Input on my AR build

I'm a noob so I gotta ask why. I want the least amount of rail to reduce weight and I don't need that much rail space.

So even with 9" being the standard length for mid lengths, it has to e at least eleven inches to cover the gas block, not the ten?

Cause in the first pic above it looks like the ten inch would cover it perfectly.

Thanks for helping me out on this.

 

longer handguard so you can get your hand out there to steer the rifle....

I'd actually run a 13" on a 16" gun But that's my preference. Watch how these guys shoot:

http://www.youtube.com/watch?v=LJQTpTljLz8

But yes, the 10 would cover the gas block, They only make a couple troys in the 10"... I'd go for something like this:

http://troyind.com/ /rail-systemsac...ree-float-rails/troy-alpha-rail-11-with-sight

or

http://troyind.com/ /rail-systemsac...e-float-rails/troy-alpha-rail®-13″-with-sight

 

I think one of the biggest mistakes people make with AR builds is to not consider the sights they will run. Are you going to run a QUALITY optic on this gun? Aimpoint/EOTech/ACOG or quality scope? If so, then proceed with your flip-ups on a free-float barrel. If you're going to run a crappy optic that is going to take a crap on you, or if you plan to run no optic, then skip the extended rail and run a PINNED fixed A2 front sight and a quality fixed rear sight.

I see a ton of new AR buyers/builders who want a tacticool extended tube and then put crappy flip-up sights on it, and then run irons because they can't afford or don't think they need a quality optic. If you think about how many variables you're adding to your sights with flip-ups...the fact that they're separated from the barrel, the fact that you're putting pressure on the handguard when using a rest or barricade which may change the position of the sight in relation to the barrel, the fact that there is "slop" in even the best folding sights when you flip them up and down...it makes zero sense to run flip-ups on a handguard unless you really need them. I'll take fixed irons in an AR over an el-cheapo red dot any day.

 

+1 Having your hand extended helps drive the weapon between targets. that holding the magwell nonsense is for airsofters.

this is a 13" troy extreme on 16" barrel.



and this is a 15" troy vtac on the same 16" barrel. this is how I currently run my weapon. I run my stock slightly collapsed so I am not overextended. but I have found that this works best for ME. but honestly I think a 12"-13" is a good start.



shitty pics sorry

 

For a good guide to show comparisons of barrel/gas system/rail lengths, there's a chart on LaRue's site...




His 12" barrel is a carbine gas system. The 16" and 18" are midlength.
A 9" rail will cover a carbine gas system, 11" will cover a midlength, and it takes 13.2" to cover a rifle length gas system.

Upper limit, you can go as much as 1" shorter than the barrel, but personally I'd go no longer than 2" shorter.

 

Andrew, 1:7 twist might be great for Higher velocity rounds and heavier bullets like 62gr. or even 64gr. most plinking ammo how ever is 55gr. and you wont get the same accuracy from a 1:7 with 55gr. ammo as you would with 62 or 64. just be sure to get a twist rate fitting to the use of the gun. Plus 5.56 isn't that great of a pig gun, i've tried, build a .308 in the future for that. Good Luck with the build, Looks good so far.

 

+1 on the twist.

Everyone gushes over it because it's mil-spec.
Well... mil-spec used to be 1:12 until they decided they needed a 1:7 to stabilize the heavier tracers.

Most competition barrels are 1:8 and are running in the 65gr range.
1:8 is okay, but it's a little hot for 55gr. 1:7 really is too hot for 55gr, but it's still tolerable... it's just not ideal, and I've seen more than a few photos of targets that look like they were hit with a shotgun from a single 55gr round... the jacket "spun off" and splattered the target.

Personally, my favorite is 1:9. It's a good middle range twist that will acceptably stabilize into the 65gr range, and won't overspin the 45gr rounds.

For the most part, I'm stuck with 55gr since the ranges in my area don't allow steel core during fire season, and it's really not a good idea any time out on BLM land.

Been quite a few recent fires (including the one in AZ) that are being blamed on target shooters.

 

I agree 1:9 is a better balance. I can get sub moa groups at 100yds with 62gr sierra bt HP out of my 16.75in barrel in 1:9 ruger AR

 

This is not to thread jack or to measure dick length here

MY EXPERIENCE with my 16" 1:7, it will shoot 1-1.5 MOA at 100yds with XM193 55gr .250BC 3200MV
absolutely no keyholes.

and for hunting big game I load 77gr Sierra OTM 2800MV .372BC. Drops hogs out to 300yds with a head/neck shot placement.

I dont think I could recommend anything but 1:7. My barrel seems to shoot it all, and shoot it well.

 

Keyholing comes from understabilization.... 72gr out of a 1:12 will (likely) keyhole.

The 1:7 will stabilize the 55gr just fine, but at ranges longer than 100yds, you'll start to get an increase in spiral drift, and there is a loss of velocity which will start to hammer bullet drop at longer ranges.

 

Don't worry about spin drift under 500 yards with under 100 gr. projectiles....

 

this is my last off topic post.

a bullet which is "over stabilized" can keyhole because the over twist will stand the bullet slightly on end. however, the bullet maintains its straight trajectory. An under stabilized bullet actual tumbles and twists through the air like a poorly thrown pass and the trajectory can be unpredictable.

My groups actually maintain moa and tighten to sub moa as the targets get further. 100 out to 450yds.

and 556/223 dont have enough ass for a bullet to over stabilize and shatter the jacket unless its possibly a 36gr at 4000MV in a 1:6.5

 

Thanks for that comparison but can you explain how that ten inch rail won't cover my gas block based off above picture?

Someone on here said it would so I went ahead and ordered it this morning and it's already shipped. I understand what you guys are saying about having more rail to control the rifle but I just wanted the rail to be long enough to cover the gas block and being as light as possible.

Hope the rail covers it; little nervous now.

 

You'll be fine.

 

Ruger Sr556

 

This is

the results of home made ammo and a little luck.
that's 30 rounds of custom ammo at 3 inch bull at 100yds off a bipod with an eotech.

 

I would love for someone to explain to me how this happens. Bullets track away from the center boreline in various directions and then track back in the opposite direction toward the boreline as the distance increases? Excited to hear this one.

 

X2

 

Oh rly? Here's a simple fizicks lesson so you can understand..

Go spin a quarter on a completely level surface. The quarter will spin quickly on its vertical axis, while also rotating in a gradual inward spiral until the quarter completely stabilizes on the centerline of the spiral.

Now picture this, the spinning quarter is a model of a bullet, from the shooters perspective, as it exits a barrel (as it pitches and yaws) until it completely stabilizes in flight.

Now, the bullet never leaves the trajectory "cone" (center bore line). Like I said, the moa of the group tightens, not the actual group size! So at 100yds, let's say I shoot a 1.5" group. That's 1.5 moa. At 400yds I shoot a 3" group. That's .75 moa. The group size has grown in inches but decreased in moa.

Shooting a 1.5" group at 100 and a 1" group at 400 is impossible (given no human error or atmospheric interference)

Whiskey out.

 

That's normal. This is why "How much MOA" your rifle shoots is a gun rag thing and not a gun range topic.