what is the best crown?

[vegas steve]

my other thread was hijacked with off topic posts so lets try it again. so far my smallest groups have been with an 11 degree crown. what do you guys think is the most accurate crown shape with all other variables identical?

 

[FEENIX]

It was probably "POOFED" due to unnecessary comments!

 

[Bart B]

what do you guys think is the most accurate crown shape with all other variables identical?

First, with the bore axis turning exactly on center in a steady rest, make an 11 degree recessed face to the muzzle's edge cutting from the bore out. Then use a lapping ball about 1.5 times the groove diameter to crown the bore out at a 40 to 50 degree angle to a few thousandths past the groove diameter that's extremely uniform all the way around.

What are the "other" variables, anyway?

 

[vegas steve]

It was probably "POOFED" due to unnecessary comments!

it was at my request,for having too much of this exact kind of crap on it.

 

[vegas steve]

First, with the bore axis turning exactly on center in a steady rest, make an 11 degree recessed face to the muzzle's edge cutting from the bore out. Then use a lapping ball about 1.5 times the groove diameter to crown the bore out at a 40 to 50 degree angle to a few thousandths past the groove diameter that's extremely uniform all the way around.

What are the "other" variables, anyway?

yes, this is how i finished my most recent barrel and i must say it shoots very well so far. the other variables are : scope,rings,base,loads,temp,barometric pressure,wind,bedding,shooter ability,ect.

 

[Bart B]

variables are : scope,rings,base,loads,temp,barometric pressure,wind,bedding,shooter ability,ect.

I don't understand how they influence how the muzzle's crowned, faced or otherwise shaped and machined. Please explain why they're important to facing/crowing muzzles.

 

[vegas steve]

I don't understand how they influence how the muzzle's crowned, faces or otherwise shaped and machined. Please explain why they're important to facing/crowing muzzles.

i must have worded it wrong. i wasn't refering to the variables affecting the the crown shape itself,i was eliminating these variables for accuracy sake,making the scenario equal for all crown angles and styles.the only reason i mentioned them this time is because of my last variant of this thread kind of went south dwelling on the variables instead of the threads main topic.

 

[vegas steve]

one thing that i have noticed with the 11 degree crown on my last 3 barrels is that they all love flat based bullets,even at distances where the boat tail should group better.i was always under the impression that the 11 degree crown was better with boat tail bullets, and a flat or recessed 90 degree crown was better with flat based bullets. what i have seen from my own barrels has been just the opposite.

 

[Edd]

one thing that i have noticed with the 11 degree crown on my last 3 barrels is that they all love flat based bullets,even at distances where the boat tail should group better.i was always under the impression that the 11 degree crown was better with boat tail bullets, and a flat or recessed 90 degree crown was better with flat based bullets. what i have seen from my own barrels has been just the opposite.

Are you going to show the data that led to this conclusion?

 

[vegas steve]

no it would take too long to post 4 years of load testing on my last few barrels.

 

[Edd]

I have no interest is seeing 4 years of data but I am interested in knowing the difference in the aggregate average.

 

[vegas steve]

my gain twist pac nor supermatch barrel with an 11 degree crown shot consistent groups in the .080 to .095 @ 100 yds using sierra flat based bullets. i worked on loads for quite some time using similar weighted,better coefficient boat tail bullets like burger vlds and never reached this kind of consistency. when i stretched the groups out to 750 yrds i seen the same difference in accuracy between my best flat based load versus my best boat tail load,which from a physics standpoint should not have happened. my spencer and my schneider barrels netted the same results.the flat based bullets should have fallen out and strayed at 750 compared to the boat tails, but to my amazement they did not. they shot remarkebly better even at this distance.

 

[Bart B]

my gain twist pac nor supermatch barrel with an 11 degree crown shot consistent groups in the .080 to .095 @ 100 yds using sierra flat based bullets.

That's better than what Sierra's gets with their flat based bullets shot from rail guns' match grade barrels in their indoor test range, as far as I know. What caliber and style were these bullets?

Flat based bullets well balanced when spun fast will shoot more accurate than boattailed ones that ain't so perfectly balanced. There may have been a slight difference in bullet diameters between the flat based ones compared to the boattail ones which caused the difference in accuracy for that barrel. Sierra had problems with this some years ago when the jacket material they were getting did not coin, cup, draw and shape to consistant jacket dimensions; they had to change suppliers.

 

[vegas steve]

your gonna laugh when you read this bart but i swear on my mothers grave it's true. the bullets are sierra varminter hp's,tested against much better accuracy oriented boat tail bullets. the test gun consists of a bluprinted savage action,pac nor barrel chambered in .243 ackley improved, a machined aluminum stock made by myself a few years ago, topped with a burris black diamond 32x scope.