Question on 12 ga Fiber Load Pressures

[Frank Kernan]

Excellent, thanks very much. I downloaded the 12 ga chart and it will give me a good place to start. I have pretty much all I need right now. This is a winter project so I probably won't get the loads tested until spring. I've used Tom Armbrust in the past and that's who I'll go too. When I get it done I'll make the results available here.

[Keith Doty]

I load some fiber wad roll crimps for "classic" duck hunts but in 10 ga. so I don't have any data to offer but do have some experience.
Straight wall cases best. Find a "plastic" load you like, figure out your load height needs (probably different and very likely to require a spacer between the nitro card and wad), load a half dozen and have them tested. I'd load a batch at the same powder charge you use with plastic wads and another with about 1.5 grains more powder for TEST PURPOSES ONLY. I think your standard load will test lower in both P/V and a small increase in powder will put you back at similar P/V.
Shotshell loading is a bit weird in that sometimes things that you'd think matter little can actually change the pressure and velocity a great deal. Simply substituting a wad for a similar one can drastically change the P/V numbers. Especially pressure.Testing is very cheap in the scheme of things. I use the folks at Precision. Pretty quick and they send you a copy of the lab worksheet.