Assuming the guns are offered for sale in the UK, they will need to be 'in proof'. If they are, then they should be safe for the loads for which they are proofed.
I assume the .019 is near the muzzle, in which case, the pressures are low and from that aspect, not a worry. BUT, walls that thin are easily dented. They may also indicate the gun has been fine bored - possibly to remove pitting. This may have taken the barrels right to the verge of proof limits.
You need to establish;
- that the guns are in proof
- at what size the proof was passed (.719, .729 etc)
- what the present bore dimensions are
- that any pitting present is minimal

For example, a gun proofed for a 12 (.729) and currently measuring say .737 is in proof, but only just. Any further fine boring will not only thin the barrels further, but also put the gun out of proof.

Last edited by JohnfromUK; 03/29/14 04:54 AM.