Bullet Set-Back and You.

[Panzercat]

My Remington r1 Threaded has been great. It feeds everything and does not fail. It even consumes those problematic semi-wadcutters with ease. I love the gun.

But it's hard on ammo. Set-back is not a phenomenon I've witnessed before. In fact, i didn't even know it was a thing until i started noticing my defensive ammunition shrinking. My xdm never had a problem with shrinking ammo, nor any other pistol I've owned before it. Sure it probably happened, but not enough for me to notice.

The r1, however, abuses my ammunition. I'll come home at the end of the day, eject the round and actually notice my 45acp shrank. So of course i research this phenomenon and readup on rotating ammunition etc, but my question then becomes how much should i care? It almost feels like this is an internet meme thing creating a bunch of drama when th solution is to just fire the darn bullet anyway.

So i guess the question here is two-fold. First, is set-back going to damage me or my gun? I imagine it'll create some higher pressures, but enough to worry about? Second, is this a symptom of a bigger problem? Again, my pistol is doing this fairly often.

Anyway, happy trails and thanks again.

[earlmck]

That's a really good question Panzercat. And especially since we know that short, fat cases are really sensitive to big pressure changes with little length changes. I put the question to QuickLoad using Lyman's 255 grain LSWC and COAL 1.275" in a 5" bbl., and here is what QL says:

With 5.2 grains Bullseye, 865 gfps and 19K psi, 65% case full of powder.
Same 5.2 grains Bullseye, dropping COAL to 1.140", 985 fps and 41K psi, 111% full (so I don't think there is room to get shorter).

With 6.0 grains Unique, 880 fps and 19K psi, 77% case full.
Same 6.0 Unique dropping COAl to 1.175", 970 fps, 32K psi, 111% full.

With 6.5 grains Herco, 870 fps and 18K psi, 85% case full.
Same 6.5 Herco, dropping COAL to 1.200, 940 fps, 26K psi, 111% full

With 9.5 grains Blue Dot, 880 fps and 18K psi, 97% case full.
Same 9.5 Blue Dot dropping COAL to 1.230", 930 fps, 24K psi, 112% full.

With SAAMI max pressure 21K psi, all the short loads do exceed SAAMI, but you might not notice the Blue Dot load whereas I'd guess the Bullseye and Unique loads might get your attention with almost double or at least exceeding by over 50%.

So I'd say it depends on your load how much trouble you could get into...

Oh yeah, I just tried with WW231, 5.6 grains for 857 fps and 21K psi, can shrink to 1.13" which would get 975 fps and 52K psi. So that would surely be a Wow!

[JerryB]

Earl, since the .45acp chambers on the case mouth could you do a roll crimp and still chamber ok?

[J Miller]

Panzercat,

Hand loads?
Factory loads?
Both?

Joe

[Pete44ru]

.

IME, bullet setback in 1911's is usually caused by a feeding-into-the-chamber issue, cured mostly by a higher magazine catch and/or new magazine(s).

.

[GunnyMack]

If this Ammo you are noticing set back in is factory defense loads I'd get chamber length/throat checked, if just chambering a round causes it then chamber throat isn't right...
If your reloads are doing it then you need some more crimp.
As mentioned, headspace on the case mouth so ya gotta get it just right.

If you chamber a round then eject it loaded does the bullet move?

[Sixgun]

If this Ammo you are noticing set back in is factory defense loads I'd get chamber length/throat checked, if just chambering a round causes it then chamber throat isn't right...
If you chamber a round then eject it loaded does the bullet move?

Right....factory loads should chamber without any setback...they know these things and will not load bullets with an ogive that will press against the rifling....it's called "Saami specs". rare..but it does happen with off the wall companies.......Give your barrel a good "look see" right past the chamber mouth to see if there is anything unusual that looks out of place.

Handloads? Common, especially with semi wadcutters where the front driving band is full diameter.....seat the front band even with the case mouth. -----6

[Panzercat]

Panzercat,

Hand loads?
Factory loads?
Both?

Joe

Sorry, relevant data, huh?
Factory.

The sig vcrown stuff and hst. Not exactly scrub defensive ammunition. Standard pressures, no +p

[AJMD429]

I've read (either the Speer or Sierra reloading manual I think) that in the 9mm Luger, a very small shortening of the round can cause a near-doubling of the pressure, and thus be very dangerous.

If the 45 ACP can be considered just a larger version of the 9mm (I realize that's not entirely true, but they are proportionally pretty similar, and fired in similarly-designed guns), then one might surmise the 45 ACP could develop dangerous pressures with bullet set-back as well...

Perhaps a more 'segmented' crimp' like the 'rifle' type Lee FCD would work, if the non-crimped parts of the case still would hit the chamber-end.

[piller]

I haven't reloaded anything for .45ACP or 9mm, but I am pretty familiar with the Lee FCD for rifles. It seems as if a Lee FCD rifle style would probably work for the .45 ACP to prevent setback. I have had 1 .45 auto, and have had a cartridge suffer setback one time after it had been cycled a few times. I used an impact bullet puller to move the bullet back out and messed with my .45 Colt dies to tighten it up a tiny bit. I had to try, adjust, try again. After a bunch of tiny adjustments, it seemed right. It cycled without setback, and was then set aside to be fired at the range the next trip. When fired, there was no noticeable difference with it and the other rounds fired. I made sure to avoid a roll crimp.

[earlmck]

So just how much did your shortest one shorten? From playing around in QL it looks to me like if the worst is shorter by .05 or so -- go ahead and shoot 'em. If some can shorten by 0.1" -- well that might be a bomb. If some can shorten by 0.15" -- now that is a bomb.

[J Miller]

Panzercat,

How is the ramp and throat on this pistol? I've had a bunch of 1911s and on a couple the ramps were rough and steep and on a rare occasion I'd get bullet set back. So I polished and throated a couple of them and that solved the issue.

Joe

[Nath]

Panzercat,

How is the ramp and throat on this pistol? I've had a bunch of 1911s and on a couple the ramps were rough and steep and on a rare occasion I'd get bullet set back. So I polished and throated a couple of them and that solved the issue.

Joe

I'm with Joe on this one .

N.

[marlinman93]

This setback may be from the bullet nose hitting the feed ramp hard and pushing the bullet back into the case. A simple check is to feed a single round into the chamber and then gently lower the slide. If it fully closes, then there's no chamber issue and it's the ramp.
My concerns would be if the loads are hot and setback puts them over safe pressures. I'd also be concerned about accuracy with bullets not consistently at one COAL.