Hello, my friend has a Remington O3 A3, and want to know what cal. it is. Its an old milatary gun that has been "sportarized". It does not say what caliber it is. Did they make more than one caliber in the O3A3? I have saw the O3A3 in 30-06, but just curious if it was made in any other cal. Serial number is 3776671. any information on this gun would be greatly appreciated. Thanks

Original caliber was .30-06, but all bets are off if it's been "sporterized". Have it taken to a reputable gunsmith for a definitive answer.

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Originally posted by bkmastr:
Hello, my friend has a Remington O3 A3, and want to know what cal. it is. Its an old milatary gun that has been "sportarized". It does not say what caliber it is. Did they make more than one caliber in the O3A3? I have saw the O3A3 in 30-06, but just curious if it was made in any other cal. Serial number is 3776671. any information on this gun would be greatly appreciated. Thanks

It could have been rechambered for some magnum .30-caliber round by whoever 'sporterized' (ruined) it.... But since the .30/'06 was the US's official rifle cartridge from 1906 until 1957, including all of WWII when the 03-A3's were made, why in the world would any of them have been originally made in any other caliber??

As said, the '03 in all its forms was only made in one caliber, .30/'06. (Except the originals in .30/'03 and they would fire .30/'06 amo safely.)

You say "sporterized?" What do you mean. Does the barrel have its original markings or is it a brand new, round tapered tube. (Military were stepped.) Many "sporterized" by throwing away the top of the hand guard and refinishing the stock. Myabe shortening the stock. And when they were older and had a few extra bucks, drill and tap for a scope... (Pre 03A3, the cheap WW II version, they came with walnut stocks.) These are still probably .30/'06. Although, as said, it was possible to rechamber for something "magnum." This was the beginning / purpose of the 308 Norma Mag. Practically the same as the .30/338 WCF Mag.

Chamber casts are quick and easy. Melt sulfur. It is available in garden centers, tech pure, cheap. $0.99 or 5 lbs or so. Do it outside. It is not explosive but if it catches fire, it stinks. Inside? You might sleep outside for a long time (in the dog house or worse???). Plug barrel ahead of chamber with tight patch. Squirt of WD 40 doesn't hurt. Find funnel. Make funnel with tin foil, paper... this is not hot. Pour into chamber. Let cool. 3-5 minutes. Push out GENTLY. If you break it, start over... and be more careful. Any machinist and any gunsmith should be able to look at the cast and tell you what the chamber is. Might have to measure a bit, but definitive. luck.