how many times will you chamber a round

[Boriqua]

How many times are you comfortable chambering the same round in a semi auto handgun

I should know the answer to this having been shooting for some time but.... At one point I had no problem rechambering the same round over and over.

At others I would swap out the first chambered round for another in the mag and for some reason ... Now I obsess over bullet setback. Perhaps because I only started reloading some 5-6 years ago and generally think more about cartridges. Before that didn't give it much thought.

So how many times before you think you should just send it down range?

[QuietM4]

How would the bullet setback increase with each cycle? Unless you are constantly changing pistols while using the same ammo, the barrel chamber dimensions don't change, so the bullet isn't going to move. I won't use hand loads in my edc gun, so it's all factory ammo for me. If you are using hand loads, why don't you just measure the OAL compared to other rounds in your magazine.

I don't even think about it, but I also don't unload my gun every day...just once a month when I clean the pistol.

[Boriqua]

The chamber size doesn't change but the bullet is hitting the ramp each time. I have had some guns with a rather steep ramp and you can feel the transition as it enters the chamber. My Rick It stands were like that. A definite thwack clunk as it chambered. I only carry factory ammo and don't worry about my reloads since once chambered they are shot. I mention reloads because it's one of those things that once you realize how it all works .... Well sometimes to much info is a bad thing.

[QuietM4]

Grab a set of calipers and measure it. Easy way to answer your question.

It won't do you any good to measure it against the other rounds in the magazine...they will all be slightly different...even factory rounds aren't all exactly the same dimension...they just have to fall within a spec +/-. You could take a brand new round, measure it then chamber it and re-measure. Record your results, and check it each time you chamber it. It might change, it might not. But as long as it's in SAAMI spec, I don't see an issue.

Another way to look at it; if a manufacturer released a pistol that, when chambering a round, created an unsafe condition in the round, their lawyers would s*** a brick and that gun would be recalled or it wouldn't exist. And you would have most likely heard of this issue.

[Boriqua]

I like the idea of measuring even if it's just for my own peace of mind.

I probably download my gun 3-4 times a week since I like to dry fire my carry guns even if it's just 20 or so times when I do it. I also like to practice draw and dry fire. Then. ... Back into the gun.

[Tenring]

Bullet setback is real and dangerous.

I don't keep a count but do inspect my rounds.

Not so much an issue with my reloads, but have seen some manufactured ammo with some short rounds. Speer had some major issues years ago and I would not even shoot their stuff for a long time. Not on topic but...

[DrEarlCordova]

Once, maybe twice.

[was21]

2 things can happen with repeated chambering.... bullet setback and possible primer degradation due to priming compound cracking.
The first happens more often than most know because they just fire off the round and never know it even happened.
Pressures do go up on deeper seated bullets.... whole stack of reloading manuals / articles showing pressure increases.

Semi auto rifles without springloaded FP’s ( AR15/10) will show light dimple on primer from chambering... not uncommon.... repeat enough times and the priming compound can fracture and dislodge causing erratic ignition.

Some will mark the primer with a sharpie after 2-4 chamberings and then just rotate the round to the bottom of the mag .... when the whole mag is marked/cycled through then the mag full is fired off... assuming none were setback.

With that said...
Other than a few batches of factory recalls bullet setback in factory ammo is rare, especially if it is a sealed round as in some govt/le spec’d Ammo. Just choot it and don’t fret it unless you can see the setback.
YMMV....nothing is guaranteed with ammo! Over many years smithing I’ve pulled numerous squibs..... replaced several blown barrels .... all with factory ammo. Many more due to reloads.

Pulled down some factory SD 45 one time that had 3 /10 with NO flasholes drilled....

[Flash]

SAAMI specs maximum OAL, not minimum and OAL doesn't get longer with time/rechambering.

The only setback test I've ever seen done scientifically was by CCI/Speer and it showed it wasn't a major problem as pressure stayed in a safe range. There was also an unscientific test done by Lucky Gunner that showed the same thing.



Lucky Gunner Setback test:

Battered Bullets: What Impact Does Bullet Setback Have on Function?
Experiment Conducted by: +Andrew Tuohy

I have been conducting experiments relating to firearms for a number of years, some of them quite mundane and others rather unorthodox. Many of the unorthodox experiments have never come to light, either because nothing of value was learned, or because I had decided to compile their results over a long period of time before releasing the data.

One series of tests which falls into the latter category relates to what, exactly, makes guns blow up. We've all seen photos of exploded firearms and bloodied hands or faces that result from a "kaboom," or catastrophic failure of a firearm or the ammunition it fires. As a result, a lot of people exercise an overabundance of caution relating to any ammunition that "looks funny" to them - even going so far as to discard cases with tiny dents in them, for fear of causing an explosion.

While it's always a good idea to err on the side of caution when working with items that contain 1,000 times more pressure than a car tire, it's also a good idea to have an understanding of what can really cause a catastrophic failure. And my experimentation has shown to me that the common knowledge relating to this topic is entirely wrong.

Many others have performed experiments of this type in the past - my interest in the topic was piqued by a conversation with a ballistician who told me of a test performed decades ago by a famous writer. The details of the test made me immediately think, "There's no way the gun didn't blow up!" But not only did the gun not blow up, it exhibited no signs of damage.

Which brings me to the test I conducted using a Glock 22 and some Speer Gold Dot ammunition. I had observed minor bullet setback over a long period of time with this firearm/ammo combination. "Setback" is when the bullet is pushed into the case, sometimes by repeated chambering.

Armed with the common knowledge that .40 S&W was especially susceptible to pressure issues from bullet setback, and that the Glock 22 would blow up if you looked at it wrong, I set out to find exactly what amount of bullet setback would cause a catastrophic failure.

Because I was absolutely certain that the gun would blow up, I took several precautions. First, I clamped the pistol in a vise and fired it remotely using a trigger actuating device. Second, I started with the tiniest levels of bullet setback, using a reloading die to push the projectiles into the case. Third, while firing the Glock, I made sure to put an adequate barrier between myself and the firearm. I then took seven cartridges and set them back at .005" intervals, to a maximum of .035" bullet setback.

I then fired all of these cartridges. Surprisingly, the Glock didn't blow up. Using a dye penetrant designed to identify small cracks, I carefully inspected the barrel and slide. They showed no signs of damage or impending doom.

I scratched my head and tried to figure out why it hadn't turned out the way I expected. I was determined to find out the "zone of danger" for a .40 S&W Speer Gold Dot and a Glock 22 in terms of setback, so I set a few more cartridges back with the press and headed to the range - but not before I grabbed a hammer, too.

As I feared, the further-setback cartridges had no adverse effect, so I slowly looked between the hammer and some of the remaining intact cartridges. I set one cartridge, bullet up, on a smooth hard surface and delivered a solid blow to its face. The result was ugly - the hollow point deformed and the case was bulged a tiny bit, the bullet set back a significant distance.

Due to the bulged case, I had to use the hammer to "ease" the slide into battery. I crossed my fingers and stepped back, then activated the trigger.

No obvious damage.

I took another cartridge and hit it twice, then a third and hit it three times. The end result was disgusting and hardly recognizable - the cartridges were badly deformed and required a solid hit to the rear of the slide in order to chamber. And yet neither caused the firearm to blow up. I hit a few more cartridges with the hammer, but didn't have the heart to fire them - I figured the poor Glock had had enough punishment.

Back at home, I used the dye penetrant and found that the barrel and slide remained undamaged.

Why did this happen?

Well, Glock has revised the barrel since the early "unsupported chambers" which left the pistol with such a bad reputation, and they also beefed up the frame since the earliest iterations of the .40 S&W. And while certain powders, when used in .40, can cause dangerous pressure spikes, manufacturers of commercial ammunition wisely test and select powders that are not as susceptible to changes in temperature or, obviously, bullet setback.

So while I'm not saying that you should attack your ammunition with hammers, I am saying that you should not fear tiny amounts of bullet setback with commercial ammo - at least when it comes to pistol cartridges like the .40 S&W, and especially when you consider that some factory ammo has a natural variation in overall length that does not result in a dangerous condition.

What do you think? Is this something you’d like more details about? If so, let us know. If there is enough interest, we'll publish an in-depth LuckyGunner Labs post detailing more experiments related to chamber pressure.

[Boriqua]

Very interesting. Especially his extreme tests with the hammer.

I guess the only part missing from the article which would have been of interest would have been the amount of setback that chambering produces in the gun he tested. Probably not a real quantifiable thing across a range of hand guns because like I mentioned.. I have had some that you can feel are slamming into a ramp due to the angle and others that relatively slide the round in to the chamber.

For giggles I may sacrifice a couple rounds and test with calipers to see what kind of setback happens over how many chamberings

[Flash]

I used to shoot at Ted's and around once a year a LEO would come in with setback rounds (Gold Dots) and he'd give them to me to disassemble. Turns out every time he went into his house, he unloaded his duty weapon and when he left the house, he loaded it. Did this multiple times per day and ended up with 6 or 7 rounds with setback.

After he shot and left, I disassembled them the quick way on the range.

[xerts1911]

Great thread, good info.

[Tenring]

Pulled down some factory SD 45 one time that had 3 /10 with NO flasholes drilled....

[deanq]

Twice... max. Bullet set back happens when you feed into the chamber. New, old, reload, re-manufactured, it doesn't matter. You WILL get bullet setback. maybe not on the first feed cycle, but it WILL happen.

[Boriqua]

Alright .. Trying to avoid the second half of my exercise this morning .. I decided to do a little test.

Not very scientific but you decide its value.

I loaded a 40 S&W FMJ into an empty case but I did leave in the spent primer. I figure the trapped air in the case helps to act against bullet setback and the powder wouldn't make a real difference unless you were packing the powder to the bullet.

The bullet is not plated it is an actual FMJ at 180 gr. I didn't use plated or coated because I thought either of them might deform at the nose enough to alter the "test." FMJ is unforgiving and would transfer all its energy to the brass.

I used a lee die set which includes as the final step the Lee crimp die. it is exactly loaded as I would load any other round except for the omission of powder.

I am using kind of a cheapy caliper but I thinnk its accurate enough. I get a little variance on the final number but it depends how hard you press. I tried to take the measurement so the round could just move up and down kind of how you would use a feeler guage when adjusting valves.

I used my M&P as my test gun because it probably has the tightest chamber of my 40's and in slow release it bangs the top of the chamber on feed pretty hard as it enters.

I didnt ride the slide. I am a sling shot guy and I loaded the round into the mag and slingshot the slide as I would any other time I shoot each time between measurements. Its exactly as I use the gun. I put the dummy in the mag, slingshot, removed the dummy measured it and repeat.

These were my results
Starting length 1.1500

Chamberings
1. 1.1500
2. 1.1500
3. 1.1500
4. 1.1500
5. 1.1495
6. 1.1495
7. 1.1490
8. 1.1490
9. 1.1495
10. 1.1495
11. 1.1495
11. 1.1495
12. 1.1490
13. 1.1490
14.1.1490
15. 1.1490

I think we can throw out 7. and 8 as me applying to much pressure and not being consistent but like I said .. its not scientific and I am not a machine that can accurately apply pressure each time.

I did a couple more and the 1.1490 I started getting at chambering #12 is good. I got the same measurement over the next 3 so 16,17 and 18 stayed at 1.1490.

Then I got bored and didnt feel like doing 50 of these so would there have been more set back? Maybe, but over18 chamberings I went from 1.1500 to 1.1490. Certainly not enough to cause a pressure spike

For information purposes .. I was loading all my 40's at 1.1200 and have shot HUNDREDS through my Sig but at that length my M&P was balking at my coated bullets.

Was21 suggested lengthening the cartridge and lo and behold they work fine in the M&P now. It only had problems with the coated and I am assuming bullet profile as I have shot at least a couple hundred cartridges at the shorter length using plated or FMJ without issue in the M&P.

There were absolutely no over pressure signs using the shorter cartridge and the Hogdon sight calls out the OAL at 1.125

You draw your own conclusions. Its not like I am in a lab .. just some observations using one cartridge type in one gun
Alex