The only one that I'm aware of who is known for anything remotely like this is Ralph (RDTS) who modifies standard 94 locking pieces for his SD builds. Since he also makes a 40 cal SD build, you might check with him what he uses.
I'm no technical guy, but I also think it depends where the metal is removed and whether that area was specifically hardened. In other words, I thought a piece isn't necessarily hardened uniformly, but hardened in areas that are required because of contact. Or, I could be wrong.I'd also drop a line to Mike at RCM and ask when he is planning a run of .40 SD locking pieces. I could be wrong, but I thought the final step to making a locking piece is heat treating to harden the surface. So if you machined the surface wouldn't that remove the hardened surface?
To my knowledge that is not correct. The "#24 LOW" is the current standard LP of both the full size MP5-40 and MP5-10. The #26 is out of production. Like putting a 100 degree LP in a 9mm SD, a #24 in a .40 SD I would think would cause over function. I'm sure "Bronco75" could enlighten us on LP hardening. If it were my .40 SD project, I would get the right LP. If it is a RCM .40 SD barrel, then I would get the LP from RCM. Yes, Ralph does make a .40 SD. Does he use a different port configuration in .40 S&W like that he uses in 9mm? Does Ralph's 9mm SD use a custom LP he makes or can a standard HK SD LP be used in one of Ralph's SD guns? I don't know, I'm asking.OP if you need a interim use locking piece a 10mm low might interchange for a 40, depending on the power level of the 40 S&W ammo.
I didn't see the OP say he was building a 40/SD, I read that to be he wanted a mp5-40 LP, couldn't find one and wanted to grind a mp5-9 to make one.
I agree completely if this is a SD build, then a #24low, is going to be wrong for that application.
Hummm... That's a thought. I have been using 180 Gr ammo which is subsonic to begin with. Maybe the ported barrel, a std. Hk 40 barrel cutLots of variables.
What barrel? Was a 40 MP5 barrel made to the 9mmSD spec?
Amount of ports in barrel etc.
Whose can? Does it turn std. ammo subsonic like the 9?
You might just need to find the right angle.
@HkCHUCK I might have an extra @26 LP.....Let me check and I PM you if I doHummm... That's a thought. I have been using 180 Gr ammo which is subsonic to begin with. Maybe the ported barrel, a std. Hk 40 barrel cut
down to SD length and alternating 2 and 3 holes drilled into the groves of the rifling, is mitigating the recoil impulse sufficiently to cause the
intermittent failure to eject. The suppressor is a S&H Arms 9mm one I filed a Form 1 on and registered as a new caliber 40 S&W and had the
baffles opened up slightly to accommodate the slightly larger diameter of the .40 round. The suppressor itself is 12 inches long and fills up
the cage completely so I am guessing its about 1.6 inches wide.
I think I am going to get some hotter / lighter .40 ammo and try that.
Thanks for your input.