Bullet setback question


March 21, 2009, 12:31 PM
I have read on here and other places about the danger of chambering the same .40 caliber round numerous times because of bullet setback. I recently "saw the light" and switched from .40 to .45 in my carry gun and was just wondering if the risk of bullet setback was the same in the .45 as it is in the .40. I carry a glock 36 with one in the chamber but always clear the chamber when I get home and store it just magazine loaded. Before with my .40 I would rotate the rounds, and am just wondering if I need to do the same with the .45.


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March 21, 2009, 12:42 PM

Bullet set-back can happen with any straight-wall semi-auto pistol caliber.

They are not firmly roll-crimped because they must headspace on the case mouth.

If you want to keep tabs on it?
Take a black Sharpie pin and mark a ring around each new cartridge touching the case mouth before it is chambered the first time.

A quick glance will tell you if the black ring has disappeared into the case from continued chambering.


March 21, 2009, 12:54 PM
I would imagine that the likelihood of bullet setback is more a function of ammunition quality than of caliber. You could get a lot of ammo with light crimps that will set back on the first chambering, or with tight crimps that will never set back.

I think a more important question is why are you clearing the chamber each day? If you don't do that, the setback issue will go away. Also, the more administrative manipulation you do the more opportunity you have to make a mistake and be rewarded with an unwanted BANG! Why not just load the gun and leave it that way until you shoot it at the range?

March 21, 2009, 12:56 PM
Thanks rc for the quick reply!

I figured as much but just thought I'd ask. I just wasn't sure if since the .45 operates at lower pressures than the .40 if that would make it less sensitive. I guess in any case it's better to be safe than sorry.

March 21, 2009, 12:59 PM
Hammer, in response to your question, I have small children, and even though I keep my gun locked in my safe after I take it off, I just like the added security of them being too small right now to rack the slide if they found their way into the safe somehow.

March 21, 2009, 01:03 PM
Here's a little trick that works pretty well. Strip-off 2 to 4 rounds from a full magazine. Load the gun with this partial magazine. Replace the partial magazine with a full one. When racking the slide, do so with a certain measure of violence-pull/push it back until firm contact with the frame stops the motion, let the slide cycle freely to put the gun back into battery. This technique is particularly effect with 1911 variants.

The Lone Haranguer
March 21, 2009, 02:04 PM
I've fired setback .45 rounds with no ill effects (on the range only, not for carry). I would not do it with a .40, which has a bullet taking up proportionately more of the case and operates at twice the pressure.

March 21, 2009, 06:09 PM
I have experienced the set back issue in all of my 45 acp 1911s. i have learned that I can limit it by +1 the pistol with an empty magazine, sort of like the way jfdavis58 explained, only i just put one round in an empty mag and load the pistol. when I charge the weapon , I dont charge it forcefully, thus putting less stress on the chambering round. I do this with all of my 1911s and so far it has worked.
I have a Glock 31 in 357sig that does have a set back issue, although I do not fire the impacted rounds for fear of losing fingers or a hand. I do not have the set back issue on any of my other Glocks (22,21,30,17).
I always unload my pistols when I am at home, even my carry weapon. I do it for safety purposes.

March 21, 2009, 08:52 PM
Ok I have a question. Why not just drop a round into the chamber and release the slide? What is the advantage of letting the slide strip the round out of the magazine?

March 21, 2009, 09:01 PM
Well, having the extractor catch the case rim is a big one. On my Springfield V16, it will not grab a case if it's already in the chamber, to my thus-so-far knowledge. However, on another 1911 I have, it will (as well as Glocks). Maybe it depends on the firearm entirely, or just the extractor. Either way, not having that extractor grabbing on to that case could lead to a bad malfuction if you had to depend on it to save your life.

March 21, 2009, 09:49 PM

To expand on D-Day's post, when a round is stripped from the magazine, it slides up the breech face and the rim slips under the extractor hook. If you just drop the slide on a chambered round, the extractor hook needs to be pushed out to go over the rim. There may not be enough space or spring tension for that to happen.

So maybe no extraction, or maybe a broken extractor. In any event, it's not recommended.


March 22, 2009, 07:26 PM

+1 Robriboflavin

When you drop a live round into the chamber and then drop the slide into battery , there is a very high chance that you will damage the extractor. On a 1911, you will end up either severely damaging the extractor or snapping it off , taking the pistol out of service. I have also seen damaged case rims as a result of this type of loading.

I have not heard of a pistol design/manufacturer that allows this type of loading, but I havent been around as long as some out there.

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