Muzzle crowns....industry observation
- Thread starter Hold_Over
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@Dairyboy That is a nice looking crown. Which tools did you use to accomplish that crown? I see that you said you used a brass screw and JB Bore Paste. Did you also use a padded vise and a hand-held drill? Anything else? In your "before" photo it almost looks as if your barrel had a very slight crown.In the after photo your crown is much wider and deeper. My question is, does the crown angle or size matter much in airguns in regards to reducing turbulence upon the shot?
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The deeper and more acute the crown angle, the more critical that the crown be coaxial with the barrel bore. Also the more obvious if the barrel bore is not concentric to the OD. Else, due to the low muzzle pressure of typical airguns crowns, anything from flat to 60 degree included angle cones are typical and should work equally well, assuming a clean burrless transition. A 45 degree edge break is typical to minimize burrs; and that alone is really all the crown you need.
Below is the crown on my Baikal MP-46M single stroke pneumatic .177 target pistol. Some people might tell you that the crown too deep and the angle too acute because some other configuration is better. Meanwhile that crown shape on this pistol is devised to encourage air flow to stick to the surface and encourage the air leaving the muzzle to "fan out", away from the pellet travel axis. So, acting a simple airstripper, for free. Clearly this crown shape works fine for low power, low pressure applications, based on the grouping ability of these pistols.
What about higher power applications? Personally I prefer a shallower crown at about a 90 degree included angle, with a purpose built air stripper ahead of it. But, "handsome is as handsome does" should be how crowns are assessed.
I used a brass screw to lap the crown shown below on a Marauder muzzle that had nasty dings in it from the factory. By the time all the dings I objected to were out, the hemispherical crown was quite deep. The worst ding was the one at the bore line, indicated by the red arrow - below. The angle of the crown where it met the bore was around 45 degrees per side, due to the ratio of brass screw head hemisphere diameter to barrel bore diameter:
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@subscriber Thank you for a detailed and well thought out response to my question. I’m learning little by little in this area and your response helps me.
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The flat recessed crown shown above does offer some protection to the bore edge from accidental bumps. Valuable, for unshrouded barrels that will be used without any form of protection, such as a moderator.
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Brand new Anschutz HP 9015 BR50. Sprayed pellets all over the place (well, a 10 shot 23mm group at 25 yards is 'spraying').
Sent Anschutz photos and they didn't want to know about it.
Have now cut barrel shroud back to expose the crown, and re cut it in a lathe.
Shoots OK now. Can do pretty much 5 shots into the same pellet hole, then I get tired!
Yeah, it's sorted now, but should never have left Anschutz in the condition it was sent to me.
The barrel crown is back inside the outer shroud by about 95mm, so the shroud had to be cut back.
Anschutz just bung an end mill down inside and call it done.
They really should be ashamed about this (but they're not).
Sent Anschutz photos and they didn't want to know about it.
Have now cut barrel shroud back to expose the crown, and re cut it in a lathe.
Shoots OK now. Can do pretty much 5 shots into the same pellet hole, then I get tired!
Yeah, it's sorted now, but should never have left Anschutz in the condition it was sent to me.
The barrel crown is back inside the outer shroud by about 95mm, so the shroud had to be cut back.
Anschutz just bung an end mill down inside and call it done.
They really should be ashamed about this (but they're not).
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Hi @Ezana4CE, in case you hadn’t run across it yet, here’s a link to the thread where Dillon reworked the crown on his Taipan.
@nervoustrig I don’t think I saw it. I did find your thread on accurizing barrels and have been studying it. Thank you.
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The crown on my new Barra 250z is mediocre at best, and 1/2 of the leade is horrible, but it stacks MRDs at 50 yards. 100 yards is terrible...
Barrels are $40. I order two. We'll see what those are like and go from there...
Barrels are $40. I order two. We'll see what those are like and go from there...
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