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AR-15 build...need help with barrel.

Vitorum

Vitorum

Sergeant
Full Member
Minuteman
Dec 26, 2010
408
2
36
TN
#1
Hey guys what's up. Working on an ar 15 build with an Ops-4 ambi upper receiver and Ax556 lower receiver. I've found the barrel and forend that I want but I'm a little confused about some things. I'm going with this barrel:
http://www.midwayusa.com/viewProduct/?productNumber=794051

Now I'm confused on the barrel specs. It is a 1 in 8" twist rate. What is the difference between that and a 1 in 9" twist rate? I'm guessing increased velocity and accuracy of the bullet with the 1 in 8 over the 1 in 9?


and this handguard:
http://www.mountsplus.com/AR-15_Accessories/AR-15_Scope_Rings/SMC-EVO-RAIL-9EX.html

Can this gas block be used with the setup I have in mind here and will have a high enough profile to run flush with the forend top rail?
http://www.parts4ar15.com/ar-15_accessories/product/GS-JP-A.html
What additonal parts do I need for the gas tube setup? Obviously the gas tube itself...
http://www.blackweaponsarmory.com/ar-15-gas-tube-mid-length.html


Also need to know what to do about a barrel nut and a handguard endcap. Or do I even need an end cap with this setup?


Sorry about all the questions guys. This is my first time doing this and I've done all the research I can up to this point. Please assist if you are willing. Thanks a ton.
smile.gif
 
#3
Re: AR-15 build...need help with barrel.

The 1/8 twist is a compromise between the 1/7 mil-spec barrels and the 1/9 commercial barrels. The idea is that it will be more flexible than 1/7 with a wider range of bullet weights. But it will be faster than the 1/9 so that it can shoot heavier weight bullets better. Some 1/9 don't perfrom well with the heavy weight 5.56 rounds (mainly the 77grn stuff).

The Samson handguard will not need a cap and <span style="text-decoration: line-through">will come with a barrel nut</span> uses a standard AR barrel nut. Just get a standard barrel nut and torque it down correctly. I personally have not be happy with the support I have recieved from Samson after the sale. Samson has been horrible in my experience in support of their products. On the other hand, Troy makes a very similar product and does back their stuff without questions. I have lost some bolts for their handguards and inquired to replacement cost. Troy just ask for my address and I recieve them at no cost 3-4 days later.

As for an adjustable gas block, take a look at the Paladin Machine 3-way gas block. It is made for suppressed shooting, but they will custom make them to your needs. They come with a 3-way adjustable setting: full on, partial on (for suppressed shooting) & full off. They will do it to any size you want. Full on functions like a normal gun. Partial on barely ejects brass without a suppressor. Full off makes it into a single shot. It is also only $70 or so shipped. I had one on a 6.5 Grendel build and absolutely loved it. I really need to get one for my 18" 5.56 build.

The JP Rifles adjustable gas block uses an allen head bolt. It can be fine tuned, but it can also slip out of adjustment if you don't put thread locker on it. It isn't a bad gas block, I just like the lever over the allen head bolt.
 
#4
Re: AR-15 build...need help with barrel.

1:8 Twist rate stabilizes heavier bullets better than 1:9, typically. Should shoot a variety of weights from 55-77 grain. Looks like your setup should work. May want to get specs on the block to make sure it is level with the rail on the HG. The hg looks like it uses a standard AR barrel nut.
 
#6
Re: AR-15 build...need help with barrel.

Xris, you are doing the right thing asking plenty of questions, could I ask why you are running an adjustable gas block, are you going to mount a suppressor in the future. Also I personally think and its just my opinion that theres better options out there than the forend mentioned. The 1/8 twist should digest the heavies just fine and allow the compromise of running some lighter weight bullets. Good luck with your build.
 
#7
Re: AR-15 build...need help with barrel.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: mjh</div><div class="ubbcode-body">Xris, you are doing the right thing asking plenty of questions, could I ask why you are running an adjustable gas block, are you going to mount a suppressor in the future. Also I personally think and its just my opinion that theres better options out there than the forend mentioned. The 1/8 twist should digest the heavies just fine and allow the compromise of running some lighter weight bullets. Good luck with your build. </div></div>

Yes about your question concerning the adjustable block.
Are there any other forends out there that are very close to what I have in mind? And thanks.
 
#8
Re: AR-15 build...need help with barrel.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: yellowcarbon</div><div class="ubbcode-body">Sorry, the Samson does clamp on to the standard barrel nut. I corrected my post. </div></div>

It's cool. Thanks.
 
#9
Re: AR-15 build...need help with barrel.

I really love that forend. Ive been looking for months for one that I like. Does anyone know where I can find one extremely close to this one because I absolutely love it.
 
#11
Re: AR-15 build...need help with barrel.

This barrel with rifle gas and m4 ramps

http://www.rainierarms.com/?page=shop/detail&product_id=449

This handguard should offer you the same functionality

http://www.rainierarms.com/?page=shop/detail&product_id=1710

Maybe this too

http://www.jsesurplus.com/midwestindustries-2.aspx

Gas block is your choice (get a clamping one imo) and of course you'll need a gas tube and gas tube roll pin. If you haven't bought your bolt carrier group yet get it from the same place as your barrel and have them check headspace prior to shipping.
 
#12
Re: AR-15 build...need help with barrel.

The lower the twist rate, the heavier bullet you can shoot. My upper is a 1 in 7 and I use at least a 62 gr.
The rail that you are looking at appears to be made for a combination gas block/front sight. That is the reason for the cut out in the front.
If your gonna add a front sight to that gas block you have pictured, it should work fine.
You could go with just a low profile block and get a rail that simply extends over the block. Then you could add a front sight to the rail itself.
I simply cut the front sight off of mine, and then sanded and refinished the gas block. Then ordered a 9 in rail that extends over the block. Looks pretty clean.
The AR platform is very versatile. You can do so many things with all the different products available out there.
 
#13
Re: AR-15 build...need help with barrel.

Those forends you guys found are pretty nice. But can I run full quad picatinny rails on it if I so choose?
 
#14
Re: AR-15 build...need help with barrel.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Xris</div><div class="ubbcode-body">Those forends you guys found are pretty nice. But can I run full quad picatinny rails on it if I so choose? </div></div>

If you want 4 full rails you are better off buying a quad rail foreend and then putting some rail covers on it to protect your little fingers but you don't need it. Those forearms I linked have removable extra sections (you can purchase more) to allow you to mount whatever you want, whereever you want it. Most people just have a bipod/foregrip and maybe a flip up front sight, if that.
 
#16
Re: AR-15 build...need help with barrel.

Xris, have had a JP adjustable block for many years a top quailty product. BCP makes some very good suggestions with both a quality company like Rainer Arms and a top notch barrel from WOA. I run a rifle lenght smooth forend from YHM on my 18inch upper, it meets my needs. Heres a pic, to give you some idea what I mean.
IMG_0853.jpg
 
#17
Re: AR-15 build...need help with barrel.

^ Sexy! lol I was just checking out that same forend. I actually really like it. Can you by chance remove those front 2.5 inch rails?
 
#19
Re: AR-15 build...need help with barrel.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: mjh</div><div class="ubbcode-body">Xris, unfortunately no, but at least they serve a purpose, I am using three out of the four, bipod, sling and front sight (although not pictured). </div></div>

O well still looks cool. Somone mentioned to get a forarm that already had rails on it that I could remove. I would like that but who make a good one?
 
#22
Re: AR-15 build...need help with barrel.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: TheOneTwo</div><div class="ubbcode-body">Just an FYI, those spectors are really noisy. Anything touches it and it makes a ding noise. I did not care for mine at all. </div></div>

Interesting...O well it's fine with me. Thanks for telling me though I would have never guessed.
 
#24
Re: AR-15 build...need help with barrel.

TheOneTwo, thats actually good to know, I thought about buying the Specter but went with the smooth freefloat instead. Funny I don't find my rail noisy at all, actually it pretty solid and theres no tiny noise, even if I bang metal againist. Perhaps since I KG coated it that helped reduce the noise, but overall its a pretty solid piece of metal.
 
#25
Re: AR-15 build...need help with barrel.

I want be able to remove all rails and add ones where I need them or even four full lengths rails if I so choose. I just don't want one with a lot of circular holes in it like the troy forend. I Love the way the spector is configured but if what TheOnetwo say it's its loud than I don't know if I want it. Is it loud when you shoot or just bump metal against it?
 
#27
Re: AR-15 build...need help with barrel.

"FailZero BCG, Magpul furniture, and ATI 15" Free Float Forend"

Caption on second picture. Also has a few links further down where you can buy the stuff he used in the build.
 
#28
Re: AR-15 build...need help with barrel.

Ok so ATI makes it. But I can't find a midlength. They only seem to have a carbine length and rifle length.
 
#29
Re: AR-15 build...need help with barrel.

I did not notice it being real load when shooting, but when stuff hit into it. Metal, plastic, any thing a little hard and it lets off a nice ding sound.

Also it does not have any kind of anti rotation bolts in it. So it can move on you with much torque. So don't plan on mounting a front sight on the rail itself or anything else that needs to stay tight.
 
#30
Re: AR-15 build...need help with barrel.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: TheOneTwo</div><div class="ubbcode-body">I did not notice it being real load when shooting, but when stuff hit into it. Metal, plastic, any thing a little hard and it lets off a nice ding sound.

Also it does not have any kind of anti rotation bolts in it. So it can move on you with much torque. So don't plan on mounting a front sight on the rail itself or anything else that needs to stay tight. </div></div>

Well in that case I'm going to have to choose the lesser of to evils imo. So I'm going with the samson Evo 9-ex. It's so sexy. I really wish I could somehow put this ati Cap on it though. This thing is bad ass!
http://www.opticsplanet.net/advanced-technologies-ar-15-forend-nose-cone.html.
I wonder if I got the regualar mid-length samson evolution forend if I could manipulate it to fit. Even if it doesn't exactly fit and the diameter is the same I could totally custom fit it. and let the gas tube pass through it using an exposed gas block. Or maybe I could get my gunsmith to cut that ATI forend to 9in. Then fit the ATI cap on the end of it. It shouldn't be that hard but I think even I could do it if I had enough patience and a steady hand.
 
#31
Re: AR-15 build...need help with barrel.

Have any of you ever messed around with the brownells AR-15 digital build. It's pretty sweet. This isn't why I intend my rifle to look like at all but I build what I liked the most from there selection. lol for some reason the bolt carrier group wont appear inside the upper receiver. It's behind it for some reason.

Mybrownellsar15build.png
 
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