Headspace Issue.

[Sailormilan2]

I have a decent shape Vz24 Lion Crest receiver that I thought I'd build into an open sight sporter. I have pretty much decided on the 400 Whelen. Not the Brown Whelen, the standard Whelen.

I understand that there maybe headspace issues, but I think I may have them solved.

Big question, how much shoulder is necessary to headspace properly?

Okay, here is the situation. Most people think that the 400 Whelen is a necked UP 30-06 case. Which has a shoulder diameter of .441".

Actually, the 400 Whelen is a necked DOWN 30-06 basic brass case. The striaght walled 30-06 before it is necked down. The actual shoulder diameter for the 400 Whelen is supposed to be between .458-.462".

If we compare to the 35 Whelen:

Shoulder diameter is .441", neck dia. is .388", leaving .053" for headspacing.

The 400 Whelen on a 30-06 case:

Shoulder dia. of .441, neck dia. of .436, leaves .005", not good.

Proper 400 Whelen:

Shoulder dia. is .462", neck dia. is .436", leaving .026".

Is that enough"

400 Whelen seems to be a good thumper, and it is nice to hold 5 rounds in the mag of a Mauser.

Any comments anyone?

[z1r]

The 9.3x57 has .039 difference between shoulder & neck diameters. It is also well known to have headspacing issues. Even when the datum distance is correct (passes the gage test) you can and will run into problems IF your chamber is not cut tight. That is the culprit with the 9.3x57, most have generous chambers. Mine is a full .010" larger at the shoulder on fired cases than on unfired. I'm too lazy to do a chamber cast to see what the actual chamber dimensions are but they are at least 0.10" larger than the case. I've had to take to necking up new brass to .375 then partialy resizing the neck down to leave a false shoulder. I also back my die off to move the shoulder forward, or rather the false shoulder. This gives a decent crush fit that chambers easily but prevents primers from backing out. I'm looking at having Lee make me a neck sizing die.

 

I'd suggest that if you go this route, you size so that your shoulder is also slightly forward, then neck size only. To be honest, other than the novelty, I see nothing to be gained by this caliber choice. Not that that ever stopped me.

 

One thing that would concern me is that that case has for all intents and purposes no body taper. Feeding could be a real issue.

[Sailormilan2]

Thanks, z1r. I was hoping you would answer. I did some searching after I posted, and found some answers, but I wanted to wait and see what kind of answers I would get here.

It seems that the 411 Hawk, which is a blown out -06 case and a 40 cal bullet, is essentially the same thing. Apparently though, the shoulder is moved foreward giving more powder capacity.....................guessing about 2-4 grains more.

Actually the 400 Whelen has a larger shoulder than the 411 Hawk, .462" vs. .454", with almost the same shoulder angle.

Apparently though, the die makers all base their dies on the the 30-06 case, and size the shoulder down too much, back to .441".

But it looks do-able.

 

http://www.z-hat.com/smashing_the_headspace_myth.htm

[z1r]

I think it is viable but as the article you included confirms, it is very important to maintain those critical measurements. Where will you get the dies? Be prepared to pay mucho to have RCBS make you some. LEE wants about $50 just to make me a proper collet neck sizing die. Even if I partial neck size, the blown out shoulder gets sized down considerably.

 

I think the .375 Whelen would be neat. There are lots of good .375 bullets and they are less expensive than .411's. Cost would be the biggest issue keeping me from tackling this project. Since this is already a wildcat round why not base your whelen off the 9.3x62 case with it's slightly larger body. That might allow you to use .416 bullets and gain a little extra capacity?

 

Keep us informed.

[Sailormilan2]

It looks like the 375 Whelen is based on a 30-06 case, as it uses the same shoulder.

Using 9.3x62 brass may be the way to go, as I priced 30-06 basic brass from Hunningtons and it is better than $1 each piece.

[z1r]

Ah,

 

I was thinking in my sleep deprived state that the .375 whelen also shared the larger shoulder of the .400. Were that the case it would be very very attractive from a problem free standpoint IMO.

 

Seems no matter how you slice it, a 400 whelen is for all intents and purposes a one off project necessitating custom dies and reamer. Of course you will have a very unique piece when done and one that you obviously are passionate about. Hard to put a price on that!

 

I reviewed my copy of handloader where the hawk cartridges were originally written up in and the velocities for a 300 grainer, 411 hawk were listed at only 2300 fps +/-. Heck, the 9.3x62 can equal or better that and costs a whole lot less.

 

I think that as long as you maintain tight tolerances the headspace issue will be a non issue. From that respect I think the project has merit. Keep us appraised of your progress. What type of stock, sights, etc?