?

To Gijs, and others, not all the nuts are steel. Actually I haven't seen one in steel. All three of mine are brass, and at least 2 (purchased new) were not locktighted.

I emailed Donny asking if he could have his machinist (is it John H?) make a small batch of jam nuts with 6+ mm allen centers, the stock nut takes a 4 mm, at least on mine. If he can't/won't than we should fine someone else. No damage, no mess, no issues. Not free, but the right solution.
 
To Gijs, and others, not all the nuts are steel. Actually I haven't seen one in steel. All three of mine are brass, and at least 2 (purchased new) were not locktighted.

I emailed Donny asking if he could have his machinist (is it John H?) make a small batch of jam nuts with 6+ mm allen centers, the stock nut takes a 4 mm, at least on mine. If he can't/won't than we should fine someone else. No damage, no mess, no issues. Not free, but the right solution.

You are absolutely right, there are some brass one's around, but they are also brass color, and they have the spring guide attached (the long pin) They indeed have a 4mm hex.

Most full power, and .22+ versions have the steel nut like Chuck is showing, which has a 6mm hex. The hex is easily stripped, because it is very, very thin.

A lot of the guns with the steel nut also have a hammer weight. Easier said, the guns with a hammer weight have the steel nut, ad the one's without hammer weight have the brass one. The brass nuts are better than the steel nuts, but can only be used for the lower powered versions who don't need a hammer weight.