Hello
@damageINC,
Glad to hear you got your R5M back together and shooting after our recent discussion. I use the same pellet around 890 feet per second in my R5M. I have a few thoughts that might help your accuracy. I don't usually punch paper for groups with mine, I sight it in using steel spinners and repaint them when necessary in order to read my hits and check my zero. I cannot say with any personal data how well mine is doing with flyers but I have some general tips.
I agree with
@jwrabbit123 about checking your magazines carefully and look for any burrs or tight chambers that might be damaging your pellets.
When I cycle my action, I always do it slowly and deliberately, especially charging slowly in the forward direction where the pellet is pushed through the magazine and seated in the lead-in area. I try to make the most consistent and repeatable charging action each time without rushing it.
I also lube my pellets with a combination of krytek finish Line wax and a little bit of ballistol. I do this by dripping the lube into a round corelle cereal bowl, pouring in a tin of pellets, and gently shuffling them around the way a chef sautes vegetables, flipping them back on themselves against the rim. I rotate the bowl 90° every few flips until all the lube looks well distributed. This usually dislodges any flakes or debris that might be on the pellets and then I wipe the bowl and any excess lube out afterwards with a paper towel. Sometimes there are a few flakes. Yes you could say I saute my pellets haha. Some of this lube transfers to the o-rings on the magazine o-rings and helps the pellets slip through easily without damaging skirts.
Another thing I do is when I load my magazines, I tap them gently, forward face down, on a wood surface to seat the nose of each pellet flush with the front of the magazine, so each pellet has the exact same chambering travel distance when charging.
You might want to remove your breech block (see excellent video from Edgun West It's easy to do) and inspect the entire breech area for any burrs or debris. You can clean or swab away any deposits or lube from the breech O-ring and transfer port area. You might need a magnifying eye loupe and a flashlight to inspect the transfer port for any burrs and use a dental scraper if necessary to smooth out any rough edges you see.
I also extensively polished my barrel, first with JB bore compound and then simichrome polishing paste.
If you take the stock off you will notice there is an access hole for lubricating the hammer/trigger sear areas. The surfaces are exposed when the hammer is uncocked. I cleaned these and applied some molybdenum disulfide grease to the mating sear surfaces without changing the trigger pull weight adjustment and my trigger action is much nicer and more consistent.
And finally as far as technique goes, I find that maintaining some shoulder pressure, keeping the butt pressed into my shoulder, provides more consistent results. I most often shoot (pesting) with a bipod in a standing position from door frame or against trees and anchor one of the feet against an object and lean into the butt a little bit with my body. I frequently grab the other leg with my off hand as a grip and pull the rifle into my shoulder a bit with a gentle cheek weld.
Since you've recently done some repairs on your valve, it may take a while to blow out any little blobs of silicone lube that might have worked their way up from the transfer port. It may help to pull a patch or two through every few magazines.
Good luck and have fun shooting!
Feinwerk