Setback a big concern?

[fade1000]

Hello all. I've been lurking at THR for awhile, but now have a question I wanted to ask.

I've heard that chambering a round repeatedly can cause setback of the bullet, which in turn can cause kabooms.

If one was going to carry a round in the chamber does setback become a concern? For instance, do you eject the chambered round every night when you wipe your carry gun down (possibly resulting in setback when the round is chambered latter), leave it in and just steer clear of the trigger are while you wipe the slide down (seems dangerous), or just not wipe the gun down (possibly leading to rusting of the parts exposed to perspiration from concealed carry)?

I hope that makes sense. Thanks in advance for any advice you all can offer.

-Dean

 

[JohnKSa]

It can be a concern with some bullet weights in some calibers--particularly the 180gr .40 S&W loadings.

Repeatedly rechambering a round can cause setback, the same effect can also be obtained by seating a bullet too deeply into the case while reloading.

If you have to rechamber rounds repeatedly, then you should probably check to see if they're shrinking in overall length. You can do that with a caliper (and compare the length to a new round that has never been chambered), or you can set the rechambered round next to a brand new round that has never been rechambered and eyeball them to see if there's a height difference.

I rarely unchamber/rechamber--to facilitate that, I carry guns with very durable finishes so it's not necessary to fiddle with them each night.

 

[Vern Humphrey]

One trick is to use a Quenitics inertia-style bullet puller and a taper crimp die. If the round gets short, put it in the puller and give it a few whacks to "walk" it back to proper OAL, then run it through the taper crimp die to keep it in place.

You can also run new ammo through the taper crimp die -- it tightens the crimp and actually can improve reliability.

Of course the best solution is to shoot up and replace your carry ammo regularly.

 

[DragonRider]

I only will allow a rechambering of a carry round in 9mm or .45 twice, then I will put it to the side. .40 SW is my primary carry and will only allow chambering once before it gets put aside. I try to shoot a IDPA competition every 3 months with carry ammo and these 'extra' rounds to maintain the slightly different feel.

It's worth the money (for me) the 5-10 rounds per month this uses up of carry rounds.

John

 

[Wiley]

From what I have heard, the problem is predominately in .40S&W and pistols with unsupported barrels. Some Glocks are an example.

What happens is that the setback reduces the case volume which increases the presseure in the case. It then blows out in the unsupported area of the barrel. Commonly called a KB or KaBoom.

As long as you are aware of the problem it is not a big concern.

 

[Standing Wolf]

Simple solution: never unload your gun.

 

[coylh]

-- http://www.equipped.com/Kel-Tec_SU-16_Review.htm (good review BTW)

 

[ball3006]

How do you know for sure.....

that the cartridge you just chambered in your gun did not set back? The only pistol I have that ever set back a bullet into the case is my CZ50, then only if there are more than 6 cartridges in the magazine. Haven't figured out how to solve that one yet. I guess I am lucky. I don't have sweaty hands so I never see rust from touching my guns. My blued Kel Tec has not been wiped down for several weeks now. However, I use LPS2 as my wipe down lube which is a very good rust preventer.........chris3

 

[Deathrider1579]

My 1911 has a tendency to slam the first round into the lip of the chamber .

I have had rounds where the bullet is about 1/2 the way down into the caseing... Not sure what to do with those rounds.

-DR

 

[Ryder]

How do you know for sure that the cartridge you just chambered in your gun did not set back?

Does the refridgerator light go out when you close the door?


You can test your crimp by firmly pressing the bullet down onto a hard surface. If they hold overall length doing that they are probably ok. Even so some guns chamber smoother than others and the best way to be sure is to eject unfired rounds after chambering and examine them.

Crimp strength is not just a problem in autos. A light crimp can cause "reverse setback" in revolvers due to recoil. Lengthened rounds can bind your cylinder.

 

[pete f]

And in some calibers (40smith being one) the case wall is thin enough that really trying to get a good crimp will sometimes bulge the case lower down and cause the round not to chamber, delicate issue. 45 colt (or LC to some) will also bulge the case walls when you try to lever on a hard crimp if you do not have the die set just right.

 

[mete]

Tests [Hirtenberger]have shown that with the .40S&W if the bullet sets back .10" you will DOUBLE the perssure from 35,000 to 70,000 psi !! Just don't let the slide slam forward .

 

[Richard.Howe]

Here is a discussion on that very topic. I learned a lot.

http://www.thehighroad.org/showthread.php?t=164968

 

[fade1000]

Thanks

Thanks for all of the responses everyone.

-Dean

 

[Rockstar]

I don't see merely wiping the slide down while the pistol is loaded as a problem, assuming reasonable intelligence and judgment on the part of the wiper.

 

[Technosavant]

It depends greatly on the caliber. .40S&W, setback is a major concern. .45ACP, no worries. I still don't chamber a particular round more than 2 or 3 times before setting it aside- the 4th time it gets chambered, it is at the range just before the round gets fired. Sometimes I notice some setback, sometimes I don't notice any at all.