M40 Mount Questions

[Mossyrock]

Gentlemen;

I am in the gathering phase of an M40 build. It looks like I have a correct serial number range, 6-digit Remington 700 action inbound. This brings up a problem with regards to the correct mount. Needless to say, the correct Redfield square-cornered mount is more rare than an honest politician. I understand Badger Ordnance made a run of repro mounts but, depending upon who you talk to, they may be out of the mounts to fit the early actions. This brings up an interesting question: what is the difference between a mid-1960s Redfield Jr. mount for a short action model 700 and a modern one? Can the newer ones be modified to correctly fit, or is it a bridge too far? Any and all input would be greatly appreciated.

Mossyrock

 

[Macca]

The rear bridge is lower in the pre letter serialed rifles so the current Badger mount won't fit.
I believe it would technically be possible to have the forward underside of the mount milled (relieved) to accommodate the differences in bridge heights, but that's something you'll have to organise with your smith.
Or you'll have to use the rounded corner Redfield bases-preferably the type with the less rounded edges.
Refer to the M40 build guide to see the differences.

 

[M40_A1]

What I don't understand is why I've never come across any reference to the Marine Corps fussing over the difference. Maybe because the 10X Sniper is so stout you can tighten everything down and the scope won't be damaged?

 

[MescaBug]

What I don't understand is why I've never come across any reference to the Marine Corps fussing over the difference.

Same here. Those who says it doesnt fit never actually tried it. Both bases (40X and 700SA) fits both pre-1974 receivers and the later. The M40 was zeroed to 500y, even if the base is not leveled, there is more than enough elevation adjustments.

I have a 700SA base on my 6-digit. Will take some pics.

The difference between the highest point of the receiver ring and the receiver bridge at its centerline on the Vietnam-era USMC-M700 sniper rifle was .117 inch (±). The height of the one-piece JR base furnished by Redfield (“Base, Special, JR 40X”) was .200 inch (±) at the front and .345 inch (±) at the rear. As such, the base was approximately .028 inch (±) higher at the rear (“tapered”) when attached to the receiver. By comparison, according to information provided by the Redfield firm, the standard one-piece JR base intended for the Remington Model 700 short-action rifle (pre-1974) was .196 inch (±) at the front and .322 inch (±) at the rear, a difference of .009 inch (±) when the base was mounted. The dimensions for the Junior (JR) base used with the original USMC M700/M40 sniper rifle were established by Redfield. It is not known if a similar base was made available to the general public.

The difference is slim. Does that make sense?

 

[Mossyrock]

Same here. Those who says it doesnt fit never actually tried it. Both bases (40X and 700SA) fits both pre-1974 receivers and the later. The M40 was zeroed to 500y, even if the base is not leveled, there is more than enough elevation adjustments.

I have a 700SA base on my 6-digit. Will take some pics.

The difference between the highest point of the receiver ring and the receiver bridge at its centerline on the Vietnam-era USMC-M700 sniper rifle was .117 inch (±). The height of the one-piece JR base furnished by Redfield (“Base, Special, JR 40X”) was .200 inch (±) at the front and .345 inch (±) at the rear. As such, the base was approximately .028 inch (±) higher at the rear (“tapered”) when attached to the receiver. By comparison, according to information provided by the Redfield firm, the standard one-piece JR base intended for the Remington Model 700 short-action rifle (pre-1974) was .196 inch (±) at the front and .322 inch (±) at the rear, a difference of .009 inch (±) when the base was mounted. The dimensions for the Junior (JR) base used with the original USMC M700/M40 sniper rifle were established by Redfield. It is not known if a similar base was made available to the general public.

The difference is slim. Does that make sense?

In other words, the difference is so minute that it won't be noticed by us mere mortals.

 

[M40_A1]

Same here. Those who says it doesnt fit never actually tried it. Both bases (40X and 700SA) fits both pre-1974 receivers and the later.

And, of course, you are correct. I have yet to see a Redfield Junior base box marked "Pre-74 700-SA" or "Post-74 700-SA". LOL! No one cared then, so I don't know why some make it such a big issue now. Interesting that even the bases themselves were never completely aligned with either bridge height to begin with. Thanks for sharing.