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Discussion Starter #1
As much as I have searched, I can not find any info on the proper Installation of a new(different) barrel on a 39 action.
I want to install my oct shorty barrel on my 39A action, then top it off with Boyds "pepper" laminate stock.

I have a large vise and wood barrel blocks, Fabbing up a action wrench, so removing the old barrel will not be a problem.

Question is, how do you "index" the new barrel to the action?? (make sure the sites are straight up when the barrel threads tighten.
then how do you set the head space once the barrel is installed?

Thanks,
Slack
 

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I am assuming (could be my mistake) that the barrel is already chambered. If so the headspace should be off of the 22 rim and already set. One way that I have indexed barrels is to use 2 ea. 3 ft. long pieces of 1/4 inch square stock (from lowes or home depot). Clamp the receiver/barrel in a vise. I tap the front sight out of the barrel and balance one at the midpoint of the square stock in the dove tail and balance the midpoint of the other on top of the back of the receiver. Step back a few feet and look down the barrel from the bore end. When it is indexed properly, you will only see one piece of square stock.
 
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These are threaded into the action. Typically - a "new" barrel would be fitted onto the receiver and torqued down. Mark the top and bottom. Then you would match mark the barrel to the receiver. Unscrew it, cut all your chamber extractor and ejector slots, dovetails and slots for the sights, tube, barrel bands, and wood mounting. Then finish up the finish and screw it back on. Viola!

This is probably the sort of thing you would leave for a pro gunsmith who deals with these sort of things regularly - because you can twist your receiver or really mess up things if you don't have the right tools.
 

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Discussion Starter #5
This is a "New" to this receiver barrel.
Not a new barrel blank.
What I was wondering is,, is the marlin receivers and barrels machine to such exacting tolerances, that when you screw the "new to me" barrel into the receiver and tighten it up, the barrel will end up correctly indexed, with all the sight and ejector groves in the correct relation to the receiver??
If not,, how is the replacement barrel "indexed"??
 

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only way to tell is to screw it in and see where the dovetails/sights are when tight. I've watched an expert do barrel change but never done it
 

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Discussion Starter #7
So you have seen them do it??
When it does not exactly line up after tightening,, how is it adjusted? are there shim stock washers to get it to move clockwise? how about getting it to move the other way, THAT is my question.
I have scoured the internet for days, yet this appears to be a deep, dark, lost secret??

only way to tell is to screw it in and see where the dovetails/sights are when tight. I've watched an expert do barrel change but never done it
 

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This is a "New" to this receiver barrel.
Not a new barrel blank.
What I was wondering is,, is the marlin receivers and barrels machine to such exacting tolerances, that when you screw the "new to me" barrel into the receiver and tighten it up, the barrel will end up correctly indexed, with all the sight and ejector groves in the correct relation to the receiver??
If not,, how is the replacement barrel "indexed"??
Hope for the best but plan for the worst. It may be fine, it may not. The only way to know is to torque the barrel on and see.

This is where you would like a gunsmith with some experience with this sort of thing.
 

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Discussion Starter #9
I am hoping once torqued down it will be "Indexed"
BUT, I am planning for the worse.
I am capable, I have the tools/shop to perform most any work, BUT I need to know the method or procedure to adjust the indexing.


Hope for the best but plan for the worst. It may be fine, it may not. The only way to know is to torque the barrel on and see.

This is where you would like a gunsmith with some experience with this sort of thing.
 

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I would use smooth round barrel & put a scope on it then no worries over index.:beer::flag::eagle:
 

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I would think that if it didn't tighten in far enough to have everything in line it would need some machine work to turn in farther. If it would go past center when tight it would need machine work to go one complete turn farther and then the chamber would require work to get it back to standard specs for the the 22 cartridge. I have swapped barrels on 700 Remington actions and when screwed in tight the head space was right but the sight holes might come out on the side or the bottom. There is a gun smith in western Md. that does Marlin 39 A work and does it right.
 

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Discussion Starter #13
Thanks Bandit,
I was thinking it would need machining if it had to go "Just a bit more",, but was hoping there was a shim washer if it went to far.
 

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Thanks Bandit,
I was thinking it would need machining if it had to go "Just a bit more",, but was hoping there was a shim washer if it went to far.
Slackdaddy you are in Md. with an excellent gun smith in the western part of your state that does very fine work. I would have him do any work for me and never have a second thought on the quality of the work performed on the rifle. I can give you his phone number and you could call him about the work to get it indexed right. Using shims to get it indexed as far as sights being straight would throw the head space out of spec. You would be better talking with the gun smith in Md.
 

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if it needs shim between barrel and receiver headspace will be off. do you have a lathe? mill? if you go the other way and trim barrel and extend threads then trim end of barrel back and rechamber, cut extractor slot in correct position.
basically if it is not right when tightened into receiver its a can of worms best left to experienced expert. just $0.02 from an old phart who is a hobbiest not an expert
 

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I would use smooth round barrel & put a scope on it then no worries over index.:beer::flag::eagle:
Mike if it was just a shooter grade rifle that was going to be used for hunting it would be OK to do what you said with not worrying about indexing. The next problem then would be that the mag tube being fastened to the barrel by a dovetailed in hanger would throw the tube out of alignment and then would require that to be fixed and would most likely also need the mag tube groove in the fore arm altered for the misaligned tube. Trying to fix one issue some times can make a couple more that will need to be taken care of. For me it would be gun smith time to get it right.
 

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if it needs shim between barrel and receiver headspace will be off. do you have a lathe? mill? if you go the other way and trim barrel and extend threads then trim end of barrel back and rechamber, cut extractor slot in correct position.
basically if it is not right when tightened into receiver its a can of worms best left to experienced expert. just $0.02 from an old phart who is a hobbiest not an expert
^^^^^^^ Right on.
 

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Thanks Bandit,
I was thinking it would need machining if it had to go "Just a bit more",, but was hoping there was a shim washer if it went to far.
In most cases, if the barrel needed rotated "just a bit more" tighter it would just be a matter of applying "Just a little more torque". That is how I watched the gunsmith install a new barrel on my M1 Garand and it it how it works for AR15s (they have a torque range of 35-85 ft. lb. to allow you to index the barrel and line up the gas tube).
 

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Discussion Starter #19
I hear you all,
I have a receiver wrench and barrel inserts for my vise. If it does not "end up" being indexed when tightened, I will send it over to scotty's
 

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Baseless encouragement

Slack, I see your comment about having searched this... I did too, a couple of years back. On the umpteenth iteration of slightly different search terms my weak google-fu coughed up one single thread about an actual and productive barrel change on the 39A.

Two comments: First, it's my recollection that the posts in that thread ran very much like the comments offered here in response to your request here, from "just do it, and let us know how it works out", to find the best gunsmith and let a them work it... My further recollection is that the OP in that thread weighed all the suggestions, but went ahead with his proposed barrel swap and to his relief (and surprise) the replacement barrel indexed correctly the first attempt. I also vaguely recall that there was mention of a proper action block, and you have acknowledged that you've considered that need.

Second (and lastly): It's my recollection... just that. I can't find that thread now, so no linky for you, and if I bookmarked it, I don't know where I bookmarked it. Oh, and it seems that as I age, that's pretty typical with respect to my recollections - I recall things that I just can't validate. In fact, I suspect that some of the things I remember best never actually happened... carry on, sir.

Let us know how it works out, eh?

'tool
 
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