I recently had a (horizontal) jam when I slingshotted the top (8th) round from my Checkmate mags (in my 10mm Kimber Eclipse Custom II).  Significantly, I've never had a jam when slingshotting a round from an almost empty mag.  I tried releasing the slide on the full mag using the slidelock instead of slingshotting, and didn't get any more jams.  But I've done some experiments chambering the top round (using the slidelock), and then ejecting and inspecting the chambered round.  I found that the bullet was usually getting pushed back slightly into the case, and after two or three trials (with the same cartridge), the bullet was sometimes pushed back enough to show a slight gap in diameter between the bullet and the case mouth (OAL decreasing from about 1.250 to as little as 1.200).  This was with DoubleTap 180gr Nosler JHP's (my carry round (along with 150gr and 200gr DT Noslers)).  When I tried the same experiment with a single round in the mag, there was still sometimes some bullet "push-in", but much less severe than with the full mag.

It may be that most 10mm 1911's might not suffer from this bullet push-in, at least not as much, but I don't have any experience with any other 1911's, so I can't really say.  Otherwise, my gun has been cycling well lately.  (The problem with bullet push-in is that, unless you eject and inspect the cartridge, you don't know if it's occurred or not.)

I tried the same experiment with Underwood 180gr Gold Dots, and there was much less push-in, although there sometimes was a little.

I then tried some DT 155gr Gold Dots (thinking the difference in the DT vs UW push-in was perhaps due to the different curvature of the Noslers vs the Gold Dots.  But the result was that the DT Gold Dots had just as much bullet push-in as the DT Noslers.  So I've concluded that UW must crimp their rounds more tightly than DT does.

One other comment: I've never noticed a difference in the amount of recoil that I feel with the rounds I shoot from a full mag vs an almost empty mag.  It seems to me that if the pressure increase due to the bullet push-in were very great, I should be able to feel it in the recoil.

I also suspect that any increase in pressure I get from the amount of bullet push-in I'm seeing with the DoubleTaps, might still be no more than the pressure with the Underwoods with no bullet push-in, because the Underwoods are slightly hotter than the DoubleTaps ... I think I can feel a slight difference in the recoil of the Underwoods vs the DoubleTaps.  I've also never seen any signs of over-pressure with the DoubleTaps (other than flat (filled-in) primer craters on the DT 200gr rounds).  I've occasionally seen missing primers with the Underwoods, but never with the DoubleTaps.

I have found that may Nosler bullets are slightly smaller in diameter 0.3990" - 0.3995" as measured in the pull-downs.

The setback can raise chamber pressures...If you hand load you can pull them down and resize the casing without depriming, then re expand the case mouth with just enough flair to accept the base of the bullet, then seat bullets to depth and in separate step apply the finish crimp.

best regards!

Mike, If you need help PM me!

I have noticed that some platforms are more prone to bullet setback than others. The 1911 is most definitely more prone to it say, than a Glock. I know this because I have owned six 1911's over my lifetime. I have also noticed, as you have, that some ammo manufacturers are more prone to bullet setback than others. Winchester, for example, comes to mind.

Agree 100% with Shadow....be wary of bullet setback creating higher pressures in your 10mm ammo, especially with the hot stuff.

Good luck!

Quote from: The_Shadow on November 29 2014 06:08:03 PM MST
[...]
The setback can raise chamber pressures...If you hand load you can pull them down and resize the casing without depriming, then re expand the case mouth with just enough flair to accept the base of the bullet, then seat bullets to depth and in separate step apply the finish crimp.
[...]

I don't have any reloading equipment, and even if I did, I don't think I'd want to mess with my (near) full-spec carry rounds.  (The only reloading I ever did was many years ago (mid 60's), for my .41mag Ruger Blackhawk, in order to get a mild round for target practice ... I just had one of those hand-reloaders from Lyman that looked like a nut-cracker.)

I think I'll just be very vigilant about looking for any signs of overpressure ... I always collect my casings and inspect them closely, to see what I can learn from them.  If I do decide that the pressures are getting excessive, I'll switch to the Underwoods.  But I really doubt that the DoubleTaps, even with the setback I'm getting, are hotter than the Underwoods without any setback.

I just wish that the 1911 chambering process weren't such a violent, chaotic process (at least, it is for my particular 1911, and I suspect that it is (at least to some extent) for all 1911's) ... seems like a crazy way to design a gun to me.  It makes me really appreciate the simplicity of my S&W69 .44mag DA/SA revolver ... I've actually been carrying it most of the time since I bought it last spring.

Thanks for all the responses.

BTW Mike, good catch on the setback issue, many people aren't as observant to the situation that can occur as ammo is cycled in their firearms.    As the load and unload sometimes daily, for various reasons this can happen over the cycling a little each time.

I sent you a PM to consider sending the affected ammo for pull-downs, We could document them here in the pull down section and show what's inside.  Afterwards I can put them back to where they would be safe to shoot and test again.

Even if they were done previously doing them again shows consistency of the loading process.

One other thing I may try on my next range trip is to try going back to my original Kimber mags (made by Metalform, I think), instead of the Checkmate mags I've been using for quite a while.  (Kimber has recently switched mags, to the Checkmates, I think).  The Checkmates have been more reliable for me in the past, but I've had some recent gunsmith work done, and that might change things as far as the best mag is concerned.  The original Kimber (Metalform) mags have weaker springs in them, compared to the Checkmates.  Since, with the Checkmate mags, the setback I'm seeing is much worse when feeding from a full (8 round) mag than when feeding from an almost empty mag (1 round), that implies that the problem is exacerbated when the round is harder to slide out of the mag.  So the Metalform mag (with its weaker spring) might reduce the setback.  Worth a try, but it won't be acceptable if it doesn't cycle as well as the Checkmates.

I tried chambering a DT 180gr JHP from a full (8-round) original Kimber mag (made by Metalform, I think), releasing the slide with the slidestop, and then ejecting and examining the cartridge for setback.  I saw no setback for the first cartridge (three trials), and a fairly small setback on the second cartridge on the 3rd trial (from 1.242 to 1.232). So the setback problem was improved over the Checkmate mag with the DT 180gr.  But not as good as the Underwood 180gr with the Checkmate mag (no setback at all there).  However, with the DT 180's and the Kimber mag, there WAS still some markings on the casings, and a bit of deformation to the front of the bullet.  I saw little or none of that with the UW with the Checkmate mag.  Next time I'm at the range, I'll probably try to shoot some DT's with the Kimber mag, and also some more UW's with the Checkmate mag, just to get more experience with the reliability of the cycling for those two situations.

Quote from: Mike_Fontenot on December 01 2014 06:57:02 PM MST
[...]
  Next time I'm at the range, I'll probably try to shoot some DT's with the Kimber mag, and also some more UW's with the Checkmate mag, just to get more experience with the reliability of the cycling for those two situations.

I did that at the range today, and had a jam on the 2nd round in the 3rd (Checkmate) mag of Underwoods, due to a primer falling out of the casing and staying in the gun, jamming the next feed.  So I'm going to stick with the DoubleTaps for my carry rounds.  (I had seen a few casings with missing primers for the Underwoods about a year or so ago (before I picked DoubleTaps for my carry round), but the primers apparently always got ejected along with the casing, and never caused a jam.

For the DoubleTaps out of the original (round-follower) Kimber mags, I had no problems with the two mags of 1+8 that I shot.  So that might end up being my carry mags, but more experience is needed before I make that decision ... for now, I'll stick with the DT/Checkmate combo, since I haven't had any jams in about 10 mags.

Mike this is why testing is very important to being sure things are working as they are designed and suppose to work.
It is one thing to get the performance but without the reliability it is a game changer. 

Good report and best regards!