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Posted: 2/7/2026 2:13:56 PM EDT
[Last Edit: Digger440][Edited]
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I have a Pro2A Tactical G20/21 magazine lower that appears to have had the mag release cut too high. I am checking in here to verify what I am thinking or to see if I am possibly overlooking another cause. The issue is repeatable with every magazine I try. Mag in the photo is a factory G21 13 round magazine. From both sets of photos you can see the two lower bolt lugs are too low and cannot pass over the mag. The first two photos are of a I do not have a blowback bolt to try unfortunately. My thinking is bore centerline is what it is and a blowback bolt would have the same issue. Please correct me if I am wrong. I dont remember where I got the lower as it has sat in my safe for a several years. Pro2A Tactical does not have a record of me buying it, so I got it from some other vendor or maybe here in the E.E. It also complicates matters a little that since I acquired it my state went full communist, so just buying another brand cant happen. Your eyes and help are appreciated and I can provide more pics or measurements if necessary.   Pro2A Tactical upper  
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"All of a sudden, I found myself in love with the world. So there was only one thing that I could do, ding a ding dang my dang a long ling long "
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Originally Posted By Postal0311: You need to try the proper bolt. They are shaped differently. https://www.brownells.co.uk/WebRoot/MediaDefinition/userdocs/skus/l_100026111_6.jpg?sig=3603f240be0b979c011359c3541b638f01f995ac5819da901d91c5645ab06eea Who is RHW? I'm guessing they made that set up to run on Grease gun mags and nothing else... |
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I used that picture as an example. A Glock mag is single feed, a single round in the middle. The AR mag is dual feed, rounds alternate being on the left and right. A bolt for that sort of mag will have wider cuts on the bottom to clear the feed lips and a single lug in the center for stripping the round from the mag and feeding. The AR15 5.56 bolt uses its lugs to strip a round from either side of the AR15 mag, so it has material that would hit the feed lips of your single feed Glock mag. |
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blowback lowers present rounds different than DI/RDB lowers cause the bolts are completely different. as well as single vs double stack mags if you want to use a DI 45 upper with glock mags, you will probably need to get a CMMG lower. not sure what other lowers works. otherwise stick with blowback i have a Pro2A 10mm blowback PCC aswell as a 45acp upper for it. even tho the lowers are basicly the same, the mags between 10mm and 45 are different heights. i made it work by modifying the mags. but when i tried an RDB upper there was no real way for it to work without alot of work i have long abandoned my P2A blowback 10/45 and gone DI/RDB for everything. still have it but it but never use it |
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Sorry it has taken a couple days to respond, life got busy. I edited the OP as originally I mistyped the brand of the upper. The upper is a RMW Xtreme 45 DI, not RHW. RMW uppers are supposed to run fine with Glock mag lowers (QC10, DDLES, etc.) in addition to M3 mag lowers. Archive link of RMW upper on Glock and M3 lowers Back to my original question, would anyone be able to take a measurement from the top of the mag catch to the top edge of the lower for comparison on their Glock lower? Measurement would need to be on right side (release button side) of the magwell approximately .125 back from the front edge. The magwell is cut on a slant which is why I am picking a spot to measure from. Originally Posted By Postal0311: You need to try the proper bolt. They are shaped differently. https://www.brownells.co.uk/WebRoot/MediaDefinition/userdocs/skus/l_100026111_6.jpg?sig=3603f240be0b979c011359c3541b638f01f995ac5819da901d91c5645ab06eea They are shaped differently if you are building a blowback gun. A blowback bolt is completely different and cant be compared to a DI bolt. The bolt in the photo is the correct .45 ACP DI bolt that came with the RMW upper. |
"All of a sudden, I found myself in love with the world. So there was only one thing that I could do, ding a ding dang my dang a long ling long "
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You have a Rotary delay blowback upper....with a standard blowback lower. You MAY be able to get it to function correctly by cutting the mag catch to position the rim of a cartridge in a mag at the bottom of the bolt pocket. You will also need to fabricate an over insertion stop to heep the bolt from pulling the mag up as it feeds. If near Macon Ga.....swing by the shop and I'll take a look...... Rudy |
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