Over the past several years, I have been asked if Magpul Ranger Plates will work on USGI 20 rounds magazines. I asked this question several times myself, with little to no answers. The answer to this question is yes, they will work but some modifications need to be made. I posted a response on how to modify the plates to work, on AR15.com back in 2009, it has since been archived. I pulled the archived text, uploaded my origonal photographs and modified it for this write-up.
Modification of the locking plate for the Ranger Plate is needed for this to work on the magazines. If you are using Colt/NHMTG/USGI 20 round magazines, you need to cut and dremel the Magpul locking plate to fit past the GI magazine locking floor plate tab. It is important to note: you may only be able to put 19 rounds in the magazine to seat it on a closed bolt, after this modification. I mentioned losing a round in the L-Plates article for USGI 30 round magazines (http://looserounds.com/2012/10/14/magpul-l-plates/). You must weigh the benefits of losing a round vs. the gain of a better grip pull from a magazine pouch.
The floor plate lips on USGI 20 round magazines are a little larger compared to 30 round USGI magazines, so sliding the Ranger Plate on will take a little work. Remember to use a small tool to push the floor plate tab down, to slide the ranger plate on, (tough but will work).
Basic Tools Needed:
Dremel, screwdriver or punch and razor blade.
After removing the USGI floorplate from the magazine, line up the Magpul locking plate with the bottom of the magazine. Estimate the location on the Magpul locking plate, behind the USGI locking tab, to score the locking plate with a razor. Score the Magpul locking plate with a razor on both sides and break off the excess.
Dremel down the Magpul locking floor plate to fit behind the magazine locking tab. Dremel a little at a time, making sure the Magpul locking plate won’t touch the magazine locking tab. You may have to dremel the Magpul locking plate down generously to make it work. This allows room to place it in and remove it without touching the magazine locking tab.
Place the Magpul locking plate in magazine. Turn it to the side, the floorplate tabs on the USGI 20’s are larger than USGI 30’s and it may take some work to get it in.
Sliding on the Ranger Plate. This takes some minor elbow grease as the floorplate tabs are large. Once you reach the locking tab, use a tool to push it down into the magazine slightly so the Ranger Plate will pass over it. I used a Glock tool.
Slide the Ranger Plate the rest of the way on and check that the locking plate has locked up into the Ranger Plate.
Now you’re done. Function test the magazine and run rounds through it to confirm it is working properly.
Notes / Updates:
Newer 20 round after market mags, like Brownells, what are very good, have a different floor plate, similar to USGI 30 round mags. They may not need to be modified as the USGI spec mags. When looking at the floor plates, you can tell a distinct difference.
USGI spec 20 round mags will have a round take down hole and locking tab slot in the front of the mag. Magazines like the Brownells 20 round will have the take down hole in the back and no locking tab in front. The thickness on the magazine floor plate tabs is the same, on the magazine body. So adjust your Dremel measurements appropriately. Also, a slight Dremal cut where the magazine floor plate tabs are located might be appropriate, on the locking plate, if you can not seat the Magpul Ranger Plate. The locking plate is for locking the Ranger or L-Plate in place, using the spring.
With all magazine, I have had to down load by at lease one round. So this is something you should think about. 19 rounds vs 20 rounds. As a former LE Officer and Instructor, I always downloaded 30 rounders to 28 & 20 rounders to 18. You can comfortably insert a 19 round mag with a Ranger or L-Plate, on a closed bolt. LE and MIL guys have been down loading USGI 30s and 20s to 28 & 18 for 40 years, to seat on a close bolt. With these mags & plates, a one round download is more than appropriate, and in most cases you get a better overall functioning magazine with 29 or 19 rounds.
Now that I have been using this combination for years, I feel this is a reliable option for those who want to run Ranger Plates or L-Plates on USGI 20 round type magazines. This will give you the extra grip to pull the magazine from a pouch. If your running a DMR/SPR or other precision AR style rifle and prefer to use USGI 20 round magazines, the addition of Ranger Plates on your USGI 20’s may be a benefit for you.