Lightweight .308 AR Complete. With Range Report...

[Glockslap]

Lightweight .308 AR completed, with range report...

I'd like to thank those of you who have waited patiently while I completed my project.  <munch>
My goal was a fully functional, 7.62 carbine that weighed well under 7lbs w/o a magazine or sights.  I'd say my goal was achieved at just under 6 1/2 lbs  8)



Again, this is a fully functioning semi-auto rifle with a full 18 inch barrel, A2 flash hider, and forward assist (non-functioning due to lightweight bolt; I may add a dustcover later).  Obviously, a few more ounces could be shed with a 14.5 pinned, or 16 inch barrel, but at the cost of velocity-and I want this to be a hunting piece capable of getting 97% of what the caliber's velocity/energy has to offer.

Dressed, with an empty 5 shot magazine, Aimpoint Micro, and highrise mount, she still checks in at a svelte
7 lbs 1.5 ounces (w/o ammo), which is the configuration I range tested with today.

[img width=810 height=473]http://i154.photobucket.com/albums/s248/miamidave101/20121216_125321-1_zpsaeada045.jpg

[img width=810 height=607]http://i154.photobucket.com/albums/s248/miamidave101/20121216_124819_zps4566eb61.jpg

Prior to range time, I cleaned the barrel (very dirty!) and lightly oiled the bolt.

Adjusting the JP gas block, I fired several rounds to fine tune it.  I figured mil spec 145 FMJBT South African 7.62 surplus would be the lightest load ever shot through it, and subsequently noticed it needed a bit less gas as it broke in further. 

Playing around I found what I felt was the "sweet spot" and after 30 rounds of the SA started running some heavier factory soft points that were loaded much stouter than the SA.  Once gassed correctly, it stripped and fed all rounds from a full magazine without a hitch, solidly locking the bolt open when empty-both from the bench, and standing (different recoil impulses from each).  I did not bring a 20 round magazine, but I have no doubt it will run the same.

Throwing on the unsighted Aimpoint red dot just to get some "go-by" groups, generated the following from a seated rest (no sandbags).  All 5 shots were fired relatively quickly-roughly 5-7 seconds apart at the 25 yd line:



I expect that group to get slashed SUBSTANTIALLY with a magnified optic, decent trigger, some barrel break in (50 rounds today), sandbags fore & aft, and waiting for the barrel to cool down.  The pencil barrel starts to heat up pretty quickly... 

Overall, with the above mentioned I feel it has the potential to easily be a solid 2 MOA gun with most ammos, maybe even less than 1.5 with match?

Compare it to a DPMS 7.62 AP4 16 inch barrel (carbine gas system):



Recoil?  Not even remotely harsh and way far from punishing.  I feel an 8lb semiautomatic 12 gauge with birdshot kicks substantially more.  One person at the range, who had never fired a .308 before, commented on it being a pussycat-not much more than his 5.56 experiences.

I'm guessing it has everything to do by not being over-gassed, the lightweight bolt, and mid-length gas system all factoring in to it's performance. I can't imagine what it would feel like with a compensator on it-but again-not this thing's purpose.

Eventually I will add an optic that will weigh in at around a pound, and a sling, making for a loaded (5 rounds) package a bit over 8.5 lbs, making it a pretty handy walking around the woods gun in just about anybody's book.  It will also handle almost anything on earth, especially with the capability of charging it with some fully loaded 20 round magazines as backup  <thumbsup>

Anyway, thanks for stopping by.  Here is the link to the original thread for reference:

http://308ar.com/forum/building-a-308ar/build-a-light-weight-308-ar/

Edited April 24, 2013 by Glockslap

[unforgiven]

You proved it was possible brother Glockslap,Great job on that build.And as a byproduct it looks good. <thumbsup> 8)

[Glockslap]

Thank you!  I am sure, some manufacturer will take my lead some day  :o

5.56's IMHO should weigh 5lbs, and the 7.62's 7lbs...

[imschur]

very nice

[Glockslap]

I just noticed my shoulder is a little tender today, lol...

[98Z5V]

Great job on that rifle, man!  <thumbsup>

[Magwa]

Nice job I bet that pencil barrel accounted for alot of weight lose I am thinking of getting one myself , have you done any rapid or substained fire yet how is the heat ?

[Glockslap]

Yes the P-barrel is very thin, and light.  Chopping off four inches and welding the A2 FH for a still 16 inch legal barrel would lighten the gun a bit more, and the adjustable gas reg still make her work. 

Still, it being a .308 set up for the woods, I want the round to have enough poop to zap anything on the map that says 'Merica  <thumbsup> (with the right bullet). 

Recently picked up a lightweight scope, now waiting for the rings, and from there I will give you boys the final "wet" weight with a load of five 168's in her (and 20 for grins).

Once all put together, I will strive for "true" 100 yard "first round" accuracy with a five shot 168 match ammo group, to include barrel cool down sessions and bolt tensioned for each shot against a four round magazine.

Follow up accuracy will be a 5 round group in maybe under 30 seconds (timed) just to show how the barrel works under heat stress.

[Jgun]

That IS very impressive. i made an effort to build a lightweight .308 AR, and mine came in at around 8 lbs according to my bathroom scale. My gun was built with a lightweight Kaiser receiver set, along with a CTR carbine stock similar to your's. I put an 18" carbine fiber wrapped barrel on mine as well. The two things other than the possibility that my barrel outweighs yours, that I'm assuming are heavier on mine, are the 13" Larue railed handguard, and the heavier DPMS BCG. Do you think that your CF free float tube and JP carrier could account for over a pound in weight savings as compared to the parts I've used? Also who's pencil barrel did you use?

[.308LiteHunter]

Hey glock,

I read through the post about your journey in building this lite set up, and its cool to see a range report. I bought the DPMS light hunter, and have been very impressed with it. I was wondering what your experience has been with recoil..does it get more noticable the lighter you made your gun, and if so are you planning on making any mods ( adjustable gas block, buffers, springs etc ) to reduce the recoil?

[Glockslap]

http://www.ar15.com/forums/t_3_121/610941_.html&page=1

[darb]

Very nice write up, all the right things in the right places to achieve your goal. Mine is 12lb fully loaded out the door, that is another story. Thanks for the post.