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View Full Version : upper receiver, barrel profile, and crown ?'s for my 1st lightweight 223 upper build


steve_77
06-25-2010, 3:41 PM
Granted this is my first "upper" build and im more into target shooting and hunting with "crowned" bolt action rifles barrels i have a few questions:

1)
I was looking to build a lightweight .223 for hunting - and was initially looking at the bushmaster carbon fiber uppers but have since decided against that route and am only considering metal uppers (aluminum or otherwise) - was curious i know alot of people have rated the forward assist as a kind of useless item - was wondering about the need for a forward assist as well as the brass deflector and dust cover was looking at something like this :
http://www.parts4ar15.com/ar-15_accessories/product/FTT-LP.html
but wanted to get some feedback - ive shot my other AR quite a bit and dont recall ever seeing the brass deflector 'dinged' up from use 末- guess i was looking for some advice on how to proceed for a minimalist yet reliable lightweight build (the only thing i DONT have is the upper receiver) I have all the other parts..... and FYI plan on using this upper with one of those ACE entry stocks... perhaps that puts my face too close to the ejection port and so i should definitely not rule out the brass deflector yet.

2)
Second question comes to barrel profiling: the M4 barrel on the muzzle end in front of the gas port there is a approx 1" "U" shaped notch 末 is this for the bayonet ? why does it get really skinny from .720 near the gasblock to .610" (bottom of U shaped notch" then back to .720 then an inch or so near the buzzle back down t0 .700 to the threaded muzzle at .595 or so .... whats up with that 末 why not make it .720 for the gas block and .610 all the way to the muzzle 末 what is the purpose of it getting thicker again?

3)
i already stated that i have a treaded barrel - is there a way to have this threaded portion have a proper crown ? Im in CA and cant have flash hider and cant stand loud muzzle brakes 末- so for now have knurled nut on the end - but there is no "crown" - can i get one cut into the threaded portion or will the threads need to come off entirely for a good crown? is there a problem if is its not crowned? Im used to hunting rifles with a target crown - what can i expect from this barrel without a crown?

audiopro74
06-25-2010, 7:16 PM
No help on the first 2, howevr I have read that a 11* crown is optimal for accuracy. Any more, or less is said to destabilize the air behind the projectile in ways that are not conducive to accuracy. Check them out. They offer some nice stuff. I should be recieving my upper from them in a few months.

hnoppenberger
06-25-2010, 7:31 PM
1) brass deflectors DO work. totally different without it. ejects directly back.
the only thing that would be nice for hunting is a dust cover. it is important IMO. brass deflector, eh- if your ok with it ejecting directly back, then its no big deal. forward assist- not needed. your only hunting, no need to slam a good bullet home. if its dirty clean it.
BUT its cheap enough to just get a basic a4 upper from CMT to build on. its not very heavy at all with a pencil profile barrel. you would only save a couple ounces running a slick sided upper.

2) M4 barrels have a m203 notch. this is to adapt the nade launcher.

3) you can run a regular target crown, which is available from model 1 sales. however, in pencil profile, it may only come threaded, check. I personally would not run less than a gov't profile barrel due to possible damage and warping from field use. keep in mind, using a flash hider will not reduce accuracy at all with the setup you have in mind. and it may only produce at best 1.5-2" groups at 100 because of light barrel, no freefloating.


-honestly, my hunting buddy runs a 16" bull barrel upper from DPMS with a free float tube, and the thing is STILL lighter than my 20" remington SPS tactical, both weapons used for predator hunting.
-that 16" bull barreled upper groups almost as good as my SPS- we are talking well under 1moa next to my SPS which is anywhere from .25-.50 MOA with match loads.

for a hunting gun, you can run a 16" medium or heavy profile, which is both considerably lighter than "bull" (basically extra heavy). your going to want to run a free float tube. its free accuracy at the cost of maybe a half pound.
my basic STAG 4h heavy barrel upper'd gun went from 1.5" groups with a scope to .75" groups with just a badger free float tube. the 2 stage trigger got it even tighter. this is running a vortex flash hider which supposedly also improves accuracy (certainly does not hurt it.)

I have not seen anything to be gained with a regular crown, as long as you dont over torque the flash hider. i would consider a muzzle break as well to help maintain sight on target through the scope at long range. keep in mind a lighter gun will recoil more.

-MY ADVICE. tough up. a 6-8 pound 16" hbar or medcon ar-15 should be no problem to hike around with for an adult male. I am no OPERATOR and I carried a mauser 98 with a large scope through the forest up north for a whole weekend. (11 pounds loaded) invest in a good sling.

hnoppenberger
06-25-2010, 7:37 PM
also, assuming you read the laws posted here, you should have no issues running a flash hider unless running a U-15 stock or otherwise. but a muzzle brake if not hunting at night has some serious advantages as well. again, advice is to nut up.

if your barrel is threaded, then your only option would be have a smith cut the treads and crown it, if you were looking for that micro amount of lost accuracy.
the most important part of the end of the barrel is that its not messed up, it just needs to be consistant. -but assuming your not running a freefloat tube, throw any amount of group improvement out the window with a good target crown. you will also be limited by the profile of the barrel- Im assuming its a m4 profile? which would be acceptable for hunting at the lightest- much better than pencil.

i guess it comes down to what you need- how tight does the thing need to shoot? big difference hunting ground squirrels or prarie dogs at 3-400 yards or iron sighting pigs close up...

personally, i want the gun to be as accurate as possible. I am no crack shot, especially under pressure but it would kill me to know i may have made the shot if I would have a better weapon system- especially for little extra money.

bjl333
06-26-2010, 2:05 AM
Some of the materials from this thread might help you a little bit. This was a discussion about building a super light weight AR. Again some of the material will be for you but not all.
http://www.calguns.net/calgunforum/showthread.php?t=313707

EDIT: You had mention you wanna use the ACE Entry, why dont you wanna look into the ACE Skeleton Stock. It is longer and still very light. Just a thought .....

Paradiddle
06-26-2010, 8:14 AM
I would PM AR15barrels and have him work up an upper for you. He can profile the barrel any way you want, he is local (LA) and his prices are very fair.

www.ar15barrels.com

You could also just buy a used Remington RL15 and be done with it. I think there is one in the for sale forum now. Or a Stag hunter, or RRA light coyote, or whatever pre-setup hunting rig the other vendors have.

Jeff

hnoppenberger
06-26-2010, 9:58 AM
+1 on the r15. they are a nice setup. ditto on what i've heard about the RRA light yote- good blends of lightwieght with accuracy.

steve_77
06-28-2010, 2:00 PM
cool guys, thanks for all the tips - now i know that notch and how its for the 203 GL mount, and as for the other features (brass deflector etc..) - ill just end up getting a A3 receiver (keep it simple), guess my main concern now is the crown issue - I'lll hit up ar15barrels to see if the barrel can be crowned with a thread protector in place.

Id ask him to make me a custom barrel but like the fact the the lightweight barrel i have is chrome lined and 1:7 twist (which he apparently doesn't offer) - as plan on using 69/70 gn bullets... thought the chrome lined part would also help with heat issues on the small dia barrel.

Looked at the ace skeleton stock but technically a "ca thumbhole" , but will check out the post bjl333 was kind enough to suggest.