2Piper,
I read your comments on the round bolt and thank you for your observations plus the mention of other shotguns that have them. Apparently is not as rare as I thought.
You mention the load bearing cross pin in the Mod 21. From the pics I have seen it seems that the cross pin is supported by frame metal on the front, so the load is not borne by the pin alone.
The lack of a central bridge does raise some questions. On the other hand I wonder how much actual contact between the rear lump and the bridge (and hence support) there is during firing. I have tested with smoke a couple of my doubles and there does not seem to be any load transfer between rear lump and bridge, ie no detectable contact. Also, when a gun is off the face and the barrels are refitted, ie taken back a few thou, this contact would then be lost even if it existed when factory new.
I wonder if the gents who own Mod 21s can help with this question of the lock up of the round bolt. Have any of you had any experience with Mod21s shooting loose and the subsequent repair required to put them back "on face"?
Any had any problems of a loose action camming itself open during firing? I have heard of this problem with some OUs but not with a SXS.
As a non American non British European I do not harbor any alliance for any style of shotgun. And also have never had the chance to actually handle a Mod 21, there are none in my area. The reported strength of the action does fascinate me though since it seems to flout accepted (by the British) tenets of shotgun design. I wonder if there were British guns in that endurance test carried out by Winchester where the Mod 21 was pitted against the rest.
The 21 barrels have a tensile strength of 115,000 pounds per square inch. In a 1932 ad Winchester fired the 21 with 3 1/4 drams of powder and 1 1/8 oz. of shot with the lug, lever, and locking bolt removed.
Case hardened frame guns have about half of the tensile strength (94,200 lbs vs. 174,600 lbs.) and elastic limit of the Win 21's blued frame.
Winchester tested the 21 with violent proofs (50% higher charges) against a Fox, Ithaca, Parker, and LC smith. The Fox failed after 80 rounds, the ithaca after 56, the Parker went 305, and they say records for the smith was lost but it also failed. The 21 went 2,000 rounds and was still in good working order.
*Herbert G. Houze, "a study of strength"
