A client came to me with a 9mm conversion upper with magwell adapter for STEN mags, complete upper and conversion bolt.
The 9mm conversion bolt uses a return spring combined with a modified AR15 firing pin.
But the 9mm conversion bolt had some spiderweb cracks on the boltface due to failure of the return spring.
I was able to fabricate a brand new firing pin and spring to replace the worn parts.
And instead of needing a brand new bolt of at least $350.00, I was able to brush / brushing the firing pin channel:
BRUSHING invloves:
- drilling out Firing Pin Channel
- threading in a Hardened Steel Rod
- re-drilling Firing Pin Channel into the Threaded Steel Rod
A final modification was
ramped / ramping the bottom of the 9mm AR Bolt to allow use of Standard AR15 Lower Parts ..... especially the stock AR15 hammer