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

[hoz53]

Just make an opposite cone that threads in the tenon, slides down and hits the cone and locks down. Then measure it with the pma woolums tool that jkohler posted. Keep it simple with no guessing

thats what im gonna do thahks

 

[hoz53]

There are no flat at the bottom of the cone on any actions I know
See attached 25d Bat and 30d Panda

thanks for those drawings Tim

 

[hoz53]

I simply measure with the depth gauge on my calipers down to the outside of the lug and cut the tenon to that length. I then cut the cone about halfway to depth. I put the bolt into the receiver in the locked position and screw the action on to the barrel until the bolt contacts the cone. I measure the gap between the receiver and barrel shoulder with a feeler gauge then cut the cone that much deeper plus .005". To measure the depth of cut, I set up a dial indicator to indicate the carriage movement. No trial and error, no special gauges, no fuss. WH

Now I was thinking of trying to measure down along the side to the lug like you say but wasnt sure how accurate i could do it. Thought of getting one of those depth gauges with the flat slender rod. Sounds like a good way you have to do it you use. i will try to get the measurement and see how close i can come. I may end up doing it this way--- Thanks Much

 

[Stumpy1]

Very few actions use that type cone. HS precision and one controlled feed defiance ive seen do. They are such a pain they are avoided for the most part

Thanks! I ask, because I have two Barnard P's whose barrels have the breech end match the bolt face like I drew -so there is a flat face counterbore, then the cone.

Further question -it seems that the flat face would expose less brass than running the cone down into the chamber? Again, trying to learn.

I found a picture of what I mean

Thanks Guys!

Frank

 

[Roeder]

Thanks! I ask, because I have two Barnard P's whose barrels have the breech end match the bolt face like I drew -so there is a flat face counterbore, then the cone.

Further question -it seems that the flat face would expose less brass than running the cone down into the chamber? Again, trying to learn.

I found a picture of what I mean

Thanks Guys!

Frank

You are correct. For those actions with a flat on the nose of the coned bolt, it is best to cut the tenon to match . How much of the case is exposed would depend on the depth of the recess, but I know of at least one example that requires the matching flat on the tenon to give a safe, fully supported chamber.

 

[hogpatrol]

There are no flat at the bottom of the cone on any actions I know
See attached 25d Bat and 30d Panda

Gunwerks actions have the cone/flat. Like Dusty posted and at least for me, a PIA.

 

[butchlambert]

My early Stiller receivers had a flat and cone.

 

[gunsandgunsmithing]

My early Stiller receivers had a flat and cone.

Yep.I had a B series Viper drop port that I shot for several years that was coned like that. I posted an old print on the other thread about cones. It was taken from Stiller's site before he sold out. .580 od flat then 14° cone for the remainder. Chambered a bunch for it and others like it.

 

[INTJ]

I am probably missing something here, being a permanently newby to chambering.

I cut the tenon about .020" long. With a BAT I use the measurement they give. I assume most custom action companies have drawings available. On many other bolt actions, Frank DeHaas and others have drawings. If I have a barrel, as when I get a rifle as a donor, I measure the barrel itself with a caliper. If all else fails I measure the depth of the threads in the action itself with a caliper.

On the New M-70 I just chambered I looked at drawings, measured a factory barrel, measured the custom barrel I took off the action, and measured the threads on the action. I noticed that there was a small flat then cone on the factory barrel, but the custom barrel was all cone like a BAT. None of that matters as long as as everything clears and fits.

After cutting the tenon a little long I thread the barrel and make sure the action will snug up to the barrel. The things that can leave a gap after initial threading are too long of threads, not enough depth in the relief groove, or a shoulder step that's a little too long. I work through all that until the action tightens on the barrel with good contact.

Then I cut the cone. While I have used the compound in the past, I much prefer a breech tool like PTG makes. It's WAY easier for me. I get the cone close, the thread on the action with the bolt in and snug it up. I then measure the clearance between the shoulder and receiver with a feeler gauge.

I add the desired cone clearance to the feeler gauge and I know how much more to cut. I check bolt to cone clearance with Plastigauge or by measuring bolt fore/aft movement.

No special tools are needed. I suppose a production shop wouldn't have time to do all the test fitting and remeasuring. However I am a hobby 'smith and for me that extra time taken to hand fit everything is part of what it takes.

 

[hoz53]

I am probably missing something here, being a permanently newby to chambering.

I cut the tenon about .020" long. With a BAT I use the measurement they give. I assume most custom action companies have drawings available. On many other bolt actions, Frank DeHaas and others have drawings. If I have a barrel, as when I get a rifle as a donor, I measure the barrel itself with a caliper. If all else fails I measure the depth of the threads in the action itself with a caliper.

On the New M-70 I just chambered I looked at drawings, measured a factory barrel, measured the custom barrel I took off the action, and measured the threads on the action. I noticed that there was a small flat then cone on the factory barrel, but the custom barrel was all cone like a BAT. None of that matters as long as as everything clears and fits.

After cutting the tenon a little long I thread the barrel and make sure the action will snug up to the barrel. The things that can leave a gap after initial threading are too long of threads, not enough depth in the relief groove, or a shoulder step that's a little too long. I work through all that until the action tightens on the barrel with good contact.

Then I cut the cone. While I have used the compound in the past, I much prefer a breech tool like PTG makes. It's WAY easier for me. I get the cone close, the thread on the action with the bolt in and snug it up. I then measure the clearance between the shoulder and receiver with a feeler gauge.

I add the desired cone clearance to the feeler gauge and I know how much more to cut. I check bolt to cone clearance with Plastigauge or by measuring bolt fore/aft movement.

No special tools are needed. I suppose a production shop wouldn't have time to do all the test fitting and remeasuring. However I am a hobby 'smith and for me that extra time taken to hand fit everything is part of what it takes.

for me the point was how long should the tenon be. On a counterbore or flat breech action its easy to measure it. I dont measure the old barrel tenon on these actions ,if there was an old barrel to start with, because i want the barrel fitted with the clearance i want, not what someone else set.
on a cone bolt you cant measure it by just sticking a depth mic down in there to the lugs. you can but you dont get the correct measurement. At least not the measurement I want. i knew before i started this thread i could get the coned action tenon measurement with a little trial and error. i just wondered how other people do it without having to do trial and error, and i found out in this thread. Thanks to those guys that provided me this info. i have one of those counterbore cutters for Remingtons. Yep it makes it easier but for me part of fitting barrels is to be able to single point all of it. that is what i have worked toward and i can do it now. I like that. differant strokes for differant folks- its all good- Im glad youre enjoying it and are another shooter out there among us. Thanks

Oh In other news -- I just machined an Ar-15 barrel out of a piece of an old remington 700 Varmint barrel. Enjoyed it-Ive been wanting to do that for awhile.

 

[INTJ]

for me the point was how long should the tenon be. On a counterbore or flat breech action its easy to measure it. I dont measure the old barrel tenon on these actions ,if there was an old barrel to start with, because i want the barrel fitted with the clearance i want, not what someone else set.
on a cone bolt you cant measure it by just sticking a depth mic down in there to the lugs. you can but you dont get the correct measurement. At least not the measurement I want. i knew before i started this thread i could get the coned action tenon measurement with a little trial and error. i just wondered how other people do it without having to do trial and error, and i found out in this thread. Thanks to those guys that provided me this info. i have one of those counterbore cutters for Remingtons. Yep it makes it easier but for me part of fitting barrels is to be able to single point all of it. that is what i have worked toward and i can do it now. I like that. differant strokes for differant folks- its all good- Im glad youre enjoying it and are another shooter out there among us. Thanks

Oh In other news -- I just machined an Ar-15 barrel out of a piece of an old remington 700 Varmint barrel. Enjoyed it-Ive been wanting to do that for awhile.

I still don't understand. I have only done coned bolts and determining tenon length is the easiest thing I have to do. I either use the manufacturer specs, measure an old barrel, or measure the action threads from the receiver face to the end of the threads.

 

[Dusty Stevens]

I still don't understand. I have only done coned bolts and determining tenon length is the easiest thing I have to do. I either use the manufacturer specs, measure an old barrel, or measure the action threads from the receiver face to the end of the threads.

What are you measuring when you say action threads from the face? That doesnt really have anything to do with tenon length unless im missing something. That measurement could vary wildly according to what side of the action face you measure from

 

[INTJ]

What are you measuring when you say action threads from the face? That doesnt really have anything to do with tenon length unless im missing something. That measurement could vary wildly according to what side of the action face you measure from

From the front of the receiver down the wile length of the action threads. It measures the same all the way around the receiver. That measurement is the maximum length the tenon could be and still allow the action to tighten up to the shoulder.

 

[hoz53]

I still don't understand. I have only done coned bolts and determining tenon length is the easiest thing I have to do. I either use the manufacturer specs, measure an old barrel, or measure the action threads from the receiver face to the end of the threads.

using manufacture thread spec will get you close but may not always be correct- best to check yourself. same with an old barrel- it may not be correct or to the standards i want. measuring the length of threads in an action is not the correct way to measure for tenon length. you measure from action face to front of lug and subtract clearance dimension you want. On a cone bolt, because of the taper you cant just measure with a depth mic like you can a flat breech or counterbore. you gotta figure a different way. you can just use trial and error sure but there are ways to measure it so you dont have to.

 

[INTJ]

using manufacture thread spec will get you close but may not always be correct- best to check yourself. same with an old barrel- it may not be correct or to the standards i want. measuring the length of threads in an action is not the correct way to measure for tenon length. you measure from action face to front of lug and subtract clearance dimension you want. On a cone bolt, because of the taper you cant just measure with a depth mic like you can a flat breech or counterbore. you gotta figure a different way. you can just use trial and error sure but there are ways to measure it so you dont have to.

I think I see. You are wanting to figure a measurement so that you cut to that measurement and everything fits. I am happy to leave the tenon long, get close, and then fine tune. I think your way would be faster for sure. My way is more cautious and slower.

However, the tenon can not be longer than the action thread length unless you are using a Remmy style recoil lug. Meaning if the threaded area is too long on a cone action, you won't be able to tighten up the the shoulder. So my method of checking thread depth is indeed correct. And everything is set when you cut the cone to the correct clearance.

You way is still faster......

 

[hoz53]

I think I see. You are wanting to figure a measurement so that you cut to that measurement and everything fits. I am happy to leave the tenon long, get close, and then fine tune. I think your way would be faster for sure. My way is more cautious and slower.

However, the tenon can not be longer than the action thread length unless you are using a Remmy style recoil lug. Meaning if the threaded area is too long on a cone action, you won't be able to tighten up the the shoulder. So my method of checking thread depth is indeed correct. And everything is set when you cut the cone to the correct clearance.

You way is still faster......

im a hobbyist like you and im not in any hurry, i just want to know these things. As i said i could just use trial and error like you are describing. If thats what you wanna call correct and thats the way you wanna do it and it works for you fine.

 

[Dusty Stevens]

I think I see. You are wanting to figure a measurement so that you cut to that measurement and everything fits. I am happy to leave the tenon long, get close, and then fine tune. I think your way would be faster for sure. My way is more cautious and slower.

However, the tenon can not be longer than the action thread length unless you are using a Remmy style recoil lug. Meaning if the threaded area is too long on a cone action, you won't be able to tighten up the the shoulder. So my method of checking thread depth is indeed correct. And everything is set when you cut the cone to the correct clearance.

You way is still faster......

Check the drawing for a cone bolt panda. Thats how you make them longer than the threads

 

[INTJ]

Check the drawing for a cone bolt panda. Thats how you make them longer than the threads

Yep. Checking the drawing is the first thing I do..............

 

[Dusty Stevens]

Yep. Checking the drawing is the first thing I do..............

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.

 

[INTJ]

im a hobbyist like you and im not in any hurry, i just want to know these things. As i said i could just use trial and error like you are describing. If thats what you wanna call correct and thats the way you wanna do it and it works for you fine.

I would call it more cautions. I am sure the "correct" way is to measure and cut to that measurement like you do. I still don't trust my machining skills enough to do it that way. I like to see the part in place as I progress with machining. I cut threads the same way. Not to a certain depth, but when I get close I start test fitting and take a smaller and smaller cut until I get the fit i want.