant or not, but the brain synapses just fired in that direction, so I thought I'd mention that little oddity as well.

Betcha OldFuff can offer a thought or two about that as well.

45ACP PowerBall allows for a bit of primer flow into the firing pin tunnel in my Officers Model. Although I clean the firing pin tunnel to be certain there is no metal in the tunnel, I haven't seen any evidence of primer metal coming out on the pipe cleaners of the dental picks that I use. Nor is there any evidence of sheared metal on the recovered brass. I just don't shoot a lot of it, even if I could afford the experience. It does feed though.

I know that shot placement is more important than ballistic potential. But with aging eyes, arthritic hands, and rotator cuff surgery, some of us need all the ballistic help we can get.

fulloflead might be well advised to find Stephen A. Camps web site 'handguns and hi-powers' and give a bit of thought about Mr. Camps obversations regarding +P and +P+ ammunition in the BHP as well as the use of Wolff recoil springs.

Just a couple of random thoughts, and I would appreciate your comments as I do use Cor-Bon ammunition with some degree of regularity. I do use XtraPower firing pin return springs on the Colt Officers Model and Wolff 18.5 rated recoil springs in the BHP.

fulloflead is right in that this has become intestering and you gents have a lot to offer. 'Appreciate hearing more of your thoughts.

Thanks,
salty.

 

[fulloflead]

Salty,

I'll look up that website, thanks!

About that revolver...
It may be something completely different. Really LOW power revolver loads do strange things.
Normally, the pressure causes the brass to expand and 'stick' to the cylinder walls and actually not slam back against the recoil plate, so if there's some space there, the primer could back out. But with a low-power load the brass doesn't really expand enough to stick in place and the case will slide back against the recoil plate. Maybe that's what happened with your primer/wax loads. I've shot some low-power 44mag loads that caused the sides of the brass to get toasted because it allowed hot gasses to seep back next to the brass instead of being sealed out like they would be with a normal-pressure load. I've also experienced this from having too much of a coating of oil inside the cylinder. I keep the chambers pretty dry now.

I think the idea is that I need to have my firing pin stay forward LONGER, not less time like I would have with a stronger firing pin return spring.

I'm curious about that site now, so I gotta go.

.

 

[Jim K]

I don't want to get too bogged down in this, but Saltydog's question deserves an answer. The two events, primer flow and firing pin retraction are separated by a millisecond or so. The first, as I said, is caused by the firing pin not having enough momentum to keep the primer metal from flowing back under pressure. The higher the pressure and the less the momentum, the more this will happen.

So a stronger firing pin spring will decrease the firing pin velocity and momentum (momentum is mass times velocity) and contribute to the primer flow condition; it can also cause misfires. But the spring also has to be strong enough to retract the firing pin immediately. If it does not retract it fast enough in a dropping barrel pistol, the firing pin will drag in the primer as the pistol unlocks (link-down timing is a big factor here, but not the only one). The firing pin spring has to be in a delicate balance, something Browning knew, but some spring makers forget when they tout their products. In other words, a stronger spring is not the solution to every problem, as much as spring makers would like to pretend otherwise.

Jim

 

[RecoilRob]

I experienced this same problem with a Belgium HP a few years ago. The rounds WERE a bit on the stiff side but only flowed into the FP hole on the HP.

That gun turned out to have a very short rifling leade that seemed to bump the pressure of whatever was being chambered. I found it when trying to load some 147 RNFP lead bullets. The rounds would chamber fine in 7 other guns but refused to go in the HP. I had to seat the bullets over .050 deeper to chamber them in the HP which caused some BIG pressure problems! I abandoned the heavy bullets in that gun and sold it to a friend who feeds it 115's only.