Tuning The best thing you can do to your PCP as soon as you get it......

That was fascinating. I'm curious to hear other folks comments/opinions regarding this procedure. 

I agree, most low- to mid-priced guns will benefit from touching up the crown. Even high-end ones at times. 

The brass screw technique works well, so well in fact that I continue to use it after getting a lathe. Here’s an example done that way:



My approach and a few other barrel accurizing topics are covered in the following thread
https://www.gatewaytoairguns.org/GTA/index.php?topic=130555

Well that gun in the video dont seem to be crowned at all, i would be extremely WTF if i saw that on a new gun, even one that just use air for propellant.

I agree, most low- to mid-priced guns will benefit from touching up the crown. Even high-end ones at times. 

The brass screw technique works well, so well in fact that I continue to use it after getting a lathe. Here’s an example done that way:



My approach and a few other barrel accurizing topics are covered in the following thread
https://www.gatewaytoairguns.org/GTA/index.php?topic=130555

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Jason - have you ever re-crowned a poly barrel? If so, how is it done?

Yes it works the same way. Go slow and orbit the drill to avoid making a Reuleaux triangle and you’ll get a nicely uniform bevel. 

i like the idea and will probably try it .. it should probably be pointed out though that if you have a gun with a nice finish on an exposed barrelthat compound is sure to strip it off the end , before somebody pops back in po'ed lol ...

Great idea,. I'm definitely going to be trying this at some point.

As for polishing off the finish, and rust concerns, some cold blue applied would help.

Yes it works the same way. Go slow and orbit the drill to avoid making a Reuleaux triangle and you’ll get a nicely uniform bevel.

Click to expand...

Thanks Jason. The crown that you did in that picture is THE benchmark for crowns in my mind!

Jason, could you please list down the size brass screw and head diameter on this tread? It’ll make it easy to find. Thanks.

I generally use:
#6 for .177 
#8 for .22 and .25
#10 for .30

The size isn't critical beyond it being desirable for the head to be large enough to stay fully engaged with the bevel as you randomly orbit the drill. Or if you find you're slipping off the end of the barrel when you orbit to a shallow angle, that's a clue you might want to step down to a smaller head.

Sometimes I'll cheat and use a smaller screw. For example, if I'm dealing with a .177 and the crown already has a uniform bevel but a rough finish, I may move down to a #4 and establish a secondary bevel to clean up the burr.

What _is_ important is that it is a true round head screw, not a more common pan head or other semi-round head.

Had my superior heavy liner re-crowned by Hein Frommann here in South Africa. The other liner is my original Slug A. It’s made an exceptionally accurate liner even more accurate. All my liners that I use across my two Impacts have been re-crowned.

Had my superior heavy liner re-crowned by Hein Frommann...

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You know, that just sounds like the kind of guy who would know how to crown a barrel

Gents,

I think the best thing you can do for your PCP as soon as you get it is to thoroughly clean the barrel. And then go shoot it. If it doesn't shoot, then take a look at touching-up the crown (the above given a reasonably presentable crown in the first place).

I had a customer ask me to bed and crown a new-to-him Remington 788 in .222. I asked him if he had shot it, and he said no. I told him to shoot it first and if it didn't shoot, we'd explore those options. No sense spending time, effort, and money on a gun that didn't need it. We'll, he called back a couple of weeks later and said that Deuce shot dots. Saved him some coin...

As the depicted re-crown is a DIY project, you won't be out much money if you do it right out the gate, and my above tale isn't apples to apples, but I'd still shoot it first. Personally, I'm loathe to screw with a good shooting gun, but I highly doubt you'll hurt anything if you do it correctly.

The method in the video is completely legit, though, having been around for many a year. I have 3 different sized brass balls with dowel pins pressed into them that I got out of an old-time gunsmiths estate that were made just for this purpose.

I've used JB Bore Cleaning Paste using the drill method. It took a little longer, but it worked. This was for a touch-up job, not a full-scale crown renovation...

Whatever you use, don't apply a lot of pressure with the drill. Let the abrasive do the work. If you use too much pressure, you run the risk of smushing-up the bore/crown, particularly with an airgun barrel, which I would imagine are softer than a PB barrel (if somebody knows this for sure, do tell).

Justin

I generally use:
#6 for .177 
#8 for .22 and .25
#10 for .30

The size isn't critical beyond it being desirable for the head to be large enough to stay fully engaged with the bevel as you randomly orbit the drill. Or if you find you're slipping off the end of the barrel when you orbit to a shallow angle, that's a clue you might want to step down to a smaller head.

Sometimes I'll cheat and use a smaller screw. For example, if I'm dealing with a .177 and the crown already has a uniform bevel but a rough finish, I may move down to a #4 and establish a secondary bevel to clean up the burr.

What _is_ important is that it is a true round head screw, not a more common pan head or other semi-round head.

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Allen head, slotted, or Phillips?





just kidding, lol. Thanks, Jason!

I'll go with the Clean it, Shoot it, and if need be...Fix It.

I don't think any one mentioned a visual inspection of the barrel bore before re-crowning.

I have had more than one OEM barrel that had over a 1/4" of tool chatter marks at the muzzle. In these cases no amount of time with a brass screw & compound will fix the problem. Before starting that bad 1/4" of barrel wound need to go.

Another thing to note when using the "Brass Screw" method. The Brass being the softer of the two will give way to the steel barrel. I had some barrels that I couldn't get the finish I wanted in a reasonable amount of time. I swapped to a steel S/M screw and the project was finished in little time.

The brass screw and grit thing doesn't help if the muzzle face isn't cut square to the bore. Keep this in mind. 

This can be fixed by hand with a proper fitting pilot and an aircraft countersink. Brownells sells overpriced versions of the same thing. 

If you have a burr from a crown job that was done improperly on a lathe, it can help there. 

But if it is cut square to the bore, and has no burrs, you can certainly ruin a good shooting barrel by overdoing it or doing a sloppy job with a brass screw. 

Something to keep in mind before jumping into this on your new gun. 

Personally, I don't use the screw thing at all. Just a cheap lathe and a good dial test indicator.