[OneBarfly]

Hello,

I recently aquired another 1919A4 bolt. Upon inspection, two small areas around/near the sear were ground down in a free-hand manner. Was this a modification of some sort? Why? Also, this bolt has way more proof marks than my other bolts. Is this a clue? Thoughts? Do I return it?

Thanks in advance
Rich

 

[Dave B - Great Lakes Arms]

Not much of the bolt locking recess left...personally I'd return it.

As to why.....good question. Does appear to be right around where the sear spring pin comes through the bottom of the bolt.

Looks like a real early nickle steel bolt unless there iss just no finish left on it.
It is a Buffalo Arms bolt.

 

[slowfire]

I would return it, that just doesn't even look right.

 

[Roc Rat]

I had a trigger problem on my USGI build,, The bolt could not be cycled more than once between shots,, ie, you had to pull the trigger after each cocking cycle or the bolt would hit the trigger and would lock there. I surmised after some deep thinking that if I created a ramp at that spot on the bolt it would guide the tip of the trigger past that block. It seems that I am not the only one to think of this after seeing your picts. My 30 06 runs perfectly with this modification,, I've had no problems at all. If you think about the fireing cycle, it will have no effect on the bolt lock up, which is the most important thing at that part of the cycle.
I don't know why this issue came up on my build,, my 308 shorty build never had any problems doing multiple bolt cycles,,, go figure

It just occured to me,,, can you see if that bolt is a 30 06 bolt,, there are slight differences, and if it is,,, perhaps it is a mod that helps a 30 06 bolt more adaptable to the semi build. These guns were never designed to fire semi,,, sometimes you just have to tickle these puppies. I know the mod cured my cycling problems.

 

[loboslanding]

I can't tell for sure from the photo, but it doesn't appear that the bolt has been milled for semi use so if that was a full auto problem where the fixed disconnector end of the trigger was banging into that hump, then it looks like a trigger stop screw wasn't properly adjusted or got stripped or damaged in the field and an armorer relieved that area to fix the problem.

If it has been milled for semi use then those grind marks appear to be a fix-it for a trigger disconnector problem that used to occur on some early semi builds and/or it was a trigger travel problem. If the end of the trigger disconnector is too flat it will bang into that hump in lieu of riding over it when the trigger is pulled and the bolt flies rearward...seen it myself. If you look at the end of a KMP trigger disconnector you will see that it is more rounded and sloped to help it ride over that hump and not bang squarely into it. Look closely at the photo below and you can see a slight wear mark about 3/8" wide where the disconnector rides over that hump.

I've had to radius the end of some early disconnectors a tad to get them to work properly. A sure sign was that you would pull the bolt back and at about 3/4" it would feel like it locked up...that was the trigger disconnector banging into that hump on the bolt. If you cycled it enough times it would round off the disconnector on it's own...if it didn't break first. The second photo is one of Tomt's old triggers during development before the modification was made.

Also, that's why I run the trigger stop screw on my lockframe up as high as possible (before tightening the locknut) to get as much trigger travel as possible so the front end clears that hump completely. Some guys raise the trigger stop screw only enough to trip the sear and then lock down the locknut without realizing that on these semi's you really need all the trigger travel you can get so the above problem doesn't occur or a trigger gets broken. On some guns this is why a trigger plunger doesn't work well because they can't always be raised enough with some older trigger designs to give enough travel and still reset the trigger.

That ground area won't hurt anything, but you don't know how hot someone got it while doing that grinding or what other experimental mods have occured. Before I'd spend the money having it milled for semi use I'd send it back.

BTW, that's also why I put a smear of grease across that hump before every shoot...helps the disconnector glide over that area better...especially using a Crankfire.