This 50 BMG reamer holder is unique in that you can adjust the reamer to enter the bore of the barrel by adjusting the three thumbscrews. Once adjusted in, the reamer is supported for no drag withdraw and plunge of the reaming operation. The tension springs give a constant force to the reamer to stay seated on the dead center in the tailstock. The holder comes with the dead center.
The greatest advantage is the 360 deg. hold on the reamer. Ever try to tap a straight hole by turning and holding onto one handle of a tap handle? The same thing happens when reaming. The reamer tips 90 degs. of applied pressure and the pilot rides hard on the top side of the rotating bore.
Radial alignment is corrected with this reamer holder. Axial alignment is not. The axial displacement in the ram of the tailstock will provide what is needed. That is if the correct alignment procedure has been preformed to the lathe and tailstock for reaming operations, i.e. chambering for rifles! Tailstock alignment procedure for turning a true shaft IS NOT the same thing and will never give you true center lathe axis thrust for chamber reaming!
Helpful hint: If you don't know how, or your tailstock simply can't be realigned, then one of the manufactured floating reamer holders on the market is what you will need to purchase to correct axis misalignment and give you the ability to ream straight chambers. But, on a floating reamer holder, nothing guides the back of the reamer, it goes where it wants. If the reamer starts crooked, it stays crooked, no matter how the barrel is lined up. It's up to you, my system where you know you're straight, or the others where you hope you're straight.