I just got my hands on some Jamison .505 Gibbs brass, and there is NO WAY that it will chamber, even after being resized with the sizing die tight against the shellholder.

Didn't someone else have this problem, and how did it work out?

I will not have a rifle to try it in for a few more months, but my Jamison brass from an early run seems to measure a few thou undersize in most dimensions. I thought the last person who mentioned having had a problem with Jamison brass was using .416 Rigby. In which area is yours out of spec?

Dan,
not trying to be arguementative...

if you full length resized brass, and your die went all the way down, forcing the brass to conform to the die ... this makes the brass SMALLER than the chamber

that could mean any of these
1: the brass is too long
2: the neck is too thick (if you are trying loaded rounds)
3: the die and chamber don't match
4: the rim is too thick or too large a diameter for your bolt to properly close.

so, I suggest resizing a piece of known good brass, and a piece of jamison, do NOT put a bullet in the case, and doing a quick visual check..

then try both in the chamber.

then put a bullet in an otherwise empty case, and measure the new neck diameter

jeffe

I was not aware of any previous Jamison .505 Gibbs problems.

I was aware of the A-Square-made factory ammo for CZ having problems in .505 Gibbs.

In fact, the cure for me was to get Jamison Brass in .505 Gibbs and load my own ammo. This made a good fit in my CZ .505 Gibbs Safari Classic.

The recent problem with Jamison brass was indeed with initial start up of .416 Rigby brass.

The problem there was that the extractor groove was not cut deeply enough. This has been fixed.

I noticed that the rim thickness of Jamison 470 Mbogo basic brass (same as .416 Rigby) was 0.065" whereas other makes have about 0.060".

Sometimes the offending brass will be within specs everywhere but the extractor groove. Apparently this is easy to fix with a lathe at the factory, and will be "right-on" in the future, for Jamison.

Chamber neck and loaded ammo neck diameter incompatibility is another tricky area, as Jeffe also mentions, if nothing is obvious from comparing fired brass using the calipers.

I currently have no problems with Jamison brass in .505 Gibbs or 470 Mbogo (from Rigby basic).

There is really no such thing as a "standard" Gibbs chamber. But if brass that won't fit yours will pass in and out of the same die as brass that will fit, it almost has to be either too thick in the neck with a seated bullet, or a shell holder that is too thick for that particular die body and the combination won't push the shoulder back far enough on this particular new brass to fit your particular chanber. Does the old fired brass look neck-sized when you run it all the way to the shellholder?

Tigger,
Shell holder problem you mention is the third good point here.

We should all hope for brass to be a bit smaller than the CIP max specs or the Birmingham Proof House specs, which I think might be the same in this case.

Anyway, Art Alphin's drawing in the A-Square manual is a good one, and is the same as the Birmingham Proof House in every way. I still am not sure what got screwed up between CZ and A-Square for their first batch of ammo for the .505 Gibbs. But it was all scrapped and a second batch was produced WILL chamber in the CZ rifle.

Then we should all hope that our .505 Gibbs chamber is a bit bigger than our brass.