Here we go heading down this rabbit hole…
I found myself in the same situation as you describe, so the hunt was on.
You are correct they are 6-40 and the
factory length is a odd one.
Another observation, I did not like how the factory head socket seems to strip out somewhat easily.
Details as observed:
Factory -VS- Soultion (5/16 6-40 socket-head)
OAL .456 / .429
THREAD .321 / .294
HEAD .135 / .135
HEAD DIA. .199 / .219
Ok with these
factory numbers in mind I went on the hunt,
I found 2 options that were close 5/16(.3125T) & 3/8(.375T) again
factory is (.321T/ .456-.135=.321)
I could trim the length of the 3/8 screw but felt the loss from .321 factory to .294 as measured on the 5/16 screw (.027) was nominal.
The 5/16" was selected, didn't want to trim screw length to pick up .027.
I could trim the head back if I need the length. Note: I have never felt the need.
The difference in the head dia., (.020) I have noticed that this is not a problem with the Stainless Grip Frame, Sometimes a problem with Carbon and ALWAYS a problem with Brass, EASILY adjusted with the lathe or even chucked up in a drill. Should be noted that the socket quality is better than the factory screw. IMO
No nylon in the non factory screw but a little
lock-tight blue on final assembly works just fine.
Found non-factory screws ($2/2) are a excelent solution to expensive & sometimes hard to acquire factory screws, AFTER a little fine tuning, -VS- pay big money for factory screws.($15/2)
Finally, find yourself this tool, it lets you get into the tight space with surgical accuracy, control & ease.
Want some of these screws? drop me a PM. Trade ?, I like firearm related patches.