design and alloy

[Ian]

What did you say....it's all an educated guess until the trigger is pulled.

 

[fiver]

yep..

we can give up all of the experiences we have, but the gun don't read so good and isn't into should, has, formula's, etc. it is what it is
all we can do is follow the basic steps, make an educated guess based on what has worked in the past and try one of them.

 

[bns454]

When you guys talk of molds with too much unsupported nose what does that mean and how to decide what is too much ?

 

[Brad]

When you guys talk of molds with too much unsupported nose what does that mean and how to decide what is too much ?

Excellent question. I will be interested to hear the answers.

 

[fiver]

there is basically 2 areas on the nose that are unsupported by steel.
the part at the front that slopes to the point or flat.
and the part in front of the drive band.
the part in front of the drive band is where the slump occurs the hardest.

if you have a long bore riding nose it is only held in place by the rifling and the amount of engraving it has.
when the rest of the bullet get's shoved forward, the area in the open part of the throat is bashed outward.
then the nose is trying to turn the bullet.
the softened mashed alloy is still tryin to outrun the front nose part.
take your hands and press your thumb and forefinger together facing each other about an inch apart,
now move them from your right to your left, twist your left hand while pushing straight with your right.
this will help you visualize what is happening for part of the process.

 

[bns454]

Then the desirable mold design would have contact with steel from case mouth forward,except for the tip.Maybe I am not following all this.Cant the band be taperd down to match the throat.

 

[fiver]

yes.
that's exactly how the 165-A is shaped.
the xcb design is too you just can't really see the taper because it like 1.5*.
in a loverign design you see it easier because you measure each band and it's a bit different.
I think your following it just hasn't clicked yet.

 

[fiver]

 

[bns454]

Looking at the 165-A,the the front band rests in the freebore ?,the taper from .31 down to .30 is where the bullet rests against whats called the ball seat ?

 

[fiver]

the above bullet is a copy of the 308 throat.
you can see how little airspace is left after the bullet is set into place in the rifle.
the only place for alloy to move is out into the rifling and that is from the portion of the nose already set into the rifling.

 

[fiver]

yeah and the .3 shown is closer to .301 on the nose.
if you notice there is the end of the chamber, then that ball seat area that is .310 the same diameter as the front drive band, and then the taper into the rifling pretty much matches the taper on the band.

 

[bns454]

ok,but now that 308 throat is different than the throat in my 8x57,I have no step at the start of the rifling,right ?

 

[fiver]

I don't think you do.
yours is more like a 30-06 throat only without any real taper to speak of.
it is really similar to saami.

 

[fiver]

 

[Tomme boy]

@bns454 is your rifle a military rifle with the military chamber?

 

[fiver]

those saami numbers look real strange until you see it's actually a long freebore right there.
and that a RN bullet is supposed to be sitting in there filling it up.


no Tomme he has a 700 classic just like mine.
same crooked chamber, his actually is a bit straighter than mine is.

 

[Tomme boy]

@fiver don't know if you knew you could tag people or not? But is that drawing the military chamber?

 

[fiver]

but it has a throat similar to the one shown, only the free bore is a lot shorter.
it fools you into thinking it is a tight throat until you measure it and see it really is barely a 0* taper like that.

that's the Saami one I could find I'm sure it is military, and Remington shortened it.

 

[Tomme boy]

Don't know what Shaw used on the one they built for me but that was NOT the throat it had. It had more like the 308. It was almost too tight.

 

[fiver]

I bet they put a 325 wsm throat in yours.
I am pretty disappointed in my rifle I really wanted one and expected it to shoot well.
it does about 1-1/2"s with whatever I throw at it so not too bad but I expected more from a Remington.
I keep debating on rebarreling it and cutting it into another 7x57 Ackley, or making it a 6.5/0-6, or just shooting it.