OK, here is what you do. Stoney Point makes an "overall length cartridge" gauge. But you can make your own. This works for all calibers but lets take a 223 to start with. Take a fired case from your rifle, deprime it, without sizing the neck. You want a neck that will take a bullet that will just slide into it without much pressure, maybe little or none. Drill out the primer pocket with a 1/4 inch drill, clear thru the case. Now take another case and do the same thing to it. This second case can be forced into the hole drilled into the base of the first case, May take a little pressure but that is good. Now before you do this, find a small screw, say 10-32 or thereabouts, drill the rear case perpendicular to the length, near the base, with the appropriate drill so you can thread this hole for the 10-32 screw. The reason for this is that you are going to assemble the first case,(that will fit your chamber) with the second case driven into the hole in the first case base. The key to this is a piece of cleaning rod, or a piece of wood dowel or whatever that will slide thru both holes and into the bore of the rifle when these two joined cases are inserted into your rifles chamber. Set your desired bullet into the mouth of the case going into the chamber, with the rod inserted into the rear of the second case. Push the empty cartridge case into the chamber, then push on the rod, pushing the bullet forward until it contacts the lands. When it does, screw the 10-32 screw down and lock the rod in place. Remove all this from the rifle and knock the bullet loose from the lands. Re-insert the bullet into the case that went into the chamber till it contacts the end of the rod. Measure the overall length of the end case with the bullet in it and that is the max. overall length that you can load with that bullet in that rifle. It will be different for each different bullet, as the ogives are different. I have measured it for all the bullets I shoot on each calibre I shoot in each rifle. I can tell when I am 5 or 10 or 20 or what ever thousands off the lands I seat the bullet. I have one rifle that like bullets seated either 0.020 or 0.040 off the lands and nothing else. I know this is long and probably confusing. This is not my idea, I found this on some "gun" site. And it had a picture, which made all this clear. Just remember, that each bullet in a particular case will have a different cartridge over all length. (COAL). This is due to the different ogives of different bullets and where they contact the lands. It may not be much but a Hornady will be different from a Sierra, etc. Different weights will be different. You will find that some bullets cannot be seated in the case at all and still contact the lands. The lands will be too far away for any of the bullet to be in the case. In that situation the bullet will have to "jump" to the lands. Most benchrest shooters like to have the bullet just touching the lands or jammed into the lands. As to why the WW 45 JHP stuff shoots as good as it does is a complete mystery to me as it has to "jump" about 1/4 inch before it contacts the land. Now I guess I have confused everyone but a few that have already done this. I wish I had a drawing of this so I could post it, that way all could see how simple this really is. I have one of these made for each caliber that I shoot, and data recorded for each bullet I shoot, as to maximum overall cartridge length for that bullet. And I still have trouble finding that "best load". But for me that is where a bunch of the fun is. At least when I find a load that shoots good, then I can start fooling around with seating depth to maybe make it better.....or worse.
Wheeeeee. That was longwinded. I am sure Quicktdoo will have a link to the picture of this contraption, that you can make. How about it Tim. You the man with all the links.