I came across a Tokyo Arsenal Siamese Mauser in excellent condition and decided to convert it to a shootable caliber. As I happen to have a lot of terrific Greek 303 surplus ammo and I reload .303 British, it was a no-brainer what to convert it to.

I took it to a trusted Mauser-centric gunsmith. It was re-barreled with a varmint weight 1-10 twist 24 inch .311 barrel. The stock bolt handle was re-contoured and turned down. A Timney trigger was installed and a new semi-inletted sporter stock was added. The stock was by far the most work. I still have not finish sanded it and applied its final finish.

So what happened? It immediately became clear that the extractor was not big enough to grab the smaller rim of the .303. There are no other Mauser extractors that are adaptable to the Siamese action. The only answer was to weld it up and re-profile it. Fortunately, that seemed to be no problem to my gunsmith and in relatively short order that was done. It now extracts the 303 cases perfectly.

The good news is that it feeds the 303 really well from the stock magazine. 4 rounds in the magazine box run perfectly. 5 rounds will work if you pay attention to how you put them in.

As with most custom barreled, glass bedded Mauser actions, it's stupid accurate, even with surplus Greek ammo. If there is any notion that the 303 is not accurate, let me dispel that rumor.

Did the project make any sense...well, no. Not if you add up what I spent. I could have gotten a very nice Savage 110 in 308 that would have been at least as accurate, which I did. I have to tell you that I will pickup and shoot my Japanese 303 British rifle way before I ever touch the Savage.

I still believe the 303 British is the best cartridge to convert a Siamese Mauser to. The reason being is that the extractor issue is fairly easily fixed. Almost any other caliber seems to have magazine feeding issues, which the 303 doesn't seem to. I also have a Siamese Mauser in 45/70 and it is a single shot. You load one, fire and then fiddle with the next to get it to go.

On paper the 7.62x54r Russian looks like a better candidate but for some reason doesn't feed as well out of the magazine...not sure why but magazine feeding issues seem to be harder to solve than the extraction issue.

I thought about doing a 303 Gibbs or some other 303 based wildcat but again, the magazine feeding issue may come up. I like the 303 and am perfectly happy handloading it when I want to do something special.