I have a Brno model 2 (zkm 452) that l wish to shorten the barrel on.

I work with with several machinists that have all the skills and equipment for machining virtually anything, but they are not into guns.

Do l need to buy a muzzle crowning tool or can the muzzle be cut on a decent lathe using normal tools?

What do l tell them to machine?

Regards

George

Key issue is to cut the barrel off square. Radius tip or recessed target crown. When I didn't have a crwon tool I used a brass screw/bolt so that the head was just larger than the bore then some lapping compound.

Poor man's version of this.
http://www.midwayusa.com/produ...to-8mm-caliber-brass

Cut is square if for some reason it doesn't shoot it is easy to try again.

If you have a lathe, you will automatically cut it off true. Crowns can be several different configurations depending on how you feel that day. You do not need to buy a special crowning tool; if you want the traditional radius crown, just grind a tool bit to make the crown. If you want an 11 degree muzzle, which is popular with match shooters, or any other angle, you can cut that with any lathe bit. A break in the rifling can also be added without a special bit as well. You can just recess the muzzle a bit, leaving both surfaces at 90 degrees. What do you tell them? Whatever shape of crown you want. Crowns are only for protecting the muzzle rifling in case you stick the muzzle on a rock. Otherwise, assuming a true muzzle, crowns can be any shape.

The barrel will be faced off on a lathe.
I now understand that the recess can whatever shape l want.

What l still don't understand is what to to at the actual rifling. Do I just do a light chamfer?

Yes a light chamfer, the method of creation was explained by ramrod.

jump to 1:10 in the following video.
http://www.youtube.com/watch?v=OorpZlG28fI

My two best-shooting target rifles have recessed crowns and the last little chamfer was done with a brand new center drill. My gunsmith said there was no way he could sharpen a tool that fine, so that's what he used.

I usually don't break the sharp muzzle edge when I do a recessed crown; just be careful with cleaning rods. I have also used old Mauser bolt knobs dipped in lapping compound; keep it moving whilst your barrel is spinning so you don't cut a groove in your tool. Your bullets like sharp, clean exits.

Same here. I dont chamfer at the rifling after I cut a crown. My favorite type is a deep recessed counter bore that leaves an outer ring of steel to protect the crown

I like to cut crowns through the headstock with the rear end supported in a spider.

You don't need a special tool for crowning, you just need a REALLY sharp tool to do a good job. I personally like to cut a slight chamfer even on a recessed crown.

Any machinist worth his salt will know how to do it with what he has on hand.

Just show him a picture of what you want and he will reproduce it.

just let him know the bore to face must be square and burr free. He'll do the rest.

Excellent, l'm sure it will be sorted now.
Thanks to all who responded.