just a heads up. i just figured this out.
with all three of my DS lowers the bolt release works on USGI and Lancer mags
with one of them the bolt release works with all PMags - no issues what-so-ever
one of them the bolt release works with old PMags, but not with M revision PMags
with the other the bolt release will not work with any PMags
how weird is that?
i guess that’s another strike against DS lowers 
none of my other brands of lowers have any issues like this. just thought i would share.
I posted on the general forum I’m having the exact same problem with an lmt lower right now.
so weird. i dont understand it at all.
doesnt matter if the mags are full or empty.
i dont know enough about how this stuff works to be able to explain WHY this happens
That’s because Lancer mags are awesome. I steal them basically, since most folks say “Look, another plastic magazine.”
yeah they are awesome.
they’re my favorite mags as well…even before i realized i had this issue with two of my lowers.
Do you think the magwell might need some judicious grinding? Perhaps the P-mags simply don’t have the proper geometry? A little sanding on the P-mags maybe? Probably better to sand/grind the P-mags than the receivers. Or, trade the P-mags for Lancers?
naw, i’ll just keep them as is. they work fine in 5 out of the 7 of my lowers.
and in one of my lowers it likes the old PMags, just not the new ones…i only have a half dozen of the new ones.
its really not that big of an issue for me, but if they were my only two rifles, yeah i’d figure something out, whether it was modifying the mags or selling them.
at the range i mostly use USGI mags anyway, so it doenst bother me too much. just wanted to let others know about the issue and maybe have someone explain to me why this is even happening.
dont get too down on the lowers- i have absolutely no consistency with pmags in any of my lowers- LMTs, Aeroprecisions, Sun Devil, MEGA, etc… doesn’t matter. some drop free from all my lowers, some drop free from some of my lowers, some dont drop free from any of my lowers.
and it’s not just pmags- brownells mags are the same way. first thing i do when i take either out of the package is bust out the dremmel, i don’t even test fit first- pmags get the lugs zapped off the back, and brownells get a run down the seam. they all drop free from all lowers after that.
yeah its not a drop free issue tho…that’s almost to be expected
its the bolt release…which i really cannot explain at all.
oh… i dont get it, then- is it not locking?
nope. locks back fine.
on one DS lower the bolt release wont drop the bolt on any PMags, either full or empty.
on one DS lower the bolt release wont drop the bolt on M revision PMags, either full or empty. works fine with the older PMags
on one DS lower the bolt release works fine with all PMags
all three lowers have G&R LPKs…except for the lower that works with PMags…that one has mostly a G&R LPK…but i accidentally installed a del-ton bolt catch cos i got my parts mixed up when i was putting that lower together.
txdukklr is having the same issue with his LMT Defender 2000 lower too. i really cant figure it out at all. maybe it has something to do with LMT bolt catches? both of my lowers that exhibit this issue also have LMT marked bolt catches installed.
like i said. its not a huge issue for me - just annoying.
and i’m really not trying to trash anyone here. i’m just completely stumped by this. the whole thing with LMT bolt catches just occurred to me, when i read about txdukklr’s problem and realized my one lower without the G&R (LMT) bolt catch works fine with PMags. for all i know this is just a coincidence. we’re only talking about a sample of three or four here.
before i was sure it was the DS lowers…but now i dont know
yea- sounds like its time to give doublestar a call.
where you get three gee and arr LPKs? i havent been able to get one… i gave up a while ago, though.
i got the LPKs a while back.
the last kit i just installed tho cos i was waiting on parts for the upper.
i finally got the parts for the upper and built the whole rifle the other day…just waiting for another member to ship me a set of handguards and the rifle will be 100% done
that is the one that works with PMags…and didn’t get a G&R bolt catch, cos i accidentally grabbed one out of my spare parts bag instead of the G&R LPK bag
i hate futzing with bolt catch roll pins. they are a pain to take out once they are in. i might just live with the annoyance. i dont mind using Lancers and USGIs on two rifles i guess.
then again if i swapped out the parts i would know for sure what the issue is.
as far as calling Double Star…i dunno…i’m not convinced its a problem with the lowers anymore. not sure what the issue is. might be the LMT bolt catches found in the LPKs i used…might not be. might be the lowers…might not be… i really can’t say i’m not going to blame anyone. i’ll just live with it for now.
more confused than ever now.
the one DS lower i thought was good with PMags…the one without the LMT bolt catch…well its good with 30 round PMags
20 round PMags are another story
whatever.
i don’t think i’ll ever find out what’s going on here.
seems like i’m not going to be buying any more PMags tho. which is a shame. they feed so well and they’re so durable.
i give up.
Keep us up to date please.
I have 2 DS lowers that have been great. The drop free with every mag I have tried from early PMAGs to Rev. M PMAGs to Lancers. The bolt releases work just fine as well.
Have you got a set of calipers? You just need to sit down with the lowers and mags and write down the conditions each lower (by serial or number them) is giving you and with which mags (again, number them). Start looking at the items that would cause this issue - ie.
By “out of spec” below, I mean could be out of spec or could be in spec but tolerance stackup of more than one component could lead to out of spec condition, but just not one feature
Mag release position in lower out of location resulting in mag seating too high in magwell?
Bolt catch position in lower out of location resulting in bolt catch not releasing the bolt?
Bolt catch lever out of spec not releasing the bolt?
Mags out of spec resulting in bolt hitting and stopping on the mag follower instead of picking up the round and chambering it?
Look carefully at the components and visualize the mechanics of what happens when pressing the bolt release and see if there are any red flags jumping out at you. Look for signs of witness marks on these components indicating irregular function. Measure and compare the comonents of the setup that works to the one that doesn’t. Take the upper off and insert mags into the lowers that work while operating the bolt catch and do the same with the lowers that don’t work - what’s different?
Focus on the lowers and mags first. If you can’t find an issue there, start looking at the uppers and bolts, but I’d bet you’ll find it in the lowers or mags.
I’m sure you can find the issue. Obviously something is different from the setup that works to the one that don’t.
…
too much trouble.
easier to just buy more USGI and Lancer mags.
i’m cool with it. i’ve agonized over it enough. i dont need to pour over it more looking at my bolt catches and all 30 of my PMags with a leup and calipers. i’ll just use the PMags with my other rifles.
probably the only easy fix would be to mod ALL the mags…and its just too much of a pain. i might wind up trashing some of them and then they wouldnt work with ANY of my rifles
and i know for a fact its not the uppers. i’ve isolated the issue to the lowers.
thanks for the advice tho…i do appreciate you trying to help me.
I had to sand new P-mags to fit my Sun Devil lowers right after the initial design change. I recently picked up a couple more recent production mags and they worked fine. I never had an issue with any of the older P-Mags.
its the u on the back of the pmags.
If you look at a usgi it’s cut away allowing a lot of the plastic guide to show, the same area on the back of the pmag has alot more material.
I think that the issue is the pmag not the lower. on the right side of two pmags I ever so slightly shaved off a few mm of the mag and it works flawlessly.
yeah…that’s what i figured.
looks like i have 30 PMags to file away at 
thanks for the info, glad to hear you only need to remove a little material