Lightweight SR25 build

[mattwaage1]

Well with these lightweight "the fix by q" rifles floating around I was kinda intrigued by the idea. But after hearing some accuracy reports on them I was a bit nervous to drop the coin.

Then the other day I got to thinking, I'm betting I could put together a lightweight SR25 that would shoot as good or better and be within the same weight range.


So the goal is a 7-8 lb rifle (unloaded without optics)
Some 6mm or 6.5 chambering.
.75moa or better mechanical accuracy.

So who has built one?

What components would you use?

Would you get a factory rifle and change some parts out or start from scratch?

Is it possible?

 

[RidiculousMetacarpus]

JP LMOS is a start from experience (any "large" frame bolt).

The lightest i was ever able to get to was 7.25lbs w/out optic or mag. This was w/ 16" lo pro barrel pictured below. NOTE THIS IS 308!

Heck the rings were 5oz pigs, lol you could go lower.

As for accuracy, it shot better than i did for a semi. One grouping (Hornaday 150 sst @ 100):

Overall it was too pissy to be consistent. I found it awkward to bench shoot, too uncomfortable. If you want a MOA avg, i'd say it was 1.0 +/- .25 if using good factory ammo. This was a "budget" faxon barrel by the way ($100 barrel). Again, this was 308.

Edited for parts list:

JP LMOS carrier & bolt (forget the weight, but hella light versus standard)
16" Faxon barrel, 34oz (was never intended as "precision")
Apex Machine 12.5" handguard, 10.4oz (not the lightest, but loved how it felt)
Standard upper/lower from Aero 24.7oz
Magpul STR stock was 12.7oz
LPK was 2.7oz
Standard carbine tube, spring, buffer, end plate, port cover was 10.7oz
Standard barrel nut 1oz
Hogue grip 3.1oz
Rings were a pig - 5.1oz

Still ended up <7.5lbs. I could see one going <7 easily by merely using a lighter handguard and a lightened receiver set. Of course, if you want "precision" and 6.5, i assume you want a much longer, and thicker barrel (mine was a pencil profile lol), so add 8oz.

 

[Spblademaker]

Think of how it would have grouped with an optic. ?

 

[RidiculousMetacarpus]

Oh i know right?

 

[Potss]

So this thread will be of great interest: http://www.m4carbine.net/showthread.php?181495-New-Ultra-Lite-AR308-build Basically a guy who was a member here (but during scout) built a 4.8lbs AR10 that (he claimed) still shot 1moa. He gives the list in that thread.

I will copy-past here:

Upper Parts:
2A Armament Xanthos Upper receiver 7075 T6 @ 9.00 ounces
X-Caliber 416R 16 inch fluted barrel @ 31.3 ounces
2A titanium gas block @ 0.60 ounces
Gas tube mid length @ 0.80 ounces
titanium muzzle brake @ 0.65 ounces
Clark Custom Aluminum barrel nut @ 1.18 ounces
AR 308 carbon fiber hand guard 1.60 ounces in mid length 10.5 inches
Toolcraft Titanium 308 BCG @ 11.80 ounces with ti firing pin
Vltor charging handle @ 1.25 ounces

Lower Parts: Total weight 18.60 ounces with SSA-E trigger
2A Armament Xanthos lower @ 7.30 ounces
Mag Pul K grip @ 1.7 ounces
V7 titanium grip screw 0.113 ounces
V7 Mag catch aluminum 0.173 ounces
V7 Aluminum/titanium selector 90 degree 0.293 ounces
V7 aluminum AR 308 takedown pins 0.26 ounces
V7 tool steel bolt catch 0.31 ounces
Smoke Composite stock 3.3 oz.
AR308 carbine buffer (no weights) 0.85 oz.
NF polymer trigger group 0.65 oz with titanium trigger pins
SSA-E trigger group 2.6 ounces with titanium trigger pins
DPMS carbine buffer spring @ 1.5 ounces
Titanium buffer retainer, mag catch plunger

4.8lbs total.

Now this is a good list, but he goes a little extreme on weight cutting. You could have a higher probability of accuracy, durability, and usability if you were willing to gain another pound or so by going with something like this:

Upper

- Barrel: 16in rifle gas Craddock Bartlein nitrided with JP Extension $800 ~35oz (Proof is around the same weight).
- Upper: 2a Armament Xanthos $325 ~8z.
- Port Door: V7 Ultralight Port Door $38 .3oz + Rod $8.
- Handguard: V7 2099 Mlok Enlightened 13in 10.6oz $339.
- Gas Block: SLR Rifleworks Sentry 7 Titanium clamp on $150 .8oz.
- Bolt Carrier Group: V7 Titanium Carrier $369 8.5oz, JP High Pressure Bolt assembly $215 3.5oz.
- Gas Tube: V7 Inconel $70 1.3oz.
- Charging Handle: Armageddon Tactical GMS-10 Gen II $92 1.9oz.
- Muzzle Device: Any of the V7 Titanium ones, but really I'd run a suppressor if I were you.

Lower

- Lower Receiver: 2a Armament Xanthos $325 ~8oz.
- Takedown Pins: 2A Armament Titanium $47 .25oz (V7 is .353oz).
- Safety Selector: V7 Titanium Ambi $74 .42oz + Detent & Spring: V7 $4.
- Mag Catch: V7 Titanium $46 .26oz.
- Bolt Catch: V7 S7 Tool Steel $31 .39oz.
- Castle Nut: V7 Titanium $35 .35oz.
- End Plate: V7 Titanium $35 .26oz.
- Grip Screw: V7 Titanium $7 .1oz.
- Trigger: TriggerTech Adaptable AR PVD $265 2.27oz. +V7 Titanium Trigger Pins DLC $17 .1oz
- Buffer Tube: V7 2055 $76 3.7oz.
- Buffer Spring: Tubbs Spring $30 1.5oz.
- Buffer Weight: KAK AR15 Configurable Buffer Kit $47 1.7oz (could go Taccom to save .7oz, but nothing reciprocating then).
- Stock: Roger's Super Stock Delux $37 7.3oz. You can go lighter by going with a Smoke Composites stock, but no adjustability.
- Grip: Hogue 15 degree $17 1.5oz.

Total Weight ~6.15lbs.
Total Cost ~ $3475.

Now fair warning, I've heard the Xanthos has some receiver flex from some people, while others say that isn't an issue. Don't have one myself to test or I would. And to answer your question, yes you are going to have to build if you really want an AR10 that is accurate, lightweight, and reliable. Some factory rifles hit 2/3, but not 3/3. However, you can always pay a quality smith to build it for you if it seems intimidating.

 

[mattwaage1]

I know kicking around the idea I had a "precision" lr308 built back in the day and it was a bear to get to shoot good. Dunno if this is a rabbit hole or just that rifle.

 

[mattwaage1]

Thanks potss that's a lot of good info there!

 

[C_R_Slacker]

Or you could buy a fix and have any barrel you want spun up for it. My buddy has a 16" 308 fix. Does it shoot bugholes? No, but it's around moa or a little less depending on ammo. (He doesn't have a bartlein/tooley barrel) I shot three rounds from it the other day, first time I've shot it, and it was a .8-.9 moa group with 168 fgmm. To me, that is plenty good for what the gun is.

I built an ar10 with a 16" spr-ish profile 308 barrel. I didn't try to go super light weight, but I didn't do anything unnecessarily heavy either. It weighs 8.5-9 pounds naked. To go super light with a large frame AR, i feel like you're going to have to make some compromises that make the gun less ergonomic, less accurate, or both. That or go super expensive, which brings me to my original point. For the money it would take to build something similar, just buy a fix and have a custom barrel made if it doesn't shoot.

I've looked into building a short, light 308 or 6.5 for my next rifle, and you just can't build anything like the fix. Adjustable, folding stock, mag fed, full length handguard, user changeable barrels without a vise or action wrench, under 7 pounds, $3,000. People pay $4,000+ for custom rifles all the time around here. People also complain constantly that a $3,000 rifle (the fix) won't shoot 1/2 moa. Well, take the difference in price between a fix and a full custom and have any barrel you want made for it. You can buy the accuracy to fix the fix, but you can't buy the other features that make the fix unique.

 

[TheGerman]

 

[GrandpaDeadLegs]

Gosh I am kinda new and fuckin hate acronyms, but can still appreciate the difference between SR25 and AR10 - this meme fella may be on to something

 

[mattwaage1]

Sure lemme fill in everything with "large frame ar, lr-308, SR25, AR308, ar10a pattern yada yada yada" to keep everyone happy.

 

[GrandpaDeadLegs]

Now we can sleep at night thanks close enough is for the grenadier forum

 

[MSTN]

Here's an 8 pound, 2 ounce 22" 6.5 CM:

It's a way sub-MOA combo. You could hit 8 pounds easily by going 2" shorter, or swapping to a lighter buttstock.

It's easier to go lightweight on a big block build if you stick with a .308. The barrel can be shorter and lighter in weight, and you can use lighter weight bolt carrier.

Here's an even 7 pound .308:

 

[C_R_Slacker]

Nice builds. I wasn't prepared for how much heavier large frame ar's were than small frame. I was expecting about 8 lbs and ended up with about 9. I love the gun, but wish i had paid a little more attention to weight.

 

[Coffee_and_Pipes]

Here's an 8 pound, 2 ounce 22" 6.5 CM:

View attachment 6987935

It's a way sub-MOA combo. You could hit 8 pounds easily by going 2" shorter, or swapping to a lighter buttstock.

It's easier to go lightweight on a big block build if you stick with a .308. The barrel can be shorter and lighter in weight, and you can use lighter weight bolt carrier.

Here's an even 7 pound .308:

View attachment 6987937

Hey MSTN,

What led you to go with the Battle Arms receiver set over the Xanthos if you were going lightweight? I don’t have experience with either, but I’m thinking through a parts list for a potential lightweight .308 build, and am interested in hearing your thoughts on one vs. the other.

 

[mattwaage1]

Here's an 8 pound, 2 ounce 22" 6.5 CM:

View attachment 6987935

It's a way sub-MOA combo. You could hit 8 pounds easily by going 2" shorter, or swapping to a lighter buttstock.

It's easier to go lightweight on a big block build if you stick with a .308. The barrel can be shorter and lighter in weight, and you can use lighter weight bolt carrier.

Here's an even 7 pound .308:

View attachment 6987937

Those are some nice looking units what'd you all do?

 

[Potss]

Damn MSTN, those are some killer builds. How do you like the Xanthos?

 

[KYAggie]

https://www.snipershide.com/shooting/threads/lightweight-2a-arms-xanthos-6-5-cm-build.6877340/


Here’s a thread about a 6.5#, 6.5 Creedmoor I “put together”, before I was told that one simply just does not put together a SR25. Glad I didn’t know that before I did it. Anyway, mine could have been lighter had I used a pencil weight barrel; likely closer to 6#. I love this gun, it’s my go to hunting rifle now. You should definitely go for it.

 

[mattwaage1]

https://www.snipershide.com/shooting/threads/lightweight-2a-arms-xanthos-6-5-cm-build.6877340/


Here’s a thread about a 6.5#, 6.5 Creedmoor I “put together”, before I was told that one simply just does not put together a SR25. Glad I didn’t know that before I did it. Anyway, mine could have been lighter had I used a pencil weight barrel; likely closer to 6#. I love this gun, it’s my go to hunting rifle now. You should definitely go for it.

Looks like a good build!

How'd the accuracy wind up? Does it place shots with confidence?

 

[KYAggie]

Well, I have not shot it since the hog hunt. Sadly, my wife of 27 years took a hard left turn about the same time and later in the year filed for divorce. Just got the judges signature last week, so at least I’m grandfathered with deductible alimony, or “maintenance “ as they call it in Kentucky. Kept all my guns, the house, my truck, and I have great relationships with our kids; she got a pile of money and I’m about broke. All that chaos kept me from the range all summer. Fortunately, I should have a lot of free time when the weather warms to get this back to the range and see what it will do with some match bullets and H4350. I was very confident with consistency of both the barns and accubond LR bullets and how they performed in it. I expect it will turn in sub MOA groups with match bullets; only time will tell. I do not excpect sub 1/2 moa, but that’s not what I built it for.

 

[MSTN]

The Xanthos receiver set and matching forend are very, very nice!

 

[KYAggie]

Thanks! Everything I have purchased from 2A-Arms has been top quality stuff. I was in Boise, ID earlier this year for work and I stopped by their manufacturing facility. It was full of the latest modern machinery. I highly recommend their stuff.