new lightweight AR project complete

[taliv]

aside from the fact that it is the ugliest AR i've ever built, I'm pretty happy with it.

so when i was planning it this spring, these were my calculations

6.00 oz mag tactical lower
8.55 oz regular lower
------
2.55 oz savings

4.8 oz mag tactical upper
7.15 oz regular upper (stripped)
------
2.35 oz savings


7.7 oz BCM KMR 13"
13.9 oz DD Lite rail 12.6"
------
6.2 oz savings


total savings from magnesium-aluminum alloy parts: 11.1 oz

old stuff:
--------
24.00 oz 16" lightweight BCM barrel
5.55 oz LPK
11.8 oz BCM BCG
5.6 oz H buffer and action spring
2.4 oz gas block and tube
2.9 oz ALG ACT trigger
5.0 oz mil-spec receiver extension
1.4 oz BCM CH
-------
58.65

7 oz magpul CTR with thin buttpad
=====
84.15 oz = 5 1/4 lbs total projected

I wound up using those parts except for the magpul CTR. I used the MFT Battlelink minimalist stock instead. given the rounding, it actually came out pretty close to expectation.

this is what it looked like before i added the rail and vortex flash hider


it was 5 lb 2.0 oz with everything but the flash hider.
i didn't realize how heavy that FH is. i'm going to look for something else.
in fairness, i have a few oz of lube in there as well

still 5 lb 6 oz is not bad, considering i didn't use any plastic or carbon fiber in the receivers/barrel or an aluminum bolt carrier etc.
If i wanted to spend the Titane money, that would drop 5.3oz off of it.

definitely needs an aimpoint micro T1

 

[bangswitch]

5lb 6oz is a featherweight. Upside is it will handle like a dream and you could carry it for miles; downside is felt recoil, even with a good buffer system. Have you fired it yet?


My AR 300BLK build came out at 8lb and 2 oz. I wasn't trying to save weight, my focus was on the best possible parts, and $$$ be damned.


I think your rifle looks great. Good job.

 

[Arizona_Mike]

aside from the fact that it is the ugliest AR i've ever built, I'm pretty happy with it.

so when i was planning it this spring, these were my calculations



I wound up using those parts except for the magpul CTR. I used the MFT Battlelink minimalist stock instead. given the rounding, it actually came out pretty close to expectation.

this is what it looked like before i added the rail and vortex flash hider


it was 5 lb 2.0 oz with everything but the flash hider.
i didn't realize how heavy that FH is. i'm going to look for something else.
in fairness, i have a few oz of lube in there as well

still 5 lb 6 oz is not bad, considering i didn't use any plastic or carbon fiber in the receivers/barrel or an aluminum bolt carrier etc.
If i wanted to spend the Titane money, that would drop 5.3oz off of it.

definitely needs an aimpoint micro T1

You moved more quickly than I did. I have the magnesium upper at home, a 10" KMR rail and the 14.5" fluted version of that barrel (without the handguard shoulder and fluted on the way)--may come in around 21.5 oz. I also have a plug for the "make a jam worse" button and aluminum door hardware on the way too. I'm going to run with an adjustable gas block and an empty buffer.

 

[Quentin]

Wow, 5 lbs 6 oz is impressive!

My semi-lightweight AR comes in about 13 ounces heavier. I used standard 7075-T6 receivers and a CTR stock, 9" MOE handguards, standard A2 front sight and standard A2 flash hider, which all add weight. The MBUS2 rear sight adds 1.5 oz I believe. And the H-buffer adds an ounce over a standard buffer.

My AR breaks down like this:

Daniel Defense Upper with 16" CHF pencil barrel, DD M16 BCG, A2 front sight, A2 flash hider, BCM Gunfighter Mod 4 charging handle, MOE handguards and Magpul MBUS2 rear sight = 3 lb 15.0 oz

S&W M&P-15 lower with DD LPK, BCM receiver extension kit & H-buffer, MOE pistol grip and CTR stock = 2 lb 3.7 oz

Pinned together, the rifle comes in at 6 lb 2.7 oz

I have an identical AR except for a BCM pencil barrel instead of the DD pencil that weighs 2 ounces more. DD barrels are light that's where the 2 ounces is, both barrels are 16" midlength pencils. The BCM has a BCM BCG instead of DD but they weigh within 0.1 oz of each other.

 

[taliv]

mike, how much does alum door and plug save?

yeah, quentin, and i could make it a good bit lighter but wanted to stick with durable parts

the standard bolt carrier is 9.4 oz and i have a 3.6 oz JP aluminum bolt carrier, which would save me 5.8 oz

i would have got the fluted version mike mentioned, but i ordered that barrel years ago. would have saved me .5 oz

and a bare muzzle (and less lube) will save me 4.6 oz

i do have an H buffer in there, which is 1 oz savings if i drop to regular.

total that would be another 11.9 oz

btw, i don't remember the mod, but my CH is the medium latch.

 

[taliv]

and to tell you the truth, i ALMOST SBR'd the lower and went with a 12" barrel, but i just didn't trust the lower yet and didn't want to blow $200 and wait a year on the stamp for a lower that might now work out so well

 

[TIMC]

Nice rifle. Never understood the gotta make the lightest rifle possible thing. A 6 pound or a 8 pound rifle will really make no difference to 99% of hunting or shooting scenarios, especially with light recoiling poodle shooters. Of course you could say what is the need for 99% of my collection too. I do like the looks of your rifle, nice job.

 

[taliv]

heh, honestly TIMC, i was just bored. i get the urge to push limits every now and then. i shoot matches and carry a 17 lb bolt gun. you're totally right that 5 vs 7 lbs really doesn't matter. but if i had to, swapping them would let me carry 10 more lbs of food or water. just an interesting exercise to see what the new magnesium-aluminum stuff will really do.

 

[TIMC]

Ok, I'll go that. Like I said there are thoughts of needs on everything and I am more than sure I have a lot of stuff that you and probably many others would have no clue what my thought process was for getting. Again it is a looker with clean lines so you done well!

 

[newfalguy101]

Last night I put together a lightweight AR for my wife, honest it IS for her ( LOL ) .

New Frontier Armory poly complete lower
SAA M-4 upper

Just under 6lbs ( no sights or mag )

 

[Trent]

Looks good Taliv!

Now.. you need to post the 3-pos range report.

I've found light rifles to be a blessing and a curse for short range offhand (e.g. 200 yards standing on across the course). You can stay on target longer without tremors and fatigue, but they're "bouncy" - very difficult to hold steady as you don't have inertia working in your favor.

I actually prefer a mid-weight rifle with rear-weight (buttstock) bias, for offhand shooting. Chose the VLTOR eMod stock on mine with the battery compartments. Shoot with irons, no electric gizmos - the battery compartments are used for ballast.

 

[Arizona_Mike]

FA hardware weighs 21.79g (0.77oz). Plug should be very light. Not bad for $8.
Steel dust cover hardware weighs 21.30g (0.75oz). The parts I am replacing with weigh 10.5gr. I am going to be a little conservative and go with V7's 45% lighter number and say 0.41oz for a savings of just over 1/3 oz. If I did not want a matching FDE door I probably would not have bothered.

It's going to be about 1oz in weight savings for both parts.

Mike

PS: My measurements and estimates:
3.8 oz Magnesium Upper with aluminum door and no FA
6.3 oz 10" BCM KMR
0.76 oz Mid length gas tube
1.38 oz Syrac 0.625 Adj gas block
11.8 oz BCM BCG
21.5 oz 14.5" enhanced light weight barrel fluted
1.4 oz BCM CH
-------------------------------
47oz (before muzzle device) for the upper (50-51oz?)

For the lower I am looking at the CAV15 which is 28oz populated but I will take off 1.9oz by running an empty buffer. Add 4 oz for a muzzle device and I am looking at 4 lb 13 oz???!!!

Mike

 

[taliv]

Now.. you need to post the 3-pos range report.

I've found light rifles to be a blessing and a curse for short range offhand (e.g. 200 yards standing on across the course). You can stay on target longer without tremors and fatigue, but they're "bouncy" - very difficult to hold steady as you don't have inertia working in your favor.

I actually prefer a mid-weight rifle with rear-weight (buttstock) bias, for offhand shootin

ha! no, after i get a red dot zeroed, the only shooting this gun will see is ipsc cardboard and maybe some 100-150 yard steel. but i do agree and generally prefer a rear weight. that's why all my other ARs are like that.

mike, can't wait to see that thing put together. i like the longer rails so i can put my hand out further, but if i had it to do over, i probably would have got the 10" instead of the 13.4"

 

[Trent]

OK, Ok fine... use some SR1/SR21/MR31 reduced targets and do 3 pos anyway. Those are all 100 yard reduced targets simulating sitting rapid fire/standing slowfire (SR1), prone rapid fire (SR21), and slowfire prone (MR31)

If nothing else those make outstanding practice targets. Putting a round in the black on command will keep you in the A on other pursuits.

 

[Arizona_Mike]

My aluminum door hardware is here and I am getting lower numbers for the upper. 5.044 oz with the aluminum dust cover, cover rod, and no FA. 6.155 oz as provided by Magtech (4.8 oz stripped).

Stripped Magtech upper= 4.635 oz (lighter than 4.8 oz claimed by website)
Steel duct cover, rod and spring: 21.32g = 0.75s oz
Aluminum dust cover, rod and spring:11.60g = .409 oz

The Aluminum door looks very nice, like it fits the receiver more nicely than the steel one.

Mike

 

[Arizona_Mike]

The FA plug arrived today and the weight is minuscule (2.8g/0.099oz).
The total weight of the Magtech upper with aluminum door hardware and FA plug is 145.7g/5.14oz.

Mike

 

[Arizona_Mike]

Fixing my math! I was way over when I added it up first.

A bunch of stuff came in the last 24 hours.
Barrel (BCM enchanced light weight fluted): 583.1g (20.57oz)
BCM mid-length tube and roll pin: 21.54g (0.76oz)
BCM KMR10 rail and hardware: 185.9g (6.56oz)
Trifecta (Specwar mount) FS: 111.8g (3.94oz)
BCM CH: 1.27oz

Add to that 1.38 for the gas block and 11.8 for the BCG M16 bolt and 5.14 for the modified upper and I am looking at an upper weight 3lb 3 1/2 oz.
Running a CAV 15 lower with empty carbine buffer should get me down to just under 78 oz (4lb 14oz).

Spending the real money for a lightweight BCG could take me into even lighter territory.

Mike

 

[taliv]

sweet. looks like that BCM barrel is 3 oz lighter than mine. i thought their site said it only saved half an oz

 

[Arizona_Mike]

The fluting only saves about 1/2 an ounce. The enhanced lightweight profile (no handguard/gasblock shoulder) is lighter than the lightweight. Also my barrel is 14.5" not 16".

Mike

 

[taliv]

ahh, that explains it

 

[Arizona_Mike]

My actual weight of my BCM Gunfighter medium latch is 1.234 oz. (the large latch is 1.27) My actual weight of my BCM M16 BCG is 11.629 oz.

I tried a Wilson AccuTac flash hider which is about 1.44 oz lighter than the Trifecta--It's about the same as an A2 birdcage. I will test silencer POA drift with the pencil barrel and if it is excessive I will go with the AccuTac instead. The big suppressor mount on the Trifecta looks odd on the pencil barrel. I can test on my conventional registered SBR lower before I have to pin the FS.

I put together the upper. My digital scale only goes up to 1kg but I have an analog scale.
My actual fully assembled upper with the AccuTac FS is coming in at a disgustingly light 3lb 1oz! This will put my entire rifle at 4lb 11oz (est.) when I get the lower done.

Mike

 

[Arizona_Mike]

Loss Mass BCG Choices and cost/oz.

Baseline: BCM M16 MCG: $169
Adams Arms Low Mass BCG: $251 (+$82, -1.82oz ext., $45.05/oz)
JP Low Mass BCG: $370 (+$201, -2.5oz, $80.40/oz)
BoomFab Titainium BCG: $579 (+$410, -4.7oz, $87.23/oz)

Mike

 

[Field Tester]

Taliv and others,

How far do you take this? Do you look at light weight screws, pins, bolts, springs, etc...?
How about lighter weight lubes (or using them sparingly)?
Do you also look for lighter weight mags?
What about ammo? Do you try and use certain weight brass and powders?

I hope I'm not coming off condescending, I'm truly earnest here.
I find the subject fascinating. Only through experimentation can we find advancement.
At what point do you find diminishing returns?

 

[taliv]

it's fascinating to me too, but i can satisfy myself mostly on paper doing the math. i didn't want to spend a lot of money on it. my project started when i found those $199 magnesium lowers for $49 and couldn't resist buying 2. the rest was mostly built with spare parts i had lying around. of course, once i started, i couldn't resist buying a BCM KMR rail. i had the barrel already or i would have got the same one mike got.

mike is taking it much further than i am, even replacing the steel doors and FA.

many years ago i built a lightweight build that was carbon fiber upper and lower and carbon fiber handguard and a carbon fiber wrapped 17" barrel with a titanium compensator, and a JP aluminum bolt carrier. it's under 5 lbs, but it's also not very durable. the BC apparently is only good for a couple thousand rounds before the bolt rings wear down the aluminum and won't seal. and the CH wore off the latch so it won't stay closed anymore and reciprocates with the bolt.

so my goal with this one was to not compromise on durability.

my LPK in a bag was 5.5 oz so it wouldn't surprise me if you could shave 2 oz off that, but it would cost more than i'm willing to pay, since the parts would have to be custom (or some airsoft chinese knockoff)

ammo is the interesting thing... i always looked at 223 ammo as a giant compromise from the start. i mean the whole point of it back in the 1950s was to get something that weighed less than 308/30-06 so guys could carry more of it.

still, there appear to be people working on advances

these guys are out of business but sold a plastic cased 223
http://www.thehighroad.org/showthread.php?t=79577

this is much more recent
http://www.pcpammo.com/ and claims to save 30-50%
http://www.gunsamerica.com/blog/plastic-cased-ammunition-from-pcp-ammo/

 

[Field Tester]

Looks like Natec already folded. I couldn't find any info on them and their website no longer works.
Still interesting stuff though. Still needs more research and testing, but cool nonetheless.