Hello, I've got a 590A1 and based on this artilcle (http://www.firearmstactical.com/briefs10.htm) I keep it loaded with #1 buckshot (16 .30 caliber pellets). The Remington 1 buckshot gives a nice, evenly 6-8 in. spread at 10-15 foot range. I think its about 1100 fps. I tried some Federal low-recoil, hi-energy 00buck but the recoil was about the same to me as the remington 1 buck.
From firearmstactical (URL above):
"Summary
With the right load, a shotgun can be very effective in quickly stopping the deadly violence being perpetrated by a criminal who's invaded your home.
If you're worried that a missed shot might penetrate through a wall and harm others, load your shotgun so that the first one or two cartridges to be fired is number 6 or smaller birdshot, followed by standard lead #1 buckshot (12 gauge) or #3 buckshot (20 gauge). If your first shot misses, the birdshot is less likely to endanger innocent lives outside the room. If your first shot fails to stop the attacker, you can immediately follow-up with more potent ammunition.
With birdshot you are wise to keep in mind that your gunfire has the potential to NOT PRODUCE an effective wound. Do not expect birdshot to have any decisive effect.
Number 1 buckshot has the potential to produce more effective wound trauma than either #00 or #000 buck, without the accompanying risk of over-penetration. The IWBA believes, with very good reason, that number 1 buckshot is the shotshell load of choice for quickly stopping deadly criminal violence."
The article is considerably longer and is v informative.
BTW cheaperthandirt has pretty good prices on the Remington 1 buckshot. I also compared the patterns from federal 1 buckshot (as reccomended in the article) to that of the remington & preferred the Remington!
Good luck - Dave