I'm trying to get an MP5K in 10mm in functional shape and am having a problem with the locking piece. The gun came from the builder in bad shape, and had a 120 degree SD locking piece in place. With this in, the bolt gap was about .015".

Thinking the gun would eventually tear itself apart with this locking piece, I swapped in a #24 piece (90 degree) from my full-sized MP5/10.
Now my bolt gap is 0.

Doing some reading online, I see that the #24 and #27 locking pieces are both 90 degrees, with the #24 intended for the full-size MP5/10, and the #27 intended for the MP5K.

Before I buy a #27 piece (or #28-80 degrees) online, can anyone tell me if there is really any difference between these two locking pieces, or if I should just replace my rollers with oversized ones?

Thanks

ETA- Sorry, this may be better suited for the HK section. Please delete.