Threading Barrel
I'm very good when it comes to working with hand tools and doing small gunsmithing jobs to include drilling & tapping. Once something is explained to me I think I have a pretty good take on whether I can do it or will screw it up.
A friend of mine bought an FN SPR with a 5/8X24 (AR 10 type 30 cal standard)threaded barrel. The threading was poorly cut and I'm using a hand cranked die to chase the threads & clean them up. So far, so good. My question is regarding using the same die on a barrel that already is threaded, but threaded to a different pitch & LPI.
I have a MAS 49/56 and the barrel is threaded. The muzzle "device" in CA may or may not be considered a flash hider and that triggers our foolish AW laws - I leave it off just to play it safe, I happen to think it is an FH. Of course it makes the rifle look like crap, I think. A muzzle brake, on the other hand, is perfectly legal but of course finding one for the MAS 49/56 threading is impossible. Since I have the 5/8X24 die I'm considering trying to re-thread the barrel allowing me to attach an AR 10 brake.
Is it possible to "thread over" existing threads on the outside of the barrel? I'm thinking that if I do this the AR 10 brake will "pick up" the 5/8X24 threading as a pathway, follow those cuts and the original threading won't interfere.
Possible?
A friend of mine bought an FN SPR with a 5/8X24 (AR 10 type 30 cal standard)threaded barrel. The threading was poorly cut and I'm using a hand cranked die to chase the threads & clean them up. So far, so good. My question is regarding using the same die on a barrel that already is threaded, but threaded to a different pitch & LPI.
I have a MAS 49/56 and the barrel is threaded. The muzzle "device" in CA may or may not be considered a flash hider and that triggers our foolish AW laws - I leave it off just to play it safe, I happen to think it is an FH. Of course it makes the rifle look like crap, I think. A muzzle brake, on the other hand, is perfectly legal but of course finding one for the MAS 49/56 threading is impossible. Since I have the 5/8X24 die I'm considering trying to re-thread the barrel allowing me to attach an AR 10 brake.
Is it possible to "thread over" existing threads on the outside of the barrel? I'm thinking that if I do this the AR 10 brake will "pick up" the 5/8X24 threading as a pathway, follow those cuts and the original threading won't interfere.
Possible?
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Number one..this is in no way a hand job. If you even have any chance of getting this right it's going to involve the use of a lathe. It would be very poor policy to "thread over" and existing set of threads. 0 -
+1 XXCross It is really hard to start a die square by hand. For a few bucks you could buy a spare, plug the holes, mill in some slots to make it a ported vs flash hider. https://www.apexgunparts.com/index.php/cPath/52_135 0 -
Thanks for the responses.
One of my issues was finding the part should I decide to fiddle with the existing FH. That the device has ports is fine, it's the large, open front that causes an issue. In CA a "brake" is generally recognized as having a smaller opening, just over bullet diameter. A better approach would be modifying the muzzle device - for $17.00 a copy that's viable.
Great website. They're definitely getting some of my money!0 -
Always mess with the cheaper part.
Using a metric thread gage measure the MAS muzzle thread.
Then take the barreled action to a trusted machine shop and have them
run the metric pitch in the muzzle brake and give you a nice class 3 thread.
There should have enough remaining thread to give you a strong joint.
Give him both pieces so he can give you a nice fit.0 -
You aren't going to get the right thread by going over it with a different thread die.
You need to re-cut the tenon and then re-thread it.0 -
Quick follow up question.
I bought this die ....
http://store.carolinashooterssupply.com/servlet/-strse-1036/Threading-Die-5-fdsh-8x24-308/Detail
... and chased the threads on an already threaded barrel. Is the screw on the side of the die body used to regulate the cut a bit? Backing it out allows the die to close a bit, cut a little deeper - or is it set and shouldn't be adjusted at all?0 -
quote:Originally posted by dfletcher
Quick follow up question.
I bought this die ....
http://store.carolinashooterssupply.com/servlet/-strse-1036/Threading-Die-5-fdsh-8x24-308/Detail
... and chased the threads on an already threaded barrel. Is the screw on the side of the die body used to regulate the cut a bit? Backing it out allows the die to close a bit, cut a little deeper - or is it set and shouldn't be adjusted at all?
Threads have what are called different classes of fit. This refers to how much contact there is between the threaded male and female surfaces. And how tightly they fit together when assembled.
Given this and that you have already chased the existing threads with the die nut. I wouldn't be doing anything else until you attach the muzzle brake or flash hider you intend to use to the barrel.
If they were intended to be mounted with an interference, i.e. (tight), fit. Chasing the threads might have already caused problems. You don't want a break or flash hider that will move even the slightest amount do to barrel heat/expansion/recoil, whatever.0 -
Trying to over-cut an old thread will likely cause alignment issues.
Do you really want to risk a bullet strike inside your muzzle attachment?0 -
This kind of work has to be a precision job. It needs to be done in a lathe with thread cutting tool bit, not by tap and die by hand or in a lathe. Bad Bubba jobs result.
Muzzle attachments have to be concentric with the bore or bullets will
be deflected by uneven gas flow around the bullet as it exits the muzzle.
Properly you should strive for a class 3 thread.0 -
quote:Originally posted by rufe-snow
quote:Originally posted by dfletcher
Quick follow up question.
I bought this die ....
http://store.carolinashooterssupply.com/servlet/-strse-1036/Threading-Die-5-fdsh-8x24-308/Detail
... and chased the threads on an already threaded barrel. Is the screw on the side of the die body used to regulate the cut a bit? Backing it out allows the die to close a bit, cut a little deeper - or is it set and shouldn't be adjusted at all?
Threads have what are called different classes of fit. This refers to how much contact there is between the threaded male and female surfaces. And how tightly they fit together when assembled.
Given this and that you have already chased the existing threads with the die nut. I wouldn't be doing anything else until you attach the muzzle brake or flash hider you intend to use to the barrel.
If they were intended to be mounted with an interference, i.e. (tight), fit. Chasing the threads might have already caused problems. You don't want a break or flash hider that will move even the slightest amount do to barrel heat/expansion/recoil, whatever.
All the devices thread on by hand now save for one that is a bit tight. I should explain that the original threading was done poorly by an otherwise very good company and left a few obvious high points. Chasing the threads took out the high points, the cutting die turned very easily, almost by hand with no tool. If the screw on the die body is meant to be backed out, thereby causing the die to cut a touch deeper that's what I'd like to know. If on the other hand it is used to set the cut I'd leave it alone.0
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