The 0000 is the Repro. Austin, did you measure a true 0000 frame Repro? I once did but have misplaced my notes. Your chart shows a dimension for the 000 frame that does not agree with TPS, page 527. The Parker Brothers .410 was almost always built on a 000 frame. As I understand it, all 0000 frames were made in Japan. 00 frame .410 Repro barrels are usually marked 0000, but it is not a true 0000 frame. They are mismarked barrels installed on 00 frame 28 gauge receivers.

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Bill ; The table on pg 527 shows DIM A as 13/16 as I found on the 6 000 frames that I measured. The question is - does the 0000 repro frame measure 13 /16 ? or is it 12/16?

Best, Austin

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The 1/16 inch per digit or 1/16 inch per zero size progression indicates that 000 corresponds to a 7/8 inch firing pin separation. Do any 7/8 inch separation guns exist? There are a few 20 ga hammer guns that are close at 29/32.

Best, Austin

Austin, I thought your first post indicated the 000 is 7/8. I misinterpreted your reason for posting that chart with the 7/8. The "progression" does not work in this case. Only my faded memory tells me that the 0000 pin separation is the same as the 000 frame. I may be mistaken and will not know until I locate my notes. Of course, the rest of the 0000 frame doesn't look anything like a Parker Brothers 000 frame even though the pin separation may be identical. Maybe Jack Skeuse realized the error in the Parker Brothers "pin separation progression" and decided to correct it sixty years later. The 0000 would be true to the progression at 13/16.