I have seen minor feeding issues in a number of rifles which were AI chambered. Mostly the issues involved the shoulder of the case contacting the top of the chamber before the action rails were ready to let it go. Not too difficult to remedy but there nonetheless.
I have, for years, disputed the reduced bolt thrust claims for AI cartridges. I also dispute the reduced brass flow claims. I do not dispute the claims for reduced trimming but do dispute the cause and effect.
Regarding the measuring of case heads as a pressure indicator: there is no question that, by the time a case head is expanding, you have already exceeded recognized limits by a substantial margin. Rocky Gibbs' belief that the brass was the weak link- in a strong, modern, rifle- while it may have had some basis in fact, ignored industry-established maximum operating pressures.
Ackley wrote of loading until the primer blew then backing off a couple of grains. Again, this was a good way to push the envelope and then some.
When I compared standard, AI, Gibbs, and magnum cartridges back in the day, I used case head expansion because that was all I had as a means to guage pressure. The maximums at which I arrived may have been too hot for regular use (and probably were) but I was at least able to run each cartridge at roughly the same maximum pressure.
I have always been a bit fascinated by the Gibbs cartridges because my grandfather had one and because Rocky Gibbs was the first real gunsmith I met personally (I was 14 at the time). I doubt that I will build myself a 270 Gibbs but I still have a piece of brass from Grandpa's rifle which I used to get my headspace gauge measurment and I've had the reamer for about thirty years. Maybe I will. GD
