Troubleshoot This-2

[1911Tuner]

Aight ladies and laddies...A brain-twister for ya to ponder on.
This is one that slapped me between the eyes about 2 years ago
on an older, pre-ILS Springfield Mil-Spec.

The problem:

Severely flattened primers with evidence of extrusion into the firing pin hole
on almost every round fired. Other than this glitch, function was perfect
except that on one occasion, a piece of sheared primer caught in the
firing pin hole caused the gun to misfire.

The firing pin was to spec on length and diameter. A new firing pin spring had no effect. The recoil spring was 16 pounds. The mainspring was a standard replacement spring (Wolff 23#)

The ammunition was hardball-spec, or the equivalent reload.

The firing pin hole wasn't oversized or damaged. The breechface was smooth and the dimension was in-spec at .488 inch.

The mainspring housing had been swapped for an arched Smith & Alexander w/lanyard loop and the stock mainspring cap, cap retaining pin, and plunger were used.

There was a fitted King's trigger in the gun, and the trigger broke at a crisp
5 pounds, even.

The link was correct in length and function, and the barrel was neither riding the link, nor standing on it in battery. All timing checks proved to
be within spec, and there was no sign of any damage to the slidestop crosspin or link.

The fix...once diagnosed...took 15 minutes, including the time for disassembly/reassembly and test-firing three rounds.

Hint: It's the LITTLE things that getcha...

And....GO!

 

[Black Snowman]

Flattened primers? Wouldn't that normally be an over-pressure issue? Maybe I've been reloading too long
I'd check the chamber and bore for spec. Doesn't sound like it was binding anywhere that might have made it lock up too long but you already said the timing was OK.
That really only leaves the exctractor that I can think of but I'm not sure how it woul be involved in flattening the primers . . .
I'm looking forward the solution to this one.

 

[R.H. Lee]

Novice guess. Sounds like maybe the pistol was slightly out of battery (the slide was within a hair of not fully forward) caused by an overly tight barrel bushing.

I have no idea what I'm talking about.

 

[1911Tuner]

re:

Riley and Snowman...both good guesses but...nope.
Ammo was hardball spec. Chamber was fine. Function was
flawless except for the one misfire episode.

Remember that I said the fix took about 15 minutes after
findin' the problem...Never mentioned how LONG it took to find it.
Don't ask...It's embarrasin'.

 

[Black Snowman]

Riley: Novice doesn't begin to describe my gunsmithing skills. More like "Part time quasi-hobbiest amature" I do love to troubleshoot things though so I had to chime in.
Didn't say anything about replacing parts . . . to flatten the primer without over-pressure wouldn't something have to be battering the back of the brass? That's why I was thinking a chamber issues. Too small and it could over pressure. Too large and it would act like the firing out of battery issue. I figured Tuner would spot an out of battery gun in a heartbeat so didn't go that route.

Since FP length was mentioned I'd say firing pin channel not deep enough would be my final answer. Am I the weakest link?

 

[cordex]

I've got it!

The firing pin stop had dropped slightly and ...

I have no clue what would simulate overpressure effects other than some sort of bore obstruction or tight barrel which we all know Tuner would have spotted right off.

I really enjoy these, Tuner. Keep them up!

 

[R.H. Lee]

I dunno. I suspect some sort of an open breech condition. but if it were too far open, hammer would not drop (disconnector and all that). Maybe something to do with the chamber being too deep?? Cartridge too far forward??? But that would require replacing the entire barrel. I just dunno

 

[HSMITH]

Two piece barrel, barrel swaged down at the very beginning of the rifling from poor fit between the two pieces, like an inverted 'ring bulge'?

I've seen it before but it ain't a 'little thing' like you alluded to. I suppose it could have been a burr in the end of the chamber too. It most certainly sounds like an overpressure problem, but the causes can be hundreds if not thousands...

 

[1911Tuner]

The Problem

The problem didn't have anything to do with pressures. It was a mechanical problem with the gun, and more precisely a tolerance/tolerance stacking issue.

The primer will flow back into the firing pin hole under certain conditions not related to high pressures. The firing pin was not titanium, and the spring was a standard replacement part.

The ammo was both PMC factory hardball and a reload consisting of a 230-grain RN bullet and 6.5 grains of Unique...a healthy, but not overcharged standard load for the .45 ACP.

It's the L-I-T-T-L-E things that getcha...

 

[1911Tuner]

Barrel Ring

HSMITH...GOOD answer! An issue that I've seen once or twice,
but not the case in this gun.

It's the L-I-T-T-L-E B-I-T-T-Y things...that'll getcha! It sure
got me.

 

[sm]

Reamer in the chamber to lengthen the leade allowing the ammo to fully seat in chamber to proper length.

I have seen heavy lead build up in the leade do this.

 

[HSMITH]

OK, how about a short breechface to firing pin stop dimension or a long extractor? Holding the case off the breechface will certainly let primers flow.....

 

[Jeff Timm]

Little things.

The littlest thing in the .45 ACP is (runs to back room for -34 manual) the Slide Stop Plunger was causing something to happen with the Slide Stop?

Geoff
Who makes a WAG 'cause he's got no other clew!

 

[sm]

<whistle>
Kayleeeee!
We need a ladies perspective - Please!

If this is something so simple like a trigger spring, bevel of FP hole, burr on FP, ....

 

[Bill Z]

9mm FP in a .45 FP hole

 

[R.H. Lee]

Mr. 1911 Tuner, please report to the clueless section.

How about a hint? Is the breechface somehow set back?

 

[1911Tuner]

9mm Firing Pin?

Bill said:


9mm FP in a .45 FP hole

Another good one...but nope. It WAS a 9mm pin, but it was in a
9mm hole, as Springfield has been doin' for a while.

sm..No burrs on the pin or over-chamfered hole...


This was one of those things that happen one time in a thousand...
even WITH the same tolerance issue that this gun had. In other words,
I've seen the obvious problem on other guns, but not the same symptoms.

Gave me a dang Excedrin Headache, for sure.

Okay...last hint. A bolt-action rifle will often show primer cratering
for reasons NOT related to pressures...but remember that the firing pin spring was replaced early on, but didn't fix the problem. The primer appeared to be flattened by pressure, but it was actually the firing pin
indent being ironed out and flowing back into the hole...Pressure did it,
but it wasn't excessive pressure. I've never seen it before or since
when it was caused by the same set of circumstances.

This one is gonna have ya goin... and :banghead:

Told ya'll it was a brain twister...

It was a matter of a combined tolerance issue of less than .020 inch...
and it involved three parts stackin' the tolerance the wrong way.

Edited: Riley...Nope. The slide was in spec. The breechface was right where it was supposed to be, and the headspace was on the money.

 

[Frohickey]

My WAG... hammer would hit the firing pin and somehow would bounce off the firing pin, instead of keeping the firing pin forward.



I dunno, but I have a sneaking suspicion here that 1911Tuner's Troubleshooting lessons here is to find out who among THR is deserving of the 1911 Master Craftsman toolset with ancient chinese kung-fu powers.

 

[1911Tuner]

Bounce!

FROHICKEY!!! YOU RULE!!!

Details in 15 minutes....

 

[Frohickey]

Woohoo!!!

When you can snatch this 45ACP case from my hand, it will be time for you to leave, little Grasshopper.

 

[R.H. Lee]

... hammer would hit the firing pin and somehow would bounce off the firing pin, instead of keeping the firing pin forward.

Weak mainspring? Incorrect radius on firing pin stop?

 

[1911Tuner]

Little Things

Okay...As promised.

After callin' on all the names that are holy to show me the way...I noticed that the firing pin was pushin' the hammer back ever-so-slightly...I could push the hammer forward, and the pin would push it back at me. There was about .010 inch of slack in the hammer when it was fully down.

The mainspring cap retaining pin hole in the housing was drilled about
.010 inch low in the housing. Still in spec, but barely. The top portion of the mainspring cap itself was long on the high side of tolerance. The butt-end of the firing pin checked at .005 inch shorter than what several other pins averaged.

All within tolerance...but all stacked in the wrong direction. The firing pin was rebounding too fast to keep the primer material from flowing into the
hole, and when the barrel unlocked, the downward motion sheared the flowed part, but not always completely off. Some had a small, crescent-shaped portion left at the edge of where the primer dent would have been. Smeared would fit better...

It looked like the primer was flattened by extreme pressure, except that
it hadn't filled out to the edges of the primer pocket. Other pistols that I'd seen do it were caused by a timing problem when the barrel unlocked too early, and delaying the slide a little with a fresh mainspring or a FP stop
with a small radius...or both...cured it...but not this time.

The fix involved using the lathe to face .015 inch off the end of the mainspring cap to let it sit higher in the housing. The hammer hit the pin harder, so the pin didn't rebound as quickly. The harder smack caused the firing pin to "dwell" just a little longer,and maintain the dent in the primer until the pressure dropped...or at least that was the only theory that I could come up with. Anyway...The problem went away, and hasn't returned.

Crazy huh? It's the little things that getcha.

Kudos Frohickey! HSMITH was closin' in on it. He was nippin' at your heels there...

 

[Frohickey]

Um... if the parts are all within spec, but the tolerance stackup was making the pistol not work, doesn't that mean that the specs are wrong to begin with?

 

[R.H. Lee]

Congratulations, Frohickey. (Others, please note, Frohickey is from California. We are smart here).

 

[Jim Watson]

I didn't catch it from the description; but I HAVE seen it.
FLG calls it a "dead hammer" with little or no tension in the down position.
A short strut will do ya, too.