Ideally, a sizer will make all the pellets the same size, round out the skirts and make the pellets more uniform (except weight). When manufactured, the pellet's skirts are usually larger in diameter than the head by about 0.010 inch. This, I'm assuming is to ensure a good seal in the barrel...
FX removeable harmonic barrel tuner with three caliber bushings LNIB. My firm price is $65 shipped to your CONUS location. I do not accept Paypal or Venmo but will accept cashiers check, USPS MO, Zelle, or personal check (after it clears).
At the range yesterday, I was experimenting with different moderators and slugs on my .22 cal M3. Just for giggles, I removed the mod to see if it shot better. NOT! While the POI changed, the group size expanded quite a bit. I assume the weight of the mod dampens the barrel vibration to some...
Back to the basics, other than eye candy, what good are the GRS stocks? I had one on an Anschutz rimfire and other than the extra weight, it did not help with shooting accuracy. So the stock has an adjustable cheekpiece and buttplate: so do others.
Here's an interesting method of increasing shot count from another forum. https://community.hardairmagazine.com/threads/doug-rogers%E2%80%99-bsa-r-10-tune-doubles-the-shot-count.2196/
I have a .177 HM1000x coming from Martin with a bare barrel. I plan to start with a Donny Tatsu 30 cal moderator. Noise is not a big issue with me, but accuracy is. I have several other Donny moderators that I can try, but if necessary, I will shoot it with no moderator. I plan to shoot 100...
I have a ProChrono that I've had for almost 50 years. Still works fine. As a matter of fact, I once put a pellet right through the middle of it. Sent it back to the factory and they restored it for about $50. Have you considered sending yours back for repair?
I shot BR using the same set up on my TM1000. I shot it bare barrel. Why do you need a moderator? Other than make it quieter. Matches are usually held at shooting ranges where PBs are used. Who cares about noise.