View Full Version : Bullet Setback - Inspect your Ammo!
http://tacticalunderpants.com/img/bullet-setback.jpg
In my Glock 19, I chambered the same round (Speer Gold Dot 9mm, 124gr) ten times in a row. Each time, I measured the overall length with a digital caliper. The length did not change even 1/1000th of an inch.
I performed the same test using a S&B 115gr FMJ round. The overall length changed by 3/1000th's of an inch after 10 chamberings.
In the interest of science, I performed yet another test using my H&K USP. I chambered a Federal HST .45ACP +P round 10 times in a row, again measuring for setback each time. There was zero change in overall length.
I performed the same test using a WWB 230gr FMJ round. The overall length changed by 1/1000th of an inch after 10 chamberings.
Being the nerd that I am I performed another experiment in parallel. I measured the overall length of several rifle cartridges. I measured a box of 20 FGMM rounds, 20 FN surplus rounds, and 20 Prvi rounds, all in .308 Win. The highest standard deviation of overall length between the three samples was the Prvi rounds at 0.0055". This deviation is 83% higher than what I experienced with the pistol cartridges while looking for setback.
Even with all of that "testing" done, it cannot be assumed to be statistically valid. It would take a much greater sampling of rounds to determine the actual effects of multiple chamberings on certain ammo.
It would appear to me that bullet setback, while a absolutely verifiable, can also be sometimes overstated on the Internet. If you re-chamber a round 3 or 4 times, there may not be much cause for concern. However, it is always important to check for setback as the alternative could be very undesirable! This scenario is very possible for folks who unload their weapon each day. Any visually verifiable setback should be a huge red flag that the round is no longer safe.
My intent with this thread is to dispell the horror stories that rechambering more than 1 time will cause an explosion with your pistol. I have read about folks marking rounds with a sharpie after 1 load/unload or simply discarding the round all together. For me, this is a bit extreme. Rotating carry ammo every few months fearing bullet setback just because a round is chambered a few times could be a waste of money. I am personally comfortable rechambering a round a few times before I start to worry about setback.
willowofwisp
08-22-10, 21:37
I think bullet setback is a larger issue with bottlenecked calibers such as .357 sig..where the neck is relatively short.
That is definitely possible. I do not intend for my two pistols to be conclusive for all scenarios. I think my test demonstrated setback is a fact but it is not as big an issue as it is made out to be (at least for 9mm and .45ACP)
I would be interested to see how a common round like .40SW with its flat nose would fair.
You tested four rounds out of the millions made every year. You are going to have to do a lot more testing to have any statistically valid data.
If you did more testing, I expect you would find that the number of rounds that exhibit this problem is very small, but the problem rounds will be visibly shorter.
There was a thread here not too long ago and the hollowpoint had closed up a fair amount from rechambering too many times.
https://www.m4carbine.net/showpost.php?p=708740&postcount=38
Worth a read.
I know it happens, but I have no idea how often. I learned about it the hard way when I had an HK USP .45. A Federal Hydra-Shok had been rechambered I don't know how many times until one day I noticed it was visibly shorter than the rounds in the magazine. Up until this point I had no idea this would ever happen. Now I'm more careful to rotate ammo so the same bullet isn't always the one being rechambered.
I know it happens, but I have no idea how often. I learned about it the hard way when I had an HK USP .45. A Federal Hydra-Shok had been rechambered I don't know how many times until one day I noticed it was visibly shorter than the rounds in the magazine. Up until this point I had no idea this would ever happen. Now I'm more careful to rotate ammo so the same bullet isn't always the one being rechambered.
Usually what I do.
Its not grossly overstated if you carry firearms for a living. As a law enforcement officer, I chamber and eject at least one round every day, and this does become a problem if the same rounds are used constantly. Many times officers will come to the range to qualify with one or two rounds really mashed down into the case. I rotate my rounds frequently to offset this problem.
Ten times chambering a round is not really a valid testing set. Try it a couple hundred times, like many officers and armed professionals do every year.
My new method for tracking chambered rounds is as follows:
When I clear the round that is in the gun, I take a peek at it to make sure it hasnt been tore up by the extractor or there are any other issues. If the round appears to be fine, I place it into an empty magazine. The magazine is used for once chambered carry ammo only. Alternatively you could use an empty box, but the magazine works for me. Once it gets full, I inspect, measure, etc and carry on. I have seen no quantifiable change in OAL thus far.
It does happen and in the aforementioned 357 Sig, too often. These were from a Glock and I used to unload each evening, not anymore.
http://img.photobucket.com/albums/v374/TOM64/357sig.jpg
Forget it was factory Winchester ammo.
Complication
08-23-10, 07:49
A question like "Fact or Fiction" is a bit silly. The answer is "Fact." But the real question is "Should I worry about it, given my carry habits?"
I get to the range once a week at most. That means I'm chambering/unchambering an average of 4 hollow-points a month, 52 a year. I try to rotate the chambered rounds every now and again, but I figure shooting up that magazine every 6 months does me just fine. If I only every chamber the top round, that's 26 chambers. If I rotate them every month, that's 4 chambers per round. On top of that, as Orionz does, I inspect the round (and if it looks beat up, I toss it in with my range ammo).
A LEO, on the other hand, who chambers a round every day, would chamber a round twice as much in one week as I do in a month. He, on the other hand, has to worry much more about bullet setback.
Finally, even if you were really anal about it and threw your once-chambered hollow-points into the garbage (instead of in with your range ammo), it wouldn't be that big a waste of money. If you chamber/unchamber once a week, that's about $50 a year. Is chambering a dangerously-setback round into your carry piece that you depend on for you life worth $50 a year? Probably not. Especially when the smart alternative is to rotate rounds every now and again and then shoot up your heavily chambered rounds at the end of the year (or twice a year).
John_Wayne777
08-23-10, 07:50
It is not "grossly overstated" if you spend time in an environment where administrative requirements mandate loading and unloading firearms on a continual basis. Often individuals in those sorts of environments are not firearms enthusiasts and do not know about the potential for bullet setback. Because of their ignorance on the topic they end up rechambering the same couple of rounds over and over and over and over and over and over and over again.
If you don't find yourself in that kind of environment you aren't terribly likely to see a lot of setback. If, however, I were to pull the handguns of 100 random police officers off the street I'd be willing to bet a pretty sizeable sum that at least 1/4 of them would have bullets with measurable, if not blatantly obvious, setback.
I would also take into account wear on the case rims. Even though administratively unloading a firearm isnt exactly a harsh exercise, look at the case rims closely after chambering and then unchambering repeatedly.
There are a ton of gouges, nicks and scrapes. Anyone else ever experience a FTX on a heavily used round? I have had exactly one with a torn case in 9mm.
It would appear to me that bullet setback, while a verifiable phenomenon (notably with FMJ rounds in my test) is grossly overstated on the Internet.
Diligent effort went into your post, and it is not without useful information. Your conclusion above isn't valid however. The issue of bullet setback is very real and shooters are wise to be attentive to it and proactive in response. It occurs in mil, commercial, new, reman, and handloaded ammo, from all manufacturers. There will be some variation in how many chamberings it takes to see it, and some loads and guns will show it earlier than others, but it does occur.
I don't even need dial calipers to illustrate bullet set back. I can remember chambering ball ammo in a 1911 and watching that round shrink in 3 or 4 loadings.
I don't even need dial calipers to illustrate bullet set back. I can remember chambering ball ammo in a 1911 and watching that round shrink in 3 or 4 loadings.
right when i saw the title i though this.
Early in my career I carried a Sig P220, and issue ammo was 185 gr. Winchester Silvertips, Seemed like if I stopped my squad too fast those things would set back. I bought a bullet puller just for that ammo. Never noticed it with .40.
Thank you all for the input. This thread has been a great example of the peer review process and I will update my original post accordingly!
This can also vary from lot to lot with the same brand of ammunition.
We once got a batch of 124gr +P Gold Dot, a premium choice in 9mm duty ammo by any measure, that had insufficient tension on the bullets, we had compressed bullets in as few as 3-4 chamberings of the same round. We also had bullets fall out of the case after several times being chambered.
Back to Speer that ammo went.
Personally I see no need to constantly load and unload one's pistol unless forced to do so by retarded policies.
When we trasitioned to 9MM (Glock 19s) back in '88, we were so short on ammo that we were issued a box of 50 rounds, period. They told us at the time the supply couldn't keep up with demand. A few years later, we had plenty of ammo and tons of turned in ammo. I ended up shooting tons of chewed up, set back into the case ammo thru my 9MM Glocks, no problems at all.
Complication
08-24-10, 07:20
Personally I see no need to constantly load and unload one's pistol unless forced to do so by retarded policies.
If you're constantly making trips to the range...
I've never measured my carry rounds to see how much setback, if any, has occurred from repeated chambering of the same round. I generally only unload when something goes in the safe or to the range (to replace with FMJ) or for cleaning. For that reason I don't worry too much about it ... and I when I do reload my carry ammo I usually strip the first couple of rounds off the mag and mix them up.
My only experience with real setback was in a recent 1911 Operator's course with Larry Vickers in ATL. During a string of fire my pistol stopped making the BANG noise. I tapped, racked, but still no noise. I looked down through the ejection port with the slide locked back and saw a round was sort of lodged, nose down in the mag causing it not to feed. LAV was standing right beside me so he actually took my pistol and pulled the mag out to see what was up. He let loose a couple of fun words then removed the offending round manually and handed it to me. The bullet was set back prob half way or more. It was freaky looking. NO idea if it looked like that when I loaded it into the mag or not. I was feeding loose rounds from my pocket into partial/empty mags between strings of fire and might have loaded it up without even looking down at it. I also picked up a few live rounds off the deck and stuck them in my pocket. We were ejecting live rounds setting up ball and dummy drills, etc. and I might have picked it up like that ... someone else's trash.
Setbacks seem to be a function of pistol design, caliber, and case material.
Some pistols have a steeper feed ramps, and steeper feeding angles when stripping off the magazine. This causes more pressure on the cartridge to be loaded.
Calibers such as .357sig have a very small crimping area, and are prone to setbacks. The most solid crimps are usually with straightwalled cases like the .40S&W and .45acp. The 9mm has a tapered casing and less grip towards the rear of the bullet. Some companies like Federal Cartridge will put a cannelure on the casing to increase case friction and help prevent setbacks on the 9mm.
Aluminum cases don't have a very tight crimp, and thus are prone to setbacks. Steel cases will sometimes have a weak crimp too.
Crow Hunter
08-24-10, 11:52
I don't rechamber except when cleaning and not always then depending on where/when I clean it.
The round in the chamber is fired whenever I go to practice as my very 1st cold shot.
This has several benefits:
-I don't keep rechambering rounds
-I don't keep defensive ammo sitting in a magazine forever going through heat cycles potentially degrading the powder/primer
-It lets me see where I that 1st critical shot would be with my actual carry ammo drawing from concealment
-It gives me the reason to go to the gun store to look at cool toys when I start to run out of carry ammo:haha:
-It keeps me somewhat on the cutting edge of ammo development instead of still using Winchester Silvertips that I purchased back in 1997.
To me, the extra $ it costs me to fire off that 1 round of carry ammo each time I go to shoot is more than outweighed by the benefits.
I am a civilian however and the only time I unload my G19 is during firing and cleaning.
Complication
08-24-10, 13:10
That's certainly a straightforward solution.
I think it's safe to say:
You want to rotate your carry ammo (rounds you've chambered plus probably shooting it all and buying new stuff) somewhere between (a) every time you touch your gun and (b) never. Where you lie along that spectrum depends on your carry habits (cop unloading every day vs. civvie unloading every range trip vs. nightstand gun that gets shot twice a year).
It's probably wise to pick a method that works for you (rotate your chambered rounds every few times, shoot the chambered round each time, ignore it and shoot all your ammo up every 3 months, whatever) and, if anything, err slightly on the side of caution. After all, the amounts we're talking about are a few cents or dollars here and there and the subject is: things that could save you or your family's lives.
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