iShoot17 & others: when you indicated that the Giraud shell holder for 308 could be used for other cartridges based on the 308 cartridge and shoulder angle, is it necessary that the Giraud shell holder support the neck of the cartridge being trimmed? In other words, if using a 308 Giraud shell holder to trim 7mm-08 or 243 and others, would vibration cause a problem with the smaller (unsupported) necks being trimmed? I realize that the Giraud registers on the datum of the shoulder, but wouldn't any unsupported neck induce movement resulting in a somewhat "rougher" trim and chamfer? I do know that the cutting blade must be adjusted correctly for the diameter of any smaller neck. Thanks.
This has not been my experience, but is a very solid question. Let me take a stab at explaining (or at least give you my created logic of the topic!).
It kind of goes back to what I said about consistency in my previous post. As shooters, we try to say keen on consistency and another thing called concentricity. It goes into creating our chambers, our threaded muzzles, and even our ammo. Knowing this, concentricity is also a huge part of our reloading adventures. We know, and should be able to assume correctly, that the neck of a bottle neck cartridge is centered in the overall scheme of the entire cartridge. Whether it be the case head, body, or shoulder. This leads us to believe that the case neck, of whatever caliber, is centered to the datum line of a shoulder.
With the creativeness of Mr. Giraud and his slick engineering, he created a shell holder that is based off of a datum line; however, he even stepped it up a notch! He created the shell holder to be on a spring. This means that the shell is placed in the shell holder with no worry of any trimming happening until forced upon by the user. Setting a case in the shell holder will allow the casing to be centered and ready for trimming. Once the user starts to force the shell down towards the blade, the spring style shell holder pushes back creating a positive connection between the two and keeping the shell centered. It my experience, and thought process (although maybe it is wrong?), I have had no issues with a "rougher" trim or chamfer. I have even used a magnifying glass to examine a few pieces just to see what the heck is happing while contacting the cutter.
As long as you adjusted the cutting blade correctly (I keep 5-10 pieces of scrap brass around to make sure I was setting the cutter correctly when initially doing an adjustment), there should be no issues with using different calibers in a single shell holder, i.e. .308 Win, .243, .260, etc. Also, the trimmer is extremely stable and has little vibration. I do understand where you are coming from though. I believe I would be more worried about a trimmer that is similar to the idea of Mr. Giraud, but that didn't have a spring style shell holder. I feel there could be some issues with a style like this, but I am not an engineer, so I can't be sure.
Hope this helps answer your question!
