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+--- Thread: 24" Barrel lightweight AR build? (/showthread.php?tid=23849)
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24" Barrel lightweight AR build? - LRRPF52 - 10-22-2021
Get a Proof barrel if you want a really light 24 barrel.
A buddy of mine built a 20 Proof barrel Grendel in billet Seekins receiver set.
With a Leupold Mk.6, bipod, and OSS suppressor, it was still under 8lbs, which is crazy.
24" Barrel lightweight AR build? - tdbru - 10-23-2021
well, i am trying to do my own recommendation. did some scope swapping around. the cantilever mount and scope i took off my lightweight upper was surprisingly heavy. scope was 16 oz and so was the mount if i recall. or pretty close. so on the 20" faxon gunner tube, my rifle weighed in at 6lb 9oz. with no scope or mounts. the 4x Leupy with scope covers is 10oz. that's 7lbs 3 oz. waiting on light weight pic rail rings. according to specs i should be at 7 lbs. 5 oz or so w/o sling. probably 7 1/2 lbs with sling ready to go. by changing out scope and mount i dropped, or will drop, 1 lb off of the setup. much better. finally getting the weight down to what i think a rifle should weigh for the size of the cartridge. actually 6.5 lbs for a 6.5 Gr. would be way cool, but probably ultra $ to do it too. with optics. at least this attempt to 7.5 lbs is just the cost and wait on as set of rings. then to see how i do with it re-setup like that. recall the phrase.... put your $ where your mouth is. so i'm trying my own recommendation and will see how it works out. i'm liking the lighter weight. waiting on rings, and then see about the shootability of the setup.
-tdbru
24" Barrel lightweight AR build? - tdbru - 11-02-2021
ok, the rings finally came in. with the Leupold 4x in med height pic rail rings, the 20" Faxon Gunner upper barreled AR comes in at 7lbs. 7oz. lost about 1 lb. with changing out scope and mount. cool. with sling it goes 7lbs. 10oz. throw in an empty E-Lander 10rd mag and it is still under 8 lbs at 7lbs. 15 oz. about the best i can do so far. and probably will stay there. so to get the rig under 7 lbs, i'm not sure what i'd have to do or remove to still run a 20" tube and get under 7 lbs. however 7 1/2 lbs. isn't bad i guess, that with scope included.
regards,
-tdbru
24" Barrel lightweight AR build? - tdbru - 11-03-2021
LRRPF52,
what did your buddies 6.5 Grendel AR weigh without the bipod and suppressor? is a PROOF CF barrel the only way to get a scoped Grendel AR under 7 lbs with a 20" or longer barrel? Are there any scoped Grendel ARs under 7 lbs with 20" or longer barrels? i'd sure like to know the build sheet for one like that.
best regards,
-tdbru
24" Barrel lightweight AR build? - tdbru - 11-03-2021
hmmm..... proof research 20" CF tube is heavier than my faxon gunner 20" tube. Proof Research website lists 20" grendel CF barrel at 2lbs 3oz. Faxon lists the 20" 6.5 Grendel gunner nitride 4150 CM at 1.92 lbs. Of course the PR CF barrel will be much stiffer than the Faxon gunner profile, but for max weight savings, looks like the Faxon gunner barrel is actually lighter in weight.
-tdbru
24" Barrel lightweight AR build? - biodsl - 11-04-2021
tdbru Wrote:Proof Research website lists 20" grendel CF barrel at 2lbs 3oz. Faxon lists the 20" 6.5 Grendel gunner nitride 4150 CM at 1.92 lbs.
Lilja lists their fluted AR740 ($640) at 2.23lbs. Still not as light as the Faxon, which for hunting rifle is probably the way to go. A Proof or Lilja is a lot of money for minute of deer at a couple hundred yards, IMHO.
24" Barrel lightweight AR build? - leedstao - 11-05-2021
Why not use WWSD lower for weight saving.
24" Barrel lightweight AR build? - tdbru - 11-07-2021
Well, they didn't come out with them until after i already had my lower. I'm still not "sure" about polymer structural parts. obviously if engineered correctly they probably work fine.
-tdbru.
24" Barrel lightweight AR build? - Morvandium - 11-16-2021
I just received my 24" Grendel barrel from x-caliber barrels. (www.x-caliber.net). Maybe this will give an additional reference point.
24" 6.5 Grendel 416R with a Rifle+2" gas system, Hbar profile with thermal fluting. Shipped weight 3.7 lbs, with matched bolt and packaging. I did not weigh the barrel alone after it arrived, but I will when I disassemble the upper for cerakoting at some point.
This is what their thermal fluting option looks like. I'm sure if you had a similar custom fluting job done elsewhere, it would result in similar weight loss to what this did.
[ATTACH=CONFIG]18388[/ATTACH]
I posted some other pictures in 6.5 Grendel Photo Gallery.
It cost a pretty penny, but I got exactly what I wanted. I wouldn't do it for every gun.
The thermal fluting is 15 straight flutes on the back end of the barrel. They are narrow, deep, close together, and done at straight 90° angles to maximize surface area and linear surface at the original diameter, and material removal. While the fluting reduces stiffness slightly because it is material removal, it drastically increases the ratio of stiffness to barrel weight, and the ratio of surface area to mass. The maximized linear surface at the original diameter preserves more stiffness than typical, decorative/cooling fluting cut at angles. It's not a miracle cure, and the tradeoff is the machining takes time using small bits, so it has a steep price tag for longer barrels.
edit: stated a ratio backwards
24" Barrel lightweight AR build? - tdbru - 11-17-2021
Morvadium,
very interesting. i'd sure like to hear what the barrel alone weighs. When you get it dialed in please let us know how the x-caliber barrel is shooting for you. 5R or how many grooves? twist rate? standard SAAMI chambering spec or custom?
thanks,
tdbru
24" Barrel lightweight AR build? - Morvandium - 11-19-2021
tdbru,
Will do on sharing how it shoots, once my new glasses arrive and I can get to the range -- I'm using backup pair that's 2 Rxs old right now. I know a limiting factor when I see it -- or don't see it so well, like my reticle currently.
The barrel is 1-9 twist, 6 groove with a standard SAAMI chamber. All the build details are here https://www.65grendel.com/forum/showthread.php?24856-My-custom-6-5-Grendel.
Despite my choice for fluting to lighten the barrel, the rest of my setup is not designed with weight as a first consideration -- though some parts I chose for other reasons, like the BAD titanium takedown pins, are great light weight options. The scope, battery and sunshade come to about 2 lbs, and the MBA-3 stock is around 1.25 lbs.
I just realized my scales are either precision ones below 2 lbs, or imprecise ones in the hundreds of lbs. range. Any suggestions on a good scale? Digital fish scale appropriate for weighting gun parts? (I could justify buying that to myself without too much in the way of mental gymnastics.)
Also, I noticed that x-caliber doesn't offer 5R on 1-9 or 1-10 twists in 6.5mm/.264" barrels. The idea of radial rifling is one that appealed to me, but not enough to move me off of my desired twist rate. Is radial rifling problematic above certain twist rates at a given diameter? Or is not offering 5R in 1-9 and 1-10 just a matter of the tools they have as a result of market demand?
thanks,
Morv