Throat Lead

[charger 1]

So I got this 450 alaskan in ruger #1 shooting like wild with hornady 350's. However its not a cast shooter unless I stay very light which is useless or under ruger 459 bore size which we know wont be good. I got the throater today to take it out to .460 with a .5 degree taper to rifling. It takes the taper about 5/8" to go from the .460 to the .449 of ruger lands. Is that OK for high speed cast provided my bullet fills that throat? I'd like opinions on this cause if I end up with a cast only I love that, but if I put this long taper throat in and it wont shoot high speed cast plus then wont go back to accurate copper I'll dump in my pants. We dont want that. I know cast like starting gently but what about such a long taper to rifling start. Is that to gentle causing stripping???? Thanks boys

[BABore]

I would think that a 1.5-2 degree (3-4 degree included) taper would be more appropriate.

Did you try seating your cast bullet engaged or backed off a little? My 450 Marlin like just a bit of running room, even with a 0.452 dia. bullet nose. Group size and ES would go crazy if it touched. A 0.010 to 0.012" jump made things right. A bit more or less it didn't like at all.

[montana_charlie]

Chargar,
I really don't have enough knowledge to answer your question. But, I read a lot of things (some of which I don't fully understand) and put a lot of 2's and 2' together into a lot of 4's.

Here are a couple of 2's...

- Many BPCR rifles have a leade (the taper into the full rifling depth) that is 1.5 degrees per side. All BPCR barrels (most, anyway) are going to be used for cast bullets, and this degree of taper is very common.

- Dan Theodore is currently working on a bullet design that has two main differences from the old standby designs. The grease grooves are very narrow and shallow, and the nose is more aerodynamic than the good old Creedmoor and Postell.
In order to center up in the bore, Dan's bullet depends heavily on the bore ride section being supported within the lands. To help insure this, he has gone to a shorter taper in the leade (3 degrees per side)...so the bullet can be inserted more deeply into the barrel.

Taking '2' number 1, which says that 1.5 degrees is a known good leade angle when cast bullets are used...
And, adding '2' number 2, which says if you want to change leade angle it's better to go 'steeper'...

Comes out with a '4' that tells me you are probably about to go the wrong way.

Remember, this is a deduction based on simple logic...not something I can claim to have any true understanding of.
CM

[45 2.1]

- Dan Theodore is currently working on a bullet design that has two main differences from the old standby designs. The grease grooves are very narrow and shallow, Presumably for his dip lube, as it sounds like anything else won't work. and the nose is more aerodynamic than the good old Creedmoor and Postell. Hmmm, you got a link? In order to center up in the bore, Dan's bullet depends heavily on the bore ride section being supported within the lands. Contrary to most BP ideas and right in line with smokeless ideas. To help insure this, he has gone to a shorter taper in the leade (3 degrees per side)...so the bullet can be inserted more deeply into the barrel. How so?

[charger 1]

ok so a hard cast in a straight 460 throat that then tapers .5 degrees into the rifling with a projectile that snuggly fits in is out of the question?

[Bass Ackward]

ok so a hard cast in a straight 460 throat that then tapers .5 degrees into the rifling with a projectile that snuggly fits in is out of the question?


Out of the question? No! But identify your problem.

For bottle neck cases that have less ignition problems, I prefer a slight taper of 1.5 degree or less. For straight sided cases which just happen to be generally larger bore diameters too, I prefer about a 3 degree angle to help ignition. Because I don't choke.

Either angle will shoot jacketed. Although, it can alter ignition characteristics enough that you may need a different powder speed. If the powder speed requires you to go .... faster, this can can mean lower top end velocities. But since you can subject a large caliber jacketed bullet to severe abuse, what are you losing? Just crank up the pressure.

After all, you are only cutting in what will be cut in naturally by shooting it a couple of thousand times anyway. :grin:

But DON"T MAKE the assumption that your throat taper is going to remedy the cast situation and allow you to go to heavy charges and high velocity. If your throat is causing the problem, you will see improvement. If the bore condition is the limiter now, it will be after you throat out too.

Just so you don't have unrealistic expectations.

[charger 1]

If the bore condition is the limiter now, it will be after you throat out too.

Just so you don't have unrealistic expectations.

I understand that bass. The bore is not the issue ,its that I wanta get a longer cast bullet in, thats why I'm throating. Just worried that the 1/2 degree might be to shallow for HV cast. When I ordered the reamer from PTG the tech there told me 1/2 to one full degree was what every cast shooter was asking for, and he was hearing they were winning comps with. But then I wondered would that have been with the peanut butter slow mo stuff or fast cast

[Bass Ackward]

I understand that bass. The bore is not the issue ,its that I wanta get a longer cast bullet in, thats why I'm throating. Just worried that the 1/2 degree might be to shallow for HV cast. When I ordered the reamer from PTG the tech there told me 1/2 to one full degree was what every cast shooter was asking for, and he was hearing they were winning comps with. But then I wondered would that have been with the peanut butter slow mo stuff or fast cast


OK. let me try again.

I shoot 20-1 in a wheeler that the bullet is hitting a 1/2 degree taper on the throat into the rifling. According to Quickload, some of my loads are achieving 700 fps before they hit the rifling and I am not stripping in the slightest with this soft mix. Keep that in mind.

Now. I assume that you are going to throat out so that the bullet just chambers or darned close to it. And you seem to be a fan of rock hard. Under any senario I program, you are not traveling faster than 400 fps before you are at full rifling height assuming that is .006. Lower the height of the rifling, the sooner you hit full height, and, of coarse, you are going slower than 400 fps.

If you strip, I doubt it will be in the throat.

[charger 1]

OK. let me try again.

I shoot 20-1 in a wheeler that the bullet is hitting a 1/2 degree taper on the throat into the rifling. According to Quickload, some of my loads are achieving 700 fps before they hit the rifling and I am not stripping in the slightest with this soft mix. Keep that in mind.

Now. I assume that you are going to throat out so that the bullet just chambers or darned close to it. And you seem to be a fan of rock hard. Under any senario I program, you are not traveling faster than 400 fps before you are at full rifling height assuming that is .006. Lower the height of the rifling, the sooner you hit full height, and, of coarse, you are going slower than 400 fps.

If you strip, I doubt it will be in the throat.


Well then from what I gather from you, ptg and other various sources, me thinks I'll give er a go

[montana_charlie]

- Dan Theodore is currently working on a bullet design
Hmmm, you got a link?
Yeah...I have links and a diagram. I'll start a new thread (so we don't hijack this one) and pass on everything I know of.

Look in Molds...Maintenance and Design for a thread on MiniGroove or MicroGroove bullets (I'm a little confused about the right name to use).
CM

[charger 1]

hijack away boys.I know where I am on this