Airgun barrel choke

[lensman57]

Does anyone know where I could find some information on how much tighter a choke should be from the nominal size of the barrel?
Any help would be appreciated.

Regards,

A.G

[Shed tuner]

... as little as possible - just enough to ensure that it's tighter than any other spot of the bore.

I guess you already know this, but I think it really is the answer. Too tight a choke wastes power, and causes fouling and reduces accuracy.

[lensman57]

... as little as possible - just enough to ensure that it's tighter than any other spot of the bore.

I guess you already know this, but I think it really is the answer. Too tight a choke wastes power, and causes fouling and reduces accuracy.

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

[TonyL]

Our JB started a thread on here a while ago, A.G., detailing his diy choking method.

Maybe he'll post a little linky up.

[thisisdonald]

I think its possible to use a big pipe cutter with the blade replaced with a hardened steel washer. you can buy these for next to nothing and is definitely worth a shot before going to all the trouble of machining and blowtorching and pressing

[lensman57]

I think its possible to use a big pipe cutter with the blade replaced with a hardened steel washer. you can buy these for next to nothing and is definitely worth a shot before going to all the trouble of machining and blowtorching and pressing

Thanks, I am considering all possibilities at the moment so this one sounds good too. So far it appears that freezing the barrel to -25C is preferable to heating the collar as the transfer of heat may alter the charactristics of barrel.

If so the contraction in diameter is about 0.03mm. I have no idea what grade of steel HW have used in the construction of the barrel but apparently the most popular steel for none military use is 4140 ( not hammer forged barrels ) which is known as ordenance steel.

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.