Author Topic: Barrel wall thickness @ dovetail slot? (Read 8026 times)

Boompa · « **on:** October 28, 2015, 11:17:24 PM »

I did a search on this and found many different answers. With the current steel used in ML barrels, Colerain, Rice, etc., how thick does the barrel need to be at the dovetail slot?

Dennis Glazener · « **Reply #1 on:** October 28, 2015, 11:28:53 PM »

I use and barrel makers have told me the same thing, .100" wall between bore and bottom of the dovetail. Now make sure you understand that IS NOT the thickness anywhere closer to the breech than the hind site.
Dennis

Mark Elliott · « **Reply #2 on:** October 28, 2015, 11:40:50 PM »

You can go at that another way; the depth of the dovetails. Getz and Rice both told me that they assume a 0.040" deep dovetail for barrel tenons and sights in the design of a barrel. In other words if you subtract 0.040" at the thinnest part of the barrel you should get 0.100" or more. I have a homemade stop (just a folded over piece of 16ga steel with a few screws) on the hacksaw blade I use to cut dovetails,set to 0.320". I then cut out the little fins with a die sinker chisel and file with a sight base file. Being careful to remove no more metal than absolutely necessary, I usually end up at 0.040" deep or slightly less. I think that is the info you really need.

Acer Saccharum · « **Reply #3 on:** October 29, 2015, 12:22:02 AM »

The barrel is the structure, the backbone, of a long rifle. The tenons are merely used to hold the stock to the barrel.

This function does not require a huge lug or dovetail, because all the lugs do is hold a little sliver of wood to a bucking bronco. The vertical wood at the breech end takes all the abuse, and that's where the contact should be good.

The tang screw is the workhorse of the whole assembly, clamping the barrel into the stock, and sandwiching the stock between tang and trigger plate.

I apologize, I made a lot of reference to skeletons, sandwiches and horses. That's so guys out West, like Dave Rase, can understand what I'm talking about.

Acer Saccharum · « **Reply #4 on:** October 29, 2015, 12:30:34 AM »

That said, I seldom use a dovetail deeper than .040 on any barrel, any location.

If I use .025 steel for a folded lug, I'll cut a .025 deep dovetail, and peen the dovetail down tight on the lug wings, file it all smooth afterwards.

On a thin wall round barrel, I will make curved lugs and sweat them on with plumber's solder.

kaintuck · « **Reply #5 on:** October 29, 2015, 12:33:34 AM »

TOMTOM said "one claw' deep for a dovetail is enuff........ $:-\$
thin is 'in' so~~ just a slot for a 16ga or so sight or anything seems like it worked for centuries on these rifles.......
marc n tomtom

gumboman · « **Reply #6 on:** October 29, 2015, 05:52:43 AM »

This is a topic that could use more discussion. Today I talked to a barrel maker about a 62 caliber barrel and he suggested that I allow him to cut cut the dovetail in at the waist area. Reason is since wall thickness in the waist is so thin, it is critical to get a shallow dovetail cut in precisely. With a .030 inch dovetail slot in the waist, barrel wall thickness at the dovetail will be .065 inch on this particular barrel.

That is very thin indeed but the barrel maker said it will be fine and safe. Can other members of the forum make comments, opinions or past experience on risks or safety with such a thin wall at the waist?

Boompa · « **Reply #7 on:** October 29, 2015, 07:39:46 AM »

I brought this up because I have a barrel w/ deep dovetails cut. A few measurements and a little figuring and I realized the barrel wall under the dovetails is only .075". So far no issues but it seems awfully thin.

Dennis Glazener · « **Reply #8 on:** October 29, 2015, 04:22:13 PM »

Quote

That is very thin indeed but the barrel maker said it will be fine and safe. Can other members of the forum make comments, opinions or past experience on risks or safety with such a thin wall at the waist?

Yes I can but I won't since anything less than .100 is usually less than the barrel maker tells you is safe and anything under that is at your risk. I don't think we should discuss anything thinner on a board that is frequented by novice builders, too dangerous. Some don't even have the means to accurately measure and that can be dangerous when working with thin wall barrels.
Dennis

Dphariss · « **Reply #9 on:** October 29, 2015, 05:38:25 PM »

Quote from: gumboman on October 29, 2015, 05:52:43 AM

This is a topic that could use more discussion. Today I talked to a barrel maker about a 62 caliber barrel and he suggested that I allow him to cut cut the dovetail in at the waist area. Reason is since wall thickness in the waist is so thin, it is critical to get a shallow dovetail cut in precisely. With a .030 inch dovetail slot in the waist, barrel wall thickness at the dovetail will be .065 inch on this particular barrel.

That is very thin indeed but the barrel maker said it will be fine and safe. Can other members of the forum make comments, opinions or past experience on risks or safety with such a thin wall at the waist?

If you proof and shoot this barrel for awhile then run a tight patch on a short bearing surface jag you will likely find the bore DIMENSION has been effected and its possible to feel the dovetail cut as the tight patch is being pushed through the bore. Any cut in a barrel is a stress riser. While many modern revolvers that operate at pressures almost unobtainable with BP have thin cylinder walls they are generally made of much better material.
Barrels as thin as described in this thread tend to work harden if the steel is prone to this and many are.
I have seen photos of a TC Hawken or clone with a split in the bottom of the dovetail. But these had "modern" dovetail depths.
Measurements. Take the OD of the barrel across the flats if octagonal, subtract the GROOVE diameter of the bore. For a 50 caliber this will near .530 or even larger is very deep grooves are cut. Now divide by 2. So 1" - .530 then divide by 2. We get .235. This is flaky if a drum is used.
I would NEVER recommend a barrel wall in a ML as thin as described here. If nothing else it will be very easily damaged (bent) should the gun fall or be subjected to any bending stress.
Yeah they used to do this kinda thing back in the day. Hint. A lot of dumb stuff has been done in the past. We are not compelled to recreate things that are suspect.
Dan

JCKelly · « **Reply #10 on:** October 29, 2015, 07:22:24 PM »

That dovetail is often cut about where the shooter's left hand would be

Years ago a brand of American made "Hwakins" rifles cut the dovetail too deep on occasion. Cost some important body parts.

Oct - December 1985 Muzzle Blasts has a series on this matter.

Want a pdf, email me

Good luck with your Modern Steel barrel.

Old Ford2 · « **Reply #11 on:** October 30, 2015, 02:40:45 AM »

Great post and topic.
Thank you all for your knowledge and experience for sharing with us all.
Fred

Boompa · « **Reply #12 on:** October 30, 2015, 03:20:54 AM »

Thanks for all the good info. I'm now a little concerned about one of my rifles. As I said we figured the wall thickness to be about .075, .025 less than the norm. I can't feel any difference or irregularity in the bore when I run a tight jag-patch through it.

gumboman · « **Reply #13 on:** October 30, 2015, 01:03:46 PM »

Many thanks for the info from my side too. Now I must reconsider the barrel I was going to buy. Will have to talk to the barrel maker again.

bama · « **Reply #14 on:** October 30, 2015, 06:20:31 PM »

Gumboman, sweat the front two thimbles on and dovetail the rear one and you won't have a problem. If you need help with soldering them on come by the shop and we will do it here. We can make the lugs here if needed.

Sorry I just re-read your post I thought you were getting a oct to round barrel but it sounds like you are getting a swamped barrel. Still we can cut the dovetails on my milling machine if you want to do that.

gumboman · « **Reply #15 on:** November 01, 2015, 05:14:48 AM »

Hey Bama. The octagon to round barrel is the next project up. The swamped 62 is for a future project. I thought soldering would be the best option and I can use some help with that.

My Haines rifle is complete so I need your critique. Will drop by the shop soon so you can inspect. I shot it this weekend and it shoots great. Fast ignition and accurate.

Micah2 · « **Reply #16 on:** November 01, 2015, 05:30:33 AM »

what do yall think about stapled lugs, i.e. modified 6d finish nail? they are fast and easy, and i think safe. if they were to fail or one drilled to deep, it would not compromise the barrel any more than a vent hole.

Boompa · « **Reply #17 on:** November 01, 2015, 07:47:01 AM »

I've never owned a gun with stapled lugs but I've not heard much negative about them. I wish they were referred to as something different than "stapled". It sounds cheap.
Just me I guess.

Willbarq · « **Reply #18 on:** November 01, 2015, 09:33:56 AM »

Quote from: Acer Saccharum on October 29, 2015, 12:30:34 AM

That said, I seldom use a dovetail deeper than .040 on any barrel, any location.

If I use .025 steel for a folded lug, I'll cut a .025 deep dovetail, and peen the dovetail down tight on the lug wings, file it all smooth afterwards.

On a thin wall round barrel, I will make curved lugs and sweat them on with plumber's solder.

I just cut in a rear sight. This is where i ended up. .025 That was my Halloween horror. Got er done! file, file sight, file some more, test fit. I started too small , but alas was afraid of going to deep. It was a fright..

Dphariss · « **Reply #19 on:** November 01, 2015, 08:30:55 PM »

Quote from: Micah2 on November 01, 2015, 05:30:33 AM

what do yall think about stapled lugs, i.e. modified 6d finish nail? they are fast and easy, and i think safe. if they were to fail or one drilled to deep, it would not compromise the barrel any more than a vent hole.

Got to have enough wall thickness and then be careful with setting the depth to fit the key or pin and the staking so as to not dimple the bore. I like staples.

Dan

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Author Topic: Barrel wall thickness @ dovetail slot? (Read 8026 times)

Boompa

kaintuck

Boompa

Boompa

Micah2

Boompa

Willbarq