View Full Version : Mod the lower or the PMags?
I picked up two CDD pre-prod lowers a while back. I just got around to looking at them in any detail and I put one together using a G&R LPK, MIAD, and Modstock. Very nice. Except ... my older '07 production PMags hang up in the magwell. I have about 15 of these older production mags. These mags hang up in both of the lowers. I compared the width of the magwell's on the two CDD lowers to the three Stag lowers I have. The narrow part on the CDD's is the back part near the trigger guard. There is about .004" difference between the Stag and the CDD. It doesn't seem like much, but it does make a difference.
My question to the members is would you widen the lower or narrow the mags? I'm leaning towards widening the lower, so there will be no issues across the board with any of my PMags (later production aren't as tight, but there is still some good friction there). What would ya'll do?
Master_of_Sparks
09-15-08, 17:08
Option C: Just use USGI mags in that gun.
and lightly sanded the P-mags with some medium sandpaper. I have
a CDM4LE and 2 of my 15 p-mags would not fall from it. They were both
black p-mags w/windows. I lightly sanded ,refitted,and repeated the process
until it dropped free. One mag took all of about 5 minutes to fit,the other about
10min. If I showed you them now you could'nt tell they were ever sanded:cool: .
winner winner chicken dinner .:D
Option C: Just use USGI mags in that gun.
I always default to modding the cheaper part first, i.e. P-Mags. In this case it's also the easiest replaced since the lower is the serialized part. Although you probably couldn't muck up the lower to bad even if you tried.
Just my .02
-RD62
As stated above, I suggest sanding the mags. Most people will be surprised at how little material can cause a hang up.
read on 10-8forums that a guy was having issues with some older pmags. magpul replaced them.
http://www.10-8forums.com/ubbthreads/showflat.php?Cat=0&Number=71758&an=0&page=1#71758
Ridge_Runner_5
09-16-08, 13:06
Yep, call up Magpul, they will gladly trade magazine bodies with you...
As stated above, I suggest sanding the mags. Most people will be surprised at how little material can cause a hang up.
I hope you're right Rob. I've got 45 PMags to do (and then everyone I purchase after that) just to insure an easy release from the magwell. Although, I'm still contimplating modifying the lowers.
Limiting my use of aluminum USGI mags for those lowers is just not a reasonable option to me.
Yep, call up Magpul, they will gladly trade magazine bodies with you...
Actually, I don't consider this a Magpul issue. While the CDD lower may be within the spec's tolerances, considering I have 3 other lowers produced over 4 years that function just fine, I'd say it is a lower issue.
Patrick Aherne
09-17-08, 23:17
File that lower, carefully, and have fun!
File that lower, carefully, and have fun!
Yup, that's what I've decided to do. I was checking the dimensions last night between my 3 Stag lowers and the 2 CDD lowers. There is no difference in the width of the magwell near the front. But the rear, near the trigger, there is .01" difference with the CDD's being narrower in width of the opening. I was considering using a Dremel, but I believe a file would be more accurate for what I need to accomplish.
Eagerly awaiting your results...
I'm reserving judgement until the lower is complete and I can fully function check, but it looks like my CDD blem lower is going to have the same issue. I've only got 1 PMag at this point though, so maybe sanding Pmags as I get them is a better choice for me.
Eagerly awaiting your results...
I'm reserving judgement until the lower is complete and I can fully function check, but it looks like my CDD blem lower is going to have the same issue. I've only got 1 PMag at this point though, so maybe sanding Pmags as I get them is a better choice for me.
I will make it a point to post pics, then. I have a total of 45 PMags and they all hangup to some degree. Sanding is just not a reasonable option to me, at this point. I'm wondering if CDD has corrected this issue with the production lowers?
I'm wondering if CDD has corrected this issue with the production lowers?
Based on this thread (https://www.m4carbine.net/showthread.php?t=16740&highlight=PMAG) it certainly sounds like they're aware of any issues and are doing their best to avoid them. Our lowers (pre-prods and blems) are likely not representative.
This caught my eye:
....If you are testing with just an assembled lower then some of the PMAGs will not drop free, some of the time....
Which is why I'm waiting to get my lower all together (if I could only get my hands on a OD UBR and MOE grip!) before I take any action to fix it.
Our lowers (pre-prods and blems) are likely not representative.
I believe that to be true.
Which is why I'm waiting to get my lower all together (if I could only get my hands on a OD UBR and MOE grip!) before I take any action to fix it.
One of my lowers is complete and sitting under a Noveske N4 Light Recce. The older '07 PMags hangup in the magwell. The '08's will hangup or bind to some degree if they're empty or only have a handful of rounds in them.
Well, I got the rest of my parts on order today so hopefully I'll have my lower put together next week. I'll post up how it turns out, and if I need to shave a Pmag I'll try and get before and after pics to show how much had to be removed, and maybe this thread will a good reference for others whichever fix they choose.
I promised I'd follow up after getting my lower completed, and I got that done yesterday. (https://www.m4carbine.net/showthread.php?t=19551)
I only have two Pmags -- both from G&R this summer so I'd assume they're the latest generation. One falls free every time, one sticks every time. I'm going to play it by ear and just check Pmags as I get them, there seems to be enough variation that the tolerances on my lower (sample size: 1) stack with Pmag tolerances in a way that some stick.
As a side note, I did have an issue getting the UBR installed...the hole below the receiver extension threads (where the receiver end plate inserts to prevent rotation) did not line up with the tab on the UBR that was supposed to insert. It was too high. I had to shave the bottom of the UBR's tab slightly to make it work :( Good tight fit, now, though.
Well, I did mine. What a PITA!!!!!! I tried filing, but the 7075 was too hard and I had to go with a dremel. Not fun and not easy. I had to take quite a bit off the back end of the magwell. I also had to take off some from the front. The older '07 mags will release, but not as nicely as on my Stag lowers. The carbine has to be facing pretty much horizontal to get a easy release.
FWIW, my VLTOR receiver plate fit fine when I installed the Modstock.
I'm going to just sell the other lower over on the EE at TOS. It's not worth the hassle. I'm guessing CDD got this fixed on their production lowers.
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