Home Forums Hunting & Shooting Gunsmithing Leupold custom scope base screws

I lost two of the four screws for my Leupold two piece scope bases machined for a round receiver Sako L579. They are #6-40 narrow fillister hex socket screws with a head diameter of 0.195".

Anywhere besides Brownells that I could check for these screws? Their computer still thinks it's Sunday and won't give me a confirmation number after insisting that I change my password.

Maybe Leupold will have mercy on you. 6x40 = uncommon - fillister = uncommon

I checked

MCMASTER
Jantz
Grainger
Travers
MSC
Bolt Depot
Marshall

Are you sure they are 6-40? 8-40 and 6-48 are common sizes. If they are 6-48 you can chuck the shank in a drill and file/grind/sand the head down to size. I have a piece of 1/8" flat bar with numerous 6-48 and 8-40 holes drilled and tapped in it that I use to grind screws down to custom lengths.

My H&R was a Sako round top. It took 6-48's. My Browning Safari was a round top Sako L579 and it was also 6-48.

Yours may well be 6-40's. Check them with a thread pitch gauge or a Hillman female thread block. -Al

If they are a 6-40 screw, you should be able to find those at your local hardware store. In town, I have 3 places that I can find these screws. If they need to be even more "custom", as in fit inside the pocket of the base, I can easily file them down and reblue, grind to length or whatever. Shouldn't be a very hard venture.

Thanks. They aren't #6-40s since I hand-turned a known #6-48 into the receiver. I had measured the shank length on one I didn't lose and counted the threads with a pin and came up with 40 TPI. Clearly not a precise method. I have a thread gauge on the way as well.

I've got the #6-48 screws from Brownells (they were great about not charging additional postage on them and sent me a prepaid return label for the #6-40s!). When I grind them to length, should the threads go the full threaded depth of the receiver bridge? The screws that came with the bases originally (two of which I lost, which occasioned this post) only go about halfway into the bridge (bridge thickness is about 0.340"; original screw threaded length into bridge is about 0.172").

I thought if I ground the new ones flush with the receiver inner diameter there would at least be less space (a really tiny amount, admittedly) for dirt to collect.