Tenon Measurement to use for coned bolt action?Update***

[INTJ]

If you notice you turn down a .996dia for .110 from the back. Luckily they tell you how long to make the tenon and that same measurement is the headspace. If you just measure threads youll get a totally different measurement on each side and that can be a bunch according to thread pitch. Flat bolts are easy enough to measure to the front of the lug.

Yeah, that is why I like to have the drawing, check everything, work cautiously, and ask my local BR gunsmith/competitor/friend--especially on a new thing. I really only care about chambering for BATs and CRF M-70s, and with both of those measuring the action thread length will give the max dimension for the tenon. When BAT says the tenon should be 1.050 to 1.060, and I mark say 1.080; I know that length will thread to the shoulder because the threads are say 1.100ish. After I am threaded and snug against the shoulder I cut the cone until it clearances properly. I know this ways works, allows room for error, and has resulted in a couple of 1/4 MOA LR BR rifles.

That said I wouldn't pretend to know better than anyone else and the purpose of my participation on this thread was to understand, not challenge anyone else.

 

[paperpuncher]

So I have one of these to do It is a Defiance action with a coned bolt and has a long thread on the tennon I asked for a print and was told they dont have one so here is what I did to come up with a tennon configuration. If this thinking is flawed please let me know as of right now I have only cut this on a piece of scrap not a barrel. I took a pc of 1.250" stock about 6" long and turned a section of it down to 1.060" I made this turned dia about .400" longer than I estimated it needed to be. I drilled a .500" hole in the end to represent a chamber. I cut a cone on the end that matched the angle on the bolt nose 30* close as I could measure. Threaded the 1.060" section up to the shoulder so that it would screw into the action. I took this pc and screwed it into the action until it bottomed out on the bolt nose. I measured with a gauge pin the distance between the action face and the shoulder, then measured the entire thread length to the shoulder and deduct the dia. of the pin gauge plus .007-.010" for clearance. The only thing I have to do is make sure I match the od of the cone cut between my stub and my barrel or use a 30* point that is faced flat to measure the length of the stub thread and use again it to transfer the measurement to the barrel. I think this should work fine what say the pros?

 

[Dusty Stevens]

So I have one of these to do It is a Defiance action with a coned bolt and has a long thread on the tennon I asked for a print and was told they dont have one so here is what I did to come up with a tennon configuration. If this thinking is flawed please let me know as of right now I have only cut this on a piece of scrap not a barrel. I took a pc of 1.250" stock about 6' long and turned a section of it down to 1.060" I made this turned dia about .400" longer than I estimated it needed to be. I drilled a .500" hole in the end to represent a chamber. I cut a cone on the end that matched the angle on the bolt nose 30* close as I could measure. Threaded the 1.060" section up to the shoulder so that it would screw into the action. I took this pc and screwed it into the action until it bottomed out on the bolt nose. I measured with a gauge pin the distance between the action face and the shoulder, then measured the entire thread length to the shoulder and deduct the dia. of the pin gauge plus .007-.010" for clearance. The only thing I have to do is make sure I match the od of the cone cut between my stub and my barrel or use a 30* point that is faced flat to measure the length of the stub thread and use again it to transfer the measurement to the barrel. I think this should work fine what say the pros?

Draw us a sketch that is hard to follow. I bet its simple seeing it though

 

[hoz53]

So I have one of these to do It is a Defiance action with a coned bolt and has a long thread on the tennon I asked for a print and was told they dont have one so here is what I did to come up with a tennon configuration. If this thinking is flawed please let me know as of right now I have only cut this on a piece of scrap not a barrel. I took a pc of 1.250" stock about 6' long and turned a section of it down to 1.060" I made this turned dia about .400" longer than I estimated it needed to be. I drilled a .500" hole in the end to represent a chamber. I cut a cone on the end that matched the angle on the bolt nose 30* close as I could measure. Threaded the 1.060" section up to the shoulder so that it would screw into the action. I took this pc and screwed it into the action until it bottomed out on the bolt nose. I measured with a gauge pin the distance between the action face and the shoulder, then measured the entire thread length to the shoulder and deduct the dia. of the pin gauge plus .007-.010" for clearance. The only thing I have to do is make sure I match the od of the cone cut between my stub and my barrel or use a 30* point that is faced flat to measure the length of the stub thread and use again it to transfer the measurement to the barrel. I think this should work fine what say the pros?

I don’t know much, but I know you don’t need a 6 foot piece of stock for your trial piece.

 

[paperpuncher]

I don’t know much, but I know you don’t need a 6 foot piece of stock for your trial piece.

I edited the post to correct the error forgot to shift

 

[paperpuncher]

 

[hogpatrol]

So I have one of these to do It is a Defiance action with a coned bolt and has a long thread on the tennon I asked for a print and was told they dont have one so here is what I did to come up with a tennon configuration. If this thinking is flawed please let me know as of right now I have only cut this on a piece of scrap not a barrel. I took a pc of 1.250" stock about 6" long and turned a section of it down to 1.060" I made this turned dia about .400" longer than I estimated it needed to be. I drilled a .500" hole in the end to represent a chamber. I cut a cone on the end that matched the angle on the bolt nose 30* close as I could measure. Threaded the 1.060" section up to the shoulder so that it would screw into the action. I took this pc and screwed it into the action until it bottomed out on the bolt nose. I measured with a gauge pin the distance between the action face and the shoulder, then measured the entire thread length to the shoulder and deduct the dia. of the pin gauge plus .007-.010" for clearance. The only thing I have to do is make sure I match the od of the cone cut between my stub and my barrel or use a 30* point that is faced flat to measure the length of the stub thread and use again it to transfer the measurement to the barrel. I think this should work fine what say the pros?

That'll work for the length of the tenon. Did you include the recoil lug?

 

[paperpuncher]

That'll work for the length of the tenon. Did you include the recoil lug?

The action i have has an integral lug but if the lug is separate it would be simple enough to compensate for the thickness.

 

[hoz53]

I edited the post to correct the error forgot to shift

that will work- I was thinking of something close to that but mabie I’ll just make it like you have. I think it would be a little simpler. I’ll make it out of an old piece of barrel

 

[Dusty Stevens]

A real good place to start for tenon length is the headspace measurement.

 

[Dusty Stevens]

ill check into that thanks

Look at a panda drawing. Thats an easy one to find.

 

[hoz53]

Look at a panda drawing. Thats an easy one to find.

ok

 

[hoz53]

A real good place to start for tenon length is the headspace measurement.

i think of headspace as base to datum so i wondered wat you meant by this as that could vary alot depending on cartridge. But i see for the PPC it looks pretty close to the same dimension. Did I get it?
I measured this rem action yesterday and it looks like the tenon will be .950 to 1.00-- dont think there are any prints around for it. my coned bolt remington tenon measuring tool is in the process of being made now so i should know pretty quick. thanks

 

[Dusty Stevens]

i think of headspace as base to datum so i wondered wat you meant by this as that could vary alot depending on cartridge. But i see for the PPC it looks pretty close to the same dimension. Did I get it?
I measured this rem action yesterday and it looks like the tenon will be .950 to 1.00-- dont think there are any prints around for it. my coned bolt remington tenon measuring tool is in the process of being made now so i should know pretty quick. thanks

No you know that the headspace has to be longer than shank length or you couldnt measure it, so if you start there you can always take more off. Just so happens a panda shank is the exact length the headspace is. A bat is .024 shorter so youd be that close

 

[hoz53]

No you know that the headspace has to be longer than shank length or you couldnt measure it, so if you start there you can always take more off. Just so happens a panda shank is the exact length the headspace is. A bat is .024 shorter so youd be that close

not sure that makes sense to me. i guess it does. youre saying the shoulder in the chamber cant be in the tenon right? Mabie im chambering for a .308. if i made my tenon .308 headspace it would be a bit long. seems to me anyhow. i learned a little though. thanks

 

[Dusty Stevens]

No you measure the headspace on the action. It has nothing to do with what cartridge it is- the same action can be used for a 6br or 30-06 and those have wildly different datum measurements

 

[hoz53]

No you measure the headspace on the action. It has nothing to do with what cartridge it is- the same action can be used for a 6br or 30-06 and those have wildly different datum measurements

ok i guess i dont get that but i have appreciated all your help

 

[Dusty Stevens]

ok i guess i dont get that but i have appreciated all your help

These 2 measurements are the same- pics stolen from the webs. When you Get the measurement on the top that is called the action’s headspace. No matter what cartridge you chamber for it the bottom pic’s measurement will match that with the correct headspace gage

 

[hoz53]

These 2 measurements are the same- pics stolen from the webs. When you Get the measurement on the top that is called the action’s headspace. No matter what cartridge you chamber for it the bottom pic’s measurement will match that with the correct headspace gage
View attachment 1183288 View attachment 1183289

ok i get that-- thanks for that info

 

[Dusty Stevens]

ok i get that-- thanks for that info

So where i would start on an unknown action you dont have a print for is measure its headspace, cut the tenon that long, screw the barrel on against the bolt and measure the gap inbetween the barrel shoulder and action, add .010 to that and cut that much off of it as measured with the pma woolums barrel chambering depth mic. Thats a foolproof way. On a remington style just measure to the top of the lug and top of bolt nose, take .010 off of those measurements and cut your counterbore and tenon length accordingly.