Hello!

I'd like to first say that I appreciate the information available in this forum. The few questions I've asked have provided valuable feedback. So off with another one. :)

Dealing with a GII Recon. 16" barrel, 1" (all OD of course) from the chamber to the gas block. .748" at the gas block journal, .720" from the gas block to the muzzle threads. The barrel is heavy, the gun is heavy, and to boot its quite muzzle heavy.

It's a hunting rifle, so weight is more important than POI shift as the barrel gets hot from sustained firing. It *is* a gun I intend to use for target practice at longer ranges, but I understand the tradeoffs involved when talking about removing metal from the barrel.

What I came up with was to taper the barrel quickly to .75" after the chamber, then straight flute the .75/.72" sections. I'm tempted to consider having the front section turned down to somewhere around .69", but because that section is already comparatively thin, fluting won't be a huge difference in weight.

From what online calculators I used, the reduction of the 1" portion alone should result in almost a half pound weight loss, and fluting looks to be roughly half a pound again.

Does anyone have any other ideas I should consider, or input on my plan?

I think the fluting #'s sound a little high. you lost me on weight is more important than POI shift then follow with you do intend to shoot it at longer ranges for target practice.

Will you be doing this work yourself? if not I think it would wise to just start over with a new barrel (assuming there available already?)

Do you run a muzzle device? are you apposed to cutting and pinning? with some brakes I've seen people go between 13.7"-14.5"

now if your running a bare muzzle with a thread protector then that's fine as well.

If your doing the work yourself you can always start a little on the high side and get a feel and remove more material till you get it where you like it. I would start somewhere around a quick taper just past the chamber to say .800" then a straight taper to about .200" before the gas block around .750" then leave the shoulder around .780" with a small taper on the back side to make it look nice. then after the gas block seat I'd do another taper down to around .680 at the muzzle thread shoulder.

That should make for a nice decent do all barrel. if that isn't light enough then maybe you should think about changing stocks and work on the balance more than just the muzzle end. A balanced rifle will feel lighter than a lighter imbalanced rifle from my experience. also may want to give a heavier buffer a look as well. I'm not sure how the GII's are but my LR308 shot much nicer and didn't beat up my brass near as bad after running one of slash's heavy buffers, a vltor A5 buffer tube, and a sprinco red spring. that would add a little rear bias and help with the operation of the gun. (again assuming the GII's suffer the same issues as the 1st gen brethren)

I could have left out the target shooting portion. Just trying to get an idea of what is considered "too much" material removed for general purpose. I understand there is going to be a happy medium (or lesser of evil) in removing material, I just don't know what would be a good compromise. It's not like I intend to run a bunch of rounds through it in a hurry. I'd like to shoot at longer ranges, but I'm ok with being limited to a couple/few rounds before the barrel needs to cool off.

No, won't be doing the work myself. Unfortunately spare barrels are not available. Crossing my fingers that they start to appear in the next year or so, but by then won't matter to me. The gun is already at the shop for warranty work, I have inquired about having the barrel done while it's there.

I do run a muzzle device. M4-72, not sure whether I will go with one of the "blast forward" devices for hunting in addition to it, or just switch to a linear comp for that time of year. If the recoil reduction is as massive as testing seems to show, I may have a hard time justifying removing the brake. Suppressor would be cool, but not in the cards any time soon.

Elsewhere it was said that no shoulder was needed for the gas block, since it's set screw. I am ok with not having a shoulder, it would seem easier for the 'smith to just cut that off during the same operation, the weight savings I'm sure would be pretty minimal vs. leaving a small bump there. If I understand your suggestion, reduce barrel diameter quickly after chamber to .800, then a slight taper (.080 to .750) to the gas block shoulder. From the .748 gas block seat narrow to the muzzle thread shoulder. Makes sense, essentially ending up with a barrel that gradually reduces diameter from rear to front, instead of being similar diameter the entire length, if I understand your thoughts?

I'm running a Minimalist stock and an SLR 9" handguard with SLR adjustable gas block, so overall weight isn't horrid comparatively, but the barrel is thicker than I need it to be. I can't fit a QD swivel into the handguard because the barrel is so thick. Brass so far is doing fine, although I haven't run civilian brass through the gun after the adjustable gas block. I know exactly what loading was splitting shoulders, so I can always go back and test again with the adjustable gas block. I am kind of curious how much it helped.

Appreciate the response! :)

the profile I mentioned above would still be considered a medium contour. you could certainly go a lot thinner if you wanted to. having a tapered barrel is more rigid than say a barrel that's .750 end to end (minus the chamber obviously)

You have to look at it from a structural point of view. barrels whip, its just the nature of the beast. the strongest shape is a triangle, as it exerts force equally to all sides, a cone is still trapezoidal thus it would control deflection better than a cylinder (straight profile)

so for example say you were to profile the barrel post chamber down to say .650 then taper back up at the gas block then the fulcrum point of the whipping would be right where it goes to .650 so it has the other 12" or so of the barrel to deflect and a small angular change will be amplified by the other 12"'s of barrel. remember you want the bullet to leave the barrel when the barrel is at rest so the more the barrel is allowed to whip the higher the velocity of the change and the greater the dispersion is. think of it as a AC sine wave the high and low points are when the barrel are at rest (the nodes) and the arc down/up is when its changing direction the centerline being the barrel at rest so the center would actually be the worst time for the bullet to leave the bore as it has the greatest velocity at that point.  now the thinner the barrel or the sooner you thin it the greater the amplitude, the more rigid the lesser the amplitude meaning a lower amplitude will be more forgiving as velocity of change and distance between nodes will be less.

now hopefully I didn't lose you, the second variable of removing material is heat. the less mass there is the less time it takes to heat said mass, Powder changes velocity with heat (some worse than others) so back to our sine wave say you get a load that leaves the barrel at the tope of the node at a determined time (aka velocity) now as the chamber heats up it causes the velocity to increase and thus causing the bullet to leave sooner and no longer on the node this variation of velocity caused by temperature causes the bullet to leave the bore at a different position of the arc of the barrel whipping thus throwing shots.

that's why palma contour barrels are becoming popular in the bolt rifle world. they have a longer section of shank before the contour starts (they also have the ability to "set back" the barrel as the throat erodes) it gives more area for heat to be absorbed/dissipated where the weight is less critical and the muzzle end of the barrel contour can be less with less negative effect.

so long story short, remove as much material as you wish (within reason) but if you can get away with keeping a tapered contour it will be more rigid per mass and if you want to remove the most weight on the muzzle end the fastest method would be removing barrel length but that would require you to pin and weld your muzzle device making it semi permanent.

I had a 300 blackout barrel that went as thin as .550 in the middle and post gas block-thread shoulder. it would start stringing around 10 rounds but it was very light. everything is a compromise, hopefully I helped clarify things so you understand the effects of material removal and the byproduct. you have to decide which is more important.

Take the rifle to your gunsmith and ask him what he recommends. 308 ARs are heavy pigs anyway, he may have other suggestions as well, and can quote pricing.

I generally don't sit still for a long time while hunting. I like to cover a decent area (on foot) but go slow enough that I'm not spooking animals as I move, and due to circulation issues I can only stay in one place for a fairly short period of time anyway, which is shorter if it's colder. Generally the range I run into animals is 10-25yds. I am going to play around with sling positions once I get the rifle back, but since the stock barrel is so thick, and the handguard so slim, up to this point I haven't been able to use any of the QD positions on the handguard, so I don't know all of what may be practical. That is part of the necessity of slimming the barrel.

Where I hunt is either too brushy to hunt through, too tall to observe what is inside (until you get into it), and/or long enough range that the round and shooter have to be up to snuff hitting and killing at 400yds and beyond. There aren't a whole lot of .308 bullets/loadings from a 16" barrel that will transit 400yds and be within their performance envelope, and the ones I've identified that should, I have not yet been able to do the necessary work to ensure that they are legitimate loadings to ethically use to hunt. With very little time to get on target, a slung rifle in the situations I find myself would have given me away before I could get on target, and the animal(s) would have been out of sight. If muzzle up, it would be near impossible to move through the woods with even with a 16" barrel. Rarely I'm on a defined trail or old road with few to no obstacles. More often than not (if not in the vehicle) I'm off trail, ducking and dodging fir branches, going over or under fallen trees, weaving through vine maple and alder thickets, up or down hill, in rain or snow, where having the rifle in hand is better for balance and keeping the weapon somewhat protected when I fall.

I am working with a tailor presently to make a Fighting Load Carrier-type vest in hunter orange (required by law) that will hopefully allow me to eliminate the pack, which probably runs around 30lbs when wet. As I am normally moving, the weight distribution of the vest, coupled with having things accessible without taking a pack off, will be of benefit for the way I hunt.

funny. I thought I was the only one that used a vest while hunting. I to like the weight distribution and having everything I need at reach. weather it be a granola bar, my range finder, first aid kit or a few extra rounds. it's all right there. also stuffed a 3L camelback in the rear. I tied my bino strap into the rear carry handle which really saves your neck! then wove a snap strap into the molle to secure the bino's against my chest while hiking as them bouncing against you day in day out will make your sternum very sore surprisingly.

There certainly aren't too many wearing vests! Then again, there aren't that many people I know or see where I hunt that walk long distances anymore. I will admit, it's going to be a bit hard to put everything I presently have in the pack, in a vest, but I think I can probably pare things down a bit. Absolutely concur on stuff banging around. Not to mention, when it's time to take a seat, the vest isn't a problem. There are at least three companies that make or made orange MOLLE vests, but none of them are what I want. The camelback provision is something I'm intending to have added, other than that, the FLC is about perfect IMO.

I've been hunting (and doing other things) long enough to know what works and doesn't for me, and what will likely work that I come up with in my mind. Getting in and out of a vehicle, not being able to have a loaded rifle in the rig, sometimes having to get out and move quickly, a vest with everything in it would make it a lot easier, faster, and quieter than the pack that bangs around.

Also will be very happy to get the pistol off my belt. Ended up with suspenders to keep the pants up, and even that starts to hurt the waist, plus makes stripping down/going to the bathroom a pain when layered. Mocked up my new Kydex holster on a FLC to see how it would work. Orange grips are kind of a joke, but they were only $10, and having seen someone lose a handgun in the woods because it was so dark, I figure they can't hurt. Garmin fits a grenade pouch but obviously needs the shock cord.

Just as a followup, rifle is complete.

Unfortunately did not have the chance to revise my barrel reprofile, but probably better I did not, for cost.

Amazingly my calculations were right on the barrel, at least in the aggregate. Reprofile and fluting shaved off a total of 1lb, but I would suspect that would be mainly from the reprofile.



As pictured, 8lbs 2oz, I'm sure sub 8lbs if I took the GoPro mount and brass deflector off:

looks good but why did you add back a 1/2 lb with that monster brake? lol that thing is a beast!