Case forming for improved chamber

[robbor]

im startingmy first improved build and have some questions based on my understanding. I'm wanting to do a 300 Norma improved prob 35deg. My understanding is when u improve a case it should shorten in oal. I really don't want to shorten the neck at all. I'm worried that if I get a reamer for the improvedmeant to fireform that once formed my necks are going to be way short? I'm thinking I'd rather do a hydro die(whidden)and improve them and have a slightly shorter chamber reamer made? Also with the whidden they say you have to hit it with you resizer die after and I'm not planning on having that made till there fully fire firmed. I'm presuming it's better to have your dies made from fire formed brass vs a reamer print undersized? Thinking any variation/misalignment in chamber is doubled in actual chamber dimension. Any advise appreciated, thanks. Want to do it right the fist time and I'll be calling kiff and whidden next week

 

[JRS]

Call Cary at JGS, and explain to him what you are trying to accomplish. Great reamers, advice and service

 

[swd]

Your neck itself won't shorten but the case will suck down a bit when you blow the rear edge of the shoulder forward shortening the OAL of the case. I loose a consistant .018" OAL on my 6x47L Improved.

 

[Shynloco]

im startingmy first improved build and have some questions based on my understanding. I'm wanting to do a 300 Norma improved prob 35deg. My understanding is when u improve a case it should shorten in oal. I really don't want to shorten the neck at all. I'm worried that if I get a reamer for the improvedmeant to fireform that once formed my necks are going to be way short? I'm thinking I'd rather do a hydro die(whidden)and improve them and have a slightly shorter chamber reamer made? Also with the whidden they say you have to hit it with you resizer die after and I'm not planning on having that made till there fully fire firmed. I'm presuming it's better to have your dies made from fire formed brass vs a reamer print undersized? Thinking any variation/misalignment in chamber is doubled in actual chamber dimension. Any advise appreciated, thanks. Want to do it right the fist time and I'll be calling kiff and whidden next week

robbor,
I'm fascinated by your post in terms of the effect(s) on a casing when you go improved on any caliber. As you might guess, I have zero experience with improved calibers. But you pose some challenging issues and I'd be curious to hear what you come up with, particularly if the neck of a casing is shortened during the process, the OVERALL effect(s) on the entire casing and if any concentricity issues (not seen in regular case forming) arise. So please get back to us once you resolve the issues. Thx!

Alex

 

[Shynloco]

Your neck itself won't shorten but the case will suck down a bit when you blow the rear edge of the shoulder forward shortening the OAL of the case. I loose a consistant .018" OAL on my 6x47L Improved.

Thx for that. Answers one of the my questions and I have experienced the same when forming 30BR casings, not improved.

Alex

 

[swd]

The way I see it, and I could be wrong, is the the neck/shoulder junction acts like a fulcrum and when the lower edge of the shoulder blows forward it pulls the neck down slightly.

I think on the 30BR, when you neck up you have to loose something and that's case length.

 

[butchlambert]

You will lose no length or neck length on a PPC or 30BR if you fireform with pistol powder and a wax plug. Try it both ways and measure.

 

[robbor]

Your neck itself won't shorten but the case will suck down a bit when you blow the rear edge of the shoulder forward shortening the OAL of the case. I loose a consistant .018" OAL on my 6x47L Improved.

Thanks for some actual numbers! That's exactly what I'm talking about, losing oal