Airgun barrel choke

[adie jaques]

It was on the forums, some time ago, about choking barrels. The brief synopsis is you machine an appropriate high tensile nut to a tight fit on the barrel, cut it in half with an hacksaw, put it back on the muzzle in a large vice or press, releasing a little, turning, and squeezing frequently.
I had success with a 2" square x 1/2" thick, scrap piece of fairly hard steel, bored with the appropriate hole, centrally, sawn almost in half, but held together by a couple of mil to prevent the fiddling getting it to stay in place with two separate halves. This takes a bit more slackening and turning but gets it done without finger pinching and frayed tempers. You can tell when the job is done by pushing a pellet down the bore, using a rod, thinned at the pointed end, to avoid pushing against the skirt and opening it. It usually starts tight at the breech, easy to the last 1/2" and tightens a bit again. The couple of barrels I have done had minor tight spots along the length of the barrel, but the choke was tighter. Might help to warm the barrel, a couple of hundred degrees, not enough to damage the bluing, though.

[lensman57]

It was on the forums, some time ago, about choking barrels. The brief synopsis is you machine an appropriate high tensile nut to a tight fit on the barrel, cut it in half with an hacksaw, put it back on the muzzle in a large vice or press, releasing a little, turning, and squeezing frequently.
I had success with a 2" square x 1/2" thick, scrap piece of fairly hard steel, bored with the appropriate hole, centrally, sawn almost in half, but held together by a couple of mil to prevent the fiddling getting it to stay in place with two separate halves. This takes a bit more slackening and turning but gets it done without finger pinching and frayed tempers. You can tell when the job is done by pushing a pellet down the bore, using a rod, thinned at the pointed end, to avoid pushing against the skirt and opening it. It usually starts tight at the breech, easy to the last 1/2" and tightens a bit again. The couple of barrels I have done had minor tight spots along the length of the barrel, but the choke was tighter. Might help to warm the barrel, a couple of hundred degrees, not enough to damage the bluing, though.

Most interesting, and thank you for taking the trouble of posting the info.

Regards,

A.G

[lensman57]

It was on the forums, some time ago, about choking barrels. The brief synopsis is you machine an appropriate high tensile nut to a tight fit on the barrel, cut it in half with an hacksaw, put it back on the muzzle in a large vice or press, releasing a little, turning, and squeezing frequently.
I had success with a 2" square x 1/2" thick, scrap piece of fairly hard steel, bored with the appropriate hole, centrally, sawn almost in half, but held together by a couple of mil to prevent the fiddling getting it to stay in place with two separate halves. This takes a bit more slackening and turning but gets it done without finger pinching and frayed tempers. You can tell when the job is done by pushing a pellet down the bore, using a rod, thinned at the pointed end, to avoid pushing against the skirt and opening it. It usually starts tight at the breech, easy to the last 1/2" and tightens a bit again. The couple of barrels I have done had minor tight spots along the length of the barrel, but the choke was tighter. Might help to warm the barrel, a couple of hundred degrees, not enough to damage the bluing, though.

Most interesting, and thank you for taking the trouble of posting the info.

Regards,

A.G

[Vermin Al]

Thank you sir for your reply. I was thinking of a figure of about 0.02 mm, would you say that this is about right?
I have one of those faulty HW barrels. It groups reasonably well with 4.53 but with anything else it is shotgun. I was thinking of getting rid of the choke that appears to be the fault with these barrels and machine a brass collar and heat it up to put on the end of the barrel, probably about 30 mm long. Once it cools it should choke the barrel evenly. The dimensions will need some research but that was the plan.
I'd be grateful for any advice.

Regards,

A.G

Mine, once fouled, would not shoot anything worth a damn.

It needed frequent cleaning to remove the lead debris which accumulated in the choke.

I used VFG Intensive felts with rod and adaptor.

[Black Beard]

If you know someone with a big lathe you could try the following- needs a big diameter piece of studding ~1" and a couple of nuts to fit it.

Bore out the inside of a 3” length of studding to 15.7mm (I am guessing here- it needs to be able to fully engage with both internal and external threads and compress on to the barrel). Then taper ream the inside so that it goes from wider than the diameter of the barrel to 15.7mm. (Actually, you may want to bore out most of the length larger than 15.7mm so you are only reaming the last 3cm- it is quicker.) 1/50 taper reamers are pretty easy to get hold of. Weld the first nut on the end of the studding with the wider hole then split the other end longitudinally for 2-3cm. Screw the second nut on to the studding. Slip the studding over the barrel, from the wider end. Tap the studding down so that it slightly overhangs the end of the barrel. It should grip the barrel at the end.

Grease the threads, put the welded nut in a vice and then screw the second nut down towards the muzzle and off the studding. If you’ve done it right, the nut should become really hard to get off the end as it compresses the tapered section on to the barrel. You will need a big wrench. This will choke the barrel.

Would definitely choke shotgun- I’m not sure about a thick airgun barrel.

[Gunfun]

Why not do 2 jobs in one ?
Hand lap the barrel, but don't lap the area you wish to choke as much as the rest of the barrel.
This way you end up with a precise lapped bore and very slight choke.

[lensman57]

Why not do 2 jobs in one ?
Hand lap the barrel, but don't lap the area you wish to choke as much as the rest of the barrel.
This way you end up with a precise lapped bore and very slight choke.

The problem as I described in my OP was to get rid of the suspected " faulty " choke on a faulty HW barrel that the seller refused to take back.
For that the last inch of the barrel including the unfinished moderator thread have to be machined off and a new choke made up. I could take the risk and just try the barrel without a choke and see what happens but I have feeling that a choke is needed. Otherwise, your suggestion is a good one.

Regards,

A.G

[adie jaques]

The problem as I described in my OP was to get rid of the suspected " faulty " choke on a faulty HW barrel that the seller refused to take back.
For that the last inch of the barrel including the unfinished moderator thread have to be machined off and a new choke made up. I could take the risk and just try the barrel without a choke and see what happens but I have feeling that a choke is needed. Otherwise, your suggestion is a good one.

Regards,

A.G

I don't think I would be as drastic as to cutting the muzzle off yet, just get a 1/2 unf nut, split it in half, put it on the last 1/2" of thread and squeeze the barrel as previously described, then trim and recrown. It is much easier to achieve a choke on the thinner threaded steel.

[Gunfun]

The problem as I described in my OP was to get rid of the suspected " faulty " choke on a faulty HW barrel that the seller refused to take back.
For that the last inch of the barrel including the unfinished moderator thread have to be machined off and a new choke made up. I could take the risk and just try the barrel without a choke and see what happens but I have feeling that a choke is needed. Otherwise, your suggestion is a good one.

Regards,

A.G

Actually I was suggesting that if you cut off the choke and then form a new choke by lapping the bore except the area you want a choke.
According to this well written and informative article -
http://www.firearmsid.com/feature%20...anufacture.htm

Section on 'Lapping' - Paragraph 4 - "Lapping a bore will increase the diameter by 1 to 3 tens of a thou"
Section on 'What makes a Barrel Accurate' - Paragraph 5 - "Many think a choke of a ten thousandth of so will improve accuracy"

The advantage of lapping is you will not put any stress on the muzzle area of the barrel, it is a very slow process so controllable if frequent checks are made.
According to the article re-profiling the outside of the barrel (cutting a new moderator thread ?) can cause the bore to expand and going to fine on lapping grit can cause fouling problems.

Edit - There's a PDF, 'Hand lapping your airgun barrel tutorial' by Scott Laughlin (Charlie DaTuna) which mentions forming a choke this way, that's worth reading.

[32:1]

If choke is bad, try lapping / polishing it out, if its that bad just cut it off and recrown

Ive got two chokeless barrels and they all shoot rather well and are a LOT less pellet fussy, BigAl is ya man

Chris

[air-tech]

Or just backbore so the barrel looks the same and is the same length, no issues with front sight mounts etc.

Re freezing - if you go down that route - buy a freeze spray, more convenient than "borrowing" an industrial freezer.