5.56 f2f malf on Larue upper w/ A5H3

[Tremor6385]

hey guys I’ve got a 16” Larue Match upper on a Anderson lower with A5 RE. I’m running a Tubbs flatwire spring and recently put in an H3 Vltor buffer. I noticed at the range yesterday that when I was shooting from prone I got a fail to feed where the face of carrier got hung up on mag follower while the LAST round sat on top of mag free with just the tip poking into chamber. I’ve never seen or heard of that specific malf before and was hoping someone could shed light on what may be causing that..? I was shooting .223 69g SMK from ADI when this happened.
I swapped to my 14.5 BA SPR upper and same issue popped up once as well but can’t say for sure which ammo I was using when that happened.. I was also shooting 5.56 Bone Frog 77g OTM and PMC XTAC.
I haven’t had this issue with a H2 Vltor buffer so could it most likely be the buffer, if so, would like to know how that’s the case.

Any help would be greatly appreciated! Pics are of both uppers View attachment IMG_1286.jpeg

 

[Clayman]

I'm going to guess it's the A5H3, spring or both.

If you're not shooting suppressed your 16" would have to be horrendously over-gassed in order to need an H3 imo.

Also the A5 system uses a rifle length spring. If I remember correctly the Tubb is a universal fit for the carbine or rifle length buffer tube. Maybe that comes into play with your set up as a variable or maybe it's just the buffer weight.

I like the A5 with the springco green and h2. If the H2 works and that's the only change it's probably just too much mass.

 

[WeR0206]

I'm going to guess it's the A5H3, spring or both.

If you're not shooting suppressed your 16" would have to be horrendously over-gassed in order to need an H3 imo.

Also the A5 system uses a rifle length spring. If I remember correctly the Tubb is a universal fit for the carbine or rifle length buffer tube. Maybe that comes into play with your set up as a variable or maybe it's just the buffer weight.

I like the A5 with the springco green and h2. If the H2 works and that's the only change it's probably just too much mass.

This ^^^.

hey guys I’ve got a 16” Larue Match upper on a Anderson lower with A5 RE. I’m running a Tubbs flatwire spring and recently put in an H3 Vltor buffer. I noticed at the range yesterday that when I was shooting from prone I got a fail to feed where the face of carrier got hung up on mag follower while the LAST round sat on top of mag free with just the tip poking into chamber. I’ve never seen or heard of that specific malf before and was hoping someone could shed light on what may be causing that..? I was shooting .223 69g SMK from ADI when this happened.
I swapped to my 14.5 BA SPR upper and same issue popped up once as well but can’t say for sure which ammo I was using when that happened.. I was also shooting 5.56 Bone Frog 77g OTM and PMC XTAC.
I haven’t had this issue with a H2 Vltor buffer so could it most likely be the buffer, if so, would like to know how that’s the case.

Any help would be greatly appreciated! Pics are of both uppers View attachment 8774064View attachment 8774065

It sounds like the upper doesn't have enough gas to overcome the extra reciprocating mass you introduced by switching from H2 to H3 buffers. You usually do this to tame an overgassed gun.

Were you having different issues with the H2 and that's why you switched to H3?

 

[Tremor6385]

This ^^^.


It sounds like the upper doesn't have enough gas to overcome the extra reciprocating mass you introduced by switching from H2 to H3 buffers. You usually do this to tame an overgassed gun.

Where you having different issues with the H2 and that's why you switched to H3?

I am a newer shooter and still kinda experimenting with my setups would be the main reason for going with the H3. It feels like the Larue has more recoil compared to my Rosco K9 13.9” and 14.5” BA uppers. My thoughts were that if I could slow recoil down a touch it would, along with practicing the fundamentals, aid in follow up shots at distance.
The other reason was that I had to buy a new buffer due to my Vltor H2 buffer needing to be sent in for a warranty.

I think I will try running stock rifle length spring first and if that doesn’t work order another H2 buffer. I appreciate the help guys

 

[BCP]

fail to feed where the face of carrier got hung up on mag follower while the LAST round sat on top of mag free

Try a different lower with a regular buffer/spring, none of that extra power weight stuff.

 

[Tremor6385]

I decided to do a full cleaning on my 14.5 upper and afterwards I decided to take a few live rounds and put them in my 20rd steel Duramag. I used the CH to slowly load/extract them and found that I can consistently get that malf to occur. The last round pops out on the back stroke of BCG. I changed to Pmag and I’m not getting that issue. I’ve not had a single problem with that duramag until this point.
Any ideas??

 

[TonyAngel]

My suspicion is that you're having either a magazine problem or a problem with the lower, in that the mag catch or its location is allowing the magazine to be a bit too high in the mag well.

When shooting prone, are you using some sort of front rest or are you resting the rifle on the magazine? If you're resting the rifle on the magazine, try not doing that. If you aren't resting on the magazine, try a different magazine.

I really don't want to get off on the tangent of Anderson lowers, but although most can run them for years and thousands of rounds without problems; many just haven't run across the problems common among those receivers because they just don't do things like use the magazine as a monopod.

It's entirely possible that this has been a problem all along, but it just hasn't manifested itself due to bolt velocity allowing the bolt to overcome the hitch with the mag follower. Still, in no case should the face of the carrier ever get hung up on the mag follower.

If you're fine with the way it was running with the a5h2, just replace one of the tungsten weights in the a5h3 with a steel weight from a standard buffer.

 

[Tremor6385]

My suspicion is that you're having either a magazine problem or a problem with the lower, in that the mag catch or its location is allowing the magazine to be a bit too high in the mag well.

When shooting prone, are you using some sort of front rest or are you resting the rifle on the magazine? If you're resting the rifle on the magazine, try not doing that. If you aren't resting on the magazine, try a different magazine.

I really don't want to get off on the tangent of Anderson lowers, but although most can run them for years and thousands of rounds without problems; many just haven't run across the problems common among those receivers because they just don't do things like use the magazine as a monopod.

It's entirely possible that this has been a problem all along, but it just hasn't manifested itself due to bolt velocity allowing the bolt to overcome the hitch with the mag follower. Still, in no case should the face of the carrier ever get hung up on the mag follower.

If you're fine with the way it was running with the a5h2, just replace one of the tungsten weights in the a5h3 with a steel weight from a standard buffer.

Appreciate your advice, I’m always using a bipod/bag combo when shooting from prone. The comment regarding the problem only now showing itself after replacing the H2 for the H3 would make the most sense but since I’ve found that I can make it happen by just racking the CH slowly to load rounds makes me think the issue lies elsewhere.. To your point about the Anderson lower. The lower does not allow polymer mags to fall freely when trying to reload. I’ve found that metal mags seem to resolve that issue. I will try a different mag today and see what happens. I will also use the T2 buffer in my other lower to see if problem still persists. Again, thank you all for helping me work thru this.

 

[TonyAngel]

Just a thought, but which mags are you running? You may be able to just try a different follower.

Yeah, that isn't unusual with Anderson lowers.

 

[Tremor6385]

It’s the steel 20rd duramag with orange follower. I went to range this afternoon and experienced zero issues with my 20rd Pmags. I tried using the duramag once after I had been there for awhile and sure enough the last round failed to load. I did notice that my bolt was locked back on the latch as well. Is there a different follower I can try?

 

[BCP]

Possible your lower is out of spec and your mag is sitting a little high, or maybe your bolt catch isn't 100% where it's supposed to be. Right now just stick with Pmags since they work.