Help with Trapdoor Rifle ID please

[glindes]

Knowing what the profile of the gas escape cuts on the sides of the receiver are supposed to look like can also be very helpful when the number is unclear on a low-numbered arm. Saved me all sorts of magnifying, squinting, and guessing since I knew it could not possibly be an "8". FWIW, sometimes SA got their "8" upside-down. :-)

Mr. Hosmer, where on the receiver sides are the "gas escape cuts" located? Geoff

[Dick Hosmer]

On the early receivers, before approx. 77575*, the contour break is about midway along the top of each side wall - it very slight, a bit rounded, and can be hard to see/feel at first. On all later receivers, the profile change/step/notch occurs about 3/16" ahead of the thumblatch cut, and is much sharper and deeper, allowing significantly more room for gas (from a ruptured case) to escape harmlessly to the sides.

*I own 77593, which for many years was thought to be the lowest known deep cut, but Jack Lewis (Cowans Auctions) came up with a lower one by about 10.

[raymeketa]