One for the Gun Designers...

[R.G.C]

My undrstanding is that it is to prevent damage other wise why crown at all but I might be wrong.

And your understanding is right. If it was to have any function in directing tha gases, it would have been better to orient them forward (where they tend to go without being directed!!!) instead as driving them back!!! Guess why muzzle brakes are not allowed in competition shooting???

Also, making it 'concave' would make the bore junction angle sharper than 90°...and I have always learned an open angle is less prone to have the point damanged than a closed one...

R.G.C

[TobyH]

do you shoot a trg toby?


i eas there today as welll

No, wasn't shooting, just came to see what was going on.

And your understanding is right. If it was to have any function in directing tha gases, it would have been better to orient them forward (where they tend to go without being directed!!!) instead as driving them back!!!

I was thinking more about the effect that the crown has on accuracy. When the bullet leaves the end of the barrel some gas starts to go perpendicular to the barrel (because it is high pressure behind the bullet) so if there is nothing there to stop this gas it won't affect the trajectory of the bullet, whereas if there is something there (the crown, however small), there is a possibility it may affect the trajectory. Isn't that why they say if you have a poor crown you should use flat based bullets instead of boat tails?

Obviously damage is a concern, but if you're talking about a high accuracy rifle you would tend to be pretty careful with it and there's no reason you can't put a cap on the end whilst in transit.

[R.G.C]

do you shoot a trg toby?


i eas there today as welll

No, wasn't shooting, just came to see what was going on.

And your understanding is right. If it was to have any function in directing tha gases, it would have been better to orient them forward (where they tend to go without being directed!!!) instead as driving them back!!!

I was thinking more about the effect that the crown has on accuracy. When the bullet leaves the end of the barrel some gas starts to go perpendicular to the barrel (because it is high pressure behind the bullet) so if there is nothing there to stop this gas it won't affect the trajectory of the bullet, whereas if there is something there (the crown, however small), there is a possibility it may affect the trajectory. Isn't that why they say if you have a poor crown you should use flat based bullets instead of boat tails?

Obviously damage is a concern, but if you're talking about a high accuracy rifle you would tend to be pretty careful with it and there's no reason you can't put a cap on the end whilst in transit.

Toby,

I believe damage on the crown has a mechanical effect on the bullet, and this CAN be less a problem with flat based bullets...but who still use flat bases in longrange?.

On the other hand, it might be doubtful gases expanding freely in atmosphere as soon as the fulky "energised" plug leaves the bottle (and the room into whih they expand in all directions is exponential) has any effect on bullet path, as there is much more factors to affect it at this point than a slightly uneven repartition of gases in expansion of which speed decreases faster than the bullet does.

R.G.C

R.G.C

[TobyH]

Well thats put a myth to bed. The one about using flat based bullets I mean.

I agree that there would be very small, if any, movement caused by the exiting gases. But we need to bear in mind that these gases aren't just p**f's in the wind though, and the pressures behind the bullet are massive. Which is why If there was something for them to bounce off the refracted pressure wave may cause bullet movement. But then to answer my own question, if the crown is good, it will be an even wave!!

[woody_rod]

The crown must be exactly 90 degrees to the bore, and SHARP. As already stated, it must be protected somehow from damage, therefore the typical recess.

[TobyH]

How does that work with concave crowns, or should I say why do they make them?

[The Gun Pimp]

Toby,

Who knows - you could be onto something.

I'd be happy to convex-crown your barrel for free if you would like to try it.

Cheers
Vince

[TobyH]

I think I'd have to improve my own shooting skills before I'd notice that! But would be interesting to see...

[TobyH]

http://www.brownells.com/.aspx/pid=4162 ... HAMFER_SET

Anyone used one of these?

11 deg crowning tool. Ideally you'd want a 90 deg one first to square it off then this one to finish. How does this compare to proper gunsmith techniques (lathe presumably)?

[The Gun Pimp]

It doesn't compare!
Vince