Barrel Thread

EMcC

Well-Known Member
Hi Gents, I have a spare Blaser barrel in .308 with fixed iron sights.
I wanted to move the front sight back just enough to get the barrel threaded.
The gunsmith suggested a 15x1 spigot but that would put at least 3" of muzzle in front of the sight and make the distance between front and rear sight about 14" making the whole setup look out of proportion.
So I suggested having a 1/2"x 20unf thread which would only leave the diameter of the barrel forward of the muzzle, making it look a little better.
However, when I mentioned the 1/2" thread you would have thought I'd just told him I eat babies !!
His hands went up and his eyes nearly popped out of his head with shock.
He asked if I was serious and when I said yes, he wanted me out of his shop straight away !!
(a bit of poetic license there really)
What he really said was that he did not recommend a 1/2" thread on a .308 and suggested I think again.
I have had a 1/2" thread on a Remington .308 for a few years and had no problems, so I would like to throw this question open to the learned members of this site and any gunsmiths that may be lurking, why is a 1/2" thread not recommended for a .308 when it is probably the most common thread used across the board.
 
Eddie, we discussed this some time ago.

Gwt the 15x1 spigot and mount the foresight on the thread cover.

Photos tomorrow. Steve Kershaw will do the work.
 
my Howa has a factory 1/2" thread and its .308 on a sporter profile barrel, is the problem due to the reduction in barrel diameter if you use the same thread with a varmint or heavy barrel? ie cosmetic?
 
Moving the sight back is not that easy, it is (if like mine) held by a spot welded stud, not a threaded hole for a screw.
If you are keeping the sight on the rifle all the time you are limited to a muzzle can, in which case I'd have to side with the smith you have spoken to already.

I'm in the same boat at the moment, I have a new to me rifle, have had it for a while now, but not pulled the trigger and can't until it wears a mod.
But like yours it has iron sights that I want to keep, and being a thin profile barrel and a .30 cal a ½ x 20 thread is out of the question.
I think I'm going to go with an M14 with spigot and just move the sight back, with the right mod you only need to move it back 30mm

Neil. :)
 
1/2" unf 20 isn't ideal but sometimes that's all you have to play with, however, I'd go with 1/2" unef 28 (almost 1mm pitch) as it's a finer thread allowing more surface either side, not much granted. I wouldn't go with a spigot, waste of a barrel, if the thread isn't cut true then it shouldn't be cut in the first place. My Blaser from many years back had a thread and screw to secure it but I guess that might of changed. I would suggest that a re proof might be necessary if the barrel is tapped and threaded, not too much of a difficult job to do.
 
Moving the sight back is not that easy, it is (if like mine) held by a spot welded stud, not a threaded hole for a screw.
If you are keeping the sight on the rifle all the time you are limited to a muzzle can, in which case I'd have to side with the smith you have spoken to already.

I'm in the same boat at the moment, I have a new to me rifle, have had it for a while now, but not pulled the trigger and can't until it wears a mod.
But like yours it has iron sights that I want to keep, and being a thin profile barrel and a .30 cal a ½ x 20 thread is out of the question.
I think I'm going to go with an M14 with spigot and just move the sight back, with the right mod you only need to move it back 30mm

Neil. :)

Depends how thin the barrel is as to whether a 14x1 spigot will go on it.
 
I too recently encountered a gunsmith who would not thread 1/2 inch 20 on 308 Winchester. Apparently it is too narrow a diameter leaving a very thin barrel wall. Apparently over time this section of the barrel distorts as a result, which can be seen with a bore scope.

i left the choice of thread to his discretion, and he went for one of the metric ones. In my mind this is no bad thing. I won't confuse the mod with my 243 one and don't ever intend to sell it.
 
If you do some basic maths you will see why 1/2" isn't a good idea for a .308.
.308 = 7.62mm
1/2" = 12.7mm
12.7 - 7.62 = 5.08
5.08 divided by 2 = 2.54mm which is the thickness of barrel left with this size thread!:scared:
Not much meat there when you consider the forces going on when a .308 goes bang!
I also can't see the point of a spigot? Just another waste of good barrel metal.
A 5/8" without a spigot or metric size of +15mm would be the better option.
MS
 
It's the wall thickness of the barrel that's the issue, this coupled with the depth of thread and the relief cut for the shoulder which needs to go deeper than the bottom of the thread. The actual thread itself is ok but I prefer a finer pitch.

I thread two the other day, wall thickness was fine, it was the shoulder that was the issue, less than 1mm either side before thread, hence I had to go 1/2" unef 28, the other had 1.6mm after threading a 14x1.
 
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I wonder if the aversion to English threads is more to do with having to swap the lathe over to English from metric which I guess it was already set up for.

Myself I don't like metric threads their simply too sloppy when cut to match the gauges. Of course it also seems not many "barrel threaders" use gauges they just use the mod and rely upon others threads.
 
I wonder if the aversion to English threads is more to do with having to swap the lathe over to English from metric which I guess it was already set up for.

Myself I don't like metric threads their simply too sloppy when cut to match the gauges. Of course it also seems not many "barrel threaders" use gauges they just use the mod and rely upon others threads.

Thats a fair point, I've heard that before from a customer. He was told it takes to long to swap the gears over.

I use gauges but essentially if I matching a thread for a mod I will make it slightly tighter. Luckily I can thread in both metric and imperial with no bother.
 
Thats a fair point, I've heard that before from a customer. He was told it takes to long to swap the gears over.

I use gauges but essentially if I matching a thread for a mod I will make it slightly tighter. Luckily I can thread in both metric and imperial with no bother.

Which in reality is nonsense it takes a few minutes.

What they are actually saying is that I cannot be bothered of course it also means changing a tool or thread tip ............................................ such hardship.

James I fear that you a bit of an odd one ...................................... fancy using thread gauges.
 
My barrel has the front sight held on with a spot welded stud as opposed to a screw.
So that threw up another problem in that the barrel wall did not have the wall thickness to allow a threaded hole deep enough to hold a screw and to do another weld was out of the question because, it was suggested, possible barrel distortion.
It looks as if I am going to have to make my mind up as to whether to use it iron sighted and noisy without a mod or 15 x 1 spigot threaded with a moderator and scoped.
Or sold to one of these African Plains Game visitors.
 
Which in reality is nonsense it takes a few minutes.

What they are actually saying is that I cannot be bothered of course it also means changing a tool or thread tip ............................................ such hardship.

James I fear that you a bit of an odd one ...................................... fancy using thread gauges.

Lol Yes that sums it up...couldn't be bothered! :)

Of course I'm odd, I even have both imperial and metric pitch gauges...alas I only us 60' partial form tips...works for me. :D
 
My barrel has the front sight held on with a spot welded stud as opposed to a screw.
So that threw up another problem in that the barrel wall did not have the wall thickness to allow a threaded hole deep enough to hold a screw and to do another weld was out of the question because, it was suggested, possible barrel distortion.
It looks as if I am going to have to make my mind up as to whether to use it iron sighted and noisy without a mod or 15 x 1 spigot threaded with a moderator and scoped.
Or sold to one of these African Plains Game visitors.

Depends on your barrel dia, my Blaser was a .308, it was tapped with a small screw M4 I think, the sight was then screwed down and glued in Place.

The job might be able to be done on your barrel.
 
This is my solution to this problem, courtesy of that nice Mr Kershaw. This is on a 30/06 Blaser barrel, and if you are looking for a £50 fix, this ain't it...





 
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