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Old December 28, 2011, 08:43 AM   #14
Bartholomew Roberts
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Join Date: June 12, 2000
Location: Texas and Oklahoma area
Posts: 5,672
Quote:
Originally Posted by tgreening
What about these switched gas blocks I've read about? I'm assuming this is going to be proprietary as well. If I recall correctly these are made specifically for running a weapon silenced/unsilenced by controlling the speed of the cycling, correct?
I'm not sure what you are talking about; but I am assuming you are referring to things like the Noveske Switchblock. These basically allow you to reduce the amount of gas that is fed to the gun to account for the longer dwell time and backpressure created by a suppressor. They are neat and you can reduce action noise by turning the gas off entirely if you want.

At the same time though, the problem with adjustable gas regulators is that they always seem to be adjusted wrong and you get stoppages until you figure that out. My personal preference is just to upgrade the buffer a bit in a direct impingement AR and then monitor wear more closerly and/or replace parts more frequently (say every 6,000 rounds instead of every 10,000 rounds).

The adjustable gas blocks for the AR are proprietary parts, though I haven't ever heard of one needing to be replaced due to wear or breakage. And if you were unable to find one, you would still be able to use the normal gas block.

Quote:
.08, or .8?
My mistake, $0.85/round.

Quote:
So if I had a 5.56 I could just swap out the barrel for a .300 and be good to go? Or to be really simple two separate uppers of each caliber and swap out as desired.
Assuming the marketing hype is true, that is what they are claiming. Though if you are going to run both calibers, you want to be careful about putting the wrong magazine in the wrong upper.

Quote:
Can you explain this in a bit more detail? I've watched vids (yeah, I know) where the makers are making center mass out to 300 yrds, with barrels of less than 8". For what I want, I'm good with that.
If you are just looking at accuracy, then 5.56mm is probably the way to go since it will still be flatter shooting than .300 even in a short barrel. What I was talking about is what happens when the bullet hits an animal.

5.56mm relies on velocity to make its relatively small bullet effective when it hits something and as originally conceived, it was designed around a 20" barrel. When you cut that barrel length in half, you get a lot more noise and flash and the velocity drops. Since F=ma squared, the drop in velocity has a bigger effect on the kinetic energy available to do work (like make big cavities in jello). And if you go to a subsonic round to make the rifle really quiet, you have basically crippled 5.56mm.

.300 BO isn't very fast, so it will have a more arcing trajectory that 5.56mm that will make shooting past 200yds more challenging. However, at closer ranges it will have more mass and it was designed around very short barrels to begin with. So it will have more energy to do work. And because it uses .308 bullets, you have a very wide range of bullets to choose from, including things like 220gr subsonic rounds that can be subsonic; but still have a lot of mass and a decent ballistics coefficient.

Here is some gel testing of .300 Blackout: http://300aacblackout.com/resources/...t06OCT2010.pdf
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