Recrowning

S

Scribe

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Quick question. A recent review I read in a shooting magazine was very positive of two examples of a rifle (AIA Mk10). The only reservation was that accuracy was indifferent. The author stated that when he examined the muzzle both had been poorly crowned. In his view a simply re crowning job would impove accuracy by 50% plus. Is this likely?
 
What did he mean by 'poorly crowned' ? A proper crown means that the end of the barrel is cut perpendicular to the bore axis. Then the intersection of the end of the barrel and bore is cut cleanly , uniformly with no burrs. A 50 % improvement ? Perhaps if the crown was in very bad shape.
 
I've sporterized/restored alot of milsurps, and most excibit "cleaning rod wear" at the muzzle, and are often "dinged up" as well. In on case I had a Turk Mauser that was lucky to keep all shots in a 6" circle at 50 yards. AFter I shortened and re-crowned it, it now shoots MOA with commercial ammo (we're about to start working on some handloads).

SO, to answer your question, a proper crown is ESSENTIAL to accuracy, and it can make a HUGE difference.
 
The crown is the raised flat or rounded part of the muzzle that surrounds the bullet exit point. The crown does nothing for accuracy; it simply surrounds the bullet exit point and protects it. It is damage at that point, not on the crown, that can cause inaccuracy. On milsurp rifles with cleaning rod wear, you can recrown and correct nothing. You have to either cut off the barrel or counterbore to remove bad rifling. Restoring the crown is only the final part of the process. (Note that cutting the barrel or counterboring often won't work with the M1 rifle because it can reduce the port pressure dwell and cause malfunctions.)

Jim
 
muzzle crown

Dear Shooter:
It must be smooth and perfectly aligned 90 degrees to bore line.
Yes! recrowning properly will change your world!
Harry B.
 
I don't really have a lot to add except that I've seen several examples of very poor crowns sporting a factory finish. As Mete and Harry said, the crucial element is that they be axisymmetric. I've seen one factory crown that was so far off center it appeared to have been done freehand with a power drill and countersink in the hands of a badly hungover operator. About twice the depth of metal was missing to one side of the bore as from the other. I've also seen several handgun barrels that appeared to have been crowned with badly worn cutters or using an undersize pilot. Accuracy can be improved substantially by recrowning in these cases because a lopsided crown allows muzzle gas to start venting on one side of the bullet before the other as it exits, and this tips the bullet. The cleaning rod funneling Jim described does the same thing because it tends to favor one side, letting gas squirt past the rifling engraving as the bullet nears the muzzle.

Nick
 
I was just looking at the crown on my 10/22 and was wondering if it's worth the trouble to take it to a smith and have it re-crowned? I bought it used and didn't know back then to examine the crown.

It's pretty nicked up so I was wondering if I should have it re-crowned or just wait and buy a new barrel. Maybe some sexy target barrel? Something in a fluted bull barrel maybe? hmmmm...please advise!
 
axisymmetric - learned a new one today (and I didn't even have to look it up) thanks nick.

How much is a recrowning going for nowdays? I have a M98 that I butched and I'd like to make an honest rifle out of her.
 
remember the last couple of inches is THE MOST IMPORTANT part of the most important part of your rifle. The end is the last part to have anything to do withthe flight of the bullet. The more PERFECT it is the better.
 
Thats funny cause I am working on a piloted crowning tool. I have an alum body with t handle that has a slot and hole that holds a carbide insert, one for crowning and the other for facing and has a brass pilot for each caliber ( so its perfectly centered and if you are in a bad mood you don't destroy the lands) I remember Potterfield from midway showing us how to Crown with a drill and brass screw, and face off with a file. All I can say is good bubba job. If you don't have the facing and crowning tool, you got to unscrew the barrell, and chuck it in a lathe, and then you will have even more fun time putting it back together ( timing, headspacing, torque, etc etc)
 
While on the Subject of short cuts, I have seen a few barreled actions with the barrel stuck through the large spindle of a GOOD sized lathe being faced / crowned on "down time".

It works if you have acess to such things.
 
Brownells used to carry a crowning tool like that back in the 80's. I used it for all sorts of projects, up to and including paintball guns (works *really* well BTW). We had a lathe that was large enough to put some really large barrels through from the rear, so we did quite a few 11 degree crowns.
 
slopemeno, were you being sarcastic about that recrown tool working well? I've thought about getting one myself but I've been a bit skeptical.
 
Actually, we thought it would be a POS when we bought it, but it worked fairly well for what it was. Just one of those "whoda thunk it" moments I guess.

The down side was the work of any hand turned item like that is the cut is never as clean as a piece of machine turned work, but when you want to recrown , say, a Ruger Blackhawk where you lopped the barrel off, but you really dont want to pull the barrel to crown it, it was an inexpensive compromise. My Dad borrowed it to true up a Rossi .44 mag lever gun he shortened from 20" to 16.5", and it did an acceptable job.
 
You didn't have any problems with hardened steel pilot tightly fit in the barrell damaging the grooves? Did the blades ever go dull on you? I went to a buddy who had a 120 inch cent-cent lathe and couldn't fit my recvrd barrell in the headstock, what size lathes are you guys talking about?
 
Well, like I said before, it depended on the work. For my Dad's shorty .44 mag lever gun, I would have used it in a hearbeat. The combination of short barrel and the possibility of having to pull the barrel from the action made a hand-crowning tool look attractive. My partner built a 30" barreled Remington 700 in .300 win mag, with a full length 1.25" (IIRC) Shilen barrel and a really nice thumbhole Richards Microfit stock. On THAT gun a tool like that wouldnt make sense, and that barrel also just fit through the headstock. I cant remember the model of lathe, but if memory serves it was Chinese. It had about a 40" bed though.

If the work youre doing is precise, and you want to get the most out of the gun, maybe take your 11 degree crown cutter to a full-on machine shop.

I never could see any damage to the rifling from the hand-crown, but the pilot didnt rotate. Most barrel stock is reasonably soft, and how many barrels do you crown? If I remember, the tool set would crown, as well as do revolver forcing cones.
 
The lathes I saw this done on were all decent sized to big Leblond units... If I recall correclty a L2 spindle has a bort in excess of 2 inches?

They were not putting the reciver in the headstock, rather sticking the barrel through the spindle bore like one would do with long bar stock, most of our routine work was with nice 6 jaw chucks which I am guessing were good enough for most gunsmith work.... plus these machines were in a one off prototype shop so things were tight all around.
 
Right, thats the same way we did it as well. We had cut our own crowning tool to do the 11 degree crowns and used the 3-jaw chuck, and the 4 jaw if it was something for precision work.
 
Group from a rifle that I recrowned on my kitchen table. The original crown had been formed with a very dull cutter. There were drag marks and burrs from the tooling and the slight bevel between the muzzle and bore was assymetric.

I used some fine grit sandpaper wrapped around an FMJ .380 bullet. Stuck the nose of the bullet in the muzzle, turned the bullet & turned the barrel and kept up both until it looked right.

Seems like it worked ok. Besides the decent accuracy, the carbon pattern on the muzzle after firing was symmetric so I think there's not any problem at this point.

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There was a little bit of wind. I like to think that's why the third shot isn't touching the other two. ;)
 
One way to crown using a lathe with a hollow headstock is to put the front of the barrel through the headstock (barrel still on receiver) and use a "U" shaped tool right on the end of the barrel, that is in line with the bore. Just run the tool up against the near side of the muzzle and move it in. The inner arm of the "U" is inside the barrel. The result is a nice, factory type crown that will protect the bore exit.

Some people use a straight 90 degree "crown", which looks impressive but does nothing to protect the bore exit. Other crowns often have the same problem. Remember, the part of the crown away from bore exit has NO effect on anything as far as accuracy goes, and if it doesn't protect the bore exit against accidental damage, it is worthless, no matter how impressive it looks.

Jim
 
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