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I was interested to find out how the MARS micrometer adjustable reamer stop works so I googled it and ended up on you tube. The guy had been lent one. What I found curious was the set up he was using to chamber the barrel. He had a square collet block in a four jaw chuck with the barrel held in a collet that he had apparently dialed in. Would that even work ?. As an aside I like the idea of an adjustable reamer stop. Has any one used one how did you get on with it and what make was it.

got a link to the video please

Do you mean the PTG MARS system? They have always caught my eye however I never got around to buying or building one.

I drill first and have a spreadsheet with details of drill diameter and distance in for various cartridges to rough out and still be able to align the reamer pilot (I have a few carbide roughing reamers as well). then up to a tape mark on the reamer which is fairly close. Then test fit the action and count the turns/part turns required. Then back to the spreadsheet which allows me to calculate the depth required to finish and from this point I run in with a clock off the tail stock however you can also do it using the reamer holder face as a reference if you wish.

I watched a video of someone using collet blocks at both ends of the barrel, one in a 4 jaw and the other in a spider on the outboard side. The issue as I see it is as you tighten the collets they always pull the material inwards very slightly (This is why 5C collets have the internal thread, so stops and extension tubes can be added) I run a 5C collet chuck with micro radial adjustment on the larger machine but tend to swap to a 4 Jaw instead. I have never been impressed with idea of a 3 or 4 jaw chuck holding something that is holding something else which is why I built my D1-3 Spider all those years ago, there is zero chance of it dropping things...

Dellboy wrote:got a link to the video please

https://youtu.be/zTMjMeH2q14