I'm looking for some suggestions about shoulder angle from experienced wildcatters. Looking at a number of commercial cartridges, a shoulder angle of around 20 degrees is common. The short magnums are around 35 degrees and the Ackley Improved rounds feature a shoulder angle of 40 degrees.

When designing a new catridge, what are the important factors that influence shoulder angle? Are steeper angles harder to form?

Thanks

Steeper angles are harder to form, which is why ammo companies tend to not design them. There is evidence, however, that a steeper angle has some benefits. Anecdotal evidence seems to show that cases stretch a bit less or slower than with shallow shoulders. It also seems that powder may be held in the case better, where combustion is improved and abrasive throat erosion is lessened. It's mostly theory, but it's theory by genuine rocket engineers.

Steeper angles can also be harder to resize, collapsing inwards as the expander tries to enter the neck. They can also be harder to make a rifle feed smoothly perhaps when coupled with minimal case taper.
Cheers...
Con

Is there a good tutorial on forming wildcats. So far I've only done designs on paper using QuickDesign and QuickLoad. I have Ken Howell's "Designing and forming custom cartridges". I'm ready to take the next step and actually form my designs and need more details on the nuts and bolts of forming.

GunTech,

I have been developing and designing wildcat cartridges for over 25 years now and do know a little bit about them - what would you like to know???

In "short" barreled guns, the steeper shoulder angles do in fact give you a better burn of your powder charges and as such, does offer increased velocity over those cartridges that have shoulders with decreased shoulder angles...

I haven't shot a "standard" cartridge since the mid 1980's and I just love those wildcat cartridges....

A

I am ready to actually try making some cases. I need some basic instruction in the howtos: what gear to order and from whom.

For example, I want to neck down a 7.62x45 Czech to 0.224. Do I need several does to do this? How fat can I push back the shoulder? I want to lengthen the neck and so will have to move the shoulder back slightly.

I can post some case designs, but basically they are all derived from the 7.62x45 case.

Finally, when actually getting down to building a rifle, what comes first? Reamer?, dies?

Thanks

GunTech,
Before building the rifle get the reamer and dies made ... Manson's is pretty good at this and it'd be worth a call to have a chat and see whether they've done your 'cat before. You can have a reamer, headspace guages, plus a die reamer made by the same place ... the reamer die could then be sent to say CH/4D to have a die set made, though some 'smiths are equally good at making dies.
On the cheap ... you could try running your case into a die set from another cartridge ... say a 25WSSM, then a 223WSSM to neck down and take "a look" at your short wildcat. a 30cal to 22cal will more than likely require some neck thinning.
Be very careful with wildcats ... addictive fun that empties the wallet fast!!
Cheers...
Con

I have made a few wildcats also and have pushed many shouders back and necked lots of cases up and down. I little nuts and bolts of this for seat of the pants stuff is to have many different ties on hand. You can always have good dies made for your new pet but to start things rolling I use existing dies.

I have now a complete set of the WSM wildcat dies from 25 caliber up to 416. Since these are short and fat they can be used to neck up and down and to push shoulders back just to take a look and to fill with powder or water and get an idea of what ballistic capacity the new cat will have. Sometimes this will bulge the case at the shoulder but back to the parent case sizer or similar will straighten it up to get a good measure of its capacity. Of course for your project the WSSM dies would be the ticket. Don't try to neck down more than .010" in each step if possible. And when necking up the Redding expanders work great or the RCBS tapered expanders made for cast bullets for rifle calibers.

I have accumulated these die sets over time, when I develop a new caliber I send the reamer drawing to Redding for a quote and they usually end up makin my dies. When all the same brand they mix and match well. I can use this expander in that die, etc.

Also if making a custom reamer I cannot recommend anyone more highly than Dave Manson. He has made many for me and has put up with all my changes and screw ups and always goes the extra mile to make sure I get what I want. He is top notch all the way.

I'm not too familiar with your 7.65x45 but I would think if your makin into a 224 I would think you don't want the shoulder pushed back. Normally a caliber of neck makes for a good grip on the bullet. I pushed the shoulder of the 375 Ruger back when necking it this way and taht because it has a very short neck for the 375 caliber, only about 30 caliber. (.315")Remember forming cases can be habit forming.

get ahold of fred zeglin at z-hat custom in casper,wy

Thanks all. I'm trying to keep a caliber's worth of neck without pushing the shoulder much.