AR-15 build info.

Russ D · Jan 28, 2010

My rails look like a Magpul abortion, but I kind of like it that way. I use all types of ladders and panels but they all get covered. My main function is comfort. I like the full textured panels on the bottom, rail covers on the top and panels on the sides.

strube · Feb 6, 2010

I have a silly question... For flat-top uppers that have a standard a2 front sight post - won't the front sight interfere with an optics setup ala red-dot or other scope? Are these just designed for iron sites or are they expecting most people to change the gas block? Also, would a low profile block work or look funny if it doesn't have a free-float rail that covers it?

mayor_quimby · Feb 6, 2010

strube said:
I have a silly question... For flat-top uppers that have a standard a2 front sight post - won't the front sight interfere with an optics setup ala red-dot or other scope??

If your talking eotech or aim point people zero in the red dot to the front sight. If your talking like for me and my Acog I don't even see the front sight its a small blur.

Apone · Feb 6, 2010

Quimby is right on. Also - you can put a low profile gas block on a rifle, even if the rails don't cover it. I've seen plenty of them. The purpose of a low profile gas block is to fit under a rail system, though.

erwos · Feb 8, 2010

strube said:
I have a silly question... For flat-top uppers that have a standard a2 front sight post - won't the front sight interfere with an optics setup ala red-dot or other scope? Are these just designed for iron sites or are they expecting most people to change the gas block? Also, would a low profile block work or look funny if it doesn't have a free-float rail that covers it?

To echo quimby, what you're "supposed" to do is buy a rear backup iron sight and use the iron sights to co-witness with your red dot sight. If you've got it sighted in correctly, the red dot will line up on the tip of front sight when looking through the rear sight.

You can buy gas blocks with rails on them, which will remove the weirdness of standard handguards if you're planning on going without iron sights completely (which might be perfectly fine on a range gun). Brownells even makes a modular kit, which seems pretty nice (albeit perhaps a bit expensive):
http://www.youtube.com/watch?v=3Ks0zUdq51Q

Boondock Saint · Feb 16, 2010

Quick inquiry on twist rates. I know that faster twist rates are good for longer projectiles (which are usually heavier). Is a 1:7 twist rate too much for the lighter 55g stuff?

Solve for X, Y and Z, please.

1:9 - good for X-Y gr
1:8 - good for Y-Z gr
1:7 - good for Z gr and heavier

mayor_quimby · Feb 16, 2010

maybe something like this :

Boondock Saint said:
Solve for X, Y and Z, please.

1:9 - good for Remington/ PMC Bronze/Brown Bear/Wolf 55gr
1:8 - good for Privi Match 69 gr Boat Tail Match
1:7 - good for Hornaday BTHP Match 75 gr / Privi Match HP 75gr/ your own load

edit didnt answer the question....

you trying to buy/build a competition barrel ? The best answer from my reading is this .....

I also vote for the 7 twist over the 9 twist. The most common of the bullets people shoot are the 55 grain ones, and they'll both shoot them fine, but the 7 twist will allow you to shoot the 70+ grain stuff that the 9 twist most likely won't stabilize.

Boondock Saint · Feb 16, 2010

I've heard that 1:7 rates will end up destabilizing the lighter stuff past 100 yards, but I have no idea if it's true. It's more of a plinker/carbine than a precision gun, but I'd like the option to shoot heavier stuff if 55gr will perform out to 200 yards.

mayor_quimby · Feb 16, 2010

^ thats what I have read... I shot 62 gr privi out of my 1:9 mid length to 200 yards. I was using an AGOC @ 100 I was dead on , took 3 shots at 200 and hit the tip of the target then got lazy to run out again and make adjustments since I didn't have a spotting scope.

smokey · Feb 16, 2010

mayor_quimby said:
^ thats what I have read... I shot 62 gr privi out of my 1:9 mid length to 200 yards. I was using an AGOC @ 100 I was dead on , took 3 shots at 200 and hit the tip of the target then got lazy to run out again and make adjustments since I didn't have a spotting scope.

use a 50 yd zero

at 100 it's about 1.5" high and at 200 it's about .7" high......soo you'll hit about the same place at both distances

mayor_quimby · Feb 16, 2010

I could have rushed the 3 shots just to see if I could get a hit that far. Because I had a 100 yard zero so in this case I should have shot low but in reality shot high

I also like to use this website :

http://www.norma.cc/default.asp?Lang=2

Top right hand corner click ballistic and use the US one this also help with height of sight line

Ab_Normal · Feb 16, 2010

Boondock Saint said:
I've heard that 1:7 rates will end up destabilizing the lighter stuff past 100 yards, but I have no idea if it's true. It's more of a plinker/carbine than a precision gun, but I'd like the option to shoot heavier stuff if 55gr will perform out to 200 yards.

I read somewhere that the lighter faster bullets (40gr) will sometimes just blow up from the faster twist barrel due to very high spin rates and very thin jackets. Blow up outside of the barrel in mid air on the way to the target to be clear. I have never experienced it nor do i know of anyone who has. YMMV

smokey · Feb 16, 2010

mayor_quimby said:
I could have rushed the 3 shots just to see if I could get a hit that far. Because I had a 100 yard zero so in this case I should have shot low but in reality shot high

I also like to use this website :

http://www.norma.cc/default.asp?Lang=2

Top right hand corner click ballistic and use the US one this also help with height of sight line

cool quimby. i'm diggin the program. thanks :thumbsup:

mayor_quimby · Feb 16, 2010

^ no problem .. also so others know its not just for .223 ammo

Boondock Saint · Feb 16, 2010

Smokey thanks for that picture. That data was taken from a 1:7 twist using a 55gr boolit, and satisfies my question. Who published that?

smokey · Feb 16, 2010

Boondock Saint said:
Smokey thanks for that picture. That data was taken from a 1:7 twist using a 55gr boolit, and satisfies my question. Who published that?

i basically google'd "50 yd zero" and it was one of the better charts i saw. i pulled it off the discussion here...
http://forums.officer.com/showthread.php?t=92589

buzzzyy · Apr 14, 2010

Just ran across this nice schematic on DSAs website.

http://www.dsarms.com/pdf/AR15-SchematicPDF.pdf

might help someone build an AR

MauiWowie · Apr 27, 2010

How did it take me this long to finally see this post?
wow great stuff!

Boondock Saint · Apr 28, 2010

MauiWowie said:
How did it take me this long to finally see this post?
wow great stuff!

I could be wrong, but I think I linked you to this thread when you opened your "I want an AR" thread. :innocent0

JavaDan · Apr 29, 2010

buzzzyy said:
Just ran across this nice schematic on DSAs website.

http://www.dsarms.com/pdf/AR15-SchematicPDF.pdf

might help someone build an AR

I'm waiting for my parts to build my first AR (an M4 middy), mostly from Spikes. I don't know if that diagram will help me build it, but it sure is cool. I might hang it on the wall.

Thanks for sharing it.

AR-15 build info.

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