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Need help with odd caliber

 
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Old 08-23-2011, 07:13 PM
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Need help with odd caliber

Anyone ever hear of a 7mm Apollo Mach IV?

It's the caliber of a rifle I recently inherited. It was made by Apollo Custom Rifles in the 70s on a Austrian Voere action and barrel. At the time, it was a competitor to Weatherby (and I guess we all know who won that competition) with its own line of wildcat cartridges. It was a premium rifle guaranteed to shoot 1" groups. Here are a couple of pics:





I luckily found an original 1970s owners manual and discovered that the impressive-sounding cartridge is a 300 Win Mag simply necked down to 7mm. Sounds a lot like the 7mm Practical!

I have several problems in trying to handload for this baby. The handbook makes a lot of the fact that the barrel has some freebore and as such, can be loaded hotter than without it. Still, the recommended max loads with a 139 gr bullet of 74 gr of 4350 (3380 fps) or 78 gr of 4831 (3500 fps) seem way too hot. I'm thinking of using near max 7mm Weatherby Magnum load data as a start.

It also says that the 7mm Apollo Mach IV has a case capacity of 89.2 gr of water. That's weird because this cartridge starts out as a 300 Win Mag, and that is listed as having a case capacity of 83.2 gr of water! How can squeezing the neck down to 7mm increase case size?

Now the real problem: I bought an RCBS 7mm neck sizing die and some new Remington 300 Win Mag brass. When sizing, it was VERY difficult pulling the neck expander ball back through the case neck, so I removed it. Now I have 20 cases with an inside neck diameter of 0.262 inches and an outside neck diameter of 0.297 inches. And I when I put the expander ball back into the neck sizing die, I can't force it through the necks!

As you might have guessed, I'm a raw beginner when it comes to reloading, and this hassle may force me to just sell the rifle and go with something simpler.

Anyone have any advice?
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Old 08-23-2011, 08:46 PM
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Re: Need help with odd caliber

Yeah, you can not work the brass that much, your going to have to turn the case necks probably .008-.010" to get the outside around .319" and about .283" inside.
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Old 08-23-2011, 10:45 PM
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Re: Need help with odd caliber

Quote:
Originally Posted by backwoods83 View Post
Yeah, you can not work the brass that much, your going to have to turn the case necks probably .008-.010" to get the outside around .319" and about .283" inside.
Yep... .
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Old 08-23-2011, 11:47 PM
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Re: Need help with odd caliber

Why not use a Sinclair or PMA Tool 7mm inside neck expander and then turn the outside of the necks to remove the excess material?

These expanders are designed specifically for this task and are tapered to make the work easier than the ball on your sizing die.

My .02 for what it's worth.

On the capacity... does the body taper less on this cartridge than the 300 win mag? That could explain the extra internal room.

Keep us posted! Sounds like a fun cartridge!
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Old 08-24-2011, 02:37 PM
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Re: Need help with odd caliber

Try Hart's gunsmithing in PA. He has a ton of experience with odd calibers and may be able to get a proper set of Reading dies. If he has a reamer he can make a set of dies and guide you on what to do. Bob is a great guy. Good luck. As far as case volume it's probably like the Ackley's with the shoulder further forward with a shorterneck,w and less taper.
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