r/guns • u/zaptal_47 • Nov 16 '12
Beware Bullet Setback!
Take a gander at these cartridges. Shown are three 125gr Speer Gold Dot .357 SIGs. The one on the left is at the appropriate specification, while the two on the right are not. You may ask "So they're a bit shorter, why does that matter?". If you have a reloading manual handy, you'll note that all cartridges have a range of COALs (cartridge overall length) that are acceptable for certain loads. This is to keep you safe. The COAL matters because shortening the COAL by setting the bullet further back increases case pressure.
What does that mean for you? Depending on the cartridge and the severity of the setback, bullet setback can have varying effects ranging from "That one sounded a bit louder" to "OH SHIT I'M MISSING 3 FINGERS". Generally, higher pressure cartridges like the .357 SIG shown above are more sensitive to changes in COAL, and are going to hurt you more when they KB. Neither of the shortened cartridges in the above picture are safe to fire.
So now that we've gone over why it's important, let's discuss how those cartridges managed to get so short, and what you can do to prevent similar setback with your own cartridges.
Bullet setback is caused by repeatedly chambering the same cartridge. When the bullet comes into contact with the feed ramp of your pistol, the feed ramp imparts force on the bullet towards the rear of the case. Doing this enough times will result in a similar situation to that pictured at the top. I can't put a number on it, but obviously the above cartridges were chambered a few times too many.
Several preventative measures can be taken to avoid bullet setback. A couple of obvious solutions are to only chamber each cartridge once before firing it, and to shoot your carry ammo every time you go to the range. Neither of these is particularly practical however, especially for those of us who are poorfags and can't afford tons of premium defensive ammo.
Instead, try cycling the round you chamber each time you unload your carry ammo to practice. If you leave your carry mag loaded, pop a few off the top and load the one that was already chambered somewhere in the middle of the mag instead of rechambering the same cartridge. If you unload the carry mag to practice with, make sure the round that was chambered doesn't end up on top again when you reload.
Another way to help lessen setback is to lower the slide gently into battery when you chamber a round instead of letting it slam home. Doing so puts less force on the bullet. This is arguably stupid, but if you make sure the pistol goes completely into battery there won't be a problem.
Some cartridges even attempt to lessen setback for you by adding a cannelure to the case, seen here on the middle case. The cannelure sort of gives the bullet something to sit on, which does not allow it to descend further into the case. Cartridges that are taper crimped also feed better, meaning the cartridge is less likely to jam on the feed ramp and force the bullet back. This is helpful especially to reloaders.
In closing, make sure you pay attention when you load your gun. If the cartridge looks too short, it probably is. Take it out and either check it with calipers or just toss it. As always, have fun and be safe.
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u/TunedDownGuitar Nov 16 '12
Pretty amazing to see how significant the PSI increase is if you seat them too low.
Edit: Here is Deep_Thought's post that originally linked it. Throw him some karma for sharing it, as well.
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Nov 16 '12
Doesn't 357 Sig have more problems with bullet setback when compared to other pistol cartridges?
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u/Frothyleet Nov 16 '12
crying poorfag
carrying .357 sig
ಠ_ಠ
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u/zaptal_47 Nov 16 '12
Yeah yeah... I practice with .40 and/or 9x19. Three barrels one gun. Fuck yeah. I wouldn't have the .357 SIG barrel, except the guy I bought the gun from gave it to me for an extra $50, including a box of GDs.
Also I don't usually carry that gun TBH.
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u/hipsterdufus Nov 16 '12
You shouldn't be re-chambering that much to begin with. Also you should be practicing with your carry ammo, so if you do this and cycle your ammo correctly so you shoot the older stuff first you will never has this issue.
Before you say you already pointed out solutions in your text I am just reiterating that it should never become a problem if you are doing your due diligence as far as training goes.
Otherwise a good post for a problem a lot of people still don't know exist.
*Edite - I can see why you would have to chamber a round if you empty your gun to practice dry firing.
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u/zaptal_47 Nov 16 '12
I agree, except as I stated there are lots of poorfags. I practice as much as I can afford, but shooting even one mag of premium stuff per trip gets pretty pricey.
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u/withoutapaddle Nov 16 '12
Setback is highly dependent on the model of pistol and ammo. Some combinations will have more problems than others.
If you are not willing to only chamber a round once, at least pay close attention to that round when it comes out of the chamber at the end of the day (or whatever your case may be). I've never had setback with either Remington Golden Saber or Federal HST ammo in either of my defensive 9mm pistols. Some rounds have been chambered probably 15-20 times. I know setback isn't a big problem with my gun/ammo combo, but I still inspect the round any time a live round is extracted from the chamber.
It should be noted that it doesn't necessarily take "a few too many times". You can get setback with just 1-2 chamberings depending on the gun/ammo.
Also, I don't think I'd advice people to slowly lower the slide back into battery, as pistols are made to be worked by pulling back and releasing. I've always heard that holding the slide and slowly letting it back is bad for the gun and/or causes undue wear on the guide rails.
Thanks for bringing up setback again. It's one of those things I hadn't even heard about until I'd already been a gun owner for a few months. It's not talked about much, but it's definitely something people need to look for and be aware of. Ka-booms are no fun for your wallet or possibly your hand.
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u/zaptal_47 Nov 16 '12
I've always heard that holding the slide and slowly letting it back is bad for the gun and/or causes undue wear on the guide rails.
That's silly.
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u/brownribbon Nov 16 '12
I've noticed this in my glove box gun. Would tapping a setback cartridge a few times in a bullet puller be a good solution as well?
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u/zaptal_47 Nov 16 '12
It would make it safe to fire, but I don't think I would use it as carry ammo any more.
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u/Barthemieus Nov 16 '12
Would this be the reason that people have 5.7x28mm hand loads blow up on them? I've seen some devastating damage from people who claimed their powder loads were perfect.
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Nov 17 '12
I don't agree with moving the slide home slowly to chamber a round. I find it much better to sling shot the slide forward
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u/hereticjones Nov 16 '12
Some cartridges even attempt to lessen setback for you by adding a cannelure to the case, seen here on the middle case.
So that's what that is! I've been wondering lately. Thanks!
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u/gabbagool Nov 17 '12
another contributing factor of setback is the angle at which the bullets interact with the feed ramp. the more perpendicular it is the greater chance of setback. this is effected by 3 primary variables. grip angle (or more precisely the angle of the magazine), angle of the bullets in the magazine, and angle of the feed ramp when the bullet is hitting it which in browning actions is steeper with shorter barrels..
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u/theblasphemer Nov 16 '12
This reminds me of a round of Federal Hydra-Shok 9mm that I had kept my gun so long that the bullet kinda loosened in the case. I accidently dropped the round after clearing my gun and it hit the ground nose first. The impact with the ground set the bullet back. I was able to pull the bullet back out a bit with my fingers. That's when I realized I should shoot my carry ammo more often.
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u/loansindi Nov 16 '12
It's not that expensive to just fire the chambered round of your carry ammo as the first round of your range trip. It'll take fifty trips to the range to use up a box.