I’ve had a Willis for four years. I literally will not finish cleaning a bore without a peek with the scope. It’s just as good today as when I bought it so I do feel it’s durable. Yes it’s $300 but for me it’s paid for itself many times over.
I’m in the same boat with the Wilson. It’s just simply the best. I still use it for my bench rest rounds. I worry over them like a first litter bitch and prefer to do the campher and debur by hand. The Giraurd gets its work out on the rest of my cases which get used on steel. I’ve never used a Redding or a Forster 3 way. I have kind of a nostalgic attachment to the Redding products. They have always been top of the line. But I sure do like the way the Forster operates in that video. It also sounds like the Forster cutting head is adjustable and that would be important to me.
A borescope would answer your question immediately. If not available, running a wet patch of Boretech Cu +2 or KG12 down the tube, let it sit for 15 minutes. If it comes out blue it’s coppering. Both products mentioned are ammonia free and are non harmful to your barrel.
Fuj I’m not a wildcatter so take these thoughts as musings from a senile old fart. I do think the one caliber plus or minus 10% is a good rule of thumb. It seems to me though the purpose of the rifle, bullet used and the throat length of the chamber should be considered factors. A hunting or tactical rifle has to have enough neck to bullet bearing surface to ensure solid neck tension. Some bullets like to jump so for them throat length may be more important than the amount of bearing surface contacting the neck. If the throat is long to the bullet, a longer neck might be advantageous. But a neck longer then the seating depth of the bullet bearing surface will be of no additional advantage if the throat length is correct. There was an article on AS a while back that talked about a very accurate load with essentially no neck tension - Bullets were seated with finger pressure!!!! Wildcating is another name for experimenting right 👍