FTRB Case slips up above firing pin on breech

[Taildraggerdave]

Hello,

Had a few failures to return to battery on my Kimber Custom II today in an IDPA match. Gun has about 1500 rounds through it and zero failures after the first 100-200 rounds. I have the EGW fps on it with 16# recoil and 19# mainspring. NO dremel work or crazy polishing on the ramp or breechface.

I had about 5 failures today where the first round would get about 1/4 of the way into the chamber but the rear of the case would be well above the "centerline" of the barrel and stop the slide from returning any further. It happened a couple times from a slidelock reload and another 3 times from me slingshotting the slide.

Tap and rack would clear the malfunction during the stage. We inspected the gun afterward when the same failure happened during the Load and Make Ready phase and found the rear of case so high. Dropping the mag didn't offer any change as the cartridge was already jammed on the upper portion of the barrel at that point. Case rim is under the extractor as it should be.
I was looking at Tuner's stickys and wondered about 89 vs 90 degree angle breechfaces. Mine is stock with no obvious damage to it.

The gun performed flawlessly the rest of the match but I was able to recreate the problem at home by riding the slide a bit when chambering a round....
Lastly, all mags are 47D's and have performed 100% so far.

Looking for any thoughts or advice.

Thanks,
Dave

[twin oaks]

Check your extractor for insufficient tension, and/or clocking....though I don't think a clocked extractor would let it go that far, but it's worth taking a look at. Detailed instructions are available in the 'technical issues' area.

[John]

The rim is not going under the extractor but in front of it. Not good.

Some questions:

- is there a shock buff in that gun?
- what ammo were you using?
- did the problem occurs with the first round in the mag or first few rounds? Did it occur with the last one or last few? Any round?

[1911Tuner]

Hello,

Had a few failures to return to battery on my Kimber Custom II today in an IDPA match. Gun has about 1500 rounds through it and zero failures after the first 100-200 rounds. I have the EGW fps on it with 16# recoil and 19# mainspring. NO dremel work or crazy polishing on the ramp or breechface.

I had about 5 failures today where the first round would get about 1/4 of the way into the chamber but the rear of the case would be well above the "centerline" of the barrel and stop the slide from returning any further. It happened a couple times from a slidelock reload and another 3 times from me slingshotting the slide.

Tap and rack would clear the malfunction during the stage. We inspected the gun afterward when the same failure happened during the Load and Make Ready phase and found the rear of case so high. Dropping the mag didn't offer any change as the cartridge was already jammed on the upper portion of the barrel at that point. Case rim is under the extractor as it should be.
I was looking at Tuner's stickys and wondered about 89 vs 90 degree angle breechfaces. Mine is stock with no obvious damage to it.

The gun performed flawlessly the rest of the match but I was able to recreate the problem at home by riding the slide a bit when chambering a round....
Lastly, all mags are 47D's and have performed 100% so far.

Looking for any thoughts or advice.

Thanks,
Dave
Two possibilities...

The breechface is mis-machined and allowing the case rim to move too far up after cartridge release. A little more tension on the extractor may help...may not.

Cartridge release is too early and too abrupt. Most of the modern "wadcutter" magazines do that. They work okay in most guns...but not very well in others.

[Taildraggerdave]

Thanks for the replies.

Twin Oaks, I have an EGW FPS that is fitted to the extractor. I can still check to see if it has worn, though.

John, The case rim appears to be sliding up the breechface inside the extractor claw. When inspecting the jam, the case rim is inside the extractor claw. No shock buff. My reloads, 230gr RN over Clays, but they have been the same for the last 1K rounds at least. Problem occurred with first round in different mags. I carry two on the belt and three more in the pocket. We tried all of them between what I burned in the stage and what I pulled out of my pocket afterward.

Tuner, I can recheck the extractor tension when I check it for looseness and or clocking.

I have another match this morning so I will come back here later and post any findings. I went through the gun last night and gave it a thorough cleaning and oiling. We'll see how the day goes.

[Hawkmoon]

Why run a 19# mainspring with an EGW firing pin stop? They offset each other ... or is that your intent? What would happen if you go back to the stock mainspring?

[niemi24s]

I had about 5 failures today where the first round would get about 1/4 of the way into the chamber but the rear of the case would be well above the "centerline" of the barrel . . .

If the rear of the cartridge rides up the breech face too far, the problem must be with the machining (or casting) of the breech face guide blocks (BFGB).

Their job is to center the case rim and to limit its upward travel along the breech face.

Well-made BFGB's have a left side block with an inward arch at the top.

Poorly-made BFGB's have a left side block that has no arch, is straight, but is wider at the top. This type wears faster because the case rim makes contact at a single point. The arched ones provide contact over some distance along the case rim.

This may be what 1911 Tuner referred to when saying you breechface may be mis-machined.

If this is your situation, let me be the first to offer my condolences!

[John]

If the rim is inside the extractor claw, Niemi (and Tuner) is absolutely right. My most sincere condolences. If you can, return the pistol to the manufacturer. It means the breech face is not machined properly and allows the rim to ride higher than it should. No easy fix for that, but a new slide.

[1911Tuner]

It means the breech face is not machined properly and allows the rim to ride higher than it should. No easy fix for that, but a new slide.

Au Contraire', mon ami. I have a GI Springfield with that very issue. Solved nicely by switching to a magazine design that releases later and more gradually. Didn't intend for this to be another plug for Check-Mate's "hybrid" magazines...but that's the way it seems to have worked out.

The problem is often exacerbated by early/abrupt cartridge release, and most often on the top 2-3 rounds when mag spring tension is high...and although the hybrids completely eliminated the problem in my Springfield...another one may require using full-tapered GI "Hardball" type magazines. (Also available from CMI)

So, it seems that John Browning has trumped'em again...with a magazine that he designed a hundred years ago. :cool:

[niemi24s]

Hi Taildraggerdave:

FWIW, when a 0.480 inch SAAMI max. dia. case rim is pushed fully up under the BFGB arch in a mid-spec U.S.G.I. M1911A1, the bottom of the rim will be about 0.222 inch above the bottom surface of the slide's center (disconnector) rail.

If you have a depth micrometer or a slide caliper with a depth rod, give yours a measure and let us know what you get. Recommend removing the extractor, as its side pressure on the case rim may tend to force the case rim down a little bit.

What kind of aeroplane you got? Cheers

[Taildraggerdave]

Hi Taildraggerdave:

FWIW, when a 0.480 inch SAAMI max. dia. case rim is pushed fully up under the BFGB arch in a mid-spec U.S.G.I. M1911A1, the bottom of the rim will be about 0.222 inch above the bottom surface of the slide's center (disconnector) rail.

If you have a depth micrometer or a slide caliper with a depth rod, give yours a measure and let us know what you get. Recommend removing the extractor, as its side pressure on the case rim may tend to force the case rim down a little bit.

What kind of aeroplane you got? Cheers


Ran the match today with same failure at the end of the first stage. This time is was the second to the last round. Thought I was at slide lock, looked down and saw one partially chambered round with one more in the mag. Stage was over so I lucked out.
Isolated that magazine and came back to it at the end of the match. Topped off that mag to shoot into a berm for testing and when I dropped the slide it failed again but not too bad. Was able to push the slide forward and the round chambered.
Niemie24, I can measure the slide after I clean it.
Used to have a C182 but sold that a few years ago. Got a bunch of tailwheel time when I first got my license. Liked the name so I stuck with it.

[niemi24s]

Hang loose for a while on that 0.222 inch measurement. Just measured my Remington Rand slide with a 0.477 dia. rim and it was only about 0.150 inch down to the disco rail.

Let me check my arithmetic & slide and if there's any change I'll post it. ["now what did I do wrong", he mutters to himself while sharpening his pencil . . .]

[niemi24s]

Found the error. The distance from the bottom of a 0.480" dia. case rim (forced up under the BFGB's) down to the bottom of the disco. rail is NOT 0.222" - it's 0.118"!

Most case rims just measured were 0.475" dia., so this would increase that measurement to about 0.123" or so. That's real close to 1/8 inch.

Should have checked the U.S.G.I. slide before posting the erroneous figure, but I could smell supper being put on the table. Pretty lame excuse, huh?

Cheers.

[twin oaks]

Should have checked the U.S.G.I. slide before posting the erroneous figure, but I could smell supper being put on the table. Pretty lame excuse, huh?
I certainly won't hold you at fault there, 'cause I've never been called "late for dinner" either.:D

[John]

Au Contraire', mon ami. I have a GI Springfield with that very issue. Solved nicely by switching to a magazine design that releases later and more gradually. Didn't intend for this to be another plug for Check-Mate's "hybrid" magazines...but that's the way it seems to have worked out.

Wait a minute Johnny, if the rim of the cartridge goes under the claw, and moves up behind the claw, shouldn't the breech face stop it from moving too high up, higher than the centerline of the barrel? If memoery serves me right there are some ... "shoulders" there for that reason.

[1911Tuner]

If memoery serves me right there are some ... "shoulders" there for that reason.


If the breechface is machined correctly. Some aren't.

Luckily, my Springfield's was almost good enough. Close enough so that slowing the cartridge release and adding a little tension to the extractor keeps the rims from moving too far up. Others aren't so lucky. I've seen a couple that would let an empty case move so far up that they would ride over the ejector as the next round in the magazine moved up. The quick fure was to use an extended ejector so the case hits it before the slide uncovers the next round. Sometimes it works...Sometimes not. Luck of the draw.

[niemi24s]

Please disregard the (supposedly) corrected measurement of 0.118 inch in Post #13. It should be 0.134 inch as shown below:
http://i129.photobucket.com/albums/p232/niemi24s/scanBFGB0001a.jpg

This 0.134" is a pretty "iffy" dimension, as it's based on over 20 calculations using 10 different specifications, each with its own tolerance. The mid-spec value of each dimension was used.

It's also "iffy" in the sense I have no idea how far off your gun can be from this value and still be OK. My old Remington Rand slide gives 0.147" and it works just fine. Extractor tension will also tend to keep the case rim from going up to this uppermost limit during actual use.

The extractor will tend to force the case rim down from the uppermost position shown, so I'd recommend its removal before measuring.

Not depicted is that the case rim center is 0.043 above the center of the firing pin hole.

[Taildraggerdave]

Thanks for the drawing. Mine is .490 wide between the blocks. Mine also has the same shoulder as you have depicted. Not two vertical/parallel blocks.

Quite a difference between the vertical measurement between the cartridge case and the bottom of the slide. I get between .170-.180 depending how square I hold everything. So, clearly, my case is able to travel upwards another .040" or so...

[niemi24s]

Recommend calling Kimber and explaining the problem to them. Would like to think they'd want to correct the problem.

You might try a little more extractor tension as 1911 Tuner suggested in Post #4. This may possibly prevent the case rim from running up the breech face so far. There's an extractor tuning article in the Technical Issues section of this forum.

If that doesn't help, I'm not sure if there is such a thing a "simple" repair for the BFGB's. Got a few "hare-brained" ideas, but not sure if any of them are worth considering.

Again, give Kinber a call. I'm guessing all they'll need is the slide, so that'll save a lot of hassle with the mailing. Good luck.

[Taildraggerdave]

Just wanted to update on my progress with this problem.

Extractor tension was too loose! Putting a round in the slide and shaking it, etc seemed ok but I was apparently off in my judgement of too tight/too loose.

I had been gaming with an XD and put the Kimber on the shelf for a while. Decided to measure extractor tension a couple weeks ago and measured around 8-10oz using a homemade checker. Tweaked the extractor to get 24oz of retention. Ran the gun through an IDPA match today and it was 100% flawless.

Needless to say I am very happy to have this one back online. I have enjoyed running the XD 9 because my 9mm reloads are so cheap. Have a USPSA match next week and will now be in Single Stack instead of Production.

Thanks again,
Dave