Barrel profile for 18" AR 15?

[MichiganMitten]

I'm looking at having a Bartlein barrel made for me. The question came up as to what profile would be best for a Recce/SPR type build? At first, it was suggested that I go with a .875 gas block diameter and have the barrel fluted to increase the overall rigidity. I loved the idea of slightly increasing the weight, but perhaps increasing the inherent accuracy over a thinner barrel with a .75 gas block.

Now I tried to find a handguard for an AR 15 that would accommodate the minimum inner diameter of an SLR 8 adjustable gas block. SLR has that listed as 1.35" ID required for the SLR 8... Unfortunately, every single handguard I looked at, had 1.3" inner diameter listed.

So, back to the drawing board. I was hoping someone more knowledgeable than me could suggest the best route to go for an accurate barrel profile for an 18" rifle gas 6.5 Grendel (.75 gas block?), without creating a monster in weight. I was thinking of having this spiral fluted as well.

Thanks!

[grayfox]

My most accurate barrel is a Lilja, an AR 740, it's a 20" and IIRC a 0.740 pretty much straight profile, with the GB journal at 0.750". Tack driver and speed really good, really. I'd expect a Bartlein with the same dimm's to do even better than mine, but as to profile I'd recommend that AR740 one heartily. You can see a pdf of it online if you google it. It fits most any decent HG. Personally I'm not a fan of the 0.875 monsters, I think of those more of a specialty, LR benchrest style barrel. But I'd also be talking about a 22 or 24" barrel, so bottom line not looking to do any totin' on a hunting trip.

If you want to go 18" keep the same profile as the 740 but shorten it, keep the rifle length gas.
O yeah, call Mark at precision firearms.com and talk to him. I believe he can do you a bart or a lilja, or several other choices. Might even still have his first-time forum mbrs discount for ya. He's a got a couple of RTG deals on this forum in the vendor section too.

[A5BLASTER]

Call Mark at PF.

Tell him you want a 18 inch rifle gas with .750 gas block size and you want it to be light weight.

Flouting is one way to reduce weight but it won't be as much as you think or as much as going with a thinner profile could give.

Flutes don't increase the stiffness of a barrel they only keep the stiffness of the barrel the same while slightly reducing barrel weight. Think it's like 2 to 3 onces difference, so not much.

Long as you don't rapid fire are get the barrel hot a super thin profile like what JP rifles uses or use to use on their 18 inch grendel barrel is very accurate.

Going to a super thin profile will give you the least amount of barrel weight.

[MichiganMitten]

Call Mark at PF.

Tell him you want a 18 inch rifle gas with .750 gas block size and you want it to be light weight.

Flouting is one way to reduce weight but it won't be as much as you think or as much as going with a thinner profile could give.

Flutes don't increase the stiffness of a barrel they only keep the stiffness of the barrel the same while slightly reducing barrel weight. Think it's like 2 to 3 onces difference, so not much.

Long as you don't rapid fire are get the barrel hot a super thin profile like what JP rifles uses or use to use on their 18 inch grendel barrel is very accurate.

Going to a super thin profile will give you the least amount of barrel weight.

Fluting increases rigidity of a barrel compared to a barrel of the same WEIGHT that is not fluted. That means I can get more accuracy and heat dissipation of a given weight by going fluted. As I don't want a simple bench rest rifle, this is very desirable to me.

I'd prefer to know what I am talking about before talking to Mark at PF again. My ignorance didn't serve me well my last conversation, and it seems he is extremely busy.

I also don't want to just go as thin as possible to save as much weight as possible. That seems like a bad bet, to get one of the best barrel brands, and then remove all it's rigidity by going super thin. I'd being doing the quality of the barrel a disservice.

So I am looking for the best compromise on the weight to rigidity slider scale.

[mdram]

just explain to mark what you want. let him take it from there and make the recommendation. it is his specialty

[A5BLASTER]

Fluting increases rigidity of a barrel compared to a barrel of the same WEIGHT that is not fluted. That means I can get more accuracy and heat dissipation of a given weight by going fluted. As I don't want a simple bench rest rifle, this is very desirable to me.

I'd prefer to know what I am talking about before talking to Mark at PF again. My ignorance didn't serve me well my last conversation, and it seems he is extremely busy.

I also don't want to just go as thin as possible to save as much weight as possible. That seems like a bad bet, to get one of the best barrel brands, and then remove all it's rigidity by going super thin. I'd being doing the quality of the barrel a disservice.

So I am looking for the best compromise on the weight to rigidity slider scale.

Best of luck too you sir.

[FLshooter]

[grayfox]

Mark is good for doing biz with. As Fl says there are some other options. I just ordered mine straight from Lilja, it was on the shelf and came fast.
All told this 20" lily barrel system is about 10 lbs, with a 30 mm Vortex scope on it and MBA-1 butt stock. I don't do lots of mtn hiking or long hunting walks so I'm good with that.
Course in our younger days we'd tote 12 lb rifles all over creation Lol!!!

Roger on the rigidity thing. It maintains the rigidity of the original diameter, but cuts down the wt. Ballistic adv has some setups that take 7-8 oz off the weight and they are good shooters, maybe not the Bartlein or Lilja but right next to them. Criterion is another choice but I don't know if they flute or not. I think the "extra" wt/balance of the lilja bbl (unfluted) helps me keep the muzzle rise down.

[Jakegsxr11]

I chose to go with rifle length gas, 0.840 under the handguard,. 0.750 gas block to the muzzle.

[MichiganMitten]

just explain to mark what you want. let him take it from there and make the recommendation. it is his specialty

I'd prefer not to be pigeonholed into only working with one vendor if possible, as a solution to any question I have on the forums.

I appreciate the advice though.

[MichiganMitten]

I chose to go with rifle length gas, 0.840 under the handguard,. 0.750 gas block to the muzzle.

Which barrel brand did you go with? Also, did you go fluted at all?

What was your final weight and length?

Thanks!

[Jakegsxr11]

The total rifle weight is 8 lb 9 Oz and that includes a 23.7 oz scope, moe adjustable stock 8.5 oz, moe grip 2.8 oz, and Odin works o2 15" handguard 9.7 oz with hardware, standard forged receivers.

[biodsl]

My most accurate barrel is a Lilja, an AR 740, it's a 20" and IIRC a 0.740 pretty much straight profile, with the GB journal at 0.750". Tack driver and speed really good, really.

If you want to go 18" keep the same profile as the 740 but shorten it, keep the rifle length gas.

+ 1. I also own a Lilja 740. I suspect the profile is fine for anything short of combat. An 18" RLGS would be cool. Here's a link to the profile in question.

https://riflebarrels.com/wp-content/uploads/ar740.pdf

[Old Bob]

MichiganMitten... Are you dead set on a Bartlein barrel? If not, Wilson Combat has an 18" fluted recon barrel at 2 Lbs. Is that heavier than what you are looking for? I have their 20" version on my Grendel AR. Seems about the right weight for me personally.

https://shopwilsoncombat.com/Match-Grade-Barrel-65-Grendel-Recon-Tactical-18-1-8-Twist-Stainless-Fluted/productinfo/TR%2D65GRCRG18FT8/

[Klem]

Michigan,

In an AR I don't think you need to go thicker than .75" at the gas block. Like the other guys are saying, a Lilja 740 or 319 profile (I prefer the 319) is more than enough to be a tack driver if using a top-tier barrel like a Bartlein.

I would have a look at the machine drawings on Lilja's website for examples of 18-20" profiles that are excellent length, diameter and weight compromises.

Fluting will not make a barrel of the same diameter stiffer, it makes it lighter with more surface area for cooling. It can also introduce stress in the barrel and that will influence POI as it heats up.

The weight saving of fluting will not blow your socks off when you look at the numbers. Lilja's fluting of the 740 profile shaves a whopping 0.2lbs off a 2.4lb barrel. In his 319 profile fluting shaves 0.3lbs off a 2.47lb barrel. If I had my time again I would not spend an extra $100 or 20% to save a measly 0.3lbs.

Spiral or straight fluting...I don't know. Apart from camouflage I don't care what it looks like.

Good luck with your Bartlein.