Almost_Blameless
New member
I have heard/read quite a bit about how the rechambering of the same round repeatedly into the chamber of a semi-auto can reset the bullet seat depth and possibly cause increased chamber pressure troubles due to subsequently 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. I began the rotation a couple weeks after obtaining the pistol, after reading about the possible adverse effects.
I’ve owned and carried a Kahr CM9 for quite a while. I carry 1 extra magazine.
The magazines are always loaded and the carried weapon always has one in the tube.
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. The calipers were zeroed, and accuracy was checked every 5 rounds, with calipers never needing 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 the number of extractor claw marks, (chamberings).
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”
It appears in this case, there is no serious difference to continuously re-chambered vs never used (factory-fresh) rounds.
I DID find that there was a greater difference than I would have guessed in the factory-fresh rounds. So, I measured a box of Hornady Critical Duty 9MM 135gr FlexLock (all unused), and the entire 25 round box varied from 1.123" ~to~ 1.145" with the spread being about equally spread through that range of measurements. Again, I would have never thought there would have been this large of a spread.
So, there's some food for thought....
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. I began the rotation a couple weeks after obtaining the pistol, after reading about the possible adverse effects.
I’ve owned and carried a Kahr CM9 for quite a while. I carry 1 extra magazine.
The magazines are always loaded and the carried weapon always has one in the tube.
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. The calipers were zeroed, and accuracy was checked every 5 rounds, with calipers never needing 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 the number of extractor claw marks, (chamberings).
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”
It appears in this case, there is no serious difference to continuously re-chambered vs never used (factory-fresh) rounds.
I DID find that there was a greater difference than I would have guessed in the factory-fresh rounds. So, I measured a box of Hornady Critical Duty 9MM 135gr FlexLock (all unused), and the entire 25 round box varied from 1.123" ~to~ 1.145" with the spread being about equally spread through that range of measurements. Again, I would have never thought there would have been this large of a spread.
So, there's some food for thought....
