Gents

I had a Stainless 338 Win Mag Ruger Mark2 sitting in the safe with a completely stuffed barrel. I removed the barrel a while ago ansd the action has been sitting in the safe waiting to come to life.

I set to work one day recently to try and open the action up enough to fit something a little bigger into it.

I cut the magazine box open at the rear, straighten the flaps and rebent them a little longer. I took a tiny bit more off the front of the feed ramp and repolished it and the rest out of the back of the action.

I have also removed the bolt stop/release and will tap this further back to allow the bolt to come back further.

Anyway after a bit of mucking around I managed to open the magazine box and action to a MOAL of 3.575, just under my goal of 3.600 but close enough.

What I wanted was the biggest possible .308 round I could fit into the action without having to get a gunsmith to open the feed rails and the bolt face, a good long range rifle

I also had access to a new 31 inch stainless .308 barrel at the right price but with a slightly slower twist so this also determined what bullet length and weights I was going to use.

Like I said I tried to fit a 300 RUM into the action, but it was a no go, it needed every bit of 3.600 and some more, to fit Berger 175 and 180g VLD bullets. An Ideal action length would have been a Remington Long Magnum, but I didnt have one.

Back to the drawing baord I had about 50 338 RUM cases so I necked one down with my 300 WSM die and it looked fine. I didnt bump the shoulder back much I basically left it at the same height of the 338 Rum at 2.295

So I trimmed the new neck back from .335 to .300 (same as the calibre) and changed the shoulder angle to 35deg per the WSM instead of 30deg per the RUM.

After trimming I managed to make the case an OAL of 2.730 that is only .120 thou shorter than the 300 RUM.

Then I thought well the 338 RUM case has a width of .550 at the base and .526 at the shoulder ( 24thou taper ), why dont I blow it out to exactly the same width at the shoulder as a WSM which is .538.

You see the WSM case is fatter than a RUM case and by using the upper dimensions of the WSM this gave the new wildcat case a taper of only 12thou which is perfectly acceptable and a bit more case capacity.

The biggest advantage here is not only the length but being able to use my 300 WSM FL die with a short throw of the reloading press to form and neck size the case.

I sketched it up and sent the picture and my requirements to Dave Manson of Manson reamers . I told him I wanted to combine the body specs of the 338 RUM with the shoulder width and neck specs of the 300 WSM. Also I only planned on using 180g projectiles because I had a magazine box length problem and the barrel was a slower twist, within 24 hours I had his reamer spec drawings and he said it would be a fine case. I also believe with the 35 deg shoulder and blowing the taper out it's capacity will be close to the original and taller 300 RUM.

But I wont know this for sure until I can get it done and fireform some cases. Actually in a longer action like a Remington, with this new design and a slightly longer throat you could seat the 208 and 210 VLD out a little further and really get them going hard.

Anyhow the ball has started rolling. Admittedly being a Ruger its no target action but a good place to start, without spending a fortune

I will keep you up to date, I dont have a name for it yet,

Here's my basic sketch you can get the idea, estimated case capacity of 105g of water. SO once again it's a 338 RUM case with a 300 WSM shoulder and neck, MOAL 2.730




regards S&F

Sounds like a very good conversion to me. You can always throat for the longer bullets, seat out the first round and single load...and keep the mag full of loads that fit it.

That's what I do with my Ruger Tang, 510 Makatak...535 gr hard lead cast bullets 3 down in the coffin box or 2 down with standard Ruger bottom metal at 3.28" and one 650 gr up the spout at 4.50"...that first one is definitely a wake up.

Luck

Interesting idea.

interesting and well thought out. Have you considered the 300 or 338 Lapua? Also the 300 or 338-375 Ruger would be easy to fit and 100 grains capacity. More room loaded long too. A 338-500 Accrel would be a fun matching pair.

MickinColo

Thank-you, it does look a lot like the reamer specs. although I think we dropped the outside neck measurement to .341, because the remington brass is a little thinner than winchester brass.

Does your CAD software that you used to generate that diagram offer any other detail ?

I think I might call it a Mid Magnum or something along those lines.

Regard S&F

I have considered a similar project, but just have not had the time to pursue. Even in a 700 LA I think theUsable powder space with a 200 gr bullet would be similar to the 300RUM due to having to seat the bullet deeper to fit the magazine.

quote:

Originally posted by ShortandFat:
MickinColo

Thank-you, it does look a lot like the reamer specs. although I think we dropped the outside neck measurement to .341, because the remington brass is a little thinner than winchester brass.

Does your CAD software that you used to generate that diagram offer any other detail ?

I think I might call it a Mid Magnum or something along those lines.

Regard S&F

S&F,

The program is a cartridge/chamber design program called QuickDESIGN. The beauty of QD is, as long as you design your wildcat based on a parent cartridge that is CIP or SAAMI standardized, you can transfer the data to Quickloads and get a pretty straight Analysis of the round.



This is just an example.

The program does a little more than just line drawings.

Very, very impressive

Whats the software worth ? I think considering I like playing around with wildcat cases I should buy something like this.

I'll be using a 28 to 30 inch barrel and the twist is slow at only 1:12. I would think the velocity figures will be very very high, but I will be cheating a bit with this combination, it will give me slightly lower pressure signs and higher velocities. Like I said I wont be using the 200g + projectiles because I dont have the room.

regards
S&F

quote:

Originally posted by ShortandFat:
Very, very impressive

Whats the software worth ? I think considering I like playing around with wildcat cases I should buy something like this.

I'll be using a 28 to 30 inch barrel and the twist is slow at only 1:12. I would think the velocity figures will be very very high, but I will be cheating a bit with this combination, it will give me slightly lower pressure signs and higher velocities. Like I said I wont be using the 200g + projectiles because I dont have the room.

regards
S&F

http://www.neconos.com

Use the link above for the American source.