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Old 06-21-2019, 06:47 PM
SHI.Warlock SHI.Warlock is offline
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Join Date: Apr 2017
Posts: 36
Default Change of direction: RAR Conversion Project

I started a thread about a year ago about a 77/22 centerfire conversion. This has changed directions. I decided that the 77/22 was not the correct platform for this. Instead I'm using a Ruger American Rimfire(RAR) and a different caliber, but with the same goal in mind. A re-loadable 22lr equivalent.

Summary for those that donít want to ready the whole project: 25 ACP can be loaded hotter in a locking action such as the RAR. The RAR action isnít as hard as I had heard to disassemble and reassemble. PCP air rifles have somewhat opened up bullet options in .250 caliber.

I've been thinking about this for a few years now and with the advent of PCP air rifles I finally have a better selection of projectiles to choose from.

Here's the project: Convert a RAR to 25 ACP.

Most will think that this is a waste of time and money, it may be, but I think the results will be surprising.

Here's the theory behind my project: A re-loadable 22lr equivalent. I started out trying to swage down a 25 ACP case to 22lr specs, but soon realized that that was a really long process per case and that I was losing case capacity in the process, centerfire primer vs rimfire primer. These realizations made this a losing prospect.

I wanted the smallest reloadable case and still be in the 22lr range in velocity. Why not the lowly 25 ACP? The potential is there... Factory 25 ACP loads are weak, low pressure, and restricted to 2 bullet sizes, 50g FMJ and 35g HP. The first 2, weak and low pressure, are results of varied cheap production of pocket sized blow back action pistols. Higher velocity/pressure loads would eventually destroy some of those pistols. The 2 choices of projectiles have been somewhat alleviated by the advent of the PCP air rifle. I can get 30 - 60 grain lead slugs, not diablo style pellets, but bullet shaped slugs in .250 caliber.

The next challenge was the barrel. Not many barrels out there for .251 caliber. My research found old production rifles for the 25 Stevens cartridge to be .251 caliber. Those are hard to find in decent condition. I found one, but after I received it I found that its overall diameter was too small for the action I wanted to use. More research showed that I could order a barrel or liner in .251 caliber directly from Walther, but those have a 1-9.8 twist, way faster than I wanted. I stumble across the Track the Wolf website, and ordered a 25 ACP liner, 18 inches long and it has a 1-14 twist. This should be perfect for what I need, since 22lr and 22mag twist is 1-16. I didn't know this at the time, but they sell Tj's liners. I've read a lot of good reviews about his liners.

Now I need a barrel to put the liner in. Green Mountain sells gunsmith barrel blanks. So, I ordered a 17.5 inch blank to ream out and install the liner in. The overall dimensions after machining will be 16.5 inches long, .870 dia from the front of the action to the muzzle.

Thereís still the low pressure, slow velocities of the 25 ACP to deal with. Most factory 25 ACP ammo is loaded at 12000-15000 psi to protect the micro pistol actions and avoid litigation from owners of those pistols because the ammo destroying their guns. 22lr and 22mag have a max chamber pressure of 24000 psi. 17hmr has a max chamber pressure of 26000 psi. 25 ACP has a max chamber pressure of 25000 psi (all from SAMMI specs). In a locking action, such as the RAR action, which will handle the higher-pressure hand loads, see the 22lr, 22mag, and 17hmr pressures, I can load hotter to get the velocities that I want.

Max theoretical loads from Quickload, staying in that 24000-25000 psi range, show that I can get in the area of, depending on the powder and charge that I use, 1200-1500 fps with a 31g bullet. A 40g bullet puts me in the 1000-1300 fps range.

Now to that RAR action. Itís a pressed and pinned barrel. I removed everything from the action and drove out the pin, not hard to do. Next, I used a hydraulic press and pressed the barrel out of the action, again not hard to do. The new barrel will be pressed back into the action when the machining is completed. Then I just drill the pin groove back into the shank and reinstall the pin, still doesnít seem that difficultÖ

I may have to enlarge the radius on the bolt face to handle the slightly larger case head diameter. Iíll also have to convert the bolt to centerfire, but in the overall project thatís a small chore and seems straight forward.

The magazine feed will be a little more difficult, but I have a few ideas on that. Until I get that worked out I can single feed from a 47products tray.

I have the action disassembled, the stock 22lr barrel pressed out, the liner is in my possession, the 25 ACP reamer is in hand, and the barrel blank will be here next week. I'll update this thread as I make progress.
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