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Converting an open 9mm major to minor


kaminari
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I tried a few different searches but only got a little data out of it.

Since I'm not currently set up for reloading and I have a bunch of factory 9mm I'm wondering what would go into converting a 9mm major gun into minor?

I saw somewhere that 9mm minor might not produce enough gas to make the comp work properly. I'm guessing that just means it won't absorb as much muzzle rise, is there any other issue here?

Other than that would all I need to worry about is possibly a lighter recoil spring and maybe spacers for the mag tube?

Thanks for any input.

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Since I'm new to open and compd guns I did try some factory 9 in my trubor for s&g's and reduce rounds for sighting in. I found 2 distinct problems with 9minor in a gun designed to fire major

The factory ammo constantly jammed/ stove piped and the gas wasn't even close to enough to keep the gun flat it jumped and had alot of muzzle flip

I'd imagine you are going to have to reduce spring weights substantially between recoil and mainspring just to get the gun to operate properly

And probably reduce the barrel weight and use a barrel without a comp

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I have a Sti Grandmaster,Edge and Trojan..I reload for all of them. My current load for my edge is 133 power factor and I have fired those round in all of my 9mms. The brass

barely ejects from the Grandmaster and I would not shoot it in a match I just wanted to see if it would shoot. And it did. I load them long and use SVI mags in my hicaps and

Tripp 10 rounds in the Trojan

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Since I'm not currently set up for reloading and I have a bunch of factory 9mm I'm wondering what would go into converting a 9mm major gun into minor?

A lot of 9Major guns will run minor ammo just fine, depends on the springs and ammo. I run a 8lb spring normally and with my 140PF minor ammo, it runs perfect. On my Steel load, I have to go to a 6 or 7lb spring but it will run.

I saw somewhere that 9mm minor might not produce enough gas to make the comp work properly. I'm guessing that just means it won't absorb as much muzzle rise, is there any other issue here?

Pretty much correct. That's how a comp works so if you can't get the gas pressure up in the comp, it just acts as a barrel weight. When you start reloading, one thing you can do is go to a very light bullet, like a 95gr, and then push it up in the 1200fps range to work the comp more. Not ideal but it works better.

Also, you just take a 95gr bullet and just slow it down to 800 or so and that drops your PF a ton, feels like a .22.

Other than that would all I need to worry about is possibly a lighter recoil spring and maybe spacers for the mag tube?

Why would you need spacers? Are you shooting 38 Super in STI mags? If so, then maybe but not necessarily. Try them without spacers first and then if you have feeding problems, then go to a spacer. Also, use the steel Hardy spacers for the best results and don't glue them in - per Mr. Hardy. Remember, if you put in spacers, you have to change the follower also.

Edited by gng4life
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Other than that would all I need to worry about is possibly a lighter recoil spring and maybe spacers for the mag tube?

Why would you need spacers? Are you shooting 38 Super in STI mags? If so, then maybe but not necessarily. Try them without spacers first and then if you have feeding problems, then go to a spacer. Also, use the steel Hardy spacers for the best results and don't glue them in - per Mr. Hardy. Remember, if you put in spacers, you have to change the follower also.

I thought the normal 9mm was too short in most mag tubes so they needed a spacer at the rear of the mag tube (and matching follower). I'll definitely test it before going to spacers.

I'm guessing a comp designed for 9mm minor would work, so I might look into one of those as well if I don't hear back from the shop that built this open gun.

Thanks for the feedback, everybody! Let me know if there are any other considerations I need to think about.

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