77 Grain FMJBT Freedom Munitions rounds
Radical Firearms AR Carbine length, 1:7 barrel … no mods
ASC & Magpul Gen 2 Mags were used
Never had this occur in with 55 -62 grain ammo
I’m thinking the heavier weight round couldn’t generate quick enough recoil force, and that caused some short stroking?
All rounds fed & fired, but bolt didn’t lock back consistently. FM may have also been loaded a bit light, which has been my experience, not my fav ammo but what I had
I found gen 2 PMags to have problems with locking the bolt back in general. Changes they made at the rear of the mag where it interacts with the bolt catch on the gen 3 PMags are supposed to fix that, but I got burned on gen 2s so I went to all USGI magazines.
I would try USGI mags to narrow down the source of problems before tinkering with anything else.
If it’s at the edge of operating correctly, the mags could definitely make the difference of the bolt locking back even if it’s not the mags’ “fault”, especially since the mag interfacing with the bolt catch is so critical. I think it’s worth a shot.
Mags aside, you can check to make sure the gas block is correctly aligned with the gas port. It could be slightly occluded. Was it assembled by Radical Firearms? That alone would give me pause, their reputation is what it is for a reason.
Other than those two things, there’s really nothing else to consider. Any AR should run reliably with 77 grain ammo.
K, I’ll get it to the range and see how it does with 55 grain ammo, and my other mags. How can I check the alignment of the gas block … just if it’s centered on the rifle’s barrel? I’m aware of RFs reputation. I have other ARs of higher pedigree, but I do like a project and debugging and hey, when you’ve had a couple of beers and were awaiting the election of President Hillary, a $500 AR was too easy to click the ‘buy’ button!
I don’t think there’s a way you can check the alignment without simply removing the gas block and re-installing it correctly. It may be barely too far forward or backward rather than rotated off-center.
In 2008 I put together an AR with a 20inch barrel and a Colt receiver extention and an A1 butt stock. Yesterday I dug it out of the safe and after being cleared put an empty mag it I pulled the charging handle and the bolt did not stay open. Mind you all I never fired this rifle. I tried another mag and still the Bolt wouldn’t hold open. I tried a spare bolt assembly and sill the bolt wouldn’t hold open Tried a spare mag release, heck the original one was brand new. Nope still the bolt wouldn’t hold open . It seemed the bolt did not go back far enouth so I pulled out the buffer and sprind and it seemed to go back enough to close . i took off the but stock and I know [yeah right] there is an A1 length butt stock screw and an A2 legnth Butt stock screw. I had spare of both so compared them and the screw I took out was longer than the A1 screw but shorter than the A2 screw so i reassembled the Butt stock using the A1 screw and the rifle was fixed I still haven’t fired the rifle. The Moral of the story is [other than me being a Caboose and even I make mistakes :sad:] AR spare parts aren’t that expensive and they are good to have. The job took about 15 minutes, I should have pickup on what the problem was right away.,
Freedom ammunition is shitty ammo, this could be the problem.
You are running a budget AR that is probably not ‘‘in spec’’ in several aspects.
Both of those aspects in conjunction with one another are not doing you any favors.
My first suggestion would be stop shooting freedom ammunition, don’t shoot anyones reloads but your own. https://www.google.com/search?q=freedom+munitions+kaboom&rlz=1C1GGRV___US751US751&oq=freedom+munitions+kaboom&aqs=chrome..69i57.8652j0j4&sourceid=chrome&ie=UTF-8
ETA: Both freedom munitions ‘‘new manufactured’’ and ‘‘reman’’ ammo has endless reports of kabooms on the net.
Also, the weight of the bullet is only part of the equation, what you are describing as to your theory of why this isn’t working is not how any of this works at all… Could be that freedom munitions used a crappy powder or improper powder charge that is not giving proper pressure at your gas port to cycle your gun properly. Heavier bullets require smaller powder charges than lighter bullets, heavier/longer bullet will increase the pressure of your powder burn in comparison to a lighter/shorter bullet.
Your gun should cycle 45gr-77gr bullets with no problems so long as the right powder and powder charge is used with the bullets ( along with case length, headspace, etc ).
Bullet weight alone would not dictate if your gun cycles properly, what will be the main factor is the pressure rate at your gas port which will be dictated by the powder type and charge weight used in conjuction with the bullet type and weight etc.
Honestly, your problem could be as simple as stop shooting crappy Freedom reman ammo, your gun or face blowing up isn’t worth saving 50 bucks on a case of ammo. If your gun never had problems with other ammo, then the problem is you are shooting freedom ammo.
I’m sure many here love freedom reman, but I will never shoot it because of how many times I have heard of people blowing up their guns with the stuff. There are reasons why that stuff is so cheap.
It really isn’t so far so good. It isn’t locking back with .223 spec ammo, so the upper is losing gas somewhere. Take your gas block off and re-install it… Radical has had a pretty extensive history of really botching the assembly process, so best case scenario it is a misaligned gas block. You are just going to have to take it one step at a time and work through your rifle’s gas system to see where you are losing pressure. Honestly tho, if you use questionable ammo in a questionable upper, you just may end up with questionable results. Buy a few different brands of .223 spec ammo (not surplus 556) and see what the results are with those. If the same thing happens with the other ammo, you have an issue with the rifle… if you can shoot all other .223 and .556 but that FM 77gr, maybe it is just the ammo.