I am in the process of acquiring a Three Barrel Gun company Drilling in. 16 x 16 over 30/30. A rare configuration for an American made Drilling.
A very early gun made in NY, before they moved to WV.
And a very high grade too.

If they shot 30-30 in it they must have had it resleved and rechambered. 30-30 is .308,and 9mm is .355 and finally 9.3 was listed in two sizes .365 and .376 depending on the chambering.

Something doesn't add up there. While Frank A. Hollenbeck was from New York State, he was down in Baltimore working with Baltimore Arms Co. around the turn of the century, and then went up to West Virginia and founded the Hollenbeck Gun Co. in 1901 to make his double and three-barrel guns. After Frank went bust in 1904, local businessmen took over and the business reemerged as the Three-Barrel Gun Co. in 1905, and pretty soon, Uncle Dan's son Frank Lefever became plant superintendant. Frank A. Hollenbeck returned to New York, and perhaps he took some parts with him?!? While it appears the majority of the three-barrel guns made in West Virginia were 12 x 12 x .32-40, they were also made in 16-, 20- and 28-gauges, and a great number of rifle calibers -- .22 WCF, .25-20 Win., .25-20SS, .25-25 Stevens, .25-35 Win., .25-36 Marlin, .30 WCF (.30-30), .32 Ideal, .32-20 and .32-40. Thumbing through my copy of the old Three-Barrel and Royal Gun Co. ledger, I'd estimate that after serial number 550, .30-30 was the second most common rifle caliber.

Eldon says his barrel is marked 9mm. That means to pass Proof it had to measure .355 to pass proof. Guns had to pass proof both dimentional as well as a preasure test.

Dave,
I do plan on acquiring your articles on the a Three Barrel Gun Co. That you wrote for the DGJ. And I was intending on asking some of your thoughts on this gun after I aquired it in regards to possible value since they are so obscure and this gun is such a high grade.
The Serial number is 676. It is a WV made gun. I was mistaken. Damascus barrels in 16g over 30/30.

Eldon:

The gun was first proofed in April 1903. The bore gauge of 118.35 is very common for the 9.3 x 72 R. Then, the gun was reproofed in Dec. 1927 (I think that's a 27...). That's what the "Crown R" proof means (reproof). The "9 mm" marking was probably applied at that time. Regardless, based on these markings, there's no way it is chambered for 30-30.

I have a friend who has a Vierling in 20x20, 30/40 and 25 auto. I was with him when he bought it from the late/great Dangerous Dave Cunningham. I have not seen the gun for years, but it was a beauty and I think German. The gun was like new. He paid, back then, $5,000.

Now comes the question can a 30-30 be put into a 9.3x72R and fired? This might explain what is going on. Kind of scary but the seller needs to be informed.

I would be surprised if it fits in the chamber that it dose not split the case when fired. If I were him I would stop doing it.

I have informed the seller. They have not fired the gun in years and do not intend to do so again. I am having him measure the groove diameter with some calipers. He should be getting back to me.