AR15 cycling issues with handloads

[tstanek]

Hi there,
I ran into a problem that I can't figure out. When developing a load for my .223 Rem AR15 with 69 Gr SMK bullets, VV N133 powder, CCI BR4 primers the rifle does not cycle. I am satisfied with the groups on the target and the powder load should definitely not be under the minimal treshold. With that said thing I don't get is that the load worked for me with Lapua cases without any problems, not a single time the rifle hasn't cycled.
Brass resized to the same headspace, with same die, bushing, mandrel, trim, ... basically the whole procedure has been the same. But now with ordinary S&B cartridges rifle doesn't cycle at all, but still shooting good (same) groups as before. I know the Lapua has thicker walls and therefore less volume, but somehow I don't think that difference could be the cause, also I would expect worse/different groups. Does anyone have an idea what it could be?
Thank you in advance and have a nice day!
T.

 

[rweaver00geo]

what kind of ar is it? did you build it or is it factory? Does it have an adjustable gas block? What length barrel and wheres the gas port? Im thinking gas issue?

 

[redbullitt]

Cases are where id look first if you can make it run just by swapping to lapua brass.

Details on the sb brass? New or fired? Or are they Sb loaded factory " cartridges?

What kind of malfunction are you seeing specifically?

Lock back on empty mag?

 

[PinesAndProjectiles]

Is the rifle not ejecting brass? Not feeding brass? Need more details.

My guess is you’re seeing higher pressures with the Lapua brass and this is helping your rifle to cycle properly.

What are your average velocities with each brass type?

 

[tstanek]

what kind of ar is it? did you build it or is it factory? Does it have an adjustable gas block? What length barrel and wheres the gas port? Im thinking gas issue?

The rifle is Schmeisser LRM 18 , with 18' heavy barrel, 1:9 twist with factory adjustable gassblock, was 2200 $ so it's quite decent quality and have no issues with the gun whatsoever. I've already cleaned whole gass assembly, tried to adjust gassblock with no success.
The exact issue is that it doesn't feed new round when ejecting fired one with no problems. In 1 of 10 - 15 rounds it does cycle, but I haven't found the difference in the cases which do cycle and those which don't when I inspected and measured spent brass.
It cycles with every factory ammo I've tried so far...and with hot / overpressured loads.
What I also encountered is that sometimes the bolt doesn't completely close and I have to push forward bolt assist to close the chamber, bur then it shoots normally. No diffence when measuring those rounds which cause this issue again.
Velocities are around 2860 fps with the current brass I'm having issues with. But it was pretty much the same as with Lapua's. I'm using once fired Sellier Bellot brass collected from the range, some fired with this AR15, some from another AR15's.
I've tried to use VV N135 instead of N133 with powder charges resulting in the best groups being pretty much similar for those 2 powders - 23,6 Gr, and both are on the edge of pressure signs...so that doesn't seem to me as it's caused by too low powder load.
What about trying different primers for example?
thanks a lot in advance and sorry for being quite that long and not answering sooner.
T.