Threaded barrel question.... Might be out of most smithy`s league

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Polomax

New member
1st of all I need to stress that what I do is build custom HPA/PCP guns and have always wanted to try something like this but I do not have the equiptment to make these items. I`ve read up on it for several years now and have finally decided to see if I can have one built or threaded.
I work with .483 DIA .25 and .22 Lothar Walther barrels so this doesn`t leave much for threading only .4 threaded length is needed....also the .483 DIA doesn`t leave much for a 90deg shoulder..... So I was thinking maybe a adapter that slides onto the barrel and secures with a grub screw with a 1/2-28 threaded end will work something like the photo attached. doing a adapter this way will leave plenty of threades and also the 90deg shoulder needed for the muzzle can. does anyone here make such a adapter ?? I`ve only seen a couple different variants of something like this but they were all done in 1/2-20 and I need 1/2-28.... any information would be greatly appreciated from any smithy here... Thanks
 

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By no means am I a gunsmith, but I do have some experience in a machine shop. The device you shoe should be well within the abilities of an average machinist who can cut threads.

I would question the ability of one grub screw holding this device to the barrel. I think I would want some more positive way of holding it onto the barrel. I've built some slip on compensators and they definitely need heavy duty attachments.
 
this isn`t going to be mounted on a powder burner it is going to be used on a Co2/HPA Airgun these are High Power guns which have had the Valves set for Bulk rateing causeing Higher power then normal Co2 or factory Air guns. FPS rateing will still be under the 1000 fps im only useing the muzzle can to cut the load report of the Co2 and YES I KNOW all the laws and regs about Silencers in my area I have several legal Suppressors.

I was even thinking maybe even thread the barrel and the adapter that would also be ok and be more stable Vs. the grub screw... The main thing here is I do not have enough material on the .483 barrel to thread 1/2-28 so the adapter can have any thread pitch/size it would need to attach to the barrel. I do know the grub screw works for use on the Co2 guns very well as long as there is atleast 2" of the host barrel slid into the adapter, 2 or 3 grub screws can be used if need be... I have checked several machine shops and not one yet will touch this project for ONE piece...... That is why I posted it here to see if someone here might wanna give it a try. :D

The muzzle cans im useing are all under 4 oz`s made from Aluminum/Stainless threaded ends. so it`s not like I wanna hang a 16 oz can off the end of the barrel and expect it to hold.
 
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The only way that these things get made as a one-off are as labors of love! I'm neither a professional smith or machinist, so maybe it takes me longer than most to get things set up, but I've found that even with the right tools, these things can take MANY hours to do well. I've made devices that are similar to Browning's BOSS for rifles that I've built ... and although they were a little more complicated (being 3 pieces with mating threads), if I were to value my time at all, the devices would have been the most costly part of the rifle by FAR ... and that includes the Leupold scope with the QD rings!

By the way, I'd go for a very light press fit if you want the center of your can to line up with the center of your bore ... a set screw attachment will drive it off to one side. If it is REALLY close, it might not matter, but a slight interference fit (even 0.0001") will guarantee that you are centered.

Maybe there is a lathe in a class you can take at the local junior college?

Saands
 
"but a slight interference fit (even 0.0001") will guarantee that you are centered."

I believe less than .0004" clearance is going to be a press fit.

The part is not that difficult to make, but I'd be concerned about alignment. Are you sure the OD of the barrel is concentric with the bore? Most threads cut on a barrel are set up concentric with the bore not the OD.
 
Good point on bore/OD concentricity ... you'd want to verify that before using the OD of the bbl as a reference.


Saands
 
threading

Sir;
If I understand you correctly you are concerned with having enough shoulder to but up against your action?
If so, there is a very satisfactory method of curing your problem!
Turn the threads on your barrel shank long enough to accomodate a nut like Savage does (and now Mossberg) and set your barrel up like that!
Four threads will hold your barrel safely in the action. With the nut you can thread longer than that! Am I correct in my understanding or not?
Harry B.
 
threading

Sir;
By all means, a "grub screw" will not hold to your barrel! I looked at the picture and the nut will snug right up against your action shoulder and when screwed up tight will act exactly like a shoulder!
This way you can set your headspace wehere you want it, snug up your barrel nut and there you have it.
Harry B.
 
I got ya on the use of a nut..... But I think I still have a slight problem with the barrel DIA being .483 in you honest opinion is this enough material to thread 1/2-28 or will I only end up have slight marks where the threads could be..... :confused:
 
Double depth of a 28 TPI V-Thread is .046", .0023" per side. So at .483" you will lose .0085" depth per side. You will lose 37% of the thread depth. Assuming the nut has 75% thread then you have 38% engagement. Not what I'd strive for but you can always make a test piece and see what it "feels" like.
 
Polomax: 7/16 X 28 should work for what your wanting to do, and threading the barrel will make sure that the adapter is centered on the bore. I don't think a can on an "air rifle" will run afoul of the BATF regulations, but then I haven't checked either.

P.S. If you use the lock screws that your thinking about, you run the risk of distortion in the bore. Evan a small screw will apply much more pressure than most people realize.
 
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Im good with the BATF my $200 tax stamps are paid for what I own so im sure they won`t care what I put my Suppressors on :D
 
G’day there,

I am a Tool-Maker by trade and can tell you that you can cut any type of thread you like. Who says it has to be a standard thread, you can cut any OD, pitch, angle & depth that you want both internally and externally. Maybe you wont be able to go to the hardware shop and get a tap & die set but any machinist worth there salt can cut a matching thread to your specs especially with the CNC machines of today even a manual lathe and competent tradesman should have no problem.

As far a press fits if you did a thermal interference fit it will be basically one piece and never come apart. Heat the female piece (Even slightly) and put the male piece in the freezer, press the two together quickly and they will be solid, you would not be able to separate them again without extreme difficulty if at all.
 
threading

Sirs;
I agree, you can cut any thread you want.
"Shrink fit" - let me explain something:
At Springfield arsenal, during WWII they fit a barrel to another action which is as you describe - the barrel needed an extension on it so it could be properly fit to the action. They machined a piece and precision bored it to make it a "shrink fit" on the undersized barrel, they did exactly what you've been told and "shrunk" it to the barrel - not only "shrunk it" but also installed several taper pins to be sure! When fired (30-06) the "shrunk" fit came loose and ended up down-range!
Now, we know that the 14 inch Naval guns (rifles) were built with liners which were "shrink fits!" But that's a different story. The length of the fit was considerably longer than you are working with.
In the AR15 (M16) barrel there is a breech end THREADED on the barrel - this is not a shrink fit but a threaded one - you can fire safely a 338/06 with the barrel sholdered up to the action hand tight but not "shrunk!"
If you are building a rifle with any pressure at all, or if you want a barrel correctly fit to an action you need at least 75% thread fit! That means you need the correct "major" diameter to thread. 75% thread will hold 90% of what a 100% fit will, and four good threads, technically will hold all the bolt will take in torque!
Harry B.
 
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