Gunsmithing Silver Soldering Barrel Nut?

coleasterling

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I've been working on a "poor man's" switch barrel system based off of a Marlin XL-7(uses the same barrel nut system as the Savages). It works really well as is, but I would like to speed up the time to swap barrels. As of now, I've just been using a go-gauge and screwing the barrels down on top of it, then tightening the nut. The whole process takes about 3 minutes, but I'd like to get it under a minute.

Also, headspace isn't just extremely consistent this way. I am getting small poi changes when reinstalling the same caliber barrel from this, which are about about a quarter to half moa.

I was thinking about using a low-temperature solder, such as the Hi-Force 44 stuff from Brownells(flows at 475 degrees F) to lock the barrel nut in place on the barrel, essentially making it a shoulder to headspace off of. Keep my torque relatively consistent when tightening, and my poi change should be consistent as well, correct?

Anyone see a problem with this approach? I would apply flux to the top fourth(or less) of the joint between the nut and barrel, set headspace, tighten nut, then heat and solder for each barrel. I could then use my nut wrench(which I have integrated into the stock) to tighten the barrel without having to worry about setting the headspace or checking with gauges each time as it should be the same.

Thanks for the help!
-Cole
 

jwSubMOA

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Re: Silver Soldering Barrel Nut?

If you do this you will cause more problems for yourself.The poi changes you get are likely from slight differences in trueness of the reciever face and face of the barrel nut.If I were doing this I would try Red permanent Loctite because if you heat the barrel and nut you'll warp the crap out of it.You could also have a couple of small setscrews added to the barrel nut.
 

coleasterling

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Re: Silver Soldering Barrel Nut?

I like your line of thought, but am not sure you're correct. Even if the poi changes are from the nut and action face being out of true, locking the nut in place will ensure that the nut and action are out of true the same way every time. The poi change should then be repeatable, which is perfectly acceptable. Also, the solder's flow temp is too low to warp anything.

I do like your set screw idea. I might try that before anything. Thanks!
 

Top Cat

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Re: Silver Soldering Barrel Nut?

You want the barrel aligned the same way every time. Your POI changes are more likely due to bore runout variation than headspace variation... same thing really.

It would be a simpler solution to make a timing mark on the barrel and receiver, and use barrel indexing rather than HS as the indicator... that solves the headspace measurement as well.

Also, find the point the barrel runout is aligned to the top side and fix it there.

TC
 

swd

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Re: Silver Soldering Barrel Nut?

I would always expect the poi change your getting from taking a barrel on and off. If the action has been single point trued with a barrel fitted pretty tight you might see less.

I would just refer back to Top Cats post and go with it.
 

Shooter21

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Re: Silver Soldering Barrel Nut?

If solder the barrel nut not only are you going to screw up harmonics, which will change from shot to shot if done, but at .475 you may way warp the barrel. Remember metal will expand quite a bit from 0-100 F. 0.001" will change your POI... Setscrews. Remember also that the barrels are stress relived before milling. DO NOT ADD STRESS POINTS
 

coleasterling

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Re: Silver Soldering Barrel Nut?

How will harmonics change from a few extra grams situated an inch away from the action? Honest question!

For setscrews, it would muck up the threads at the point they are tightened, but the point loading wouldn't be significant enough to hurt anything.
 

Shooter21

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Re: Silver Soldering Barrel Nut?

Silver solder is softer than steel, a lot softer. It will absorb some harmonics but amplify others just as lead does. Every shot heats up the barrel a few degrees. The steel in the barrel and nut will expand consistent with one another, the solder will either be slower or faster, depending on ambient temp. Also the solder will dissipate heat faster. The solder will expand
more than the steel in the small variations because of it's low melting point....
Were just trying to save you from screwing up your barrel, but do what you want with it...
 

horseshoe3

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Re: Silver Soldering Barrel Nut?

I'd go with Top Cat's idea.

Also, by soldering the nut to the barrel, aren't you making it the same as a conventional setup only more complicated and fragile? The nut would act just the same as a shoulder - until it broke loose.
 

toolmaker

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Re: Silver Soldering Barrel Nut?

Why are you concerned about switching barrels in under a minute? Just curious.
 

coleasterling

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Re: Silver Soldering Barrel Nut?

Tool, I say under a minute...The time doesn't really matter so much. It is all about making it more fool-proof and consistent. If I don't have to worry about setting the head space each time, then the whole process goes a lot faster, easier, and results in a better, safer rifle. I want to make it to where a 5 year old could do it.

Now, I started this thread to get opinions, and I value all of them. Thank you everyone for the input!

Horse, yes it would, except that there's a surface to mate a wrench to now. How would you do that on a regular barrel? I'd be leery of doing any machine work to it.

Shooter, thanks again for the replies. I'm still not convinced there would be a harmonics issue. I'm a Mechanical Engineering major and I am VERY familiar with materials. If I had the time, I could set up a simulation to find out for sure, though. We'll just have to agree to disagree until I try it
smile.gif
 

sandwarrior

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Re: Silver Soldering Barrel Nut?

coleasterling,

I wouldn't be worried so much about the harmonics as the fact that once you silver soldered your nut to your barrel there is no changing it. The silver solder gets into the grain of the steel and you won't ever get it out again. This whole point is about not being able to set your barrel back.

As for the set screws, I think that's a good idea. If you're worried about bunging up the barrel threads then do like Wilson does with their dies and put a nylon insert in the hole to clamp it to the threads.

I do see what you mean about turning the nut instead of the barrel and it shouldn't be a problem. Just in case, I would still do like topcat said and make index lines from barrel across nut to receiver with the most runout on top. That is, of course, if the run-out is within tolerances.

I know you said it isn't so much about the time as making it fool proof. What about getting a full diameter barrel and having flats machined on the base of the barrel and skip the barrel nut? It'll be more expensive but dead on every time.
 

Hellbender

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Re: Silver Soldering Barrel Nut?

Get some good epoxy and glue it in place, then if you don't like it, you can remove it with a little heat.
 

former naval person

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Re: Silver Soldering Barrel Nut?

Like Hellbender said: Degrease the nuts and barrel shanks and install the barrels with with Devcon Titanium (or steel) and it will be there until you and your propane torch want to take it off.
 

Fritzcat

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Re: Silver Soldering Barrel Nut?

Seems the torque sequence of the action to the stock can make some POI changes, as you have to remove stock to use your wrench.
 

coleasterling

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Re: Silver Soldering Barrel Nut?

Fritz, I don't have to remove the stock to use the wrench. The stock has been modified to where the wrench itself is my forestock. It works really well! I do need to make some changes to the shape, since it has more flex than I would like, but that's all easy stuff with the CNC.
 

Greg Langelius *

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Re: Silver Soldering Barrel Nut?

I think that leaving the nut free and using witness marks on the barrel and receiver is the best approach. I think that the elimination of the barrel nut's one benefit because of a very minor alteration of repeatability is simply not justified.

Use the witness marks properly and the degree of alteration may not be even perceptible.

People on this site obsess over the most infinitesimal things, yet take no account of other omnipresent factors that outweigh them as an elephant to an ant.

Think less, shoot more.

If you're going to use different barrels, I'd suggest you stick with ones intended for the Marlin. I'm not certain about this but I believe the Savage and Marlin barrels may be chambered with a different 'protrusion' value (this corresponds to the depth of the bolt face recess). Mixing and matching may carry serious issues. In any case, check on this before firing.

Greg