I use rsterne's 75% of bore rule for the maximum width. A M7.0 TP is already violating the 75% rule. You may have to go to an oval port.My 357 porting is full bore area and is producing 280fpe with a 138gn bullet. No issues with chambering past the port.
I've had a chat with a local lad who says he's using 8mm barrel opening without issues. Another one has 7.5mm opening in his gun (both Evanixes actually). That kind of makes me wonder where that 75% rule comes from as in real life it seems to be limiting us to oval openings if maximum power is desired.That's very nice work you have there Tom.
Just thoughts.. 75% may be conservative for slugs considering a long slug may pass over the port with the rear section supporting the nose, once the nose is clear of the port the rear follows without issue. I'd think a pellet would be problematic with its narrow head dropping in or catching in the the port. Also slugs are not as fragile as pellets and can possible handle more abuse with the loading process.
How about doing up a chart for us?....Bob
One other thing to note, the lead in where the transfer port is located is larger than the bullet diameter. With long oval ports and short bullets this means that the bullet is actually sinking in and touching only the edges of that port when travelling over it.
Chamber it is, sorry guys - Englisher is not my native language.
Quote from: rkr on October 22, 2014, 03:08:34 AMChamber it is, sorry guys - Englisher is not my native language.Your English is excellent! If you could just post in imperial units............ GRIN.I understand now. I make my chamber .002" larger than the slug or .359 for a 9mm. This way the slugs slide easily up to the leade and maintains correct alignment. I would expect a loose chamber to have a negative impact on accuracy and yes I would expect the bottom most quadrant of the slug to catch on the port.Tom Even Bob has conceded inches are king