Critique my AR-15 plan


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dm1333
December 30, 2006, 04:45 AM
Upper: CMMG 18" flat top with rifle length system, or
CMMG 16" flat top with mid length gas system

I want the longer gas systems because of the longer sight radius and the softer recoil. Why beat up the gun with a carbine gas system?

Lower: Stag
DPMS

Stock: ACE SOCOM or ACE Skeleton

Handguard: Free float tube from Yankee Hill or Medesha, or Daniel Defense if I hit the lottery. Whatever comes with the CMMG upper if I am still poor.

Sights: Standard front sight, Flip up rear iron (way too many to pick one right now)

Optics/Accessories: Flash light with pressure switch. Simple nylon sling. The float tube will allow me to mount a scout scope or Aimpoint in the future if I decide I want one.

Flash hider: Vortex. Since I won't be doing much crawling around in the woods I don't really need to worry about anything snagging on the flash hider.

The goal of this weapon is reliability,simplicity, light weight and accuracy. I'm really thinking of the 16" bbl, the lightest aluminum float tube I can find, and the lighter of the two stocks listed above. If anyone has an idea of how much this rig will weigh let me know. If a simple set of handguards such as DPMS Glacier Guards would be lighter than the float tube then I would go with the handguards. If the weights are equal I want the float tube for accuracy and the ability to mount a scope or optic in the future. If I can get the CMMG upper with a fluted barrel I would go for it because of the lighter weight and increased cooling.

Please feel free to shoot my plan full of holes or tell me what you think I really need. I'm a beginner at building an AR15 and still in the process of educating myself so any input is welcome. I'm planning on starting my purchasing in the next month or two.

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Zeke Menuar
December 30, 2006, 05:42 AM
Another AR-15 Noob here.

I joined AR15.com. Bought a membership to get access to the search engine and archives. I have spent days there researching.

So far.

My gun will be a K.I.S.S. gun.

Bought a Stag lower w/A2 stock from a AR15 board vendor for $235 shipped.

FWIW. If you buy the lower and upper separately, you can save a few bucks.

Got in on a mag group buy. Bought a few 30 rounders. Teflon w/magpul followers.

I'm limited to whatever my tax refund is.

Plan A is a CMMG upper, 20" govt profile barrel. Standard A2 front sight. Removable carry handle. This will run about $630+shipping. I'm only going this route is they have the upper in stock.

If plan A isn't in stock
CMMG 18" mid length.

If my budget is limited:
Stag 20" govt profile complete upper with either removable carry handle or A.R.M.S. #40 BUIS $530 shipped.

After I get all the tools, I'll add a Clark carbon fiber FF tube. No plans to hang a bunch of stuff off the gun.

If you want a softer shooter. CMMG offers both the 16" and 18" barreled uppers with rifle length gas systems.

I hate waiting for tax refunds.

ZM

Don't Tread On Me
December 30, 2006, 06:27 AM
Random thoughts:

Is it ok to have an 18" barrel with a rifle length gas system? Is there enough dwell-time with the shorter barrel length after gas port? Anything shorter than 20" I'd rather go mid-length gas system. Dissipator style ARs have a front sight base out front that is just used as a sight post, while under the handguards there's a low-profile gas block.

Vortex is definitely nice. But, for $25 less, you can get the Phantom which does just as well at suppressing flash.

The lightest FF tube is the Clark/DPMS carbon fiber tubes. Problem is, it doesn't allow you to mount anything. Also, the inside is plastic, with a carbon fiber outer.

I think PRI makes a carbon fiber FF tube that has rails mounted to it. It is light and useful, but it is very expensive.

For aluminum FF tubes with rails, Daniel Defense is the lightest IIRC. Troy is nice because it installs without the need to remove the barrel nut. For the kind of gadgets dm1333 plans to attach, the DD is the best choice if you want lightweight, FF and rails. You can get FF'ing and rails for much less money, but it won't be lightweight.

I don't think fluted barrels cool any faster. I doubt the insignificant increase in surface area makes a practical difference. Now, it does lower weight, less mass to retain heat. Lighter the barrel, the faster it will heat, the faster it will cool.

I'm a fan of the lightest possible barrel. When it comes to service-grade, 5.56 chamber barrels - there's no difference between a govt profile, superlight, HBAR, or anything else. They're all equally accurate. To get a real increase in accuracy, you must get a match grade barrel. There are some hybrids, barrels that are not match grade due to the rifling and such, but have tighter chambers which do increase accuracy. Since the non-match barrel profiles are all the same, get the lightest option and save the weight for the gym.

nipprdog
December 30, 2006, 06:29 AM
Why beat up the gun with a carbine gas system?

:confused: :confused:

never heard that one before. please explain.

Don't Tread On Me
December 30, 2006, 06:48 AM
Carbine length gas systems are harder on the bolt than the system was originally designed for. This is because it is shorter and the gas port receives gas at an earlier point in the firing of a cartridge - when it is at a higher pressure.

Bolt lugs, cam pin holes, cam pins and extractors fail (typically) at a lower round count than a rifle length gas system.

We're talking say, 8,500rds vs. 15,000rds for example. When talking about reliability, you can only speak in generalities, as examples exist that last significantly longer, and examples exist that fail much earlier.

In my opinion, if you use an M16 carrier (a touch heavier than the AR carrier) and an H-buffer...you should be good to go, and the fear of a "beat up" AR is almost irrational if you look at the big picture of AR ownership. The cost of a new bolt ($60) is nothing in comparison to the money spent buying 8,000rds.


If you're buying new, the mid-length is a good choice. It is technically better choice than a carbine length system. It borders on nitpicking, but I'd do it. If you have a carbine system now, there's no reason to switch. The mid-length is in effect, a solution to a problem that barely exists.

Chris Rhines
December 30, 2006, 07:07 AM
CMMG uppers are as close to dead-on Mil-Spec as I can tell with a visual inspection. Very good choice.

An 18" barrel with the full-length gas system will work fine. You need at least 3" of dwell to guarentee function with normal SAMMI-spec ammunition, and 18" barrel with a rifle gas system has 4.7" of dwell. No problem.

I have a Yankee Hill float tube and don't care for it - too large. A better choice is a JP/VTAC float tube with a few pieces of M1913 rail placed exactly where you want them. Super high quality, too. Runs ~150USD from JP.

Consider a fixed rear sight if money is tight. The LaRue is nice.

To the best of my knowledge CMMG does not make fluted barrels. They do make 0.625" dia. pencil barrels, and those are really light. Give them a call. A 16" midlength pencil barrel with iron sights and a JP handguard would come in at well under 7 pounds.

- Chris

Nhsport
December 30, 2006, 10:00 AM
The true beauty of an AR is you can make it any way you want for whatever reason.
For the first time buyer of a all purpose gun I question the FF tube? Adds lots of expence,I would think this money might be better spent on optics or other stuff. A well built AR is in itself a very accurate weapon and the FF will really only come into play with a competition sling at longer ranges.There are many guys out there that used to compete at service rifle matches with regular handguards and did very well. This was before the FF became THE thing to have.
For a first gun the flatop is the way to go unless you are just shooting service rifle or are dead set on the "retro" thing. (again-whatever floats your boat).I myself like the regular clamp on carry handle sight. Many of the flip ups seem to be a compromise in one way or another,the beter ones are of course expensive.
In my book a must have for any AR is a Ceiner rimfire conversion. This goody allows lots of cheep shooting indoors or out (most indoor ranges will not allow 5.56 but the rimfire is ok)

Bartholomew Roberts
December 30, 2006, 11:55 AM
Looks like a good set of choices overall... Zak_Smith has been running a 17" barrel with rifle length gas, so 18" should be good to go. I have seen problems with the 16" running rifle length gas. They act a lot like the 10.5" shorties (not enough dwell time). Some people are able to make them run; but at 16", I like a midlength gas system better.

Only other comment I would make is that I am not a huge fan of the ACE stocks personally; but that is mostly personal preference. I would just encourage you to consider using the heavier stock instead of the lighter one. I find that a rifle with good balance is worth a few extra ounces. In an AR, almost half the weight is in the barrel, so having a little more weight aft can help to balance the rifle better and leave it feeling less nose-heavy.

Zeke Menuar
December 30, 2006, 12:38 PM
The lightest FF tube is the Clark/DPMS carbon fiber tubes. Problem is, it doesn't allow you to mount anything. Also, the inside is plastic, with a carbon fiber outer.


I'll have to get reviews of the Clark FF tube to see how it works in the real world. There are a couple other carbon fiber tubes out there. Hyperform comes to mind.

The PRI tube too expensive. I can't justify a $300 tube. At least with the Clark tube I can have the machine shop guy across the street drill the holes for a 3" rail. Rifle length aluminum tubes are too heavy.

My reasons for a tube is: Accuracy.
Next, AR's with rails bristling out all over are just plain ugly. I can't stand the tacticool look on an AR. I'll concede a small flashlight, I'm going that route myself. But nothing else. I like the sleek simple look. That's my personal preference.
Won't make a decision until I get my upper and put a few hundred rounds downrange. It may shoot well enough to not need free-floating.

ZM

nipprdog
December 30, 2006, 02:50 PM
Carbine length gas systems are harder on the bolt than the system was originally designed for. This is because it is shorter and the gas port receives gas at an earlier point in the firing of a cartridge - when it is at a higher pressure.

Bolt lugs, cam pin holes, cam pins and extractors fail (typically) at a lower round count than a rifle length gas system.

We're talking say, 8,500rds vs. 15,000rds for example. When talking about reliability, you can only speak in generalities, as examples exist that last significantly longer, and examples exist that fail much earlier.

In my opinion, if you use an M16 carrier (a touch heavier than the AR carrier) and an H-buffer...you should be good to go, and the fear of a "beat up" AR is almost irrational if you look at the big picture of AR ownership. The cost of a new bolt ($60) is nothing in comparison to the money spent buying 8,000rds.


If you're buying new, the mid-length is a good choice. It is technically better choice than a carbine length system. It borders on nitpicking, but I'd do it. If you have a carbine system now, there's no reason to switch. The mid-length is in effect, a solution to a problem that barely exists.

thanks for the answer

FNHP35
December 30, 2006, 03:06 PM
While I don't have one, Midwest Industries makes a free float rail system that doesn't require you to remove the fsb. The price is reasonable and I have one of their rear sights and it's well made. Worth looking into.

Andrew

dm1333
December 30, 2006, 03:18 PM
More stuff to research before I start buying. The only reason I want a FF tube is for the lighter weight and the possible increase in accuracy. I have no desire to start hanging all sorts of stuff off of the rifle. What I listed is the end result, to start with I am going to keep the handguards that come with the upper. I was set to start buying things till Onmilo posted that CMP has 1903s for sale again and that in March they are going to be sellking M1 Carbines.

I want the mid or rifle length gas system not because there is anything wrong with the carbine length but because it is a little more "right" .

I started off shooting the A1 back in the 1980s. I like the A2 but I think the A1 handled and felt better. Since this gun is for my own use I want to get that sweet handling back and keep the gun simple.

FNHP35
December 30, 2006, 04:34 PM
I doubt many, if any, of the free float AL. rails will be lighter that the standard A2 plastic handguards. DD lite rails are the lightest, but not cheap. I have a PRI free float rail, and it's nice, but probably not worth the money. PRI also makes a free float tube that doesn't have the rail mounts. That's save some weight. If you're doing alot of shooting in a short period of time, then the AL's are better, they work as a heat sink. Keeps the chamber/barrel cooler. Again, just stuff to think about.

Andrew

Zak Smith
December 30, 2006, 06:10 PM
Looks like a good plan to me. 18" with rifle gas is OK, my 17" has run great for 2 years now.

I would recommend the JP tube if you can afford it. But if you can't, do consider just getting regular A2-style handguards and saving up $$ for a good tube later (this means LaRue if you want rails, or PRI if you want light/sleek). Unless you're shooting from a bench or bipod, you probably won't notice it for "practical shooting".

On the FH, consider just an A2. The Vortex does work really well at flash suppression, but it "rings" and is longer and more expensive than the A2. I run an A2 on my 12" SBR and it's not a big deal.

On the barrel, no need to spend money on fluting. Just get a profile that gives the weight you want. Between 0.70 and 0.75" under the handguards produces a nice balance and light weight.

I agree on the dislike of the ACE stock.. my preference is a Magpul CTR or M93, or just a fixed A1 for a fixed stock.

blackhawk2000
December 30, 2006, 07:15 PM
What's the issue with the ACE stock? I was leaning towards the SOCOM, or the new Magpul.

Zak Smith
December 30, 2006, 07:17 PM
Nothing wrong with it-- just preference.

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