Crown

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  • Last Post 18 February 2016
joeb33050 posted this 16 February 2016

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John Alexander posted this 16 February 2016

Thanks Joe.  That matches what others have found starting with Mann 120 years ago.  Severe crown damage changes the zero but groups are just as good.  The importance of a perfect crown -- another bit of conventional wisdom that is extremely doubtful. John 

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RicinYakima posted this 16 February 2016

However, it does work as a placebo for those having a bad day. Go home, polish the crown, shoot better next week. Must work right?

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R. Dupraz posted this 17 February 2016

Ric wrote:   “However, it does work as a placebo for those having a bad day. Go home, polish the crown, shoot better next week. Must work right?"     Without a doubt, and every time too! The tube on my K-98 is now 18” but was once a 24.        

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RicinYakima posted this 17 February 2016

Good one, RD.

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Ken Campbell Iowa posted this 17 February 2016

i suppose this would not be a good time to bring up that crowns have to be 11 degrees .... not 90 degrees .... not 5 degrees ...

i read that in precision shooting .... and any custom gunsmith with a family to support will confirm the 11 degrees...

ken

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RicinYakima posted this 17 February 2016

Well, it is Sierra's angle of boattail, so it must be right?

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John Alexander posted this 17 February 2016

I understand that 11.5 degrees is still OK for a rifle that is only shot offhand.

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TRKakaCatWhisperer posted this 18 February 2016

Ken Campbell Iowa wrote: i suppose this would not be a good time to bring up that crowns have to be 11 degrees .... not 90 degrees .... not 5 degrees ...

i read that in precision shooting .... and any custom gunsmith with a family to support will confirm the 11 degrees...

ken Does not the 11 degrees come from that angle providing no interference with the muzzle blast?

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R. Dupraz posted this 18 February 2016

"no interference with muzzle blast"?         Could be wrong, but thought that was what my earmuffs were for. No, wait, may have that reversed! Sure wouldn't want to start another one of them old... er.... a... new wives tales.

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RicinYakima posted this 18 February 2016

TRK,

FWIW the only reliable fluid dynamic's engineer I talked to said that at the pressure of the gases at the muzzle, the best you could ask for was 90 degrees from bullet flight. That would be a reverse 45 degree cut with a knife edge at the end of bore. And a 45 degree boat tail on the bullet, and that has been tried and didn't work for a BT angle.

My opinion is that there is not enough time for the gases to work from the beginning of the curve of the gas check till the pressure wave is so weak it is not a factor.

Ric

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TRKakaCatWhisperer posted this 18 February 2016

Ric - thanks. I'm not sure where I heard what I said about the 11 degrees. Obviously more research is needed. The 11 degrees is common, but what is the basis for it? ....

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John Alexander posted this 18 February 2016

Wherever it comes from I believe it is the pure stuff  and I don't mean good whisky.

Muzzle blast as a factor in accuracy was causing shooters heart burn in the 1890s. All kind of things were tried with counterboring, pressure relieving holes bored in the barrel and maybe voodoo dolls.  Mann ran tests by seeing the effects of muzzle blast on accuracy by shooting a 30 inch barrel and then cutting it back to eventually 12” with no significant change in accuracy.  All kind of tests since have shown that obsessing over crown is silly.

This is one very durable zombie. Less face it, shooters swallow this kind of crap like a puppy swallows a poisoned hamburger.  IMHO.

John

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RicinYakima posted this 18 February 2016

TRK,

FWIW, I seem to remember Mr. Hart, Sr., the barrel maker being interviewed in Precision Shooting. He said that he was facing a barrel and the compound on the lathe was set at 11 degrees. So that is what it was cut at. It worked well and customer was happy. So rather than making a change back to 45 he just left it at 11.

"Where one leads, others follow."

Ric

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