Does chambering a round weaken it?

[Malachi]

Ok, i just bought a Smith and Wesson SD40VE, and I read somewhere that with the .40S&W every time you chamber a round it somehow weakens it. Something about doing damage to the casing or something.

Any truth to that?

I seriously don't remember where i read it at, just noticed it while researching before deciding to go with the .40S&W over the .45ACP.

 

[fnsmoak]

Believe HALF what you see, and NONE what you hear.

If a specific firearm is damaging rounds upon chambering, the item somehow skipped QA before leaving the CNC machine, or someone has increased your life insurance while you weren't looking. This is definitely NOT an industry standard.

So you researched AFTER you purchased?

 

[Caribou]

Every time you fire a round the brass is stretched. When you reload it you form the brass back to size. After a few cycles of this the brass will crack and you will not be able to reload that casing.

If you are talking about chambering and re-chambering a round as some people do that empty their gun every night, I would not worry about the brass. In theory the brass wears each time it is chambered but the amount is insignificant. There are two potential problems you might want to be aware of though. A round that is continually chambered without being fired can cause the bullet to move back into the brass causing increased pressure from the compacted powder. This can cause damage to the gun and yourself. A round that is crimped on a cannelure is unlikely to have this problem and if it does occur it is easily visible upon inspection.

The second potential problem is with the primer. The repeated slamming of the round into the chamber can cause the explosive in the primer to shake out of the primer and into the chamber where the powder is in. Since the primer is now dead that round will not fire. This happened to a cop who used the same carry ammo for months or years and emptied the chamber every night. The cure for this is to fire the top round or two, depending on how you reload each morning, at a range session every three months or so.

 

[thechief]

Bullet Set Back

Let me put it this way, repeated loading and unloading of the same ammunition will going to develop in what we call a bullet set back. Set back in ammunition is very common especially to us who prefers semi automatic hand guns. This occurs when the bullet's nose hits the feed ramp of our pistol which causes the nose of the bullet to retract into its case the effect would be more evident after five to ten cycling of the same ammo.

What I did was to inspect the length of my defense ammo after I unload it, compare it to the fresh factory ammo from the same box and if the length was not the same I replace it with a fresh one. The net result when you are using this ammo that underwent set back is that you will have a much higher chamber pressure than desired, which could damage the ejected case or worst damage the gun itself. Some even said that too much set back can cause a KB or KABOOM in our gun, hence I always painstakingly inspect all the ammo (defensive or practice) that went into all my spare mags and in the gun before shooting. Better be safe than sorry. I am a 1911ACP person so I cant accurately give an exact measurement in millimeters or inches regarding the upper tolerances on how much is enough for ammo set back in .40 S&W.

Other prefers to use a crannalured (forgive my spelling) bullet which minimizes set back from repetitive cycling of the same ammo, but alas, the only crannalured cylindrical object here in the house is the volume control of my FM radio:angry:

With that being said, after I my range trip, I clean the gun, load a round in the chamber of my 1911 acp and it stays that way, that is in condition 1 until my next range trip.

Let us wait for our friends here in the forum to contribute their experience re. bullet set back. I am sure that everyone have also their share of experience.

Hope this helps my friend.

Best Regards and Stay Safe:wink:


Chris

 

[Malachi]

Believe HALF what you see, and NONE what you hear.


So you researched AFTER you purchased?

Before. Read the last part of my post again

 

[warcraftjs]

^^^^ Good explanation.

I believe the story started with police officers at night taking their service pistol and unchambering the round and putting the same round back into the magazine. Continued unchambering and rechambering can cause the round to have a "Bullet Set back".

If you have a set of calipers you can check to see if you are having bullet set back on your rounds. I believe it takes a Lot of unchambering and rechambering a round (and to the same one) to have "Bullet Set Back" (its basicly the slamming of the slide on the round into the chamber that would cause it).

Now I carry a 9MM and yours is a .40 so there may be a little more cause of concern for you because the .40 is already a hot round (hence why there is no real .40+p rounds, here is info on .40 rounds: Link Removed ). And set back of the bullet could set back compressing the gun powder and raising the pressure when the round is fired.

Best way around it is to move the round in the magazine, don't ways load the same round. And change out your carry rounds a little more often if your concerned.

 

[Malachi]

Thank you gentlemen, bullet set back is actually what it was. Now that you mention it I remember.

So, it can be a problem, but close inspection will easily identify any rounds that have been affected?

 

[schmidtap]

Only issue I ever ran into with my 1911, is that the rim would start to get chewed up from the extractor. Not a real big issue, just have to inspect the rounds from time to time. if it gets too bad, then into the range ammo it goes and gets replaced

 

[Almost_Blameless]

Resized rounds due to constant rechambering??

I’ve owned and carried a Kahr CM9 for SEVERAL months.

The magazines are carried loaded and the carried weapon always has one in the tube.

I have heard/read quite a bit about how the ‘bumping’ of rounds repeatedly into the chamber
can reset the bullet seat depth and possibly cause increased chamber pressure troubles due to
compressed powder charges.

My pistol’s chamber is emptied daily, and when the pistol is again carried, a round from the magazine
is chambered, and the last chambered round is returned to a magazine, in a random rotation.

The following is a report showing actual caliper readings of the rounds from each of my magazines,
plus the last 11 rounds from the factory box of ammo used as a control measure. The calipers were
zeroed, and accuracy was checked every 5 rounds, with calipers never needing to be reset.

Remington Ultimate Home Defense 9MM 124gr BJHP

Rounds were removed and numbered from each of 2 magazines.
Each round had extractor claw marks counted/marked.
Overall lengths are shown first followed by extractor claw marks.

Flush 6rd+1 carry Magazine:
1- 1.123” 6 claw marks
2-1.126” 6 claw marks
3-1.124” 12 claw marks
4-1.126” 4 claw marks
5-1.129” 12 claw marks
6-1.124” 11 claw marks
7-1.124” 9 claw marks
Extended-spare 7rnd magazine:
8-1.124” 7 claw marks
9-1.123” 2 claw marks
10-1.126” 2 claw marks
11-1.128” 3 claw marks
12-1.122” 1 claw mark
13-1.130” 2 claw marks
14-1.129” 7 claw marks
Last 11rnds UNUSED from same box of new ammo:
(control measurements) NEVER CHAMBERED, SO, NO Extractor MARKS
C1-1.125”
C2-1.132”
C3-1.126”
C4-1.124”
C5-1.128”
C8-1.124”
C9-1.128”
C10-1.126”
C11-1.121”

With the control batch (unchambered) being so varied, it is difficult to see any real disadvantage to continuous rechambering out to 12 times or so.

 

[SteveG]

I’ve owned and carried a Kahr CM9 for SEVERAL months.

The magazines are carried loaded and the carried weapon always has one in the tube.

I have heard/read quite a bit about how the ‘bumping’ of rounds repeatedly into the chamber
can reset the bullet seat depth and possibly cause increased chamber pressure troubles due to
compressed powder charges.

My pistol’s chamber is emptied daily, and when the pistol is again carried, a round from the magazine
is chambered, and the last chambered round is returned to a magazine, in a random rotation.

The following is a report showing actual caliper readings of the rounds from each of my magazines,
plus the last 11 rounds from the factory box of ammo used as a control measure. The calipers were
zeroed, and accuracy was checked every 5 rounds, with calipers never needing to be reset.

Remington Ultimate Home Defense 9MM 124gr BJHP

Rounds were removed and numbered from each of 2 magazines.
Each round had extractor claw marks counted/marked.
Overall lengths are shown first followed by extractor claw marks.

Flush 6rd+1 carry Magazine:
1- 1.123” 6 claw marks
2-1.126” 6 claw marks
3-1.124” 12 claw marks
4-1.126” 4 claw marks
5-1.129” 12 claw marks
6-1.124” 11 claw marks
7-1.124” 9 claw marks
Extended-spare 7rnd magazine:
8-1.124” 7 claw marks
9-1.123” 2 claw marks
10-1.126” 2 claw marks
11-1.128” 3 claw marks
12-1.122” 1 claw mark
13-1.130” 2 claw marks
14-1.129” 7 claw marks
Last 11rnds UNUSED from same box of new ammo:
(control measurements) NEVER CHAMBERED, SO, NO Extractor MARKS
C1-1.125”
C2-1.132”
C3-1.126”
C4-1.124”
C5-1.128”
C8-1.124”
C9-1.128”
C10-1.126”
C11-1.121”

With the control batch (unchambered) being so varied, it is difficult to see any real disadvantage to continuous rechambering out to 12 times or so.

Interesting info. Thanks.