AR15 9mm conversion bolt repair - Brushing technique for AR-15 9mm Conversion bolt

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