I was recently informed that there were some interesting replies on a thread started with my True Bore Alignment System so I checked out your sight...... awesome sight guys!.... I joined.
I don't claim to be or know much about bench rest shooting, but I am very much into long range precision shooting and am very passionate about building and doing extreme precision work. ....I will try to answer a few of your questions as well as ask a few of my own.
First lets touch on setting up a receiver in a traditional action truing jig, 4 adjustment bolts up font, four in the
rear I won't go into the method that you use to get it very near center before you even start applying your jacking bolts against the receiver, but will say this. if you are holding both ends of the receiver or barrel and only moving one at a time, your implying stress as you are moving one end while trying to hold the other end. This is minimized by soft feet and narrow feet.....none the less it is there.
next, lets talk about adjusting one set of the adjusting screws. for this example we will use the front set. you are only adjusting one screw at a time, therefore it is very easy to get more tork on one screw than another therefore depending on how much tork variance you have in your four bolts and how thick the tube you are dialing in is, will determine how out of round the receiver is influenced. then you make all of your cuts. and pray that all of your soft jaws didn't relax very much. If they managed to stay true. This is good, so you release all of your jacking bolts. Now the receiver has no pressure implied on it and it goes back to it's relaxed state as well as your trued surfaces relaxing with it. The degree could be micro it is the theory I am talking about. I do not believe in absolute true dimensions and in theory there will always be another digit we can add. I have used the 8 jacking bolt system and have always been very careful to minimize all these effects never the less I have always felt it has been a bit of a balancing act between not holding the part rigid enough and implying too much stress on the part.
With the True Bore Alignment System we are holding the receiver in either a 6-jaw chuck or a collet chuck. the 6 jaw is a scrolling chuck and when you are clamping the action you are applying even pressure on all jaws (due to the scrolling action and assuming a round surface). with the collet system almost having 100% contact over an inch and a half area. next we adjust our angular adjustment screws to dial out our angular misalignment, next we use our rotational adjustment screws to dial out the rotational run out, in doing this the stress is only applied on the True Bore Alignment System... also we have separated rotational and angular adjustment planes and although adjusting the angular plane will effect the rotational plane, adjusting the rotational plane will not effect the angular plane, therefore we do not need to "chase our tail" while dialing in barrels and receivers.
Next, lets talk about supporting the muzzle end while using the True Bore Alignment System. First, there are many ways to support the muzzle inside the spindle when using a short barrel, but for this example I am going to say we are not holding the muzzle. first the barrel is placed in the jaws of a 6-jaw chuck or a collet chuck, the barrel is dialed in to be running near true in two points, one at breech and one near where the throat will end up. so let me clarify...the breech end of the barrel is sticking out past the jaws of the chuck approx 1.25" next our jaws are holding the barrel for over 1.5" therefore from the back side of the jaw to the face of the breech we have approx. 2.75" forward the backside of the jaws. (this accounts for most of our chamber length if not all chamber length) so now we must find the RPM we must run at before our whip shows up in the rod. in my tests with the barrels I use I have been able to achieve adequate RPMS for machining while maintaining very minimal indicator movement at the end of my 4" rod extending from the barrel. in fact I have run complete thread tenonon operations with the indicator left on the rod 4" out from the muzzle, although you will see slight deflection when the cutter is at work, it always comes back to near zero run out when the pressure is released. This is the case in all chucking systems, the degree will vary depending on rigid holding and stock rigidity.
now lets talk about why I built this system....I did not build this system to shove down peoples throat or say they can not build accurate rifles without the system, this is simply not the case! I designed this system for myself as I did not like the physics of all other methods being used....including methods I used. It has been a great time saver for me and has given me peace in my own mind that I am improving my end results and that my hard work dialing in is not lost by the time the finish cuts are made. I have been using this system for a year and have been extremely pleased with the results and therefore decided to start manufacturing these for the gunsmiths and hobbyist gunsmiths that see the benefits.
Now I would like to talk about range rods. Although I use and recommend the use of the range rod with this system, range rods will never repeat as near perfect as I would like them to. therefore to take things to the next level a long test indicator should be used for final rotational run out reaching as near where the throat will end up as possible.
These are all my personal understandings and views. None were meant to offend or degrade others, just offering my understanding.
all the best,
308nate
