Wednesday, 15 July 2015

.50 AB

This is something that I have been meaning to get round to doing for a long time. I've always fancied building a deer legal subsonic rifle. The problem is that to get the required 1700ftlbs at subsonic velocities you need a 625gr bullet or heavier.

There are a couple of ways to achieve this. You could use something like a .45-70, .450 marlin, etc with a custom lead mold. Whilst a few people have told me it is possible, I think you would struggle to get the required weight in anything but .50 cal. Even in true .50 cal no one offers and off the shelf mold (that I have found) in the required weight.

So, the other option is .510 (same as 50 BMG). Then you can use the BMG bullets, like the 647gr Barnes TSX. All you need is a suitable .510 calibre pistol cartridge. There are only a couple, and they are either obsolete or wildcats. I narrowed it down to .510 whisper (wildcat, .338 lap mag case cut down and neck turned) or 50 Alaskan (based on .348 Winchester which is now obsolete).

Because .338 lap mag brass is expensive and I can't be arsed faffing around cutting down cases and neck turning I settled on 50 Alaskan. Brass is available via starline in the states and dies are available for both from Hornady. However, trying to get the brass from the states is a nightmare as I have found out. Due to changes in the law over there and the Royal Mail deciding that brass cases are ammunition in their own right, my usual supplier isn't currently shipping outside the U.S.

So, back to the drain board. After trawling saami case and chamber diagrams , I finally found that the 7mm and 300 ultra mag case is almost and exact copy of the Alaskan but without the rimmed case. If you chop the case at the shoulder (or 2.1" to be exact) you have an in-rimmed Alaskan case. The advantage of that being I have reloading data for the Alaskan from SSK industries which I should be able to use.

Ultra mag cases are still quite expensive, but not so much as lap mag cases, and you still have to trim them to length, but at least there is no neck turning. I should also be able to build it using a 300 ultra mag reamer which I have access to and a .510 neck and throat reamer from Pacific Tool and Gauge.

To make sure it is going to work I have got some cases from a very helpful lad down in the new forest and hopefully a box of 750gr A-Max's from Mike once he is back from the 50 cal world championships. This is the prototype case next to one of Pete's .450 Marlin cases and a 7.62x51 for comparison.

The other advantage of going this route, I can legitimately be a member of the FCSA once it's built!

Dies will be 50-90 govt dies because any straight wall .510 cal dies will do to an extent and that's what Hannams had in stock. Why didn't it go with .50-70 or .50-90 in the first place? Same reason as the Alaskan. Brass availability. They had the dies and nothing else. Also, depending which specs you look at, the govt calibre a are actually .515. But I'm hoping they should be too difficult to modify, and I can always make a set of custom dies with a die blank and the reamer if they don't work. They weren't expensive!

The rifle I am using for this is a Ruger No 1. Incredibly strong and perfect for unusual builds like this.

I have managed to source a laminate blank to build a custom stock for it. And the barrel is on order from Walther. A Ruger No 1 varmint profile, Match grade, 1 in 10 twist. Twist is a bit fast really but given that I've not done anything like this before and there isn't a great deal of info about I though better to go faster than slower. I also could get my now almost trademark polygonal barrel in the right twist which was a shame. Well, I could, for about £5k but that's ridiculous.

I'll put some more details and pics up as this progresses and turn it into a bit of a build thread.

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