Smith OEM bolt pics and other bolt Variation

[opee]

The bolt on the right is a Smith OEM bolt. I picked up another non-Smith bolt a couple of years ago as a spare. As you can see from pics there is a difference in the V notch, but other than that both bolts are identical in terms of dimensions. I have cycled both bolts through in the FA position and they both seem to have worked forward and backward. Have not live fired the other bolt for fear of damaging something. Wanted to get your opinions on if you know what the origin is on the non Smith bolt? Is it from a 760, etc? Considering having the second bolt notch cut to as close as can be to the Smith OEM bolt. Perhaps working with BWE on dimensions would also help him improve his offering to the S&W 76 crowd of owners out there.
Comments appreciated as to whether I should fire the gun with other bolt, or have it milled out first, or any other suggestions. Anybody have the angles of the V notch measured and written down?
Thanks, Opee in TX

 

[opee]

More pics

 

[SHURESHOT]

does it catch the sear? if so it should work. all that does is hold the bolt back when the sear is not held down.

 

[MachinegunKid1]

I have an MK Arms 760 new bolt in wrapper as a spare to my original S&W 76 machine gun. I can verify that what you have on the left side of your pics is a genuine Mk 760 bolt, although used. I would not be concerned with the minor difference in the (Rear) Sear notch position, as the rear notch in the bolt simply is served as a resting position of the Sear when the bolt is idle in forward position, and has no implications with Full Auto / Semi Auto functioning. It is there to relieve the Sear spring tension. The critical notch is the more forward position, closer to the bolt head. In Semi Auto, selector switch position, the Sear will catch this notch stopping the bolt from full auto cycling on each trigger pull. In Full auto, the sear is disengaged from the forward notch, until the trigger is released, allowing for full Auto bursts. This is typical of open bolt machine guns

 

[DINK]

The notch you are worrying about is there to allow you to put the safety on with the bolt in the forward position, locking the bolt in place. The exact contours of that notch really don't matter as far as firing is concerned. As pointed out above, the critical engagement surface is forward of the "v" notch.

 

[robertmcm]

Again, I would hope BWE would consider the relocation of the extractor in their bolt like Jim Burgess guns have. Less strain on the extractor.

 

[BWE Firearms]

I can relocate the extractors in the bolts I am going to make but for them to work in a 76-760 SMG the trunnion will need to be cut out, re-indexed, welded back in, and the receiver refinished. You will also not be able to use the original bolt again. I am not sure how many people will want to do that.

I could re-machine the trunnion so you can use both types of bolts but the trunnion will still have to be cut out of the gun to re-machine it.

 

[opee]

Yesterday, I sent both of the bolts pictured above to Richard so he can measure and do whatever he needs to be able to secure a new and reliable source of parts for the S&W 76/ MK 760 platforms.
Opee in TX.

 

[Dockless55]

Yesterday, I sent both of the bolts pictured above to Richard so he can measure and do whatever he needs to be able to secure a new and reliable source of parts for the S&W 76/ MK 760 platforms.
Opee in TX.

Thanks OPEE, we 76/760 owners need a dependable source for spare parts. I think Richard is on the right path. I like the platform and feel that with some tweaking it can become what the SEALS envisioned.

 

[cogcon]

I have a complete NOS OEM S&W76 bolt with the straight transition that I would love to trade someone for a MK-760 bolt with the curved transition. Any takers, let me know. Thanks. John

 

[ETLES LLC]

I don't have one to trade but, if you'd sell the original Smith bolt I will pay you well......

 

[ETLES LLC]

Yesterday, I sent both of the bolts pictured above to Richard so he can measure and do whatever he needs to be able to secure a new and reliable source of parts for the S&W 76/ MK 760 platforms.
Opee in TX.

Oh yeh, Thank you Sir!
I will get in line on a reproduction for sure.

 

[robertmcm]

I can relocate the extractors in the bolts I am going to make but for them to work in a 76-760 SMG the trunnion will need to be cut out, re-indexed, welded back in, and the receiver refinished. You will also not be able to use the original bolt again. I am not sure how many people will want to do that.

I could re-machine the trunnion so you can use both types of bolts but the trunnion will still have to be cut out of the gun to re-machine it.

Thanks for the info in this. Info I did not know. When you make your run of bolts could relocation of the extractor be an option?

 

[opee]

Just received my two bolts back from Richard today. One is an OEM Smith and the other is an MK bolt pictured at the beginning of this thread. Hopefully Richard was able to get all the measurements to machine new bolts so we can all enjoy shooting these guns for decades to come. Richard was nice enough to install one of his new hardened extractors on the Smith bolt for a very nominal price, so cant wait to get out this weekend and do some shooting. At least my son will be shooting this gun in 30-40 years because we had the foresight to look ahead and make the spare parts needed for a very collectible C&R subgun.