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Discussion Starter · #1 ·
I came across this image of somebody's sig pistol with a not so sig mag.
the user also has a video of him shooting with this mag below:


Im curious if anyone has done this before and can share the process since 55x mags are pricy and hard to come by right now

Trigger Air gun Machine gun Gun barrel Gun accessory
 

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Here is some additional info I remember reading some time ago... SIG 556 + SIG 556R + Galil Mags = SIGalil -
However, it looks like the lower in the pictures/video you shared is a 551-A1 lower, and not a 556R lower like the post I shared. I'm not sure what mods would be necessary to allow Galil mags to function in a 551-A1 lower. Perhaps just an adjustment of the locking lug?
FWiW-- I have used one of these with my 55X lowers. It's a decent way to save money if you don't mind modifying inexpensive and plentiful Pmags.. AR Magazine Adapter Kit for Swiss Arms/SIG SG550
 

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Discussion Starter · #3 ·
So I picked up a surplus 35 round Galil mag from my local gun show. Right off the bat it is too thick but the similarity of the mags geometry look to be very similar and could potentially be an easy modification
 

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Discussion Starter · #4 ·
I have a 20 round 55x mag and its thickness where it would sit in the magwell measures to be about ~.91"
The surplus Galil mag thickness on these side steel plate things? measures in at a little over an inch ~1.02"
So if this is going to be done around ~.05" of material needs to be removed from each side of the steel plates of the Galil Mag

If it matters, I am using calipers i got from microcenter, but they seem to be fairly accurate
Also i don't have the most time in the world so my updates might be far apart from one another but I am passionate about making this work and well we all know its possible.

Stay tuned
 

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Discussion Starter · #5 ·
Just upon view, I am using the top of the feed lips as a reference point and you can already see the similarities.
uploading pics for reference
If anyone has any suggestions, please let me know but so far it looks like the sides need to be slimmed and then the front lip might need more material, and/or the rear latch needs to be moved up a bit.
I am going to try and slim down the sides this weekend if i have the time
 

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Discussion Starter · #6 ·
By the luck of the gods I was able to get in contact with the original poster of the video.
Here is what he said about the process:

I had to thin the mag a good amount,
thin the top feed lips,
relocate the front lug and mag catch.
It was a pain and lots of test fitting.
I could only get it to work in the aluminum US 551A1 lower.
I couldn't get it to work in the steel Swiss lower

Unfortunately for me, I have a steel lower. So I guess we will see how that goes, Also access to a welder would be cool. I might pick one up from Harbor Freight and watch a few videos.
Stay tuned
 
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