Hi all,
I have a Sig 1911 that cycles ball with 100% reliability, but will not cycle cartridges with flat nosed bullets.

With the 255gr Buffalo Bore hard casts, it cycles them most of the time with an occasional failure to go into battery. I tried polishing the chamber with no effect.

With the 230gr Buffalo Bore jacketed flat nosed, it has assorted failures, at least one per magazine.

Is this just a shortcoming of the 1911?  Is it just my particular gun?  Is there something I can do (or that can be done) to fix it?

I assumed it was just a 1911 thing, but I have friends who told me that their 1911s will cycle that stuff just fine.

I can't comment about those particular bullets or Sig 1911s, but I shoot 200gr semi wadcutters all the time in my Springfields and my dad’s Kimbers.  Old 1911s and some new 1911s can have issues with non-ball ammo.

1911s are very sensitive to overall cartridge length, magazine type, and bullet nose shape. To name a few.

Yep.

My Sig Tacops is sensitive to my reloads using 200 gr plated hp's.  It feeds all types of factory loaded ammo with no issues and feeds my round nose reloads fine.  But it just doesn't like those flat nosed hp's.

I good 1911 gunsmith can tune the gun to chamber an empty case and you'll not have issues any more.

Thanks for the advice. Time to find a 1911 gunsmith.

With the slide off the gun and barrel removed from the slide, how does a round hang om the extractor hook?

Slide a round up from the bottom of the slide so the rim is behind the hook.
The hook is often so far out from the breech face and extractor force to the left so low  the round droops more than it should.

This 'bullet low' type position puts an absolute premium on the nose hitting the feed ramp at just the right angle.

The extractor should push the rim against the left of the breech face enough it does not droop excessively.

You can gently bend the extractor to increase the force it applies to the case head.

Sig 1911s have external coil spring extractors, so that won't work, but it's good to know in any case, thanks.

An 'improvement' that is not.

If you watch the slo-mo feeding cycle of the 1911 you'll see that as the bullet is stripped from the mag the bottom of the ogive "bounces" off the feed ramp, then the top of the ogive "bounces" off the top inside of the chamber, and then it shuffles it's way into battery.  Flat-nosed bullets, with their radically different ogives, interrupt this designed feed cycle.

Here's the only link I've been able to find of the video, watch past the compemsator and AR shots for the 1911 stuff.  There's a close-up of the cutaway 1991 feed cycle.  Truly amazing video, even if it's a flash movie.

https://www.trippresearch.com/tech/video.html

I'm sorry but no. The way the extractor holds the round is a non-factor in the feed cycle. Have you tried different magazines?  Especially very flat nosed rounds are very sensitive to mag geometry, angle the round is held at, release point, bullet protrusion, etc.

Aye. My M1991 eats LSWC just fine if they were loaded straight into the case without a bulge. With XTPs, I had to seat them a bit short and use GI mags to avoid the cavity catching on the ledge between the barrel and ramp.



 

Try magazines with different types of feed lips. Mine likes the wadcutter type. I get best reliability with HPs and FPs when they are seated to 1.200". Verify that your recoil spring isn't too old, but I doubt that is the problem.

Yup, wadcutter mag feed lip profile... They are designed for it.


 


ETA- This issue OP, is why a lot of modern JHP .45 ACP ammo has changed from the early JHP designs to more closely replicate an FMJ profile where it counts.

So everyone had been doing it wrong for many many years?
"angle the round is held at" would be the extractor.

How the extractor holds the round determines the angle it hits the feed ramp once the bullet is not  on the magazine follower.
The magazine follower, the extractor, and the feed ramp ALL lay a part in getting the bullet into the chamber.

One thing I have always done it to put a semi-wadcutter beside a ball round and see how close the overall profiles are.
The slight shoulder of the semi being above the case is often required for reliable feeding.
The nose being at about the dimension of the round nose at similar places.

And those slightly altered feed lips (there are dies available to help form them) can make a large difference.

Feeding ball is easy.
Getting semis to feed requires everything to be 'just right.'

The fact that this is an external extractor gun does not alter the basic feeding behavior and geometry..

I had some issues with my sig 1911 emperor scorpion feeding 185gr SWC reloads. it would cycle everything else fine but occasionaly it would FTF the last round with the SWC. I narrowed it down to one of the factory mags causing the problem. With my CMC power plus 8 and 10 round mags it is flawless.