Nosediving First Round - pistol cured itself??

Nosediving First Round - pistol cured itself?
Riddle me this - can a pistol heal itself?

I'm finishing up my Caspian Recon build. I fit the ejector yesterday and today I fit an EGW FPS and HD extractor. I assembled what I needed to test feeding, extraction, and ejection after shaping and tensioning the extractor.

There are still some rough edges here and there. I need to shave just a touch off the bottom of the barrel ramp and break the edge where the ramp enters the chamber proper.

I both hand cycled (no recoil spring) and spring cycled rounds previously through my 8 round extended Checkmate mags with no problems. I used 230gr Federal HST (my duty rounds) for the testing.

So today I assemble frame, slide, barrel, bushing, FPS, extractor, FP, ejector, slide stop, and mag catch. I load up 8 rounds of HST in an 8 round extended Checkmate mag. I try hand cycling and the first round nosedives hard into the feed ramp. All the rest of the rounds cycle smooth. I put in the recoil spring parts and repeat. Again the top round nosedives both from slide lock and slingshotting. I try another 8 round extended and an 8 round flush fit Checkmate (all with hybrid feed lips and their newest follower). Top round keeps nosediving hard.

I break out my Metalform mags from the old group buy - 7 round SS wadcutter feed lips, wolff springs. The rounds feed fine. I can hear the difference in feeding though, ka-chunk versus swooosh.

Now I'm pretty upset at this point. I've been very meticulous with this build.

I pack my pistol and mags up and bring everything to work tonight because my buddy has a collection of assorted 1911 mags at work. I figure I'll try them all and do a little experimenting. I was hoping to build a pistol that would feed anything and do so from an 8 round mag, but if I have to stick with just one type of mag, so be it.

Right off the bat, I tell him what's been happening, so he wants to see. I open the closet in the squad room and pull out a box of HST's. I load up the 8 rounders and... they all feed perfectly!

I try it numerous times with all my mags. No stoppages, no nosedives!

Did my pistol heal itself?

I start to think. (it hurt a little)

What has changed?

I think... the ammo! I had been using the same 8 rounds at home over and over when I was testing feeding before installing the extractor and ejector. The fresh ones at work did just fine. The other rounds must have set back just enough to cause a problem. I'll have to measure them when I get home.

This was a good learning experience for me and I think the big lesson is that, with duty ammo, the rule should be "Load it Once"

In addition to all those things you mentioned, there's the fact that the top round in any full magazine will nosedive more than any of the subsequent rounds. This is because support for the nose of the top round gets better as the magazine empties, as shown here:

And the top round in full extra capacity (8 & 10 rounders) magazines will have even less than shown in the pic!

Looking forward to your setback information.

OK, I measured the offending rounds when I got off work.

The shortest measured 1.192" and the longest of the eight measured 1.204". The average length was 1.200". I could also see that the reduction of OAL was due to both set-back and ogive deformation.

I then measured some brand new HST's for comparison. Of the ones I measured, the longest was 1.210" and the shortest was 1.206" for an average OAL of 1.208".

The average difference in OAL between the new rounds and the set-back rounds was .008".

I also measured some Federal 230g FMJ. Average OAL was 1.265".

The next thing I will do is to chamber, from slide lock, HST rounds of various OAL's to try to find the "point of no return" in regards to OAL and nose-diving when feeding from the top of an 8 round magazine.

My conclusion is that the Federal HST 230g .45 ACP is a short round - only .008" on average above minimum spec. This puts operating this round through a 1911 using 8 round magazines right on the edge of reliability. I'm not an ammunition manufacturer nor even a reloader, so I don't know how hard or easy it is to keep ammunition within a certain tolerance. With this in mind, for me to use 8 round magazines with HST, I'm going to have to find out what OAL's will work and measure the ones I'll use for duty/defense and ensure that the longest are the last ones loaded into any 8 round mags.

That or just use 7 round magazines.

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The average difference in OAL between the new rounds and the set-back rounds was .008".

0.008" Of setback in a round that had been chambered several times is, IMHO, not a whole lot of setback.

I've seen some handloads get set back about 0.030" in a single chambering!

There may be something else afoot causing your jams. Maybe the bullet nose design?

And, as an afterthought, the only thing I can think of about a magazine that would add to the amount of nosediving inherent in the 1911 is if the magazines' feed lips get deformed when slammed in hard and might be worth a look-see:

The deformations on each side are caused by the rim of the top round in the magazine, and because these deformed areas lie below the case rim top (where the breechface makes first contact) they would tend to cause a little extra nose-down torque on the round.

Anyway, that's my theory.

I wanted to post an update to this thread.

I finished my Caspian build and all the little details were taken care of that I hadn't done yet when I first posted this thread: polishing chamber, tensioning extractor, etc.

I wanted to check set-back and nose-dives to find out the "point of no return" with my pistol using my duty rounds - Federal HST 230gr.

I took a box of 50 HST's, measured OAL of eacj round, and loaded them one at a time on top of seven other rounds in an 8 round Checkmate, hybrid feed lips. I attempted to feed each round from slide-lock, recording whether it fed, and then measuring set-back after feeding.

I went through the entire box with no nose-dives. OAL ranged from 1.212" to 1.199". Average set-back was .0018". The highest set-back was .004" and the lowest was zero.

I then took a previously chambered round that measured 1.192" OAL. I loaded this one from slide-lock 19 times. It fed 17 out of 19 times. The round nose- dived at 1.133" and 1.128" OAL. In 19 loading, this round set-back from 1.192" to 1.125". Exasperated, I loaded it 15 more times in a row without measuring. It fed each of the 15 tries. At the end of those 15 loadings it measured 1.118" and still fed as the top round in an 8 round magazine from slide-lock.

My little experiment did not have the results I thought it would. Before final finishing of the pistol, I had experienced nose-dives with the top round in an 8 round magazine when the OAL was reduced. I expected similar results with this experiment. It really didn't happen until the OAL was greatly reduced and even then it didn't happen very often or consistently. Another observation I made was that, with the 8 round magazines, there is very little support for the nose of the top round. This allows the top round to be in either a "nose up" or "nose down" position in the magazine. If I purposely pushed the nose of the top round up, it fed smoothly. The results of my experiment were all achieved by purposely pushing the nose of the top round in the "nose down" position and they fed as noted above.

Another observation I made was that when inserting a magazine vigorously, the top round would slide a little bit forward under the feed lips. This would result in improved feeding as the nose would point higher. I was unable to get the round to escape the feed lips, though, no matter how vigorously I inserted the magazine. My only concern with this is that the extractor may be snapping over the case rim instead of the rim sliding under the extractor. I'm not sure whether this was happening or not.

Conclusion: It turns out that my pistol is not as sensitive to cartridge OAL as I thought it would be. I also now have no reservations using the HST round in the Checkmate 8 round magazines. Set-back from chambering once with a new round really also isn't much of a problem as the maximum set-back with the new rounds was only .004". I wouldn't do it more than that, though, as the set- back starts to increase pretty quickly with subsequent loading.

I seem to remember that there were some questions about the feedramp depth, angle and location relative to the slide stop pin. Since bullet setback doesn't seem to be the cause of the nosediving problem, you may have to revisit the ramp issue.

If you ever get really, really bored or locked out of the house for a while, those same tests, but with a seven round tube might be interesting.

I've said it before... JMB set everything up with 7-rd. magazines.

I don't know.

Metalworking spring technology has probabaly improved since 1900.

Checkmate now has the short skirt, dimpled follower, hybrid lips, nd spiffier springs (maybe). If I understand right, the same tube body will accomodate 7 or 8 rds.

This would be a good time for a look/see. Half of the comparison has been done.

This may not apply but I had nose-diving problems with my Fusion build. A quick check showed that I had too much extractor tension and the rounds were having trouble seating in the extractor notch.

Interestingly I thought it was a magazine problem because it only happened with a couple of mags. Those that failed had softer springs than those that worked thus there was more force with some mags to force the round into place.

A little massaging of the extractor solved all problems.

I think this solved it.

I started to worry about the frame's feed ramp, but I measured it to exactly .360" deep and the angle was right on.

I went back and tested all my 8 round magazines. I have 4 Checkmate 8 round extended tube magazines and 1 Checkmate 8 round flush fit magazine. All have hybrid feed lips and the Checkmate follower.

I discovered that it was only the 1 flush fit magazine that was nose-diving the top round. The other 8 rounders would even feed an empty case from the top of a full magazine.

Upon close examination, I saw that the rear corners of the feed lips were indented slightly, close to what Niemi24s posted in the above picture. My thumb nail would catch on the indentations and I could feel that the indentations held the rim of the round while the other magazines did not. It was apparent that the indentations were formed during the stamping or forming of the tube. It looks like the die was off a bit. If I had batteries in my camera I'd post a picture.

So, what is the best method to remove the indentations? Should I peen the rear of the feed lips down from above or blend the indentations with the rest of the feed lips from below?

I'll try to get a picture.

Here are the pictures:

This is the 8 round extended tube magazine:

This is the 8 round flush-fit magazine:

And this is the two side-by-side. The flush-fit tube is on the right:

This picture really shows the difference between the two. You can see how the feed lips on the right hand magazine would tend to trap the case rim.

So, what's the best way to fix the magazine?

Tom... I'm sure Checkmate will replace it... I wouldn't bother trying repair it and risk making it worse(and I like to tinker)... at least make Checkmate aware of the problem so they can check their current production for the same issue.

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So, what's the best way to fix the magazine?

Maybe this from Brownells would work, but I've never used one: http://www.brownells.com/.aspx/pid=...P_FORMING_TOOLS The magazine lip forming I've done is at the front of the lips. Don't know whether this thing is even capable of reshaping the aft ends of the lips.

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This may not apply but I had nose-diving problems with my Fusion build. A quick check showed that I had too much extractor tension and the rounds were having trouble seating in the extractor notch.

A little massaging of the extractor solved all problems.

Jerry, too much extractor tension can be a problem if everything else is ok. But your description is different. A round nosedives before it leaves the magazine and before the rim comes anywhere near the extractor. My explanation is that your feeding round is flying free instead of being a controlled feed. With lighter extractor tension, it is now easier for the extractor to snap over the case rim as the slide goes into battery.

Tom, even though different magazines affect your feeding, I don't believe your primary problem is magazines. Ramp placement (too far forward?) and angle would be the most likely culprit. Remove the recoil spring and mainspring housing, and gently hand feed a full magazine. Does that test give you any more information?

No problem hand feeding from the extended tube 8 rounders, just the flush fit 8 rounder. I also mic'd the magazines and saw that the feedlips on the extended 8 rounders were more tapered than the flush-fit. This results in the extended tube 8 round magazine holding the top round at a steeper angle than the flush-fit, allowing the top round to strike higher on the frame's feed ramp.

I measured my feed ramp. The angle is right on and the depth is exactly at spec. .360". I realize that increasing the depth to .400 - .420" might aid in feeding, but if I can identify magazines that don't cause a problem, I'll go that route.

I'm heading to the range for two days next week to actually shoot the pistol for the first time, so I'll give it a good workout and see how it goes.

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No problem hand feeding from the extended tube 8 rounders, just the flush fit 8 rounder.

That might be because the flush fit holds the top round up against the feed lips with more force. If so, that extra force would create more friction between the case rim and feed lips.

That additional friction would cause the cartridge to nosedive farther (if it could) as shown here:

PICTURE 404

That additional friction would also slow down the slide a little more.

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I also mic'd the magazines and saw that the feedlips on the extended 8 rounders were more tapered than the flush-fit. This results in the extended tube 8 round magazine holding the top round at a steeper angle than the flush- fit, allowing the top round to strike higher on the frame's feed ramp.

I'm not sure that really makes any difference at all, unless there's a time constraint on how long the top cartridge has to do its nosediving. If so, then starting off pointing higher would make for a feed ramp hit that's higher up. But, because of the gap between the front of the top round and the round below, I've a suspicion there's enough time for the top cartridge to nosedive down to the round below before contacting the frame ramp.

Only way to really know, I guess, is to soot up the ramp and see where the rounds hit. Would do it myself, but only have 7 round magazines.

Nice drawing, Dan. Also it relates to the many recent posts I have seen that claim extractor tension cured their nosediving. Not!

Well, Tom, I'm glad you got a chance to do some hand feeding. I agree that the ramp should be blackened with Magic Marker before your range visit so you can see where the rounds are hitting. A final thought, since you are an LEO. I think most people in the forum agree that 8 round mags have always been less than stellar because of their constant intermittent feeding problems. We know that the 1911 was designed to work close to perfect with 7 round mags. So the choice boils down to 1) near perfect with 7 rounds (assuming everything else is done right), or 2) having one extra round and being OK with "most of the time". That's what I would be thinking about, anyway.

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Nice drawing, Dan. Also it relates to the many recent posts I have seen that claim extractor tension cured their nosediving. Not!

Thanks for the kind word.

Have noticed the same thing a few times but just chalked it up to a mis- diagnosis. Here's how far the rim of a nosediver stuck on the ramp is from the extractor:

PICTURE 404

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A final thought, since you are an LEO. I think most people in the forum agree that 8 round mags have always been less than stellar because of their constant intermittent feeding problems. We know that the 1911 was designed to work close to perfect with 7 round mags. So the choice boils down to 1) near perfect with 7 rounds (assuming everything else is done right), or 2) having one extra round and being OK with "most of the time". That's what I would be thinking about, anyway.

That's exactly the point of my experimenting. I realize that the 8 round mags operate at the edge of reliability. If I can't get 200 rounds of duty ammo through them without issue I'll stick with 7 round magazines. I carried a Sig P220 with 7 rounders for about 7 years, so its not too important to me. To tell the truth, I'm on the fence about putting the 8 round mags up for WTT for some 7 rounders. We'll see how the range goes.

Tom... FYI... I have yet to find an 8 round mag that I would trust my life with. I'd rather have 7 for sure than 8 iffy in a gunfight. At current prices I can't afford the ammo to wring out every new 8 round mag that comes out, but all my 7 round mags have been used without issues for a long time now. I just watch the feed lips closely and don't let the springs get soft. Dan's mag illustrations note how increasing mag capacity increases chances for top round failure... makes sense to me.

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...note how increasing mag capacity increases chances for top round failure... makes sense to me.

It's not only the increasing magazine capacity. It's also the increasing number of rounds in the magazine - regardless of its capacity.

Support for the nose of the top round begins to deteriorate (for want of a better term) after the fourth or fifth round is loaded in the magazine. This lack of support is seen as the gap between the top round and the round below it. By the time a 7 round magazine is filled the gap looks like this:

The gap is the result of the magazine's angle and the effective aftward shift in the follower as each round is loaded. When contacted by the slide, the top round gets torqued down onto the round below as illustrated here:

Note how the bottom round is nose down against the "follower". I've some pics from others of the gaps under the top rounds in their 8 and 10 round magazines, but it's hard to tell if their gaps are any bigger.

The more I ponder it, the more I think I'll use the 8 rounders for range mags and 7 rounders for duty. The second round is more important than the ninth I reckon.

Wise decision, grasshopper!
Stay safe out there.