Re: 22-6mm ack.
Kirby (Fifty Driver) has identified in his post, the main problems associated with .224 centrefires, heavy bullets, and fast twists.
I have been using a 224 Clark for the last 20 years, which is a case that is very similar to the 22/6mmAI. The main difference between the 224 Clark and the 22/6mm AI, is that the Clark uses a 30 degree shoulder, and the 22/6mmAI uses a 40 degree shoulder.
The case capacities of the 224 Clark and 22/6mmAI are very similar, and therefore the velocities achieved are also very similar.
I have mainly used Winchester 257 Roberts brass, but have also used Remington 257Roberts brass, and found like in many other calibres, the Remington brass had about 1-1.5 grains less capacity.
Although I did contemplate using Norma 7x57mm brass, I decided it wasn't worth the extra expense, and also the time associated in the extra necking down steps. I also agree with Kirby in that if you spend several hours on preparation of Winchester (or Remington) brass, the rifle should be capable of delivering excellent accuracy.
Regarding barrel life, I fired about 1600 shots in my first 224 Clark before I had the Shilen 10 twist barrel set back, and rechambered to 22/250AI (28). My second 224 Clark (6.5 twist Krieger) had fired about 400 shots when unfortunately it was stolen about 3 months ago. At that stage the distance to the lands had lengthened only about 005 inches, which is negligible. Ken Clark (who developed the 224 Clark) believed that the use of ball powders rather than extruded powders significantly improved barrel life. However, I have not had the time or resources to verify this.
Regarding bullets. In my second 224 Clark, the 6.5 twist just disintegrated both the 100 grain Wildcat and 105 grain Little. Even the tough 80 grain Sierra MK came apart. Luckily Garry Little, a local Oz custom bullet maker, came to my aid and produced some 100 - 110 grain bullets which held together and were formed from 257 and 277 cal jackets. However, after some further testing we settled on a 100 grain HPBT bullet with a soldered lead core, that had a similar profile to the Sierra Mk. This bullet had no failures, and I plan to use a similar bullet in my next .224 Clark.
I noticed that Berger now also produce an 80 and 90 grain VLD .224 bullet with a thick jacket, which is supposed to help prevent bullet disintegration. I have ordered some and intend to test these to see if they will hold together, but would be interesed to hear from anyone who has already tried them.
As a rough guide for your 22/6mmAI, I have listed below some loads from my .224 Clark (1 & 2).
Rifle 1. Rem 700 SA, Shilen 25.5 inch 10 twist barrel.
Win cases, Federal 215 primer.
69 grain Sierra HPBT
52.0 WW 785 3723
53.0 WW785 3808
54.0 WW785 3853
54.5 WW785 3897 Max
54.5 Reloader 22 3869 Max
51.0 IMR 7828 3619
52.0 IMR 7828 3686
53.0 IMR 7828 3800
54.0 IMR 7828 3900 Max
80 grain Sierra HPBT (naturally didn't stabilise in 10 twist)
50.0 IMR 7828 3557
51.0 IMR 7828 3650 Max
54.0 Hodgdon 1000 3537
55.0 Hodgdon 1000 3629
56.5 Hodgdon 1000 3670 Max
59.0 Hodgdon 870 3516
60.0 Hodgdon 870 3596
61.0 Hodgdon 870 3658 Near Max (sl compressed)
Rifle 2: Rem 700 LA, Krieger 26 inch 6.5 twist barrel.
Win Cases, Rem 9 1/2 M primer.
100 grain Little HPBT soldered core.
49.0 ADI 2225(HRetumbo) 2,991 Mild
50.0 ADI 2225 3,091 Near Maximum
51.0 ADI 2225 3,144 Maximum
53.0 H870 2,975 Mild
54.0 H870 3,042 Mild
55.0 H870 3,089 Near Max
56.0 H870 3,158 Max
53.0 AR2218 (H50BMG) 2,963 Mild
54.0 AR2218 3,014 Mild
55.0 AR2218 3,053 Mild
56.0 AR2218 3,101 Near Max, sl compressed.
Hope the above is of some help. Brian.