Suppressor adds back pressure to the bore/the gas port, which in turns opens the bolt faster.

Next lets talk Mk262/Federal FC262 77gr OTMand type ammo, that uses a slower burning power for the heaver bullets, which pushes the peak burn dwell spike of the burn closer to the gas port as well, and so even more gas pressure down the gas port, to unlock the bolt even faster.


So since we can pretty much tell that the bolt is unlocking too soon and need to slow down the unlock, couple of ways to attack the problem.

First is heaver buffer, but until you know what weight you really need, could get spendy with playing the trial and error game working through them.

Stronger extra tension recoil spring may work, but again, playing the bind game until you find the ideal increased spring tension to slow the bolt unlock back down to normal and since the springs do tend to weaken at the 4K mark, trying to get the same extra tension spring  again, could end up with trial and error each service life spring change.

The pro's with either spring or buffer, is if you pull the can and say want to run standard 55gr ammo in the rig with its powder normal burn rate, quick swap of either spring or buffer back to normal units, and Bob's our uncle.

As for the other way around to reduce gas pressure to the B/C to slow the bolt unlock back down to normal, would be either adjustable gas block or adjustable carrier key.  

Of the two, prefer lever type adjustable  gas blocks that just have the three settings of normal, adverse, and off.  
The trick here, is to either get the lever without any ports on it so you can drill your own sizes, or to just weld up the ports and start fresh.  
Hence we turn the adverse to normal port size, so the rig can run 55 gr without can on that setting.
Next work up on the normal sizes to run the with just the heaver ammo.
the last off setting, we size that port so the rifle can run with both the can and heaver bullet ammo.
Simply, since the lever just has the three setting that you have adjusted for your different needs,  can switch it as needed dark thirty by feel alone with it simple repeats.

Short of that, then you are back to adjustment screw type gas blocks or carrier keys, where you are playing the guessing game of how many clicks/percentage turns of the screw that you need for the different settings instead.

A1/A2 buffers (one and the same) are 5.15oz, for either semi or full auto.

As for heaver rifle length buffer, there are few different ones,
https://heavybuffers.com/ar15rxh.html

The downside to going to a heaver buffer, is you are increasing the reciprocation weight, so more felt recoil.
Note, Short of say a DCM rig, where you have so much more barrel and forearm tube weight, then butt stock weight to balance the rig back out, that the extra buffer weight is not going to make a difference.

Hence this is the reason that I like to solve the increase gas to the B/C unlocking the bolt too soon from can and/or heaver ammo, with adjustable gas block to lessen the pulse that way instead.  This keeps the reciprocating mass the same with the standard rifle length 5.15 buffer weight in play so your not increasing felt recoil.

@wcreed

FWIW... I tried some of the FC262 when it first came out. I think it was around 2016 ( Yup just checked it Nov. 2016.. $17/20rds )

My batch also blew primers, in a known good rifle length gas , 20" 5.56 chambered rifle that has fired ALL sorts of 5.56 NATO ammo with all sorts of different bullets... with no issues.

I stopped using it. It sits somewhere next to my '80s IMI ball ammo.

I assumed it was running the ragged edge / over pressure wise..... so maybe yours is as well.

This stuff ?

Since the FC262 does come with stacked primers to resist the blow primer problem over all, the problems with the primers is often if the rig is set up for 223 or 5.56 nato isntead.  Hence gas system/unlock set for  55Kpsi, or 62Kpsi working pressures isntead.

Also, keep in mind that some Mil nato rigs that will be suppressed full time, their barrels do have smaller gas ports  to begin with.
Hence about a decade back, such Colt smaller gas port barrels did find their way into the civilian market, ending up having to have their gas ports sizes increased to allow them to run with 223 ammo not suppressed.

Most barrels are gas ported standard size, and with standard ammo, like M193 and M855, can get away with running a suppressor with it on a rifle barrel/full length butt stock/buffer.

Same goes for running 262 for the most part without suppressor on a full length A2 rifle. If a standard rifle is having problems, then it was gas ported larger for 223, and not 5.56 Nato isntead.
Note here, military cross wall chamber are on the slightly larger size, while civilian barrels tend to be reamed on the tighter cross wall side instead.  Due to this, the tighter cross wall chamber may be more accurate, but since it will allow for less blow-by at firing forming, it will push the working pressure of the ammo higher.


So its when you are suppressed, and running the 262 as well, that the two combines on the A2 set up for 223 ammo (not nato), and the bolt is way unlocking too soon isntead.

Heaver buffer should solve the compo for the two, but since it is going to induce a bit more felt recoils from the extra mass of the buffer moving, prefer to solve the problem running a standard weight buffer and reducing the amount of gas to the B/C instead.
Myself, if the rig is going to run the suppressor full time and only going to be Feed it 262 ammo, would just Tig weld the gas port on the barrel closed, and re-drill the port smaller size as needed instead.

Kind of a fan of the adjustable gas keys for GP, but since your putting the obstruction at the end of the gas tube, can have some drawbacks with long rapids and full auto fire (cause the gas tube to deflect, and warp over time, more that the standard back pressure of just the B/C to begin with).

So with adjustable key in play, make sure that you are pulling the Bolt off the carrier every so often, to double check your alignment of gas tube to key is staying true.