Bryco M59 mags in a Jennings Nine

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Bryco M59 mags in a Jennings Nine

Postby adam01364 » Fri May 03, 2013 11:02 am

In the old forum there was a thread about taking the Bryco M59 mags (13 rounds) and modifying them to work in a Jennings Nine. The reason for doing this was not only would you get higher capacity mags, but you could "fix" the wear on the hole used to retain the mag in place. The mag release is "a square peg going into a round hole" which is a really stoopid design. As the hole wears, the magazine doesn't seat a snugly as it should and ultimately it causes feeding issues. Once the M59 mag body was been altered, the idea was to swap the baseplate and follower from the J-Nine magazine and into the modified M59 mag.

I had a couple of M59 mags kicking around but I never got around to trying to do this until last night. But I didn't want to "sacrfice" a working 10 round magazine unless I really had to. I decided to: A) bend the M59 floorplate to fit the J-Nine, and B) try the M59 follower regardless of the lack of a last round hold open (LRHO) feature. Result: Success! No LRHO but now I have two more magazines to play with.

First I bent the M59 floorplate to match the bend on the J-Nine magazine. Pliers are crude, but effective!
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Next, I disassembled my J-Nine and scribed a mark on the M59 magazine body for the hole for the magazine retainer/release
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Here are the beginning cuts for the hole for the magazine retainer/release. I used a Dremel for the rough cuts and then finished up wth a jeweler's flle.
A word of caution: Do NOT cut into the round corner of the magazine when you make the cuts; the mag release will move inward too much and the gun will not fire. I found this out the hard way on my second mag :oops:
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Once I completed the magazine retainer/release hole, I proceeded to cut a relief for the LRHO on the magazine since the lever of the LRHO stops the mag from fully seating. Here's the unmodified M59 mag inside the J-Nine magwell showing the interference.
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In this case I used a Dremel for the entire process switching from a cutting wheel to a grinder for the final finish.
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Here's the finished LRHO relief.
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I then ran some fine grit polishing cloth up inside the magazine, followed by passing a rag through the mag 3X before reaasembly.
Three magazines compared L to R: Original M59; Modified M59; Factory J-Nine.
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You can see that the modifed M59 does not have as deep a relief as the factory J-Nine. If I get a set of J-Nine followers, I will have to grind the mag a bit more. But for now, it works just fine without LRHO.
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Here's what the factory J-Nine mag looks like with the breech open
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Here's the modifed M59 mag for comparison. You can sorta see the M59 follower does not contact the LRHO lever.
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Test time! I've cycled the modifed M59 mags with snap caps about 100 times.
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Next test will be at the range -I'll let you know how it goes!
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Re: Bryco M59 mags in a Jennings Nine

Postby Admin » Mon May 06, 2013 10:09 pm

Great work. Thank you for the posting.
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Re: Bryco M59 mags in a Jennings Nine

Postby adam01364 » Tue May 07, 2013 7:18 am

UPDATE:
Range test went well except that it appears I need to notch the M59 magazine follower just a touch. After the last round loads out of the mag, the follower just barely engages the safety and the gun will not fire. This didn't occur while I was testing with snap caps, perhaps firing the gun loosened things up.
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Re: Bryco M59 mags in a Jennings Nine

Postby 84minieldo » Tue Dec 30, 2014 12:32 am

Cool thanks
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