Bullet push-back. Is it really dangerous?

P&R Fan · Apr 29, 2015

I have read articles about bullet push-back causing high chamber pressures. I carry my Glock 23 and 27 quite a bit. I leave the mags loaded and when I unload the gun I put the round I had in the chamber in the drawer to be used the next time. I have noticed several rounds will have the bullet pushed back into the case after several loadings. I never put these in the magazines for fear they will cause a mis-feed. I am wondering how real the threat of them causing increased chamber pressures is? If the set-back is too severe I won't use them, but if it is not too bad I will use them as the first round in the chamber.
Do they cause a dangerous pressure increase?
Jim

steveno · Apr 29, 2015

how much shorter are they? the bullet being further into the case reduces the case capacity and with the same amount of powder pressure is going to increase. if it is 9 mm or 40 S & W and I would throw them away because they are high pressure rounds to start with. if is 45 acp I probably wouldn't worry about them as much but would only use them for practice.

da gimp · Apr 29, 2015

bad juju to use them......., chamber pressures rise dramatically, the deeper it is pushed. you need to start reloading with a taper crimp set correctly.

What brand are they, if factory? I'd hold off using that brand if it happens with a lot with it, or is it a new thing with just one box of factory loads?

litenlarry · Apr 29, 2015

I have noticed a few set back rds when unloading the rd in the chanmber..That is my G32, 357 sig rd..Winchester Ranger..
I just throw them away..

P&R Fan · Apr 29, 2015

I really can't measure how far the set-back is. Lets just say it's noticeable.
These are .40 S&W Winchester Silvertips.
I have fired them before and noticed no difference.
Jim

Alpo · Apr 29, 2015

This is a letter to American Handgunner magazine, January 1982. It is from Hercules powder company, telling of the "myth of Bullseye detonation", and why "light Bullseye loads" sometimes blow up guns. Part of the problem is, with a light load and large case, you can do a double charge. But the other part of the problem is in seating the bullets too deep.

The first two pix are the letter itself, and the third one is a blow-up of the drawing that accompanied it. The pressure increases from seating the bullet deeper are amazing.

Logic says that if it works with 38s, 148 grain wadcutters, and Bullseye powder, it will also work with 40, Silvertip hollowpoints, and whatever powder Winchester used.

Aticus · Apr 29, 2015

I have no pressure testing equipment but I do have a chronograph and have found a difference of 4 to 5 thousandths in bullet seating depth can have a significant effect on velocity in a 40 S&W. That tells me there is a significant change in pressure. That little difference in bullet set back is not noticeable to the naked eye.

If you are getting noticeable bullet set back in factory ammo you are chambering the ammo TOO often. I never chamber the same round more than 2 or 3 times. When I do rechamber a round I generally lay it on the top of the mag and let the slide forward to push the cartridge in as straight a line as possible into the chamber as I can.

da gimp · Apr 29, 2015

I was told that pressures can raise up to 40% if 255 gr LSWC Keith style .451 bullets are seated below case mouth in a .45 Colt ...by Ruger in around 1986.

I've seen pix of some nice model 27's/28's that blew on the .357 mag/.38 spc 148 gr HB LWC over Bullseye from around 1980 & before. there was speculation that the loads detonated instead of progressively burning as the powder lay in a shallow straight line in the bottom of the case. With Bullseye you can nearly load triple max charges in some cases....... I always considered it to be a powder that only the most meticulous reloaders & experts should use......I use the heck out of Unique, but won't use Bullseye.

Aticus · Apr 29, 2015

da gimp said:
I was told that pressures can raise up to 40% if 255 gr LSWC Keith style .451 bullets are seated below case mouth in a .45 Colt ...by Ruger in around 1986.

I've seen pix of some nice model 27's/28's that blew on the .357 mag/.38 spc 148 gr HB LWC over Bullseye from around 1980 & before. there was speculation that the loads detonated instead of progressively burning as the powder lay in a shallow straight line in the bottom of the case. With Bullseye you can nearly load triple max charges in some cases....... I always considered it to be a powder that only the most meticulous reloaders & experts should use......I use the heck out of Unique, but won't use Bullseye.

Gimp, some time ago I saw a friends Armscorp 1911 let go do to a half grain over max charge of 231. Blew part of the chamber off, the guts of the mag went out the bottom, cracked the frame and lifted the front of the slide part way off the frame rails. No injury to my friend thankfully. I don't know who made the mistake he or I but it scared the out of both of us. This was not a detonation. This was not paying enough attention.

Sudden increases in pressure can be exciting to say the least.

venomballistics · Apr 29, 2015

the importance of setback is in direct proportion to the specific load.
looking at a 357 magnum, running a max charge of a fast burning powder such as bullseye, yes, there is some potential for drama.
same cartridge with a max charge of IMR 4227 ... it could care less.
in fact, the load density with IMR4227 is such that setback might not be at all possible, as the powder is compressed, leaving no room for rearward movement

da gimp · Apr 29, 2015

Pecos Bill said:
Gimp, some time ago I saw a friends Armscorp 1911 let go do to a half grain over max charge of 231. Blew part of the chamber off, the guts of the mag went out the bottom, cracked the frame and lifted the front of the slide part way off the frame rails. No injury to my friend thankfully. I don't know who made the mistake he or I but it scared the out of both of us. This was not a detonation. This was not paying enough attention.

Sudden increases in pressure can be exciting to say the least.

Waugh....... I'd always considered them to be finely made, a little rough, but good to go........... was there a chance that the powder charge was even more off? Glad everyone came out ok.........

WR Moore · Apr 29, 2015

As others have commented some calibers are more prone to problems from setback. Relatively minor changes in seating depth can cause major changes in chamber pressures.

There is considerable documented evidence that .40 S&W will develop dangerous over pressures due to bullet setback from repeated chambering. Yes, guns have been severely damaged. Under normal circumstances the cartridge can experience very short term high pressure spikes with certain bullet/powder combinations. In fact, the FBI delayed adoption of the cartridge until a load was developed that avoided the spikes seen with 180 gr bullets. (They went with a Federal 165 gr load.)

In general, the ammunition makers suggest that cartridges not be chambered more than 3-5 times. They were never intended to be repeatedly chambered prior to firing. You can, by using ammo with cannelured bullets and/or cases, possibly extend this. [It used to be commonplace to place cannelures in the cases at the base of the bullet to help lock the bullet in place. The drive for lower prices has pretty much eliminated this except where ammo contracts specify it.]

Briefly: if you can see bullet setback, either throw the ammo away or reserve it for range firing only. I'd tend to be chicken and pitch it-or invest in a kinetic bullet puller and get it back close to OEM spec before firing.

Pootie · Apr 30, 2015

WR Moore said:
Briefly: if you can see bullet setback, either throw the ammo away or reserve it for range firing only. I'd tend to be chicken and pitch it-or invest in a kinetic bullet puller and get it back close to OEM spec before firing.

Not picking on you, just using your statement - What I question is if you are concerned about it why would you save it for range firing or some of the other -move it to the bottom of the mag etc. actions. It won't be any safer by shooting it at the range or waiting until some other time. I can understand taking it out of a carry mag so you don't have a useless gun in a tense situation, but if it's unsafe to fire .....

NCW Ray · Apr 30, 2015

And then there's this test: Battered Bullets: What Impact Does Bullet Setback Have on Function?

rwsmith · Apr 30, 2015

2 Things

Maybe you aren't sizing the case down enough so that
The expander isn't able to do its job.

A little more crimp perhaps?

Test the round by pushing a bullet on your workbench the bullet should not be pushed deeper into the case.

DeadAye · Apr 30, 2015

P&R Fan;
Stop by Harbor Freight or somewhere like that and get a micrometer or dial caliper - They may not be dead on accurate, but you can tell how much difference there is between your set back bullets and one right out of the box.

Aticus · Apr 30, 2015

da gimp said:
Waugh....... I'd always considered them to be finely made, a little rough, but good to go........... was there a chance that the powder charge was even more off? Glad everyone came out ok.........

We stopped shooting that batch and I brought them home and pulled them. I found one that was half grain over max and one a half grain under minimum. I don't think this was a gun problem. We sold a lot of those Armscorp 1911s as a basis for IDPA guns and never a problem.

tbgunner88 · Apr 30, 2015

I've heard of some people making a mark on the bullet with a fine tip marker to be able to notice any set back, it sounds like a cheap and easy way to keep a check on it.

okiegtrider · Apr 30, 2015

The short answer to the OP's question: Yes

Bullet push-back. Is it really dangerous?

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