It's PSI at the end of the barrel that you have to worry about. Find some one with a Quickload program it will tell you what you need to know. Barrel length will greatly affect your numbers.
Outlaw state bullets and Lehigh bullets are both working on subsonic 338 bullets. No idea when they will be ready.
Blowback gas system is the loudest of all suppressed setups. It is used on most pistol cases. It is just like a semi auto 22 lr. The action is held by spring pressure. When the gun is fired the case expands and holds on to the side of the camber walls until chamber pressure drops. The pressures will typically be higher at the ejection port which will give you a nice pop.
On an AR you have a hole in the barrel that gas is shunted into. It travels through the gas block into the gas tube and finally into the carrier. As the carrier moves to the rear of the gun the bolt is rotated and disengages from the barrel extension. Pressures will be less = less ejection port pop.
Gas cut offs stop this from happening and turns the gun into a K31 Swiss
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There is a member on this site that sell them. Bazooka brothers my be able to set you up.
The 460 Rowland was an attempt to put 44mag power into a 1911 handgun. Like the super it is a really stout case. They're both 45 cal. I would go with whatever had the most available brass. As long as they get your target bullet to 1050 It does not really matter which one you get. Looks like the super and the 45 mag are ready to ship.
http://www.starlinebrass.com/?gclid=...FQ9fswodqX9MJA
As far as accuracy goes, It all depends on the gun. Get a free float tube and a good trigger.
NV. Some get a laser dot scope with a NV setting and mount it in front of their gun. There is not as much shift as you would think going back and forth. What will it take to verify you zero? I just shoot the gun.
A green laser will light your NV up and render it useless. (Red too) You need an IR laser or a good IR light source. It will look like a spotlight to you.