What is bullet setback and is it dangerous?

[Potatohead]

thx for article steve

 

[Muddydogs]

I have been carrying a .40 for 5 years and have not had any set back issues. I read all the posts about how dangerous set back was when I first started carrying so I was always checking my rounds after a few chambering’s using new factory rounds as a guide. Once I started to carry my hand loads I of course new the OAL range of the rounds so checking is even more accurate and I have yet to find one that has set back. My pistols stay loaded except for cleaning and dry fire practice so the rounds are not chambered a lot.

As of right now my practice is to every once in a while transfer the top 2 rounds in the mag to the bottom and then about every 6 months check the rounds in my two carry mags for OAL and general wear. The only rounds I have pulled from the mags have been rounds that have developed an edge in the case where the base of the bullet rests. The bullet in these rounds gets pulled, the case resized and everything reloaded. I don't shoot my actual carry rounds but do shoot rounds loaded just the same except instead of new factory Gold Dots I picked up 1000 pulled Gold Dot.

 

[Potatohead]

the OAL range?

 

[Potatohead]

article was pretty interesting. made me feel better thats for sure

 

[Muddydogs]

the OAL range?

Nothings perfect, case heads can be different and the bullet base to ogive isn't always exact from bullet to bullet and depending on the nose design like an exposed lead bullet the measurements can be even further off. If i'm seating bullets to an OAL of say 1.125 it could very from 1.120 to 1.130. Gold dots are fairly close and stay around +- .003. I have loaded some pulled .40 bullets that vary as much as +- .010 and required I reduce the load as they showed some pressure signs at my normal .40 load. This is with 165 grain bullets. A couple thousands of difference is not going to make any difference.

 

[WardenWolf]

My friend nearly blew up his XD .40 with a set-back cartridge. Lucky I spotted it and told him to dispose of it.

 

[TfflHndn]

357 Sig is another round that can have setback problems because the case doesn't hold the bullet very firmly.

If you are really concerned about setback, get a bullet puller (the inertial kind, looks like a plastic hammer) and you can tap the bullet back to proper length or longer and if you load that caliber you can reseat it at the proper length. If you don't reload you can still tap the bullet out to a length comparable to others. If you really must unload and load daily, use a sharpie to draw a ring around the bullet at the case mouth. If the line disappears into the case, you know the bullet is setting back and you can tap it back out to the appropriate length.

 

[Muddydogs]

357 Sig is another round that can have setback problems because the case doesn't hold the bullet very firmly.

If you are really concerned about setback, get a bullet puller (the inertial kind, looks like a plastic hammer) and you can tap the bullet back to proper length or longer and if you load that caliber you can reseat it at the proper length. If you don't reload you can still tap the bullet out to a length comparable to others. If you really must unload and load daily, use a sharpie to draw a ring around the bullet at the case mouth. If the line disappears into the case, you know the bullet is setting back and you can tap it back out to the appropriate length.

Tapping the bullet back out and continuing to load it is bad JuJu. The case neck tension could be compromised, if its factory rounds the sealer they use will be broken and you are not sure of the neck tension. Plus unless you have a micrometer and measure the OAL its just a guess. If you don't reload then shoot the rounds ever once in a while before any set back and if in doubt just get rid of the round.

 

[1SOW]

The .357 SIG cartridge when new sort of made set-back famous. It was typically in a SD semi-auto and the short bottle-neck case doesn't provide as much neck tension/strength. Clearing the pistol at the end of the day and reinserting the same chambered rd led to lots of talk about bullet set-back problems.

As said, it's especially dangerous in high pressure cartridges like 9mm, 357 Sig and 40cal using SD hot ammo

 

[gamestalker]

Good question, and is an especially good time to address, considering so many new reloaders coming into this hobby, and at such a high rate.

As for what concerns set back presents, it can cause chamber pressures to increase unpredictably, and potentially to dangerous levels. I think a good example of this is, Speer did a test using a 9mm cartridge. they developed a normal load that was producing a reasonable average pressure of 28,000 cup at a given OAL. Then they used the same load, but this time they seated the bullet .030" deeper. The result was pressures went to 62,000 cup, that's over double the pressures as opposed to the original OAL.

Measure a single round, and then cycle it through your firearm, as you would normally do each time you load it for carry. Then take that one bullet and cycle it through the firearm 15 times or so, do it in the same manner as you normally would. When you finish, measure it again, calculate the difference and you'll then know if you have a problem, or not. If it sets back more than just a few thou, I would probably soft chamber to load each time from now on, rather than just dropping the slide. But if you experience a lot of set back, like more than .010" after only a couple times of cycling it, I would look closer at my reloading process, especially my crimp.

GS

 

[Potatohead]

muddy, i was meaning what is OAL?

 

[Potatohead]

use a sharpie

thx TFFL i will try that just to make sure

 

[Potatohead]

thx gamestalker..i will try that

 

[Muddydogs]

over all length of round. from bottom of case to nose of bullet.

 

[steve4102]

My friend nearly blew up his XD .40 with a set-back cartridge. Lucky I spotted it and told him to dispose of it.

Good job in catching that for him, but how do you know this round would have "blew up his XD 40"?

 

[WardenWolf]

Because the round was pushed back so far its shoulder was literally below the rim of the cartridge. Most likely sitting directly on and compressing the powder charge. As little as 1/10 of setback in .40 S&W will double the pressure inside the case, and this was at or beyond that. Even though it wasn't a Glock, which would make it more prone to case rupture, it would still have likely destroyed the gun or at least cracked the frame.

 

[Potatohead]

Good job in catching that for him, but how do you know this round would have "blew up his XD 40

i was wondering the same

 

[steve4102]

Because the round was pushed back so far its shoulder was literally below the rim of the cartridge

Did you read the article posted on set back in the 40. Pushed back all the way and no "Blow up".

 

[918v]

As little as 1/10 of setback in .40 S&W will double the pressure inside the case, and this was at or beyond that.

Can double the pressure, not will double the pressure.