Kirby, I will certainly be watching closely the progress of your .224AM with interest, as I am embarking on a similar project.
At the moment Richard's 100grain .224 ULD's (together with some 125, 130, & 156grn 257's) are in transit across the Pacific to Oz, and won't arrive until mid November. I have also ordered some 107 grain bullets when they become available.
As my gunsmith won't be able to do my job until early 2006, I still have time to assemble the components, and may also be able to follow your progress with the 224AM.
Since, I became aware that Richard was producing 100 and 107 grain bullets, I have given a lot of thought whether to use a case larger than the .224 Clark (63.8 grains).
I have considered using the 22/25-06 AI (est 70.0 grns), 22/7mmRSAUM (est 72.0 grns), and 22/270 WSM (est 75.0 grns), and at this stage still intend to go with the .224 Clark. (already have dies, formed .224 Clark cases, and 100 257 Roberts new brass)
My major concern with using the other cases, is at at this stage I don't have a ball powder with a burning rate slower than my current stock of H870, to be able to take advantage of the extra capacity of those larger cases. I realise that you have access to surplus W872, which appears to be slightly slower burning than H870.
My research indicates that the only other slower burning ball powder is NobelSports Vectan SP13 which was specifically made for the Browning 50 cal. Refer to this website http://www.peterlawman.co.uk/vectan.php
I intend trying to get some Vectan SP13, but may take some time.
During chronographing the 80 grain Sierra MK in my last .224 Clark,(25.25 inch barrel) I found that a load of 61.0 grains (base of neck)of H870 produced 3658 fps at normal pressure. So I estimate in that barrel a similar load with an 85 grain bullet would probably produce maximum pressure.
Using my previous data as a base, I estimate that when using the Wildcat 100 grain ULD, I should get between 3,250 and 3,350 fps, using about 58.0 grains of H870,(about 95% load density), and with the 107 ULD, about 3150 - 3250 using about 56.0 grains H870.(about 93% Load density)
My 38 years of reloading, has taught me that at 95- 100 LD, it is usually relatively easy to get acceptable accuracy, but below that level, as airspace increases it becomes increasingly finicky to achieve the desired accuracy.
As a cross check on my projected velocity estimates for the .224 Clark, my last two 25/06 rifles produced about 3325 - 3350 fps with the 100 grain Nosler BT at maximum pressure, and I estimate that a 25/06 Remington case necked down to .224 would have a capacity of about 64.0 grains, which is about identical to that of the .224 Clark (and a previous 22/284).
I will probably be ordering through a local rifle club, a Krieger 1 in 7 twist number 3 profile 27inch blank that will finish up at about 26.25 inches, and should allow me one set back and rechamber. I probably will follow your lead and order my first 3 groove barrel, but I note on the Krieger website, they don't believe there is a specific advantage for the 3 groove over the 4 groove, etc.
I seek your opinion on whether a Sako AV action would be a suitable choice, as I have a worn out Sako barrel on the older of my 2 25/06AI, and it would simplify things for me if I used that action. Bill (my gunsmith) has for 30 years always recommended using a Remington 700 action for accurate rifles. However, he was obviously able to successfully bed the Sako L61R action in my custom 25/06AI, as that consistantly shoots sub 0.5moa.
Yesterday I looked at the new Remington SPS (Retail $A800) as a possible donor action, but the blued bolt left me cold, and also worried as to quality. Am I correct in assuming that there would be no quality control differences between the various 700 action models?
I will be also following with interest your smaller (target) 25 cal case, as I have been looking for rimless case of about 85 - 90 grains to use up the supply of 142 and 156 grain ULD's I have been acquiring.
I hope the 224AM is a success, and as an avid wildcatter myself, I certainly appreciate how you are continually prepared to push the existing boundaries, and readily share your knowledge with visitors to this forum. Regards, Brian.