piston cap from T6 6061 aluminum rod for a $20 Chicom springer I bought I thought I'd post them here. Actually, the mod (along with new spring guide and MUCH honing/deburring) was successful for the .177 B3 which increased velocity from 500fps to over 700fps with CPLs and I even ended up with pretty good velocity consistency.....sigh....but alas it still ended up being a pretty good "can roller" with only about 1/2" ctc accuracy at 11 yards, not countin' a few extra fliers that spread the group about twice the size.
Anywhoo.....while the machining sequence for a R9 piston cap is a bit different due to a c-bore and cross drilled/tapped holes in the rear to secure the cap to the piston (unlike this version secured with a LockTited screw) many of the "processes" are the same. A little disclaimer here.....I'm not a "real" machinist and this is only the way I did it which might not be the best way.
Cutting a 90 durometer urethane washer to replace the factory plastic one. For my R9 caps I like to use a .030-.040 thick urethane "bumper" between the piston cap and piston and it's cut in a similar fashion. The surface finish of the bumper isn't important so I don't even swap out my parting tool for the sharp high rake tools I ground when I was cutting my own urethane piston seals a couple years back.
Face the alum
Cut to diameter
Cut the o-ring groove
Polish the groove with rolled 0000 steel wool
Drill the cap for screw
Countersink for screw
O-ring fitted to cap & OD measurement checked
Checking O-ring fit to honed & cleaned compression tube
Pix not shown here but there is a "parting operation" here:
Assembled cap on the "hammer and chisel fabricated" Chicom piston after a lot of polishing, plus facing orr the end of the piston due to EXTREME "operator induced" lathe chatter that left the surface uneven and rough as a rasp. Actually, even for a $20 springer I was a bit surprised with the amount of obvious hand filing and grinding on the parts. Oh well, it seems the attitude is that "slave labor" is cheap and the build quality doesn't matter so why automate to improve the "gutless wonder".
