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GunNut
Posts: 7,642 Senior Member
3 votes
11 votes
9mm AR upper decision...
GunNut
Posts: 7,642 Senior Member
This one is coming around. Getting closer by the day actually. Going to build a PSA 9mm AR pistol that accepts Glock magazines. Should I go with the 4" or the 7" upper? I'm leaning to the 4", this will never be anything but a true HD/close quarter PDW and most probably will get a short can down the road. But I'm willing to listen...
9mm AR upper decision... 14 votes
PSA 9mm 4" Upper
21%
3 votes
PSA 9mm 7" Upper
78%
11 votes
Replies
Get more bang for my buck.
With the price of ammo it would be good beer to boot.
I also just realized that the 4” barrel doesn’t even make it to the end of the forend and has one of them forward directing muzzle devices already tucked in there just to make it even. That won’t do...
Gel results aren't tissue - fair enough - but the 147's ARE very consistent in reaching depths within the FBI's happy numbers range across the test barrier spectrum. The lighter slugs seems to give up much of their momentum on the obstacle, making their penetration a little more variable.
Just for sake of historical relevance, it was a 115 grain Silvertip entering through the upper arm that pancaked and stopped short of Michael Platt's vital organs in the 1986 Miami shootout, allowing him to continue to shoot FBI agents until slowly bleeding out through a severed brachial artery. That was what led to the birth of the whole gelatin-based studies we use today.
Even though the construction of the bullets has gotten better, you're still confined by the diameter, bullet materials, safe SAAMI pressure specs, and the velocities they generate. A 115 grain hollowpoint lacks momentum, no matter how well constructed it is. Comparatively, it's a ping pong ball. A 147 is a golf ball. Which would you rather have someone bounce off the back of your head?
"Nothing is safe from stupid." - Zee
If you're already adding the bulk of an AR style receiver, brace, etc, why mess with the same barrel length as a Glock 19?
"Slow is smooth, smooth is fast, and speed is the economy of motion" - Scott Jedlinski
"Slow is smooth, smooth is fast, and speed is the economy of motion" - Scott Jedlinski
180 grain .40 S&W's expand at 1000 fps and less all the time. . .
. . .the notion that a 147 grain 9mm at 1000 fps cannot expand seems a bit ill-founded.
Hollowpoint tech of the '80's left a lot to be desired - in many areas. We've moved on, but the stories plague those that have not kept up and circulate still. Story of the world. . . Truth is, we've done pretty well since the mid to late '90's
As to trajectory. . .they're pistol rounds. The trajectory is going to suck. Period. Paragraph. Under a hundred yards, the differences in flight path between the weights of 9mm slugs will be effectively academic. Beyond 100 yards they will all be mortars. Best not to see a sand wedge as a driver.
"Nothing is safe from stupid." - Zee