Gunsmithing After threading, do you crown?

[jonaddis84]

I wanted to get some professional opinions here. After threading a barrel, what do you guys do to the muzzle? Ive seen some with just the bore chamfered, and heard of people crowning.

It seems like a crown is somewhat pointless if there will either be a suppressor or a thread protector on there, and in my case just a suppressor 99.9% of the time.

Does a crown still affect accuracy when youre only talking about such a small amount of it?

On the few 22's Ive done of my own, I just run a chamfer tool into the bore about 1/16" to deburr it....is this a bad practice?

Also, do you think a thread protector design like this one I did will affect accuracy?

 

[gamma]

Re: After threading, do you crown?

The crown still plays a huge part in a rifles accuracy with or without the mod.
Whenever I thread a rifle for a mod I usually try to work it where the crown doesnt get touched with the live centre at all. I leave just enough barrel protruding from the chuck that its not touched. In some cases this isnt possible and the live centre has to be deployed. Its important in this case that very liitle pressure is applied to the crown so as not to mark the crown. In some cases it will have to be recrowned, some factory barrels are so soft that its almost impossible to not mark the crown.

 

[PLeighton]

Re: After threading, do you crown?

When GA Precision threaded my FN A5-M SPR, they recrowned it as well.
(I could tell because my crown had a distinctly different crown angle than the stock barrel.)
I didn't get charged for the crowning, so I just assumed that it was part of their process.

 

[gunnergirl81]

Re: After threading, do you crown?

We recrown, and also chamfer. It doesn't take much time, and just makes sense when everything is chucked up nice and square.

 

[MikeeBooshay]

Re: After threading, do you crown?

The crown is the last thing the bullet touches leaving the barrel. It is very important to both the bullet leaving consistently, as well as the gas flow around the bullet exiting.
I check with a Qtip, to make sure no burrs, or anything are hanging in it.

Mine, after shooting, note the pattern of stuff around it. Imagine your bullet being knocked off true flight path by a tiny burr:

 

[sinarms]

Re: After threading, do you crown?

I crown everyone, why take a chance?

 

[jonaddis84]

Re: After threading, do you crown?

I guess maybe the word crown is confusing things. I know you have to crown the muzzle, as in put the very slight chamfer on the bore to knock burrs off and have a perfectly consistent exit path for gasses and what not.

More what I was looking for was whether you (on a threaded barrel) do things like 11deg crowns or recessed crowns.

The latter (11deg and recessed crowns) seems pointless to me when you are threading something onto the end, whether it be a muzzle brake or a suppressor, both of which are going to very adversely affect the path of gasses coming out of the muzzle.

Im pretty new to the gunsmithing world, and only have myself and this forum to learn for the most part.

 

[Hooper]

Re: After threading, do you crown?

While it is indicated in, I always single point cut the crown unless the customer specifies not to. Nothing else touches the muzzle face besides the single point tool.

I like to see a 45 degree on field rifles just enough to cut into both the lands and grooves.

That TP reminds me of the bloop tubes used on rimfires.

 

[gamma]

Re: After threading, do you crown?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: jonaddis84</div><div class="ubbcode-body">I guess maybe the word crown is confusing things. I know you have to crown the muzzle, as in put the very slight chamfer on the bore to knock burrs off and have a perfectly consistent exit path for gasses and what not.

More what I was looking for was whether you (on a threaded barrel) do things like 11deg crowns or recessed crowns.

The latter (11deg and recessed crowns) seems pointless to me when you are threading something onto the end, whether it be a muzzle brake or a suppressor, both of which are going to very adversely affect the path of gasses coming out of the muzzle.

Im pretty new to the gunsmithing world, and only have myself and this forum to learn for the most part.

</div></div>

Who told you that a mod or muzzle brake adversely affects the flow of gases from the muzzle.
If a mod or muzzle brake adversely affected the flow of gases from the muzzle nobody would ever use them.

 

[jonaddis84]

Re: After threading, do you crown?

You dont think a target crown with no muzzle brake would have a slight edge on accuracy compared to one with a brake? If we're only talking of this one variable (gas flow) and not recoil control.

Must be a reason the big benchrest guys just use a 1.5" diameter barrel and 50lb gun to control recoil and not just a brake.

Not trying to argue, just have these ideas in my head that I would like corrected if theyre wrong.

 

[mheckman]

Re: After threading, do you crown?

Is there such thing as a "flush" crown? Or is that just considered a barrel without a crown?

I'll add a picture in a little bit, but my palma rifle does not have a chamfered crown and it is a very accurate rifle.

 

[LRI]

Re: After threading, do you crown?

Bench guys don't use a brake because the rules don't allow for it.

10-20 guys on a firing line at once all using a brake would get old real quick. Plus you'd have people irritated because the gas dispersion is going to startle someone right as they break a shot.

A crown is simple in principle, but does require some care to execute well. I cut all my barrels at the traditional 11* included angle (5.5* per side) I don't machine a chamfer at the bore intersection. I (and a few others) believe the crisp breakaway angle aids with shedding some of the vortex off the back of the projectile as it enters free flight. It's just an opinion so take it for what its worth. I do know it isn't hurting anything and I just like the way it looks. Since I'm the boss of my little world I get my way once in awhile.

The only drawback is the end user needs to have delicate hands during cleaning. Brushes aren't too big a concern but careless use of a jag will ding the sharp transition. (sharp enough to cut your finger if your not careful)

So long as a guy is careful when pulling the jag back through (that means remove the thing prior to pulling the rod out) it'll last forever.

Good luck.

C

 

[bohem]

Re: After threading, do you crown?

I always cut the crown as the last thing. If the nose is getting a brake or a suppressor thread adapter or whatever, the very last thing I do is to cut the crown.

I also don't break the corner, I leave a sharp transition like Chad mentioned. I did it one time as a "what if I..." and the rifle shot so well that I decided not to screw around with it and just shot it til the throat needed maintenance.

Q tip check is a good one to do if you're unsure, but it's not the only method. I've personally seen a crown that passed the Q tip check but still shot like shit from a damaged crown. As soon as it was recrowned, the rifle went from 1.5 MOA @ 100yd to shooting 3 into the same hole, 5 shots into 0.3" center to center.

The crown is exceptionally important as was stated by several builders above.

 

[border_reiver]

Re: After threading, do you crown?

Yeah if you have a flat, or flush muzzle face you might want to invest or make a muzzle guide to help keep the jag or back end of an unscrewed brush beat the end of the barrel.

As far as the 'vortex', the bullet leaving the muzzle cleanly on a sharp face or with a slight chamfer 'break' will still 'jump' and wiggle a bit when it exits, it's physics. I don't reckon the escaping gas where it hits the bullets ass has as much to do with the innacuracies at supersonic, as does the concentricity and squareness the edge that meets the last of the bullet is. JMHO.