35 Whelen tapered throat

kencolamarino
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35 Whelen tapered throat

Postby kencolamarino » Sat Jul 06, 2013 2:57 pm

Am having a Winchester 70 featherweight 30-06 rebored to 35 Whelen by JES reboring and spoke to Jesse today about the throat he will cut. He said it was 0.45 inch long which I thought was really long until he told me it was tapered from 0.359 at the neck to 0.353. If I understand correctly, this is not freebore at all, but really a rifled tapered leade. Did their not used to be a provision on the program to taper the front driving band? At 0.006 divided by 0.45 that's 0.00133 per 0.1 of throat. So a 0.02 front band with bottom diameter of 0.359 and top of 0.356 would be a nice snug fit.

His bores are 0.349 with 0.359 three groove rifling, so a nice 0.349 or 0.350 bore riding nose would work.

You helped me with a 458 Win MM460550 design that tamed the ridiculous 1.1 inch tapered freebore that there was no way to fill. This 35 Whelen throat doesn't have any freebore so a groove diameter bullet stops at the end of the cartridge case and only a bore riding front or less than bore diameter ogive can enter.

I just read another post indicating the only important fit is to have a snug bore riding front, and have the cartridge neck and bullet fit the chamber. If that's the case, a bullet sized 0.359 with 0.1 or 0.2 front band with no crimp groove should chamber and leave enough front band to allow using a Lee factory crimp die to just straighten out the case mouth.

Has anyone designed a bullet for such a throat? Is anyone familiar with such a throat?

Paborn

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mtngun
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Re: 35 Whelen tapered throat

Postby mtngun » Sat Jul 06, 2013 7:46 pm

Whatever happened with your long freebore 458 ? Last I heard it would only shoot bore riders, even though they had to jump a long way ? I'm guessing the bullets were getting mangled when they slammed into the rifling. A bore rider has less bullet to mangle and the nose helps guide it into the rifling, jump or not. It was an interesting learning experience.

The 35 Whelen throat description does not make sense. If it tapers from 359 to 353, then what happens after 353 ? Surely it continues to taper ?

In any event, it sounds like the leade begins immediately after the case mouth, with no freebore per se? I don't have a problem with that.

I would put a short 0.358" - 0.359" front band on it, and a bore riding nose. Don't worry about making the bullet a "glove fit" -- I have yet to see an advantage.

If you are determined to have a glove fit, I recommend using a tapered nose die. That way you don't have to rely on as-cast tolerances. I have no clue who is making tapered nose dies these days, but they are commonly used by CBA benchrest competitors.

kencolamarino
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Re: 35 Whelen tapered throat

Postby kencolamarino » Sun Jul 07, 2013 6:06 am

I thought the same thing when I thought about it (taper to 0.353). I guess the main thing is there is no freebore and a reasonably gentle rifled tapered leade. I can live with that. 0.2 front band with no crimping groove would let me locate the case mouth on the front band with enough room to allow for eventual throat erosion and slight variation in case length.

The 550 grain sized 0.460 ends up centering in the throat with the base just still in the case. It continues to shoot just as well as the original pictures of groups I posted. Surprisingly, I eventually even got good accuracy with shorter cast bullets designed for the 45-70. I load both with an entire starch based packing peanut over the powder (I get them at Staples). Don't know exactly why, but the packing peanut appears to act as a sort of sabot in the long throat. Whatever is happening, I'm getting 100 yard groups with three different bullets (550, 400, 325) of less than 1.5 inches. I wrote it up on Cast Bullets http://castboolits.gunloads.com/showthr ... nd-Musings

Thanks for the help. I'll have the rifle back in a week or so I can see what I've got to work with and sit down and figure out a design.

Ken

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Re: 35 Whelen tapered throat

Postby mtngun » Sun Jul 07, 2013 7:02 am

kencolamarino wrote: 0.2 front band with no crimping groove would let me locate the case mouth on the front band with enough room to allow for eventual throat erosion and slight variation in case length........ I'll have the rifle back in a week or so I can see what I've got to work with and sit down and figure out a design.

I agree that you should wait until you have the rifle in your possesion.

No need for a long front band.

kencolamarino
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Re: 35 Whelen tapered throat

Postby kencolamarino » Sun Jul 07, 2013 9:30 am

Sat down with a pencil and paper and the design program and have come to the conclusion I can't get there from here.

Since the leade starts immediately (no freebore), and the leade is 0.45 long, in order to have a bullet center in the 0.349 bore, the bore ride portion has to be a minimum of 0.45, probably just a little longer to engrave slightly. Since the program only allows a 0.3 bore riding nose, that isn't going to happen. Any less bore riding, while the ogive is inside the bore, it isn't touching anything, and neither is what bore riding portion there is touching anything due to the taper of the leade. However, the bullet (250 grain) is long enough that as it moves forward and the bore riding portion enters the bore, the base is still inside the case and the front band is centered and engraving in the tapered leade. Hopefully, that fact would center things up? I'm probably making things more complicated than they need to be and should go with 0.3 max 0.350 bore riding nose, short 0.359 front band, 0.360 body and size to 0.359. When I get the rifle and confirm the dimensions, I'll order the mold.

The fellow who is doing the rebore to 35 Whelen has a pretty good rep and his rebores supposedly shoot cast and jacketed very well. This will provide a nice project for the Fall.

Ken

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Re: 35 Whelen tapered throat

Postby mtngun » Sun Jul 07, 2013 8:09 pm

-- some quick and dirty math suggests that your included leade angle is roughly 1 degree, give or take, depending on how I interpret what Jesse said. 1 degree is pretty common on benchrest rifles these days, and it's what I'm using for my 30-06 project.

-- the bottom half of the bullet will be supported by the case neck

-- the front band can be seated out until it kisses the rifling

-- you can spec the nose so that it kisses the rifling, too. The nose does not have to be 0.349", you can make the nose 0.353" or whatever you anticipate the leade diameter will be at the tip of the bore riding section. It doesn't have to be perfect since the front band is already centering the bullet and any nose contact is just a bonus. Once the bullet starts moving, the nose will engage the rifling.

-- here's a suggested tentative design, just to show what is possible. Note how I "cheated" by making the front band 0.351." That increases the bore riding length from 0.300" to 0.350". PLUS there is a lube groove between the 0.351" front band and the 0.309" band below it, so when you add the length of the lube groove, the bore riding section is over 0.400" long (you can leave that particular lube groove empty so you don't have exposed lube). Seat it out until the 0.309" band kisses the rifling, and that should put the tip of the 0.351" bore rider darned close to the rifling. Maybe it will engrave, or maybe not, subject to as-cast tolerances, chamber tolerances, chamber erosion, etc. -- but it'll be darned close to the rifling, and it'll engrave as soon as the bullet starts moving.
Image

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