[birdk9]

This is one you need to have tested before you have a major problem. Having said that I would send a 23.5 gr load and a 24.5 gr load using a CB6118 wad. The 6118 wad has really low pressures using most powders. It will also fill the hull nicely. The 12s3 and 12s0 will both have higher pressures. Depending on what wad fits best (12S3 or 12S0) you can send six of those off for testing with a 23.5 gr load.
It's $50 bucks to test two different lots. $75 for three lots. Could be the best money spent in a long time. My guns and my health are worth $75 to make sure I stay on the safe side. Once you get the results you can really dial in the load.
If you were staying at 1200 fps or slower, I would use the Federal Gold Medal data and call it good using a CB6118 wad. If you are pushing the envelope, get them tested.

Good luck and be safe.

 

[VegasJordan]

Thank you for the info, I was able to pull Nobel Sports load data from across the pond. Also connected with someone loading these types of components. The GT18 wad is close to the 12s3/12s0 and windjammer says for tapered hull