Shooting My New to Me, Winchester SL 1910, .401

[wachtelhund1]

Hi there, I'm starting to shoot my 1910 SL. This gun is a direct blow back rifle with an extremely large and heavy bolt. I made brass from 30-30 cases and have some Western 250 grain lead bullets. I drilled and tapped it for a scope base and have a Burris Mini 4X scope mounted. Load data gleaned from several posters on the internet showed IMR 4227 powder with 27.5 grains as max charge. I also have some 200 gn copper coated bullets. Max load for these was 31 grains. I fired about 20 of the 250 gn cast bullets prior to taking the rifle down to mount the scope base. Loads were then 25 grains of IMR 4227. Half of these failed to eject, not enough powder. After mounting the scope, I loaded several 250 grain bullets with 27.4 grains of IMR 4227. The first bullet cycled the massive bolt back, leaving it stuck in the open position. I took it apart and tugged on the bolt, which freed it and allowed it to close. Last night, I pulled the bullets loaded with 27.4 grains of powder and reloaded five of them with 26 grains of 4227. I fired these this morning and they cycled fine. Later today, I will try 26.5 grains of IMR 4227.
I checked the Western lead bullets they were exactly 250 grains. I could have been my cases made from 30-30 brass. They could have been smaller on the inside and developed greater pressures.

 

[bamaranger]

SLR

I 've always been intrigued with the later SLR rifles, and the .351 and .401 cartridges. The .401 ctg was head and shoulders above it's cousin, the .38-40 in terms of energy and while heavy, the SLR rifles made an argueable step forward against the lever carbine family. I would have liked to have seen the M1 carbine chambered in .351/.401, but the .30 Carbine evolved as we know it and successfully.

Your .401 project is interesting and I wait to hear the follow up results. Were the old rifle mine, I would not have drilled it.....but of course it's yours and you can do as you please. There is a 1910 SLR on Gunbroker, similarly drilled and set up like yours, I think it even has a Burris Mini on it.

 

[FrankenMauser]

Drilled and tapped it.

Your load development process seems very chaotic, rather than deliberate and incremental.
With a cartridge of this size and pressure level - and especially when paired with a blowback action - you really should be taking smaller steps. Increments should be well under 5% of a max load, not a 10% jump, right out of the gate.