Poor barrel threading
- Thread starter Austin
- Start date
It looks like either the undercut on the barrel isn't adequate or there's a slight possibility that the threaded length is too long and it's bottoming out inside the moderator (moderator construction dependant. Post a close picture of the thread and it might be clearer what the problem is. A washer that's slightly thicker than the gap would temporarily solve the problem.
Factory or man with lathe?
lets see the rest of the thread
had several mods where the length of thread internally is less than the length of the thread on the rifle
especially when 1/2" UNF is cut with about 15mm of thread length!
the crown bottoms out inside the mod
or as pointed out the undercut is not present
or worse ...as is the case with many rifle designed for a muzzle brake...cut with a step in excess of the OD of the thread itself!
lets see the rest of the thread
had several mods where the length of thread internally is less than the length of the thread on the rifle
especially when 1/2" UNF is cut with about 15mm of thread length!
the crown bottoms out inside the mod
or as pointed out the undercut is not present
or worse ...as is the case with many rifle designed for a muzzle brake...cut with a step in excess of the OD of the thread itself!
Is that an aluminium threaded bridge? Could it have galled?
Andy-shooter
Well-Known Member
Looks too big a gap to be a lack of undercut between the thread and shoulder. Most cutting tips have 0.25-0.5mm radius.
I’m guessing the threaded portion is too long for the mod or it’s a spigoted barrel and a normal mod.
Personally I wouldn’t be comfortable shooting that, the interface between shoulder and mod is what radially aligns the mod to the bore (unless it’s a spigoted barrel & mod) the threads are not necessary cut to a sufficient tolerance to ensure good alignment on their own.
I’m guessing the threaded portion is too long for the mod or it’s a spigoted barrel and a normal mod.
Personally I wouldn’t be comfortable shooting that, the interface between shoulder and mod is what radially aligns the mod to the bore (unless it’s a spigoted barrel & mod) the threads are not necessary cut to a sufficient tolerance to ensure good alignment on their own.
Austin
Well-Known Member
Thanks for the replies.
just to add more details.
Its a factory remington 700 barrel.
The threaded bridge is what comes with these aim sport mod's so you can swap them between rifles.
I don't believe the thread length to be too long as when the mod is remove and looking into it their is a long way in till it could contact anything.
i have shot a few hundred rounds through this set up with no issues but possibly i haven't had issues because im shooting a 6.5mm through a 7.7mm mod.
Hear is some more photos with the mod off looks like the threading hasn't been finished (note im a sparky so have not machining knowledge)
just to add more details.
Its a factory remington 700 barrel.
The threaded bridge is what comes with these aim sport mod's so you can swap them between rifles.
I don't believe the thread length to be too long as when the mod is remove and looking into it their is a long way in till it could contact anything.
i have shot a few hundred rounds through this set up with no issues but possibly i haven't had issues because im shooting a 6.5mm through a 7.7mm mod.
Hear is some more photos with the mod off looks like the threading hasn't been finished (note im a sparky so have not machining knowledge)
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kennyc
Well-Known Member
looks like there is no undercut between the thread and the shoulder (see pic below), that would stop the mod engaging the shoulder (unless the mod had a recess to accomodate the non threaded area )
Attachments
In my apprenticeship we learned to bore out the female threaded part to outside thread diameter 1 or two threads (overcut?). Stronger solution than undercutting the male threaded part. That is why some mil barrels do not have the undercut I presume. Hausken mods I have fit on my CTR barrels that have no undercut.
edi
edi
Andy-shooter
Well-Known Member
Yep, thread isn’t cut right back to the shoulder and an undercut should have been used to eliminate the uncut part of the major diameter.
it’s a very easy fix.
it’s a very easy fix.
That is what you think, as I said in my apprenticeship in 1980 it was already general practice to choose the stronger option in situations where it is of advantage. Yes we also used undercut but we learned and calculated that it would weaken the connection substantially. Why choose the worse solution if a good solution is so easy?
edi
kennyc
Well-Known Member
Mostly to be sure it works the relief cut is done X deeper than the root, there probably is a DIN standard for that. Anyway it is exactly where the connection has the weakest point. Meaning one weakens even further. Every one can do the maths themselves, take an extreme example such as M14 and 308 bore which is standard on hunting rifles. Stick a long mod on the front... trip and fall on the rifle. Calculate the stress.
Solution just buy a mod that fits, like a Hausken.
One has two options. Choose the weaker solution or the stronger solution.
edi
Do Remington do a "Factory Cut"?
As far as I am aware they are done in the UK. or were
As far as I am aware they are done in the UK. or were
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