design and alloy
- Thread starter fiver
- Start date
Ian
Notorious member
Your pound cast has a long, obvious throat taper and a clear step at the end of the chamber. The taper is obvious by the slight contact points on your two-diameter bullets, which I circled in red.
Draw a picture of your rifle's chamber neck, throat, and bore/groove, and grid out the whole thing. You can take diameter measurements of the pound cast along where I drew the green lines. The purple line is where I think the throat taper terminates, but you'll have to measure to be sure, in the rifling impressions. Caliper jaws inserted into the land impression of the slug from the front will show you where they start to taper.
Once you map a scale drawing of your throat, you can get an idea of angle (red lines) of the throat, and then can compare that to a bullet drawing, or just make a new drawing, indicating the number of Loverin bands and the diameters of every portion of the bullet.
Draw a picture of your rifle's chamber neck, throat, and bore/groove, and grid out the whole thing. You can take diameter measurements of the pound cast along where I drew the green lines. The purple line is where I think the throat taper terminates, but you'll have to measure to be sure, in the rifling impressions. Caliper jaws inserted into the land impression of the slug from the front will show you where they start to taper.
Once you map a scale drawing of your throat, you can get an idea of angle (red lines) of the throat, and then can compare that to a bullet drawing, or just make a new drawing, indicating the number of Loverin bands and the diameters of every portion of the bullet.
fiver
Well-Known Member
yep.
it's usually something slight like just a few degrees of taper but that little bit is what makes a mold work.
think about just a straight 90* step no throat is shaped like that.
but many molds are.
so you end up taking that major drive band diameter and shoving it into the funnel [soup can into the funnel thing] this just tears the front end up and pushes it into an unsupported nose base with a bunch of air there to support it.
it's usually something slight like just a few degrees of taper but that little bit is what makes a mold work.
think about just a straight 90* step no throat is shaped like that.
but many molds are.
so you end up taking that major drive band diameter and shoving it into the funnel [soup can into the funnel thing] this just tears the front end up and pushes it into an unsupported nose base with a bunch of air there to support it.
Ian
Notorious member
Something like this. I have no idea what your actual diameters will be, but you can do scale drawings off this. Also, Tom can cut the bands at a taper in the throat area so they don't stair-step in parallel jumps. I made the grooves narrower in the front for more support in the throat, they are just there for crimp and displacement grooves as you will only need to lube the bottom two.
The diameter of the body bands inside the case neck should be pretty much the same size as your throat entrance diameter, as measured from the pound cast.
The diameter of the body bands inside the case neck should be pretty much the same size as your throat entrance diameter, as measured from the pound cast.
fiver
Well-Known Member
you can also take out a drive band for less weight to better fit the throat area.
I know most like a bit more weight for cast bullets but I don't get so wrapped up about that.
I would rather have a little less bore ride, or weight in front of the transition area of the bullet as it were.
I know most like a bit more weight for cast bullets but I don't get so wrapped up about that.
I would rather have a little less bore ride, or weight in front of the transition area of the bullet as it were.
Ian
Notorious member
I think the nose is too small and there's no taper as drawn where your throat tapers. The base band is also a lot bigger than you probably need. Do some measuring and compare to the drawing I modified and see how that goes. The big gap between the bands in the middle and nose as the 180D is drawn won't do you any favors, either.
Ian
Notorious member
Looks like my guess is pretty close. The bands as I drew them are .050" wide and the micro-grooves are .030" each, so you can plot it out with your measurements and see where it ends up, maybe shorten the bullet if you'd like it lighter, and see what you have there. It's only a suggestion to illustrate my idea, you need to figure out for yourself what you think will work best.
fiver
Well-Known Member
it kind of depends who is cutting the mold.
if it's an accurate you don't have a lot of choice because of the meplat. [that 180 I show is about right]
if mtn. molds is doing it, I would emulate the XCB type nose because your gonna be jumping to the rifling with a 313-314 diameter.
if you go with a loverign design then the rounded one shown above is correct with just a slight amount of 312 on the side it will give you the most length to fill out the taper.
the shape will also dictate the powder speed you'll want to use, and the alloy to a point also.
it's kind of a package deal
if it's an accurate you don't have a lot of choice because of the meplat. [that 180 I show is about right]
if mtn. molds is doing it, I would emulate the XCB type nose because your gonna be jumping to the rifling with a 313-314 diameter.
if you go with a loverign design then the rounded one shown above is correct with just a slight amount of 312 on the side it will give you the most length to fill out the taper.
the shape will also dictate the powder speed you'll want to use, and the alloy to a point also.
it's kind of a package deal
Ian
Notorious member
You could do a tapered-nose silhouette style bullet, but that throat will move a lot of metal you're going to have to figure out where it wants to go and work with it, which will also lock you into a certain powder speed and alloy, or at least a combinations of powder/alloy which only work together just so at certain speeds. The Loverin is an age-old solution to big throats, but the design has quirks. Hell, they ALL have their quirks.