Shehane/improved neck shortening

[Phys86]

I am thinking about a 30-284 shehane with a 40* shoulder, but I am a little worried about neck length.

With new Peterson 284 brass at a length of 2.160, when I neck up to 30 cal it shortens the neck to give an oal of 2.155, sometimes a tad less.

For those of you who have done a 284 shehane and maybe especially those that have done a 40* shoulder on the shehane, how much does your neck length shrink after fire forming?

 

[Phys86]

No one?

Bueller...
Bueller...
Bueller..

 

[Phys86]

Anyone? I know there's a lot of 284 shehane shooters out there

 

[Alex Wheeler]

A 35 to a 40 wont suck it down too much. Leave the chamber length alone. The extra room at the end of the neck is a GOOD thing. You wont gain much, if anything though. Small increases in chamber size usually just cause you to add more powder to get back to where you started but dont get you to the next node unless the design handles pressure better. In this case the primer pocket will fail you first.

 

[Phys86]

Thanks!

 

[NorCalMikie]

And keep in mind that "most" reamers cut the chamber OAL about .020 longer that then listed MAX trim length.
So when it's time for "trimming", you may not need to. It'll be YOUR choice.

 

[Phys86]

Here's what I've got. I sent in my payment info last Friday but I'm still in the grace period of making changes. We had shortened the max chamber length to 2.172 from 2.180 just to knock a bit off since my brass starts at 2.150 only after necking up.

But if that extra space is a good thing.... Maybe I'll take it back to 2.180.

I couldn't figure out what the benefits or drawbacks might be of leaving it long or shortening it. I thought keeping it long might act similar to extra freebore in keeping pressures lower. But don't know

 

[Stan Taylor]

A straight 30-284 will do anything you need to get out of that case.

 

[Phys86]

A straight 30-284 will do anything you need to get out of that case.

But where's the fun in shooting the same cartridge that 3 other people shoot?

 

[Stan Taylor]

But where's the fun in shooting the same cartridge that 3 other people shoot?

You get a chance to beat them with yours. Lol

 

[L.Sherm]

Just be aware once you start down that wildcat road it will never end LOL

 

[Phys86]

You get a chance to beat them with yours. Lol

True! But I don't compete. I only shoot for hunting and fun.... Probably a max of 1000 rounds a year. So, I figured since the 30-284 is really hard to find a smith with a reamer, I'm just going to buy one, and making this exact cartridge has been eating at me for the last year, so I'm just going to do it.

I have a question for you since I noticed you had been shooting the 30-284 earlier this year. I've been struggling a little bit with figuring out freebore that I want. I'm going to focus on 175-200gr projectiles and probably a mix of tangent and hybrid ogive designs, and will be seating boattail/bearing surface jxn right at the neck shoulder jxn when having some amount of jump with the 200gr. What do you have for chamber neck length and freebore? Where are you seating bullets?

 

[Phys86]

Just be aware once you start down that wildcat road it will never end LOL

As long as I limit new reamers and barrel jobs to every few years, I don't think my wife will kill me haha. She is actually very supportive of my hobbies

 

[Stan Taylor]

True! But I don't compete. I only shoot for hunting and fun.... Probably a max of 1000 rounds a year. So, I figured since the 30-284 is really hard to find a smith with a reamer, I'm just going to buy one, and making this exact cartridge has been eating at me for the last year, so I'm just going to do it.

I have a question for you since I noticed you had been shooting the 30-284 earlier this year. I've been struggling a little bit with figuring out freebore that I want. I'm going to focus on 175-200gr projectiles and probably a mix of tangent and hybrid ogive designs, and will be seating boattail/bearing surface jxn right at the neck shoulder jxn when having some amount of jump with the 200gr. What do you have for chamber neck length and freebore? Where are you seating bullets?

I would go with about .180 leade

 

[L.Sherm]

As long as I limit new reamers and barrel jobs to every few years, I don't think my wife will kill me haha. She is actually very supportive of my hobbies

Mine wife does to but its Best they dont even know what you have. LOL

 

[Phys86]

I would go with about .180 leade

Really? That seems very long for seating with the boattail start at neck/shoulder jxn. Maybe I'm not calculating it correctly or thinking about it correctly.

Example:
berger 200.20x, bearing surface is ~.415

My print
0.3062 neck
0.0168 transition
0.135 freebore
Total allowable from neck/shoulder jxn to lands = 0.458

That gives me 0.043 jump with the example bullet with the boattail right at shoulder/neck jxn.

185 juggernaut, bearing is ~ 0.340
That would give me 0.118 jump with it seated the same.

Am I thinking about that right?