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  #1  
Old 11-03-2008, 10:28 PM
razor100 razor100 is offline
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Default barrel crown question

having a 204 ruger built on a remington xr100 action and McMillan stock. Which crown should i go with a 11 degree parabolic benchrest type crown or a 45 degree .090" deep recessed crown like found on the Marine Corps M40a1s and M40a3s and why? thank you for your time.
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  #2  
Old 11-03-2008, 10:37 PM
trotterlg trotterlg is offline
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The recessed crown will give you more protection from getting it dinged up, but I believe the 11 degree target crown will give you more accuracy. You will get a better crown with either if you get it cut in a lathe before you mount it on the action. Your smith can put the muzzel in a center, turn the muzzel perfectly consintric with the bore, then run a steady rest on the true part of the barrel and cut the crown without putting a pilot in the bore, Makes the most perfect crown you can get on a barrel. Larry
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  #3  
Old 11-04-2008, 11:17 AM
WayneShaw WayneShaw is offline
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Nobody has ever proven one crown is more accurate that another. A flat across crown does just fine, but offers no "protection" to the crown. Now, unless you drop your gun, or put the muzzle down on the floorboard of your truck, the crown is unlikely to get damaged anyway. Nothing wrong at all with a recessed crown, or an 11 degree crown. The 11 degree crown does offer protection.

There is more than one way to crown a barrel. Done on the lathe is definitely the best way to do it, but there are other methods aside from a steady rest and turning the OD of the barrel down.
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  #4  
Old 11-04-2008, 01:55 PM
MarinePMI MarinePMI is offline
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Wayne,

yes, there are many ways to crown a barrel, but what I think Larry was talking about was the best way to do it. Regardless of the type of crown, it is imperative that it be exactly perpendicular to the bore, therefore turning between centers (at least set up wise and then adding the steady rest) is the best, surest way to cut a crown. OD is many times not concentric to bore center (because many people profile the barrel with it chucked in the headstock, vs. turning between centers using a lathe dog and drive plate). Also, if the barrel is tapered it's difficult to square the face as there is no way to use a square to set a 90* cut across the muzzle.

Larry, hope I'm not speaking too out of line with your thoughts and don't intend to put words in your mouth...
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  #5  
Old 11-04-2008, 02:17 PM
WayneShaw WayneShaw is offline
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It is far easier and more accurate to both chamber and crown thru the headstock, than by using a steady rest. I guarantee you the majority of benchrest gunsmiths chamber thru the headstock, and they crown that way too. Yes, just about every barrel will have the bore eccentric to the OD. Why would you re-turn the barrel profile just to crown the barrel? And that is what you would have to do "between centers" in order to use a steady.

What you can't do "between centers", is use a range rod and align the bore to the axis of the lathe.
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  #6  
Old 11-04-2008, 02:42 PM
MarinePMI MarinePMI is offline
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Wayne,

I guess everyone has their preferences, eh?

I think we'll have to agree to disagree on which is an easier, more accurate way to chamber and crown a muzzle. As to the range rods, you wouldn't need them to align the barrel to the axis of the lathe if your lathe (tail stock) is set up and trued. As to re-turning the barrel profile, I'm unsure what you mean. The crown would be the last thing cut, so the profile is already been turned(?). I think perhaps we just have a different order of machining in our individual processes.

No worries though, as that is what this place is for, eh? Discussing the differences and similarities...

Good day sir!
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  #7  
Old 11-04-2008, 04:40 PM
Silverfox Silverfox is offline
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From what I have been told, the 11 crown is one that gives the best accuracy as Larry mentioned. Another thing you might want to consider if you run a brush in and out of the muzzle on your barrel is to have a dual crown cut on your muzzle. The "brush cut" is a 60 cut and is supposed to protect the crown from damage caused by the brush exiting the muzzle. I'm certainly no expert, but the logic sounded pretty good. Here's a photo of what it looks like. Sorry about the size of the photo


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  #8  
Old 11-04-2008, 05:23 PM
MarinePMI MarinePMI is offline
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Silverfox,

IIRC the 11* crown was deemed best for BT bullets, not necessarily FB bullets. I don't know this empiricly, but has been stated by several bullet manufacturers (FWIW).

YMMV...
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  #9  
Old 11-04-2008, 06:05 PM
butch lambert butch lambert is offline
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You guys better listen to Wayne. He knows what he is talking about. You get a better job in the headstock and the shape has nothing to do with accuracy. As far as boat tails are concerned, Some of the best BR shooters use them and use a flat crown.
Show me conclusive testing that shows to the contrary.
Butch
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  #10  
Old 11-04-2008, 06:49 PM
sicero sicero is offline
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I also have to go with Wayne on this. I can set up with or without the action attached and be done in 15 or 20 minutes thru the headstock with a spyder and a four jaw and two indicators. I usually cut a 90 degree recessed 60 or 70 thousands. The reamers made for cutting crowns have a changeable live pilot just like a chamber reamers so there is no reason to damage the bore. That might be an option for the lathe-less. Kenny
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