TLDR – The winning combination was a semi auto bolt carrier and a carbine buffer – the rest is the details of the range day, the 300+ rounds we fired including 100 5.56 rounds and the problems we had with the supplied full auto/M16 carrier that came with the Radical Firearms upper.
- Started with M16 carrier + H2 Buffer – Clean Gun and chamber, lubed very well with CLP.
- Shot 5 single rounds of 5.56 with M3 pmag and locked open on each shot.
- We then tried small strings of 2-5 rounds and these would sometimes lock back on empty and sometimes not… We then fired 80 rounds total of 5.56 before trying something else – firing was fine it just would only lock the bolt back occasionally.
- We then tried some commercial .223 – PMC Bronze and were surprised to see that it ran and mostly extracted just fine, however it would almost never hold open on the last.
- We then swapped the buffer for carbine buffer and it ran better, even locking back the bolt on last shot most of the time.
- Lastly we swapped in my Stag Arms semi-auto bolt carrier along with the carbine buffer… The gun would then cycle anything and everything including my low powered reloads, some wolf .223 62 grain, PMC and of course 5.56.
I wanted to make the m16 carrier work because damn it – it came with the new upper and it SHOULD work with any ammo I feed it… Well with the carbine buffer we had some limited success.
For the last shots of the day I was able to get 15 rounds of Wolf .223 off without a hitch and it even locked the bolt back – the low powered reloads however would still not successfully load the next round – the first round would eject but it wasn’t enough to force to chamber the next round or lock open on last. I'm still unsure if it will function 100% with the auto carrier and the carbine buffer with .223 ammo - no doubt it will run 5.56 with this combination all day long.
The problem is with the M16 bolt carrier. It’s a little too heavy to run low powered reloads and doesn’t always work 100% with .223 either – although it was much better this time around than last week. BUT there is another issue with the carrier besides JUST the weight… I put this m16 carrier in my Stag to see if the rifle with the longer carbine length gas system and 16” barrel would cycle this carrier with PMC or my reloads – the answer was no – not at all. In the Stag the carrier was hanging up so much on the rounds in the magazine that it would NEVER go fully home unless you wailed on the forward assist or just chambered the LAST round of the mag.
With more than one round in the mag the bolt would get stuck about halfway to ¾ of the way home – whether you slapped the bolt release or just pulled and released the charging handle – made no difference. You can feel and see the resistance the bolt is putting on the rounds in the magazine – it is rubbing the rounds below the one being chambered. I have no experience with M16 carriers so I don’t know if this is a problem with the Stag gun not being mil spec/made for FA carrier or what but I noticed some additional resistance in the Radical Firearms upper too and this is the cause of ALL of our malfunctions with the gun – other than the gas block being loose after the first outing of course!
Bottom line is - use a carbine buffer, make sure the chamber is super clean and possibly try throwing a semi-auto carrier in and you have a 100% functioning gun. I just wish I could get it to work with the M16 carrier... Maybe it need polished - or sent in to Radical?
- The gun now has about ~500 rounds through it - 200 being 5.56 - although not every single one being on the FA carrier - 85%ish? We figure it's pretty well broken in at this point...?
Thoughts?
EDIT: There's more to the story and troubleshooting but I'm trying to keep the post from being overly long - We did try several magazines as well just as we did the first outing. HK Polymer clear, Pmag gen2 windowed, pmag gen 3, lancer L5 original translucent, pmag gen 2 20 round, etc. Definitely NOT a magazine issue.
EDIT 2: OK I definitely found the issue to be the bolt carrier - the FA carrier is rubbing on the feed lips of the polymer mags like pmag gen3 etc. It slides right over GI aluminum mags without really touching them much. The source of the resistance is the bolt is grinding on my mags feed lips - anything that isn't a GI spec mag. Do M16 carriers only reliably function with GI Mags?
I should have known this was the issue all along, I noticed from the get go that seating mags like the gen3 pmag and the HK translucent require a good SLAP even empty to seat into the mag well - whereas the GIs just "pop" in with little force like you would expect.