Any one know of any big bore work besides the 45-70 from the Gibbs Rifle Co, done to a MkIII 2A1 SMLE? I'm thinking of using a Rigby case shortened to around 2.25 sized to .510 for a 535 gr bullet at 2000fs/48KPSI. The 308 mag looks like it will function as a single stack without much futzing around and hold 3-4 rounds. I have some 416 Rigby on order to make up 4 dummy rounds to check mag function for sure, but hope someone has already done the deed. Maybe recutting the rim/extractor groove to 0.534" for a better boltface fit and/or using a WSM case might work also. I'm doing a 375/444M right now and hallucinated one day thinking how nice a short barreled heavy hitter would be for up close and personal. So far it looks feasible...at least on paper and crunching some numbers through Load from a Disk... A short 500 AR so to speak.

Any thoughts would be appreciated.

Depends how big you want to go. I looked at this some years ago with a friend and we settled on using a longer 2" version of the 44 Automag as the chosen cartridge.

The "knack" is to get the thing set up right to handle a "short" cartridge. The solution is to copy the British .22 No8.

That is:

1) Set the barrel back into the magazine space by about 1/2" or whatever.

2) Shorten the bolt body AT THE FRONT by the amount that you set back the barrel.

This way you are not messing about with having an overlong bolt travel for the chosen length of cartridge.

You "measure" the actual required bolt length by laying alongside the bolt a loaded round. Its base resting on the front surface of the shorter of the two locking lugs. Cut off the front of the bolt body back to the tip of the loaded round's bullet point and rethread for the bolt head.

Set the barrel back by the amount to take up the "gap" you have created.

We too chose the 2A1 as it is the best candidate in that all the "work" on making a SMLE body handle a parallel sided cartridge has been done for you.

The other idea - that we did not pursue as we were looking at a "pistol carbine 2A1" - was to select a belted magnum case with the same rim diameter as a normal 303 case as your 308 2A1 bolt head will accept that also. This would eliminate headspace problems.

quote:

hallucinated one day thinking how nice a short barreled heavy hitter would be for up close and personal

Buy an 1897 Trench Gun?

Thanks for the information.

I've looked at this from several angles using cases from 308 through the magnums, belted and belts turned off, WSM, Rigby, Jeff, Gibbs etc keeping the case length from 2" to 2.5" to keep mag and receiver mods to a minimum and simple.

I turned some dummies out of AL to the same dimensions and taper as the shortened Rigby...3.050" COAL just short of max mag length, case 2.250", 0.350"-0.500" neck, to see how it would function in the 308 mag as a single stack. It worked except I haven't opened the receiver hole to clear the diameter. My thoughts were to use a case as large as possible so no mag mods were needed...hence the Rigby case...RIMLESS ONLY...I've read about a few conversions and the problems they had with the rimmed 45-70 case and having to make a new mag from scratch. The Rigby case would also function in a 303 mag single stack.

I want to keep this a simple and as cheap a conversion as possible. Rigby cases are about a buck apiece as compared to Lazzaroni, Jeff, Gibbs etc, at 3 to 5 times that amount, but the Rigby size dies are over $160 bucks vs about $80-100 if I stick with a belted Mag or WSM case...it needing to have the neck sizing protion cut to handle the .510 cal bullet and 0.032" of neck only.

One problem is that would result in a mighty small shoulder junction in the WSM case even if it were straight walled, 45 cal would be OK. The reamer might also be more expensive. Use of the Rigby case would be very inefficient, basically costing over 80 gr of powder to about 60 in the WSM for the same velocity with the same weight bullet, but the Rigby case would give me 0.510 cal capacity while the WSM would realistically only go to 45 cal.

Then again the 450 M or 458 WM x 2.1 will get 1900fs with a 450 gr bullet and the 444 M with 350 gr bullets and be even cheaper yet, plus the recoil would be 15-25 ftlbs less for equal velocity, without a mzl brake...But I would really rather have a .510 cal being this is probably the last of the Mohicans rifle I will build and probably never be used to hunt with...more of a boogerman in the wrong place buster, or wall hanger dream-on.

Just hoping someone was way ahead of me in doing a 45 or 50 cal using a 2A1 action and any help or direction on problems they encountered.

Oh...they won't let me have a trench gun...a 10 ga semi-auto is about as big as I go.

Thanks again