View Full Version : Cartridge Dimensions, Bullet Shape, & Failures to Feed - Recommendations Sought
robmac
01-21-2015, 09:03 PM
As I go start my search, thought I'd ask for recommendations on a 9mm SD round with the shortest overall cartridge length and the "flattest" bullet. That's the basic question....
If anyone's curious, I'll try to be brief, but the reason for the question has to do with a 2.17% failure to feed rate on new PM9 (in 875 rounds, 19 jammed against feed ramp). Of 6 types of ammo tested to date, 3 FMJ & 3 hollow points, the only ammo with 0 failures (in 164 rounds) is Remington UMC. I noticed it's shorter than other rounds, so I got out the calipers and measured all of them (multiple dimensions actually, but length is most relevant). The detail might bore some, so unless anybody wants details, for now I'll just say there is a correlation of failures to feed with both cartridge length and bullet shape. The shorter overall length cartridges with moderately curved bullets perform better in my PM9 than longer cartridges with pointier bullets. This goes for FMJ & JHP alike. I expected it when I looked at the UMC, it makes sense, and the numbers proved it.
Yes, I did the follower sanding, and I'm not giving up yet, but if I can't nail it soon, it's going back. Expecting 1 failure to feed every 8 times you put in a new 6 round magazine wouldn't be reassuring to anybody, even if the chance you'll ever need it is probably only a tiny fraction of that number itself. So at least I have a good target ammo now (and lot of good choices if I want to practice TRB!! :rolleyes: ...) but nothing to carry. Remington HTP +P JHP was the best SD BTW, @ 3.7% failure, albeit in a small sample size. I know which magazines and which rounds fail most, and now I know at least this particular gun is in fact ammo sensitive (I realize some, or maybe even most, are not, so God bless...but this one is). Hope somebody might have some insight. There's a lot I like about the gun, I'd prefer to solve this if possible. Thanks.
Ikeo74
01-21-2015, 11:19 PM
Are you shooting reloads? What was the OAL of both the ones that shoot/load and the OAL of the ones that failed to load? Plus bullet shapes not working.
Joe A.
01-22-2015, 01:09 AM
Same problem with mine with wwb and federal champion. Rem/UMC has ran perfect for several hundred rounds. All defensive ammo has also ran perfect. The ammo I was having problems with would nose dive quite frequently.
I did did recently buy another 100 round box of Federal Champion and they ran perfect.
Wished i knew the problem. In addition to the follower modication, I trimmed some off the nubbin of the slide stop that the follower engages to lock slide. That seemed to help some but didn't entirely cure the problem. Need to try some more WWB and Federals just to see. But as I stated, Rem/UMC runs fine and I keep a supply of those.
hardluk1
01-22-2015, 07:48 AM
I have a cm9 and cw9 alone with a tp40 and found that that for HP 's gold dots and xtp's run great. and no practice ammo bought or loaded at home failed to cycle .
You might want to let CS take a look at it and see if the chambers a bit short. I have always used Georgia arms canned heat loads for the first 200 rounds as its been the same quality for decades. and always 124gr in a 9mm. To short can cause as many or more problems that 2 long. When I started loading 40sw what feeds in my kahr would jamb up in my m&p . Lengthen out the OAL buy by 40ths and it feeds like its greased in the m&p. They also feed well in my tp40 . 9mm were never picky ether .
I had to re-read your tread .
Now I would say you may not causing any problems but if you have a friend that shoots small pistols that you trust !! Give him your pistol and your ammo AND some money for ammo he likes to give it a go. I bought my first kahr from a very seasoned old match shooting owner that could not make his kahr reliable. For me its was 100% good to go from the first round and is the smoothest racking pistol I own. . Who knows why but a few years later and after some range meeting he now has and CC's a cw40. It was him that messed up some how . That pistol over 2100 rounds and 100% reliable with a wide variety of bullet types and now CC'd by my oldest daughter .
I also tend to not shoot much ammo from the big 4 companies. Georgia arms for practice ammo if not reloaded and underwood for carry . Always pluck test some of the ammo you use . That's all . Good luck
robmac
01-22-2015, 09:34 AM
Thanks guys. As for Ikeo74's question, no they're not reloads. On dimensions, there is as much as a 0.040" difference between the shortest FMJ and the longest, and while I'm neither a gunsmith nor an engineer, I work enough with tight tolerance small component assemblies to know that 0.040" is a BIG difference when it comes to function of critical parts that have a bunch of stacked up tolerances. On shape, my instinct was that a less pointy shape would be beneficial, and while that seems to be the case, it may just be coincidence.
Just now I decided to check the taper of each round, from the bottom of the case itself to the neck of the case, because it seems to me that as rounds lay on top of one another in a magazine, they do not lay "flat" as it were. Turns out, the UMC also has the smallest delta from bottom to top, smaller by 0.004" than the worst performer (with incidentally, the biggest delta). So it's flattest laying in the magazine, has the least taper, and that has to matter, even without determining how many degrees rounds will cant over the course of 6 or 7 rounds.
Hardluk, thanks for the recommendations, and I completely agree with your suggestion on having another user try. I've got the perfect candidate. I'll admit if it's me...hell, I hope that it is me! I have proven to myself before that a user CAN make a gun fail in other ways. I have a bit of difficulty figuring out how I could induce a feed failure though, where it nosedives, but I have considered that with extended mags (majority of what I tested because it's what I have), that my grip and form (or lack thereof!) can somehow make that magazine move independent of the gun grip, being that my pinky finger is on it. That could be a problem, especially again, with tight tolerance parts performing critical functions in fractions of a second under extreme conditions. I did have 2 failures with the flush magazine though, but that would make failure percentage less than a quarter of one percent with the flush magazine (and half that again if I measure from when I sanded the magazine). So I will definitely try your recommendations, on both shooter and ammo.
Thanks guys, I am more encouraged now with your comments and thinking this through. Will advise how it goes!
Tilos
01-22-2015, 03:07 PM
Thanks guys. As for Ikeo74's question, no they're not reloads. On dimensions, there is as much as a 0.040" difference between the shortest FMJ and the longest, and while I'm neither a gunsmith nor an engineer, I work enough with tight tolerance small component assemblies to know that 0.040" is a BIG difference when it comes to function of critical parts that have a bunch of stacked up tolerances. On shape, my instinct was that a less pointy shape would be beneficial, and while that seems to be the case, it may just be coincidence.
Just now I decided to check the taper of each round, from the bottom of the case itself to the neck of the case, because it seems to me that as rounds lay on top of one another in a magazine, they do not lay "flat" as it were. Turns out, the UMC also has the smallest delta from bottom to top, smaller by 0.004" than the worst performer (with incidentally, the biggest delta). So it's flattest laying in the magazine, has the least taper, and that has to matter, even without determining how many degrees rounds will cant over the course of 6 or 7 rounds.
Hardluk, thanks for the recommendations, and I completely agree with your suggestion on having another user try. I've got the perfect candidate. I'll admit if it's me...hell, I hope that it is me! I have proven to myself before that a user CAN make a gun fail in other ways. I have a bit of difficulty figuring out how I could induce a feed failure though, where it nosedives, but I have considered that with extended mags (majority of what I tested because it's what I have), that my grip and form (or lack thereof!) can somehow make that magazine move independent of the gun grip, being that my pinky finger is on it. That could be a problem, especially again, with tight tolerance parts performing critical functions in fractions of a second under extreme conditions. I did have 2 failures with the flush magazine though, but that would make failure percentage less than a quarter of one percent with the flush magazine (and half that again if I measure from when I sanded the magazine). So I will definitely try your recommendations, on both shooter and ammo.
Thanks guys, I am more encouraged now with your comments and thinking this through. Will advise how it goes!
Back during the time of the follower mod discussion, HarryLee built a mockup of a mag, with one side open, so the fanning could be viewed relative to different follower mods.
It was a very graphic and showed the variation of both ammo and follower angle.
You might want to search for it :D
The goal for me, doing the follower mod was to get every round in the stack to be pushed tightly against the lips of the mag, so the feed angle was always the same from the 1st to the last.
I found topping off the mag, after chambering a round, would cause the only problems I ever had...so I don't do that:p
jmo
Ken
robmac
01-22-2015, 03:14 PM
Makes perfect sense, thanks, I will look that up. Gonna drop it off to the bro in law tonight and hope he has no issues....me, I can fix!
hardluk1
01-22-2015, 04:46 PM
.040 difference between rounds is QC issues . I used all my 9mm mags when breaking my cm9 in . 6 round metal bottom and one with plastic bottom on a 6 rounds . A couple 7 rounders from my cw9 and a 8 rounder that's my standard backup mag for ether 9mm pistol. No extension mags just regular larger model mags . Only thing I did to my followers was smooth the edges . 40ths run out in your ammo ?? There you go . Show just what I mentions with big ammo companies QC. Some pistols don't mind that but some can be picky . Kahrs are know for tight chambers too.
I just checked 20 of my Georgia arms 124gr nato loads and they run from 1.134 to 1.128 for 20 rounds with most well in the middle. Thats why I like to run there ammo for a new handgun brake in.
O'Dell
01-22-2015, 09:28 PM
I had a PF9 years ago that refused to load WWB. When I measured the rounds against other bulk ammo, Federal, Remington, etc, I found that the Winchester ammo was a good deal longer than the others, but none of my other pistols seemed to mind. Anyway, I sold the PF9 because that was just one of its problems.
For the defensive 9mm I have, in order of shortest to longest:
-Federal HST 124grn
-PMC Starfire 124grn
-Winchester Silvertip 115grn
-Speer Gold Dot 124grn
I also have Hornady Critical Defense but bullet shape is too different to have the OAL mean anything in regards to feeding. That and I don't trust Critical Defense as a carry round.
I, too, have a PM9 and HST's have been flawless in it. First round feeds fine, a little clunky sometimes but has always chambered, even with slingshotting the slide.
robmac
01-23-2015, 08:26 AM
Thanks McE, that would seem to further confirm what I found. While of your SD choices, I've only shot the HST, it was the shortest of the 3 SD's I tried, and it was the best. In fact, in the first 41 rounds, 0 failures, so I thought I nailed it, but unfortunately in the next 41, it had 2 or 3 failures, I forget exactly, don't have the info with me.
I gave my brother in law the gun last night, with a ton of various ammo. My hope is he has zero failures, because operator error I can fix, and I think he's as experienced as can be, many years and an instructor. If he has failures, then I'll be confident if I have to go to Kahr. If that's the case though, I hope they can nail it, because I love the gun otherwise, but wouldn't drop the cash to start over. The thickness of my double stack alternative does not bother me, but the Kahrs in a good holster don't feel like anything is there.
Bummed I gave him all my magazines...now I can't shoot the CW9 until he's done!
Thanks all!
robmac
01-23-2015, 08:31 AM
Edit...my bad above...it was the Remington HTP that was encouraging, not the HST, but nonetheless I'm going to try the options McE gave as well, in that order. Appreciate the length info. SD ammo ain't cheap, so I'd rather start with the shortest, and of course nowhere in specs could I find lengths without your input. Big thanks.
berettabone
01-23-2015, 11:56 AM
I used Fiocchi 115 gr. to break in my MK. Had two FTE's in 300 rds....................after that, had a few ramp dives. I put the Fiocchi's next to my Fed. HST 147gr., and they were quite a bit longer. Have never had an issue with the Fed's. I think that length is a factor in some firearms. I still have Fiocchi left, and I will shoot the rest, to see if it happens again.
Ikeo74
01-23-2015, 01:02 PM
Some of the long rounds hang up in the magazine because they drag on the front of the mag as they move up in the magazine. This can cause nosedives and other problems.
I know that 1911's like shorter rounds, and Kahrs like longer ones.... when it comes to 45acp. Dunno for sure about 9mm, but never had a failure with my Kahr 9s
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