I found these posts which discuss the pressures:
POST 1:
saspic
"This comes up all the time, I really should have saved the post where McNett (Load developer of DT ammo and a poster at Glock Talk) originally spoke to this issue on Glocktalk or somewhere.
He said that the secret to
DoubleTap's performance was not in maximum pressure achieved, but in keeping the pressure above a (relatively low) 7,000 p.s.i. for as long as possible.
When their 9 millimeter first came out, I remember him posting that the only reason it wasn't standard pressure was because 9mm fans looking for self defense ammo only consider that with +p designation. He said it he pushed it to 35,200 so it would just barely be technically into +p territory.
Notice their rather hot .45 A.C.P. isn't even +p.
http://doubletapammo.com/php/catalog/index.php"
POST 2:
jad0110
saspic hit the nail on the head.
The relationship between velocity and pressure is not simple and direct. A certain powder in a certain caliber in a certain barrel length can actually produce significantly higher velocity for the same or even less pressure than a less optimum powder choice. Take BB's standard pressure 158 grain 38 special load. It is roughly equivalent in performance to the famous Remington FBI load, 158 grain +P. But the pressure is lower. As saspic stated, a less than perfect powder choice will have a high, short spike in pressure. The peak pressure is what winds up being reported as the SAAMI pressure rating. Pressure spikes are less preferred for getting a bullet up to speed than a powder that applies more even pressure at a lower peak. Such a powder (without the high peak) can often drive the bullet to a higher velocity.
Richard Lee discusses the at length in Modern Reloading, 2nd Ed.
As for whether or not BB or DT adhere to SAAMI, I would think they'd be opening the door to hellacious lawsuits if they didn't.
Does Double Tap and Buffalo Bore really live up to its hype - THR