NitroSteel I think you have made a good decision with the Extreme.
The only reason I stay with the FPJ system is it isolates the breech from water... the moisture will not bother the 209 primer but, it is possible for water, melting snow to work by the 209 and up the flash channel to the powder... but what are the odds? pretty darn low...
I much prefer T7 to any of the pyros... and it is possible you may have to run a swab after each shot, but then again maybe not. With any of my inlines I can get 3 to 4 shots off and still get the proper bullet seat. And as BB indicates it is less corrosive than the Pyros... and with T7 it is not necessary to strip clean the gun at the end of the day, the end of the week either. What you will need to know is that the
residue, not the powder - is/can be - corrosive, and then it must have moisture to begin the corrosion process. The residue is easily removed with a simple windex patch or patches. You do not have to do the hot water bath just because you shot some T7. I am currently hunting with an Omega, it was shot on October 8 or 9th to verify POI, windexed patched and reloaded for the beginning of the hunting season on the 10th. Just for drill I did push the bullet out last week (to cheap to shoot it out). Here is a pic of the load that was pushed out onto some newspaper. The gun had been through 3 heavy rain storms and a wet snow storm... soooo I was curious... Patched the barrel with a very slightly oiled patch - then a couple of dry patches - reloaded and it is ready to shoot again.
As you can see the load was fine and the barrel was fine - been doing this for about 6 years now and no ill effects.
If you are uneasy with any of this you can always shoot BH-209 from an Extreme...
Also, what's a good (affordable) conical bullet to shoot, just in case I don't like the REAL's?
Contact - Dan at Bull Shop these are great conicals that slip-fit (he sizes them to fit your bore) with a Extreme you would probably need a .503...
Here is some pics of his conicals.... awesome animal stoppers...
http://bullshop.gunloads.com/contact.html