RRA lower and PMAGs

[82ndtrooper]

Just tonight I finished assembling the RRA-Lar15 lower with an LPK from Brownells and the KNS non-rotational Gen 2 Mod 2 pin set up.

Funny though, all the USGI mags seat perfectly and when the mag catch is pushed they all fall from the reciever, except the PMAG’s.

PMAG’s fit pretty snug and when the mag is pushed they do not DROP from the reciever, loaded or unloaded.

Can polymer expand in cold temperatures or is the RRA-Lar15 lower just out of spec ???

Any non demeaning or non sarcastic comments would be appreciated.

[JSantoro]

Not an uncommon occurrence with RRA and certain other lowers. I doubt that your lower’s out of spec, given that USGI mags do fine. There’s a fix for the Pmags.

Look at the back of the mags (the narrow side the primer end of the rounds point to when the mag is loaded). At the top 1/3, where the mag fits into the bottom of the mag-well, you’ll note 2 little flat polymer nubs molded into the mag itself. Lightly sand these nubs down, bit-by-bit, until they drop free unloaded without assistance.

For a more accurate location and reference, see Rob-s’s post at the bottom of page 1 of this thread: https://www.m4carbine.net/showthread.php?t=30029&highlight=dropping+free

Or, call Magpul, they’ll likely tell you the same thing. Not the first time it’s come up.

If anything, the polymer would contract in colder temps. That’s just science.

[82ndtrooper]

@Riverine

Not an uncommon occurrence with RRA and certain other lowers. I doubt that your lower’s out of spec, given that USGI mags do fine. There’s a fix for the Pmags.

Look at the back of the mags (the narrow side the primer end of the rounds point to when the mag is loaded). At the top 1/3, where the mag fits into the bottom of the mag-well, you’ll note 2 little flat polymer nubs molded into the mag itself. Lightly sand these nubs down, bit-by-bit, until they drop free unloaded without assistance.

For a more accurate location and reference, see Rob-s’s post at the bottom of page 1 of this thread: https://www.m4carbine.net/showthread.php?t=30029&highlight=dropping+free

Or, call Magpul, they’ll likely tell you the same thing. Not the first time it’s come up.

If anything, the polymer would contract in colder temps. That’s just science.

.

Thanks for the link Riverrine.

My PMAGs do not have the little “nubs” you are referring to. These PMAGs where purchased after the recall with the appropriate date code, but no “nubs” where you are referring too.

They slide in very snug at the top 1/3 of the mag and barely, if any, drop when the mag release button is depressed.

I swear when I installed the mag catch that these PMAGs droped fine.

ETA: I just tried the PMAG’s in an LWRC and a Les Baer rifle and they drop perfect from those two. Very strange. Agai, on the back of the upper third of the mag tower I DO NOT have those little “nubs” protuding out on the rear upper mag tower.

[Iraqgunz]

I think that it’s well known that RRA lowers tend to be a little tighter than normal.

@82ndtrooper

.

Thanks for the link Riverrine.

My PMAGs do not have the little “nubs” you are referring to. These PMAGs where purchased after the recall with the appropriate date code, but no “nubs” where you are referring too.

They slide in very snug at the top 1/3 of the mag and barely, if any, drop when the mag release button is depressed.

I swear when I installed the mag catch that these PMAGs droped fine.

ETA: I just tried the PMAG’s in an LWRC and a Les Baer rifle and they drop perfect from those two. Very strange. Agai, on the back of the upper third of the mag tower I DO NOT have those little “nubs” protuding out on the rear upper mag tower.

[82ndtrooper]

@Iraqgunz

I think that it’s well known that RRA lowers tend to be a little tighter than normal.

I don’t know if that’s a good thing or a bad thing ?

I like the upper and lower to be somewhat tight, but not every lower and upper are exactly spec’d for each other. Hence the accuwedge and rubber O ring on the front lug of the upper reciever. :rolleyes:

I just ordered 10 PMAG’s for this build in FDE since it’s my first build with FDE furniture.

Guess I’ll just have too see if these drop from the magwell, or I’m going to have to train myself to pull them out and throw them in the drop bag. Guess I could alway’s purchase 10 of the tan USGI’s with the Magpul followers and Ranger baseplates, once BCM get’s them back “IN STOCK”

Thanks for the replies gentlemen.

[Iraqgunz]

I would also dump the Accu-crap and O-ring. It doesn’t serve any useful purpose other than to ease peoples minds.

@82ndtrooper

I don’t know if that’s a good thing or a bad thing ?

I like the upper and lower to be somewhat tight, but not every lower and upper are exactly spec’d for each other. Hence the accuwedge and rubber O ring on the front lug of the upper reciever. :rolleyes:

I just ordered 10 PMAG’s for this build in FDE since it’s my first build with FDE furniture.

Guess I’ll just have too see if these drop from the magwell, or I’m going to have to train myself to pull them out and throw them in the drop bag. Guess I could alway’s purchase 10 of the tan USGI’s with the Magpul followers and Ranger baseplates, once BCM get’s them back “IN STOCK”

Thanks for the replies gentlemen.

[82ndtrooper]

@Iraqgunz

I would also dump the Accu-crap and O-ring. It doesn’t serve any useful purpose other than to ease peoples minds.

It’s just an itch that I like to scratch. :o

ETA: I just now filed down the rear of the first third of the mag tower with a steel file. There was a rather stange elongated bump. I simply filed it down, restored the color with WD-40 and it now falls free from the RRA lower just fine.

Thanks gents for the link and your replies. Problem solved. Now for 20 other mags to neet the metal file.

[Slippers]

@82ndtrooper

It’s just an itch that I like to scratch. :o

Be careful with that front o-ring around the lug. Most oils/solvents tend to break down cheap rubber o-rings, plus the upper and lower will pinch it and put additional stress on it. Eventually the o-ring will slice, and if you happen to have a magazine inserted, it will leave a little piece of o-ring floating around inside the action. Where will it go? Trigger group? Caught on a round feeding and into the barrel? Your guess is as good as mine, but that’s not something you want in your rifle.

[82ndtrooper]

@Slippers

Be careful with that front o-ring around the lug. Most oils/solvents tend to break down cheap rubber o-rings, plus the upper and lower will pinch it and put additional stress on it. Eventually the o-ring will slice, and if you happen to have a magazine inserted, it will leave a little piece of o-ring floating around inside the action. Where will it go? Trigger group? Caught on a round feeding and into the barrel? Your guess is as good as mine, but that’s not something you want in your rifle.

You are correct Sir !!

I’ve had them slice and it’s not only till I remove the upper from the lower that it actually hangs from the lug. Their pretty tight, but they do break, as you said.

Again, it’s just an itch I like to scratch.