Ultimate Liteweight Precision Grendel Build

[Sticks]

I'd probably take the Midwest SS 15" from my MK12 and put that on my middy, then the Faxon on my MK12...both of which I can not remember when they were shot last.

[twissted]

I also built a liteweight Grendel with nice parts that are durable and full of performance.20190129_131502_HDR.jpg

[twissted]

I used the same cookbook. {{{ lightweight tack driver that holds up over the years of use }}}

[bj139]

I also built a liteweight Grendel with nice parts that are durable and full of performance.[ATTACH=CONFIG]13703[/ATTACH]

That is really nice, carbon fiber everywhere.

[StoneHendge]

Cool- what Bipod is that?

[Jackjohn]

I'm new to this forum and AR-15. I started reading here about 2 weeks ago. I see this as a long term project due to money. Anyway I thought you guys would enjoy this article.

https://www.ammoland.com/2019/02/building-the-ultimate-ultra-light-ar-15-for-hunting-survival/#axzz5gmEsmDZ3

Jackjohn

[twissted]

Coldweld Accu Max bipod Carbon fiber

[twissted]

My build took over a year to collect the parts I wanted. The Blackwood Arms Ambi upper with their 6.5 bolt was the part that took the longest.
The nice part about a long build is you can put a lot of thought into what's available. Like the scope it just came out this year and so it was added at the last moment. The spec of it are stunning and once I got it on my rifle I'm very pleased with that purchase. It was the bargain of this build. I took the scope and compared it to scope costing 3 times as much. Mine is better.
I'm happy with most of this build and the parts used. There is always something new that hits the shelves that I like trying so There's a chance something could change.
6.5 Grendel (6).JPG
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[StoneHendge]

It's baaaaaaaaack!

3 1/2 years in the making. Like fine wine or aged tobacco, good things can't be rushed. 6.84 lbs scoped and 5.32 lbs unscoped. Very little weight could be saved without sacriicing performance/usability/durability. Ballistics software says supersonic to 1100 yards and it's been spot on to 550 thus far - with Varget and all of it's wonderful qualities (aside from metering )

IMG_20210314_170824_copy_974x310.jpg

The brass says Grendel and so do the mags. I bet everyone thought I'd ride off into the sunset quietly. Details to follow......

[StoneHendge]

Well, I wasn't going to let that teaser hang out there as long as this one has:

Reading through this thread, it never explained exactly what happened since it ended up in another thread. The BSF barrel ended up being the culprit behind the thermal drift and ended up going back to Rainier who kindly refunded my money. As I pondered the next step, winter came, then summer came, then all of our ranges were promptly shut down due to drought. Parts all went in a box, I relocated twice, sold the Faxon carbon fiber handguard along the way knowing I could never fully trust it again, and finally settled here in Arizona. I picked up a 243 LBC chambered blank from BHW cheap and was planning on having it turned down to a JP style lightweight profile and doing it as a custom cut pin and weld to put it at 16.1" with a VG Epsilon 6.5 attached. That became difficult in this environment so it was back in the box.

In the meantime, I've been shooting a 243 LBC (lovingly known as GiGi) in an AR match. She's an 8 twist so I can't do the sleek and sexy 105s like the Berger Hybrid, Nosler RDF, etc. It's seen it's share of use and barrels won't last forever. GiGi has a monolithic upper with a 9" handguard so I'm restricted to a middie. That makes switching over to an ARC difficult since the trend is to longer gas systems. So when Rebby announced that he had some extra limited run Lilja 16" MLGS ARC barrels, I pounced to have a replacement when I needed it. I even had him cerakote it Patriot Brown to go with GiGi's color scheme.

I wasn't even thinking about weight since GiGi is a big boned girl, so it was a bit of a surprise when I unpacked the barrel and put it on the postal scale to see that it weighed in at 28.5 oz. I repacked it and put it in the back of the closet. Who can stick a Lilja barrel in the closet? Obviously not me. I would have mounted it up right away on the lightweight build but the cerakote held me back. Who puts a brown barrel on a black rifle? The answer was always right in front of me on a shelf ( behind my bench actually), a spray can of Matte Black Duracoat that I had bought a couple of years ago for an aborted project. It took 2 weeks or so to muster the courage, but I finally did it and thus, Rubin was reborn.

The computer the weight spreadsheet was on is in storage and is a mouse fart away from permanently crashing and I may need some other stuff on there someday. This is a screenshot of the last iteration. The lower is exactly the same and tips the postal scale at 29.9 oz:

Screenshot_20210501-151316_copy_825x695.png

Hit the wrong bottom, to be continued...

[StoneHendge]

Changes to the upper are:

16" Lilja Barrel: 28.5 oz
9.5" Odin Works O2 Lite Handguard: 7.5 oz with hardware
VG6 6.5 Epsilon Compensator: a couple of ounces of so
Gas Block: Sadlak clamp on

Added all together, the upper weighs in at 55.3 oz for a total unscoped weight of 85.2 oz, or 5.32 lbs.

I went with the Odin handguard for 3 reasons. One, I don't trust that carbon fiber won't be an insulator under rapid strings of fire (and this rifle does see rapid strings of fire). Two, I want the option to install a JP Thermal Dissapator (and I likely will). None of the Ultralight aluminum / lithium alloy , magnesium alloy, etc. options would allow it. And 3, carbon fiber and the alloys (which are softer) wouldn't hold up as well shooting without a bag off of barriers, rocks, etc. I've found that 9" or so is all I need - it's where I like my bipod and it's where I like to have my left hand when shooting off of a bag, so unless it's covering a gas tube, I personally see no need for a longer rail.

Could I have gone lighter with the compensator? Probably, but function trumped weight here. Recoil abatement is important with something so light so there was no shaving ounces here. Epsilons are my personal favorite so not much thought went into it.

The gas block was supposed to be the Faxon Ultralight at around 1.1 oz. That didn't work out due to a mismatch in the tolerances of the block I had and the barrel, so I needed a clamp on. At the time in this market, a Sadlak was all I could find. It's a bit of a pig and probably weighs as much as a Superlative Adjustable, but we must make do in these times.

My trusty old 16.9 oz Vortex Viper HSLR 2.5-10x32 adorns it. It's FFP with an XLR Reticle which is a nice, thin Christmas tree that doesn't inhibit target acquisition like a Horus can. I really can't understand why Vortex stopped making this scope. It's mounted with Warne Skelitized mounts at 6.7 oz. I gave up on the Aero's after GiGi took a slight fall the night before a match and I showed up with my zero half a mil off..... So far, so good with the Warnes.

So adding it all up with the scope, it tips the scale at 109.4 oz, or 6.84 lbs. It is sheer luck, but it is also exceptionally well balanced and moves extremely fluidly between positions. Probably a bit due to having a bit of weight in the Hogue stock versus the Ultralight options out there that would compromise functionality (i.e., riding a support bag, etc).

Load development was easy. I broke the barrel in with a 100 rounds of various odds and ends lying around the bench, and then started with Varget and 105 gr RDFs. Using Varget and it's temp insensitivity is important to me with a 12 month shooting season and temps that can range from the 40's to over 100 before it's time to run and hide in the A/C. The combo with RDF's did not fail and they (and their .280 G7) are running at 2446 with a single digit SD. And sub MOA accuracy - all of the paper I've shot have 5 shot groups ranging from a little over 1/2 MOA to just under MOA. Such a light rifle magnifies shooter error: grip too hard, don't get into the bipod just right or slap the trigger a touch? It shows up downrange. I'm confident that if it was put onto some sort of bench rig, it would shoot 1/2 MOA all day long. It's my first Lilja barrel, but it certainly won't be my last.

I will note that 2446 with 105s out of a 16" is considered slow for an ARC. That could easily be around 2600 with Lever or CFE 223. Nonetheless, from a ballistics standpoint, it matches up almost exactly with what I was able to with my 22" 6.5G running 123 gr Scenars at 2560 with CFE 223. There is a little bit more drop, but a tad less wind drift. Both map out to supersonic to 1100 yards with the last environmental data in my app.

So all of this looks great on paper and from the bench, but after having thought I achieved my goal with the BSF barrel only to have it not work out, more testing was in order. Especially due to running the Ti carrier (recommended for use with .223/5.56 only) and lightweight buffer and springs (use of such not recommended with Ti carrier). So after 2 matches with my 243 LBC where 95 gr TMKs pulled a bit of an unexplained disappearing act past 600 yards, Rubin was thrust into action. And the op system performed flawlessly. 73 rounds in 5 stages of 90 seconds max and I only needed all 90 seconds once - 17 shots were it was Bang! Beep! Impact! on the last target (I am also lucky I didn't have the ounce of so lighter Wilson Combat Rodgers stock for that last shot, because I don't think I would have made it given a certain feature of that stock which made me shy away from it). Ended up being my best finish thus far - 5th overall (including large frame) out of a field of 70 and 3rd in what is basically small frame open (field of 45) with the top 10 or so all determined by the timed stage.

So what was originally anticipated to be a 9 month project took almost 4 years! Pictures and more thoughts to come.

[BluntForceTrauma]

Cool project! Looking forward to more.

[biodsl]

Congratulations, SH. A very nice build.

I will note that 2446 with 105s out of a 16" is considered slow for an ARC. That could easily be around 2600 with Lever or CFE 223. Nonetheless, from a ballistics standpoint, it matches up almost exactly with what I was able to with my 22" 6.5G running 123 gr Scenars at 2560 with CFE 223. There is a little bit more drop, but a tad less wind drift. Both map out to supersonic to 1100 yards with the last environmental data in my app.

This is amazing. As I believe and as you are proving, the 6mm ARC in a RECCE format is the pinnacle of performance for the AR.

[Sticks]

Hell of a write up. Well done.

[raamaudio]

I have a few parts that might help it weigh less for sale

Cool build, been into low weight since the early 70's, cars, bicycles, etc.....my 12" 4.2lb 65G was planned to go under 4lbs, under 5lbs scoped but it was not fun to shoot with my shoulder and other injuries so now it is a 16" 5.5lb carbine but could easily go to 5lbsz(6 scoped) and I might do so as have the parts on hand.