Crowns

A

ArtinNC

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Does the type of crown make a difference in accuracy ? Like this ? I use a 11 deg but polished .
 

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They all work fine if they are square to the bore and no burrs etc. That being said the flat or recessed flat crown would be the easier one to accomplish this.
 
me thinks there should be some clarification.
the shape of the muzzle end of the bbl has little to do with accuracy.
square to to bore.
IMHO
what counts is the transition of bore to muzzle
the last thing the bullet 'sees' is that area.
the base of the bullet passing that one little spot.
ME
with the muzzle dialed in the best i can get.....
i cut at high speed from inside out with a very sharp small tool pulled out at 45*
maybe 6-7 thou total. height of the lands plus a small touch past.
no burrs.
just me
typically my muzzle itself is flat. (90*)

ArtinNC said:
Does the type of crown make a difference in accuracy ? Like this ? I use a 11 deg but polished .
Click to expand...
 
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I was just on another Forum and they were discussing that one crown was more accurate than another . I believe that one is as accurate as any other , but some may be easer to make accurate than others . Just though I'd run it by here . Thanks .
 
ArtinNC said:
I was just on another Forum and they were discussing that one crown was more accurate than another . I believe that one is as accurate as any other , but some may be easer to make accurate than others . Just though I'd run it by here . Thanks .
Click to expand...

This.

It takes a careful lath setup to cut a crown.
Some are harder than others to cut.

Some appear to have a better chance of coming out dead on than others.

To a certain extent a method that involves less tool movement relative to the
the object being machined has a better chance of coming out 'dead on.'

You need a solid setup and minimal vibration.

3-phase motors tend to operate more smoothly than single phase.
Single phase motors rely on momentum to keep things rotating smoothly a lot more than a 3-phase.
 
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I don't believe that the type of crown makes any difference at all. They can be flat, recessed, 11 deg etc etc, as long at it is perfectly perpendicular to the last inch or two of the bore, they will work.
The only adage to the above is that i don't like "sharp" crowns on center fire rifles. Sharp crowns wear quickly and unevenly. Much better to chamfered off with a 0.010" chamfer IMHO.
I think the rimfire boys get away with sharp crowns as there isn't as much blast/powder fouling running over the crown and they are cleaned much less so not as many brush strokes over the crown..



Cheers
Lee
 
Leeroy said:
I don't believe that the type of crown makes any difference at all. They can be flat, recessed, 11 deg etc etc, as long at it is perfectly perpendicular to the last inch or two of the bore, they will work.
The only adage to the above is that i don't like "sharp" crowns on center fire rifles. Sharp crowns wear quickly and unevenly. Much better to chamfered off with a 0.010" chamfer IMHO.
I think the rimfire boys get away with sharp crowns as there isn't as much blast/powder fouling running over the crown and they are cleaned much less so not as many brush strokes over the crown..



Cheers
Lee
Click to expand...

I agree that the angle, recessed or not, or flat doesn't really make much of a difference. Just that it is indicated in well. I also agree the 5-10 thou 45° chamfer right at the bore/crown intersection is the easiest and most durable way of cutting a quality crown for any rifle. Regardless of how its cut, just verify with a loupe or other method that its clean and clear of checks or burrs and you will be ok.

I cut the rimfires the same way to help mitigate any kind of cleaning related damage possible to the crown. Also the rimfires are probably in greater need of making sure the as lathe cut crown is clean and burr free due to shooting the lead bullets vs the jacketed CF. Not saying that it isn't important for the CF rifles too but they have a much greater chance of deburring themselves from shooting than the rimfires do.

Tad
 
leeroy said:
i don't believe that the type of crown makes any difference at all. They can be flat, recessed, 11 deg etc etc, as long at it is perfectly perpendicular to the last inch or two of the bore, they will work.
The only adage to the above is that i don't like "sharp" crowns on center fire rifles. Sharp crowns wear quickly and unevenly. Much better to chamfered off with a 0.010" chamfer imho.
I think the rimfire boys get away with sharp crowns as there isn't as much blast/powder fouling running over the crown and they are cleaned much less so not as many brush strokes over the crown..



Cheers
lee
Click to expand...
after 11 degree take 100 tho. Cut on edge of bore keep concentric
 
100 thou is TEN time more than the rest of us have stated.
and no one has endorsed a specific shape of muzzle or proven "best"
 
leeroy said:
i don't believe that the type of crown makes any difference at all. They can be flat, recessed, 11 deg etc etc, as long at it is perfectly perpendicular to the last inch or two of the bore, they will work.
The only adage to the above is that i don't like "sharp" crowns on center fire rifles. Sharp crowns wear quickly and unevenly. Much better to chamfered off with a 0.010" chamfer imho.
I think the rimfire boys get away with sharp crowns as there isn't as much blast/powder fouling running over the crown and they are cleaned much less so not as many brush strokes over the crown..



Cheers
lee
Click to expand...
last makes it perfect 10 to 100 tho.
 
indicated & cut perpendicular to bore axis,some cuts have more protection for their intended purpose.
a .010" break/chamfer may prolong the cuts longevity.

a q-tip after visual inspection will help ascertain if a burr is present.

Accuracy wise,there's only one option-
try each cut on the same Bbl

If either would be the best per caliber selection,is anyone's guess.
 
11 deg. Crown

There is a theory that was tested that the 11 degree crown works best with the boat tail angle of the Matchking bullets. In all the sniper rifle barrel testing that we have done here, the 11* crown was what has been settled on. Something to do about how the escaping gases act on the bullet. All this has been verified with high speed video at the muzzle. Now we have not tested with flat based bullets, so there might be a difference there.
 
thanks for the DATA..vs opinion.
now do custom match bullets have the same boat tail angle, and what about rebated boat tail ??

MilGunsmith said:
There is a theory that was tested that the 11 degree crown works best with the boat tail angle of the Matchking bullets. In all the sniper rifle barrel testing that we have done here, the 11* crown was what has been settled on. Something to do about how the escaping gases act on the bullet. All this has been verified with high speed video at the muzzle. Now we have not tested with flat based bullets, so there might be a difference there.
Click to expand...
 
MilGunsmith said:
There is a theory that was tested that the 11 degree crown works best with the boat tail angle of the Matchking bullets. In all the sniper rifle barrel testing that we have done here, the 11* crown was what has been settled on. Something to do about how the escaping gases act on the bullet. All this has been verified with high speed video at the muzzle. Now we have not tested with flat based bullets, so there might be a difference there.
Click to expand...


That's very interesting.. Is there any actual data available online on the results? Link? I would be very interested to see it if there is..

Cheers
Lee
 
Not to diss all the high tech solutions but I once dressed the crown of a .22 RF (because it showed an uneven blast pattern) by using a brass ball in a rotary tool and fine lapping paste. Just enough to obtain a visible bright ring around the bore (probably a few thou). Bore plugged of course.

It made quite a reasonable improvement to the accuracy according to the owner.

Btw, I learned of this technique on this site many years ago.

* doggie *
 
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