Thread: Barrel Fluting

Following on from a recent post by a member here where the virtues or otherwise was discussed re barrel fluting, I just wanted to share this.

I would say my most common job is threading for suppressors (I did 6 last week) and to that end many need to be cut down, either customer requests or to maintain an adequate should for the can to screw up to. A quick selection of offcuts here shows just how eccentric the bores to O/D can be, with these only being cut back by between two and four inches (50-100mm) from the muzzles.

It is not uncommon at just this short distance for the deviation to be a mm or more !

You have to wonder what that is going to do if you further cut the barrel (fluting), not something that I care to do.

I am not looking for a bun fight and have seen lots of great work produced by many on here, just thought this might be of interest to some.

Cheers

@Fssprecision care to name brands of rifles or barrels you showed us

That would certainly cause very serious issues

That last one looks like a rimfire barrel that can fit a centrefire action

Wow. I'm no engineer but my Mk1 eyeball can see the problem. Any of those needs to be turned down so the bore is truly central before fluting.

If the last one is a rimfire that fits on a centrefire action, then it is a real engineering challenge to get things straight and true!

They all look like Tikka's to me . .. .

Originally Posted by Tentman

They all look like Tikka's to me . .. .

And he wrote " I am not looking for a bun fight " and then you wrote that !

As long as they are cream buns this should be fine
But some of those healthy buns can be pretty solid

Had the same thing yesterday.
First time thread turning for several years.
Was a bit of a pain turning a 1/2×20 thread on nearly an inch diameter barrel.
Glad the lathe had a brake as I just wouldnt have been able to wind the cross slide out quick enough.
Did an under cut as just possible to get the thread right up to the shoulder
It was a martini international I acquired from gundoc.
As it is a pain to remove barrel and I have never had a cats head I did what he suggested and used a center on the muzzle end and tried it up at the rear by the action.
Was starting to overthink it when I saw a wobble in the barrel but just ran with it for the same reason.
Bore was straight so stuck with what it was.
Only thing I didnt do from his suggestion was use a brass insert in the bore. Just used a revolving center and made up a dolly to screw on the end after threading and then machining it true to use in the steady and did a 11 deg target type crown.
I will say it was pretty central at the muzzle.
Still to shoot.
Think I will have a play making a cats head for.the future

Originally Posted by akaroa1

@Fssprecision care to name brands of rifles or barrels you showed us

That would certainly cause very serious issues

I don't think it would be fair to do so, but lets say I found this across a range of popular guns from low end 22s to mid range center fires.

Cheers

Originally Posted by longshot

That last one looks like a rimfire barrel that can fit a centrefire action

Yea it looks that far out but is a tapered off cut.....gives me an idea though ha ha ha

Originally Posted by csmiffy

Had the same thing yesterday.
First time thread turning for several years.
Was a bit of a pain turning a 1/2×20 thread on nearly an inch diameter barrel.
Glad the lathe had a brake as I just wouldnt have been able to wind the cross slide out quick enough.
Did an under cut as just possible to get the thread right up to the shoulder
It was a martini international I acquired from gundoc.
As it is a pain to remove barrel and I have never had a cats head I did what he suggested and used a center on the muzzle end and tried it up at the rear by the action.
Was starting to overthink it when I saw a wobble in the barrel but just ran with it for the same reason.
Bore was straight so stuck with what it was.
Only thing I didnt do from his suggestion was use a brass insert in the bore. Just used a revolving center and made up a dolly to screw on the end after threading and then machining it true to use in the steady and did a 11 deg target type crown.
I will say it was pretty central at the muzzle.
Still to shoot.
Think I will have a play making a cats head for.the future

Good job, I always use a brass insert in the muzzle and a live center, just avoids any issues.

I don't have a brake on my lathe but use the thread chasing dial to dis-engage and re-engage when cutting. this works for TPI threads as I have an imperial lead screw, for metric threads I leave it engaged and usually do it by hand if there is a shoulder.

Originally Posted by Bol Tackshin

Wow. I'm no engineer but my Mk1 eyeball can see the problem. Any of those needs to be turned down so the bore is truly central before fluting.

Not really an option because they are concentric at each end but must wander off in the middle, so would be really tricky work out what they were doing inside.

Originally Posted by Fssprecision

Yea it looks that far out but is a tapered off cut.....gives me an idea though ha ha ha

You could ream a .22 mag chamber at one end of the barrel and a.223 chamber at the other end and have a switch barrel rifle with only the one barrel.

The only problem I can see with that is when you try to run a cleaning patch from chamber to muzzle, it would get confusing.

Originally Posted by longshot

You could ream a .22 mag chamber at one end of the barrel and a.223 chamber at the other end and have a switch barrel rifle with only the one barrel.

The only problem I can see with that is when you try to run a cleaning patch from chamber to muzzle, it would get confusing.

You would need the 22 wmr off set a very long way to reach the firing pin
Then you would need to very accurately time the 22 wmr
Also both barrels would shoot massively off line of the barrel exterior

I have made off set liners to bring .32 RF to .22 LR 1.6mm offset
.25 RF to .22 WMR 1.2mm offset
All muzzles are perfectly concentric so timing to get firing pin strike in right location makes a huge impact on where the barrel points and where the bore shoots

Way more complex than is obvious to most

Originally Posted by Fssprecision

Good job, I always use a brass insert in the muzzle and a live center, just avoids any issues.

I don't have a brake on my lathe but use the thread chasing dial to dis-engage and re-engage when cutting. this works for TPI threads as I have an imperial lead screw, for metric threads I leave it engaged and usually do it by hand if there is a shoulder.

I will be fair and say that if I was just threading the muzzle without shortening the barrel or even if I trusted my square filing after I hacked it off I would've used the brass insert trick but will say I tried it once on a rifle years ago and it didnt work that well. I made the spud quite snug to the rifling and it was either not tight enough or not a loose enough fit as it took the rifling on one side and not the other when I pushed it in.
It threw the muzzle off.

We keep a little collection of world champions barrels off cut like these.
Let’s just say that the Chinese have the gold medal in that domain.
Yes fluting such barrel can be challenging. Inthis instance a more cosmetic fluting , not too deep could be realised. As to the question of accuracy, the barrels seems to be shooting as well as they were before the fluting. Ie : if they were shooting around 1 moa before ,they ll still be shooting around 1 moa after .

Last week I took the video of a cheap Chinese produced suppressor. The thing once screwed on a concentric thread had 2.5 mm out of concentricity at its muzzle. Despite the large diameter hole at the muzzle of that suppressor, the 22lr bullet would have still clipped it! Shocking.