I spoke to a man in the CZ custom shop who is looking at my 505 today. He told me the problem, or at least my primary problem is the ammo. He suggest I purchase ammo from Superior or Safari International. He has called A Square and complained several times. A Square states the ammo is in spec. He says the A Square rounds are over size and in particular the shoulder is too far forward and the diameter at the base is over size. I mentioned a second unknown load custom formed from Bell 577 also fail to chamber. I asked if Norma would chamber. He does not have any Norma and all his test shooting is with in house reloads. He will hold the gun while I try and locate a box of Norma ammo and send him a round.

Meanwhile I measured an A square 505 with a dial caliper. It hard to determine length to shoulder. This is what I got:

Bullet .505 [spec 505]
Neck .532 [spec 538]
Diameter at neck .598 [spec 600]
Largest diameter near the base, just above the rim .637 [spec 640]
Base to end of shoulder approximately 2.52 [spec 2.498] OVER SPEC, maybe hard to measure this.
Base to start of neck approximately 2.45 [spec 2.458]

Maybe the shoulder is tight. The marks on the ammo I kept home show the chamber is tight at the .598 diameter(near shoulder)and near the base. After that it might have hit the shoulder. CZ now has the one round I forced all the way in.

Is anyone out there using A Square .505?
Can someone measure a Norma PH 600 grain load? Or better yet compare A Square to Norma?

I assume that Norma PH 600 grain is the gold standard, and that brand should/must work.