List your load data, since problem may not be the load, but too fast of burn rate powder or too light of a bullet instead.
Also, what barrel twist, since that will determine the best bullet weight in the first place.
And the last one, check for loading data, since most barrels are Nato chambered, not 223 Rem instead, so can load to 62Kpsi, verse the 55K SAAMI pressures. Hence when it comes to Nato loads in 55 gain to push the bullet to 3250, will go with 2460, or 2230-C, over the slightly faster burning AA 2230 instead.
And no, since the powder used to get anything under a 55gr bullet is going to be too fast of burn rate, will not have enough gas port pressure, and need to limit the bullet to at least 55gr for a 1-9 twist barrel, and 62gr for a 1-8 twist barrel, 69 gr or heaver for 1-7 twist barrel.
Note, 69+gr bullet is going to use a slower burning powder in itself to get to speed, and can cause the bolt to unlock too fast, from the increase barrel port pressure that the powder is going to create, even if just loaded to 55psi.
My guess, your using Vectan powder, and if you switch to the next slower burning powder, this will push the max spike dwell towards the barrel gas port, to increase gas pressure to the B/C, to cycle the rifle better, while still working at the same over all working pressure of the round.
https://www.vectan.fr/UK/range-of-powdershttps://www.vectan.fr/images/files/Vectan-catalogue_A5-36p_BD.pdfHence in 55 gr, it shows either Tu3000 or sp10 that can be used, but take a closer look at the cup amounts, since can use more of the SP10, to bring the working pressure up, and even higher to the 62K nato working pressure as well. Hence would be using the Sp7, and working up the load with it, for a 55gr bullet.
Note, if you can get powder produced out of PB Clermont in Belgium, can get you the cross referance numbers for it, that is the same as AA 2460, but in a different commercial powder brand name if Acruate powder is not available instead.
Simply, don't confuse over all working pressure of the round itself, with what it going to produce in regards to port pressure.
Think this instead, when increasing working pressure will increase gas port pressure for that kind of relationship, and depending on the burn rate of the power, changes the curve of pressures to the port pressures amounts as well.
Hence faster burning powder than H335, pushes the max spike to the left/towards the chamber, while slower burning powder than H335,will push the max spike to the right/towards the gas port, and this will change what the gas port sees in pressure amounts, even if all the three loads where all loaded to the same over all working pressures of 55psi.
To add, pretty good burn rate chart for powders abroad, but not seeing vectan on the list.
https://www.lhs-germany.de/fileadmin/media/Mediathek/Pulver/Relative_Abbrenngeschwindigkeit_Export_Feb._2018.pdfSo would have to believe that sp10 is close to the 2230 burn rate, while the sp7, more towards the 2460 burn rate isntead. The Tu powder are Tubal/extruded, so may have a close burn rates as well, but the spherical powders are going to meter better if using a stand volume drop device.
And yes, spherical powders do take a slightly hotter primer to get them to ignite correctly, but we are not talking 220 swift amount of powder, so standard rifle primer is more than enough to get them ignite, and if you can find BR primers that are more consistent, but slightly less hot burn, still enough to get the powder ignited correctly (hence try to steer away from the hotter miltary primers, but don't go to small pistol primers, since the cups are too thin on them, and will end up with over pressure sign on the primer, even though your not close to max working pressures instead. Plus with the Ar15 having a floating Firing pin that will dimple the primer on loading, can get an AD on bolt closer with the pistol primers in play as well.
As for extruded/Tubal powder, if you are using an auto dispenser that is dropping to weight instead (like Hornady auto pro) , may be a better powder, since easier to ignite, and in most cases, cleaner burning as well.