ASSRA Forum - .22 Martini action barrel thread

Chuckster

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Re: .22 Martini action barrel thread
Reply #15 - 03/07/10 at 22:22:45

OK, DD, I am going to pick on you (in a nice way). How do you use those tools or others to determine the OD of the barrel shank before threading? I am going to start threading a barrel for an action that has something around a 15/16" x 16 thread. OD may be smaller or larger. How do I determine barrel shank diameter? Current plan is oversize test piece and trim to fit. Thanks for any suggestions.
Chuck

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38_Cal

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Re: .22 Martini action barrel thread
Reply #16 - 03/07/10 at 23:45:06

I'll step into the breach here, if you'll excuse the expression! Wink

On every Martini small frame that I've had the barrel off of, there has been a relief in the receiver to at-or-below the thread root, usually for about one thread's worth. I size the barrel shank to that diameter to start with, and start cutting my threads, using the receiver itself as the gage for their fit. Doing this, I may end up with a larger or smaller pitch diameter than is normally indicated for the small Martini's .750"-14 tpi thread, but the barrel thread fits that action as well as I can make it. I go for a snug hand fit without any shake of the action on the lubricated barrel threads, but not needing an action wrench to turn it on. On actions without the thread relief, I'll turn the barrel shank to about .010" over the nominal diameter before threading. I'm sure that others do things differently, but this works for me.

David

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« Last Edit: 03/10/10 at 14:03:40 by 38_Cal »

David Kaiser
Montezuma, IA

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Chuckster Full Forum Member Offline Posts: 187	Re: .22 Martini action barrel thread Reply #17 - 03/09/10 at 22:38:14 David, Thank you, Good advice as usual. Took a look at the relief. Seems a little oversize, but that will work. Still think I will make a test piece. If for nothing else, I need the practice. Chuck
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DoubleD

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Re: .22 Martini action barrel thread
Reply #18 - 03/10/10 at 00:27:42

Chuckster wrote on 03/07/10 at 22:22:45:

OK, DD, I am going to pick on you (in a nice way). How do you use those tools or others to determine the OD of the barrel shank before threading? I am going to start threading a barrel for an action that has something around a 15/16" x 16 thread. OD may be smaller or larger. How do I determine barrel shank diameter? Current plan is oversize test piece and trim to fit. Thanks for any suggestions.
Chuck

That's what the Inside spring caliper is for, put it in the action and open it in the threads. Take it out and measure it. That's your major diameter of your barrel shank.

Cut the threads and follow David's advice to use the action as a gage.

By the way I don't see that as picking on me, it's asking me to explain.

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Douglas, Ret.

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screwloosetc

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Re: .22 Martini action barrel thread
Reply #19 - 03/10/10 at 11:59:23

David gave you the answer. Make sure threads in receiver are clean. Continue to cut thread until you have a smooth fit. are u doing this or is some one else? You might want to seek profesional hands on help other than the advice from this group.Things get diferent when they are in front of you. When you start you dont want to stop.Dosn't take long for a wreck to happen. There are more things to consider other than dimentions. That is why you pay a gunsmith.
Tom

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Chuckster

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Re: .22 Martini action barrel thread
Reply #20 - 03/10/10 at 22:13:02

DD,
Thanks for the input. My first reaction was the radius on the tips of my spring calipers would give a false indication. Maybe I need to sharpen them. Spring calipers are not easy to use accurately. Will do some comparison measurements on the test piece.

Tom, -- You are absolutely correct, although there is a great deal of expertise on this forum. Have done several with reasonable success, but also have had a wreck. That is the price you pay to learn.
Chuck

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screwloosetc Senior Forum Member Offline Posts: 255	Re: .22 Martini action barrel thread Reply #21 - 03/10/10 at 22:31:12 Chuck You might want to practice on a plug to screw the receiver on to; to drill it for a cleanig rod hole if it dosent already have one.you can also make the plug into a guide for lapping the face of the block square. Tom
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DoubleD

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Re: .22 Martini action barrel thread
Reply #22 - 03/11/10 at 09:48:27

Chuckster wrote on 03/10/10 at 22:13:02:

DD,
Thanks for the input. My first reaction was the radius on the tips of my spring calipers would give a false indication. Maybe I need to sharpen them. Spring calipers are not easy to use accurately. Will do some comparison measurements on the test piece.

Tom, -- You are absolutely correct, although there is a great deal of expertise on this forum. Have done several with reasonable success, but also have had a wreck. That is the price you pay to learn.
Chuck

The tips of my spring spring calipers are pointed. It is the technique taught at school. It also came out of the old Gunsmith handouts from Oregon Technical Institute. I also saw the late Chuck Donnelly use the method and that validated it for me.

Using the caliper gives a better fitting barrel than making a tenon to standards.

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Douglas, Ret.

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Jeff_Schultz ASSRA Board Member Offline Posts: 255	Re: .22 Martini action barrel thread Reply #23 - 03/11/10 at 10:00:28 DD, Good tip! Thanks!
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Chuckster Full Forum Member Offline Posts: 187	Re: .22 Martini action barrel thread Reply #24 - 03/12/10 at 22:52:16 I like Tom's idea of a lap for the breech face. Might as well get some use out of a test piece. Lapping sure won't hurt anything and might help. The sholders of the breech block have already been lapped. Chuck
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38_Cal

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Re: .22 Martini action barrel thread
Reply #25 - 03/12/10 at 14:06:19

I use a barrel stub type fixture to square up the breech face, using one of Manson Precision's (www.mansonreamers.com) bolt face truing burrs, then lapping. This is mainly when I've converted a small Martini, like a 12/15, from rimfire to centerfire, and made sure that the firing pin hole is centered. I also use this setup when bushing a breech face for a smaller firing pin tip or to repair a damaged breechblock.

David

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David Kaiser
Montezuma, IA

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screwloosetc Senior Forum Member Offline Posts: 255	Re: .22 Martini action barrel thread Reply #26 - 03/12/10 at 18:16:35 have we figured out what model action we are fooling with yet? Does it have a hole for the cleaning rod? What holds it together a screw or split pin? Tom
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buffler

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Re: .22 Martini action barrel thread
Reply #27 - 03/16/10 at 18:23:35

It's definitely a Model 15, with cleaning hole, screw pin, and built-in rear sight base; the thread is Whitworth 55 degree, .750 x 14tpi. Whitworth threads have a small radius instead of a "v" so the depth of thread for 14 tpi is slightly less than, for example, an SAE. at least according to my Machinery's Handbook.
Found my spring calipers, for this size thread it's easy to see that the tip seats. BTW, from one thread to the next across the diameter is not quite the OD but probably so little difference it's trivial, and probably hard to measure with a spring caliper.
Don

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