Vetting a carry mag?

[JWH]

Firstly, you have been doing this a lot longer than I have.

In terms of gun nerd standards, Bill Reihl made an argument a few years ago here that I think makes sense for vetting a new unproven design. His argument was that each cartridge position in the magazine is unique, so to have a statistically valid test, you would load the entire mag a statistically valid number of times and fire it, tracking any anomalies. My statistics professor told me that, in general n=30 is the smallest statistically valid sample size for a normal distribution.

For me, this makes magguts and the shield mags too expensive for serious use.

I got what I do from JodyH. Use something that other people have validated (G19 for now), and when I get a new mag, it gets a box of practice ammo and a mag of carry ammo through it, then it is loaded with carry ammo and lives in the gun until the next time I rotate ammo.

Hope this helps.

[Sal Picante]

So...2-500 rounds through the same mag? Thats a huge pain in the ass for a 14 round magazine.

Sorry should've clarified that the mag is in rotation with another magazine or so. The idea is to see how it fares when it drops a few times, gets reloaded a few times, etc.
I tend to play "Calvinball" a lot during practice when vetting equipment. Calvinball is kinda like "pig" or "horse" but with guns...

I live in my head sometimes...

[MickAK]

Sorry should've clarified that the mag is in rotation with another magazine or so. The idea is to see how it fares when it drops a few times, gets reloaded a few times, etc.
I tend to play "Calvinball" a lot during practice when vetting equipment. Calvinball is kinda like "pig" or "horse" but with guns...

I live in my head sometimes...

I liked this because 'Calvinball' is a really good method of vetting equipment and I kinda wish we still lived in the era of gun magazines because 'Calvinball: Is it the right method for you?' would be a great article. I'd buy it.

[Sal Picante]

I liked this because 'Calvinball' is a really good method of vetting equipment and I kinda wish we still lived in the era of gun magazines because 'Calvinball: Is it the right method for you?' would be a great article. I'd buy it.

Well... you don't have to wait much longer: Matt Little (greybeard_actual) is doing a write up on Calvinball.

The only thing you have to ask yourself: Is it the right method for you?

[RancidSumo]

I'm too lazy to load mags at the range (I bring a big bag full of loaded mags each trip), so my OEM Glock carry mags get 1-2 boxes through them, including at least one 50rd box of my carry ammo, and I call it good.

I didn't get to that point with the MG 365 mags before I stopped carrying a 365. I was also worried about reliability, but I put maybe 150 rounds through one without issue. I think I'd be comfortable with it at this point if I could run 150 rounds of practice ammo and another 50 of carry ammo without a malfunction.

The above is with the clarification that as soon as I'm comfortable with a carry mag, it doesn't get used at the range other than cycling through the mag of carry ammo every few months.

[Sanch]

My statistics professor told me that, in general n=30 is the smallest statistically valid sample size for a normal distribution.

The problem comes into deciding subjectively what the "n" refers to. Is that 30 rounds of ammo? Or 30 magazines of ammo? Or 30 range trips of X rounds of ammo per trip?

Or is "n" referring to number of magazines themselves, as in you need to test 30 different magazines with X rounds of ammo over Y period of time each?

Then there's the added concern that magazines are wear items, and it's possible the process of testing pushes the magazine to the limit of reliability. For example, suppose the mag is good for 30 cycles before the spring wears out and reliability drops. And you test it 30 times. It passes 100%. So you start carrying it, not realizing that your testing hit the threshold of reliability.

Personally, I don't want to mess with changing the number of rounds in my mags and risk reliability issues.

[Clusterfrack]

@SouthNarc, interesting question. My approach used to be to test each carry mag with at least 5 loadings, including carry ammo. But after shooting >60k through Glock mags, and >100k through CZ mags, without a single issue that wasn’t wear, dirt, or impact related I’ve gotten lazy. I’ll carry a brand new Glock or CZ mag without concern.

But with other guns or aftermarket mags/extensions I’m highly suspicious, and test carefully. My G43 extensions were troublesome, but I only discovered it after a few hundred rounds. This whole discussion has me thinking that just having to ask the question is a clue.

[Tensaw]

. This whole discussion has me thinking that just having to ask the question is a clue.

#buzzkill

[psalms144.1]

This is a timely topic for me. Went out today to shoot and took my FM9 AR pistol with my newly acquired Glock OEM 24 round magazine. I never even dreamed that the mag would cause issues, but, first go with it I was literally getting failure to feeds with every other round. Stripped it, swapped mags, and the pistol worked fine. Finally worked through the mag, reloaded it, and, oddly enough, it ran like a champ. Doesn't matter, it goes into the "range only" box.

How are the Magpul 21s working with AR9s?

[SouthNarc]

So I fired 200 rounds through this one magazine yesterday with Jeff Gonzales at The Range in Austin. 100 147 HST, 50 115 ball, and 50 Hornady 135 gr truncated cone rounds which were kinda' funny looking. It was some random shit Jeff had.

Nary a bobble. I dutch loaded, ran the mag at different capacities with all three rounds...no failures to feed and it always locked back. I am using the Tac Dev floor plate for it. It's funny because the magazine is actually easier to load and oddly feels....smoother?

I'm gonna call this one good and carry it. Thanks to everyone that gave me constructive feedback.