Cocking cam to bolt notch clearance?

[AlNyhus]

I'm working with an old custom action that the cocking piece has been FUBAR'd up on. The new cocking pieces are really semi-finished so I needed to mill the length of the the cocking piece tail back enough so it doesn't bottom out in the cut in the bolt body. The firing pin forward travel is determined by the forward edge of the cutout in the shroud for the cocking piece. I faced off the front of the cocking piece body for adequate pin travel and reprofiled the cocking piece tail so it has approximately. 010 forward clearance in the bolt cutout when in the 'fired' position.

How much clearance on the tail piece is too little?

Thoughts appreciated! -Al

 

[jackieschmidt]

Al, I think I am reading correctly what you are doing.

Clearance is clearance. In short, if it fit’s nothing but air in the fired position, then there really isn’t a minimum as long as it has clearance.

the Usual cure for this is to take a tiny Dremel tool and move that radius at the base of the cocking curve a tad forward. Doing that doesn’t affect your overall pin travel, which in most cases should be around .220 or more.

keep in mind, the firing pin has already struck the primer before the cocking piece reaches it’s final destination.

I would think your .010 would be right in the ”goldelocks” zone.

One of my original Farley actions had the cocking piece bottoming out in the bolt’s camming curve before the firing pin bottomed out in the bolt. I cured it by taking a dremel tool and moving the base of the curve forward untill it just cleared in the fired position.

 

[boltfluter]

I'm working with an old custom action that the cocking piece has been FUBAR'd up on. The new cocking pieces are really semi-finished so I needed to mill the length of the the cocking piece tail back enough so it doesn't bottom out in the cut in the bolt body. The firing pin forward travel is determined by the forward edge of the cutout in the shroud for the cocking piece. I faced off the front of the cocking piece body for adequate pin travel and reprofiled the cocking piece tail so it has approximately. 010 forward clearance in the bolt cutout when in the 'fired' position.

How much clearance on the tail piece is too little?

Thoughts appreciated! -Al

Al,

Having absolutely no experience doing this, I would say your work is perfect!! And my great advice has absolutely no value! Lol. Carry on. I do think Jackies advice about the primer strike is very good.

Paul

 

[AlNyhus]

Thanks for the thoughts, guys...much appreciated.

It's an old Wichita 1375 that was originally built by Pindell. Along the way and lost to history, someone had modified the original cocking piece to a 90 degree configuaration...not sure what trigger was in it when that was done. As part of it's 'modernization' a couple years ago, the owner fitted a Remington pattern Jewell to it. Needless to say, issues soon developed with the cocking piece over riding the trigger sear connector bar. As new, these things only had .200 pin fall and a 35 lb(!!!) spring.

The new cocking pieces available are .085 longer on the front than the originals. Since the front of the cocking piece is what stops the forward movement of the firing pin by contacting the front 'wall' of the bolt shroud.....the new cocking piece resulted in a pin travel of about .115. I ended up milling .100 from the front of the new cocking piece...which I knew would bottom out the cocking piece 'tail' in the cocking piece slot of the bolt. Rather than deepening the cut in the bolt body...which would have been a lot...I felt that shortening the cocking piece tail was the best approach. Especially since the worst that could happen is that I'd need to get a new cocking piece.

So here's where it is now: With a replacement spring, it now breaks at 20 lbs and gives 24 lbs at full cock, pin travel is .215, pin protrussion is set at .050, the pin tip is fully contained in the bolt face pin hole when cocked and the cocking piece tail has 'air clearance' at the bottom of the notch.

The gun has a really good barrel on it chambered in 30 Major by Mike Bigelow, who just does excellent work. We'll see how testing today goes.

Will update later. -Al

 

[jackieschmidt]

Well Al, it looks like you got it perfect.

with 35 lbs of spring pressure, I bet that 3 lug action was a bear to cock.

Just one thought, Aren’t cocking pieces case hardened? From what you have described, I don’t think you took material from anything that is a critical contact surface.

 

[gunsandgunsmithing]

I think what you have should work fine. Just keep in mind that the closer the cocking piece is to the notch, the sooner it'll begin cocking. You want a little wiggle room for the handle. What is that, and old Shilen action? Now find some n120 powder and load it for about 2975ish fps. You'll love that powder, if you've never tried it. Later lots varied a bit so not sure what to tell you for data. The old stuff was incredible!

edit...I see now..Wichita. I knew I recognized it but the name wasn't coming to me until I actually read your post rather than skimming past it.

 

[AlNyhus]

with 35 lbs of spring pressure, I bet that 3 lug action was a bear to cock.

Just one thought, Aren’t cocking pieces case hardened? From what you have described, I don’t think you took material from anything that is a critical contact surface.

Yeah....it was like wrestling an alligator trying to open the bolt. The cocking piece was indeed case hardened but the 'tail' had been manually shaped so the case hardening was gone in that area. With a little tool grinder, I just tried to mimic the profile of the bolt notch. When cocking it, there's just the slightest bit of play on the upswing of the bolt handle before the cocking starts. With a bit of NECO Moly paste on it, it's pretty smooth.

 

[AlNyhus]

Now find some n120 powder and load it for about 2975ish fps. You'll love that powder, if you've never tried it. Later lots varied a bit so not sure what to tell you for data. The old stuff was incredible!

Mike, that's exactly what the owner shoots in it. With the BIB 112's on the .925s, it shoots very well.

 

[Alex Wheeler]

Al, in this case it doesnt matter much. Shortening the nose of the cp wont change firing pin fall, it will ad cock on close as you shorten it though. When I am setting up ignitions I will fit it with as little clearance as I can because that gains pin fall. But Im not alerting the nose length.

 

[boltfluter]

Nicely done Al! The most accurate rifle I have ever owned was on a LH 1375 Witchita, in .22 Waldog, chambered by Berger. That rifle was an absolute tac driver with many groups in the 1's. Brings back many fond memories.

Paul

 

[AlNyhus]

I had some business to attend to yesterday so wasn't able to make it to the range with the owner. He reports that everything works well, bolt operation is smooth and the effort needed with the small amount of cock on close is much improved. The good thing is that with N120 and the BIB 112's, it shoots little dots and X's.

The only thing he doesn't like is the 'hard' feel it has when the cocking piece forward edge (which is a 90 degree edge on the Wichita cocking piece) initially contacts the back edge of the trigger sear connector bar as the bolt goes forward. That area on a 700-style cocking piece has a slight bevel to it to help this. I showed him it would have that but didn't want to address it until it was tested for function. It won't be a big deal to dress that edge back a few degrees to smooth the transition.

When it was apart, I went over everything else on it. The bases had very, very little contact to the receiver. Just the machined surface of the underside of the bases were in contact with the receiver...and only around the base screw areas. There was an oily film between the bases and receiver that I believe had wicked up there from lubricant put on the bolt body. A little prep work, a couple dabs of ProBed and 24 hrs. cured that, though. The 'after' pic of the bases was just after being popped off the receiver prior to cleanup and radiusing of the screw holes. They are rock solid on the receiver, now. I don't normally use anything but light oil on base screws. But these got a sealing compound on them to keep any wicking from getting under the bases.

Good shootin' -Al

 

[AlNyhus]

A bit more tweakage done:

-Narrowed the cocking piece to eliminate any drag on the trigger side plates.
-Shortened the height of the cocking piece by .010 to smooth out the travel as it goes forward over the back edge of the trigger sear connector bar.

I think we're where we want to be with it at this point. Everything is loose, nothing binds and the firing pin sound is now a hard 'snap' instead of the dull 'thud' it used to make.

Working on this obscure stuff is pretty fun, actually. There's a new shroud coming and I've got some ideas for it.......

Thanks again for the advice! -Al

 

[Mulligan]

A bit more tweakage done:

-Narrowed the cocking piece to eliminate any drag on the trigger side plates.
-Shortened the height of the cocking piece by .010 to smooth out the travel as it goes forward over the back edge of the trigger sear connector bar.

I think we're where we want to be with it at this point. Everything is loose, nothing binds and the firing pin sound is now a hard 'snap' instead of the dull 'thud' it used to make.

Working on this obscure stuff is pretty fun, actually. There's a new shroud coming and I've got some ideas for it.......

Thanks again for the advice! -Al

Al,
Thanks for sharing your work. I am not a Gunsmith, but enjoy learning the particulars.
CW

 

[AlNyhus]

Al,
Thanks for sharing your work. I am not a Gunsmith, but enjoy learning the particulars.
CW

I'm no gunsmith and I'm sure as heck no machinist. Just a tinkerer. -Al

 

[Alex Wheeler]

I'm no gunsmith and I'm sure as heck no machinist. Just a tinkered.-Al

Maybe not, but the work your doing is what makes a rifle a winner. Building a rifle is NOT opening boxes, chambering and bedding then sending it out. Thats parts assembling. Good on you for putting in the work that actually matters. Id say your more of a gunsmith than most

 

[gunsandgunsmithing]

Maybe not, but the work your doing is what makes a rifle a winner. Building a rifle is NOT opening boxes, chambering and bedding then sending it out. Thats parts assembling. Good on you for putting in the work that actually matters. Id say your more of a gunsmith than most

Al has been around this stuff for a day or three and you're right, he has a better understanding of what matters than most "smiths" that have been putting parts together for a long time. He's definitely one of the good guys and typically knows what he's talking about. I always enjoy reading his posts. Glad to see him actively shooting and posting again. Hes another gearhead that likes fast cars and accurate rifles. Seems to be a common theme...not sure if it's the perfectionism or the competitiveness, or maybe both.

 

[Dusty Stevens]

Great work reviving an old classic. That 90deg cocking piece was for an anschutz trigger in a briley hanger. That was the ticket back then when a 3 lever conversion remington was the IN thing