When I was trained in the corps I was tought to make a super tight sling lock on my arm, to the point of causing nerve damadge to my sling arm. Now I see free float tubes up the wazoo, & it's suposed to cause better accuracy by not pulling the barrel. The next thing I notice is all sorts of sling attachments that are for the front sight, or gas tube rail. I may be crazy but it seams to me that having anything touch the barrel with any pressure at all seems like it would take away from the accuracy. My question is why does the tork on the muzzel brake affect accuracy, & why?

For starters, by using a DCM tube hand guards, the barrel never touches the tube, and the sling point is on the front of the tube.  You can sling up as tight as you want, and only deflect the tube, leaving the barrel untouched by the sling pressure.
Take a good look at a DCM rifle and you will see two sling attachment points.  The first being at the front sight on a standard rifle, and is not used. The second is just behind the front sight and is attached to the end of the tube, and is used for the attachment point of the sling.

As far as you’re questions regarding brake nut torque? As long as the nut does not deform the threads, then there is no pros or cons.  The real difference would be if a barrel tensioner were used between the end of the barrel and the front sight.  This will allow the front portion of the barrel to be kept in tension.  Basically, the device is just a piece of tube that fits over the barrel, and is jammed into the front sight by the muzzle device.

If your thinking about a device like the Browning Boss, it is used to make the barrel slightly longer or shorter to allow the bullet to exit the barrel during a high/low point in flex (think barrel harmonics and counter weight).

Hope this helps.

Thanks Dano, but I read somewhere that making the muzzel brake to tight could affect the accuracy. Also I see alot of pic's of weapons with free flot tubes, or ras & front sight sling attachments on them, or other points that would put pressure on the barrel. I do understand that free float systems should have the sling attached to the tube somewhere. Why is it though that we (Marines) could shoot a human target at 500 meters with open sites with a sling pulling so hard sideways on the barrel? I mean I cant see where it would have much consistancy from 1 trip to the range to the next.

The marines only told you that you could do that. In combat by the time you got all dressed up into that tight sling position you speak of you would already be dead.

That's for range work only. You can easily get 6" of deflection from a tight sling.

No, searcher's got a point! I remember doing the same thing, getting solid hits at 500m, and this with a M16A1 with the despised "pencil" barrel! So, if I can shoot Expert with such a rig, why bother with a free float?

Getting hits on a person size target is not even coming close to the limits on a service rifle. Within this loose confine, anything they can do to tight your position, and get you to consistantly hit, makes them happy.
In serious service rifle competition, winners and losers are measured in inches (in hundreds of yards), not targets. One removes all the varibles, as it would be impossible to sling in with exactly the same tension, in the same place, every time, you remove this varible. Freefloating the tube and mounting the sling from it greatly helps.
For "combat" use the handiness of the carbine is deemed more important than 1/2-3/4 MOA differance when slinging in, and so there are several sling gadgetry things.

I thought the reason for a sniper tightening the sling and his body was to provide a more stable platform for the rifle i.e. reduce bodily movements?

I remember a converstaion with an Army Marksmanship Unit member about this subject during the 1980s about this at a clinic (do they even have rifle teams at the high school level anymore?).

He said that using a tight sling with an M16 did effect accuracy, particularly at long ranges, and would significantly change your point of impact due to the barrel "flexing." The difference was, that if you were consistent, and "tied in" the same way every time, including for zeroing, you would have the roughly same difference every time, and would retain the ability to accurately and consistently hit your target. That explains how you could consistently get long-range hts with a tight sling. But, if you want to stay accurate, you would always have to use a tight sling with a weapon zeroed for that, or at least know your offset aiming points for no sling.

Here's something that will just never understand...

The very High-Speed KAC folding front sight is mounted on the FF RAS.

Shouldn't it be on the Barrel?
If the the Barrel is isolated from torque by the FF Tube, does it make sense for the Front Sight to be on the part that is getting all of the torque?

I've never understood this, how weapons designers as sharp as the guys from KAC could come up with this.

Am I wrong here?

Yes, using a tight sling attached to the front sight will change the point of impact.  In some cases, the change is rather dramatic.

In competition, we used to mark our slings with marker for the different lengths reqiured for several shooting positions (offhand, sitting, prone).  This way, we were able to accurately reproduce the same sling pressure at each firing line during a match.

Oh, and yes, we were using M16A1s during these competitions.

I too shot expert with the M16 service rifle when I was in the Army.

But.........since I am not shooting at the enemy anymore, I enjoy making little holes as close togeather as I can.  So I use all the accuracy tricks.  One of them is free floating the barrel.

Rambosky

The best shot I ever witnessed was done by a fellow Marine from the 500 meter range. He was on a different relay than me, on the target next to the one I was pulling. Remember this was done with a tight sling setup. The 500 meter target is a human shape from about the waist up. He had put one center mass into the chest, & after the target was marked with the white spoter disk, which has a pin slightly larger than 5.56mm, & sent back up. His next shot keyholed the pin out of the target & droped the spoter down in the butts!!! now that's 5 1/2 football fields away Around 30 to 60 seconds apart, & after stopping to mark previous shot in range book! Understand I am not a smart-aleck, but in a cqb situation is free floating an M-4, or an AR-15 going to make enough difference to justify the cost/tactical advantage? I mean, even a piece of crap AK-47 can somewhat hit a target at 200 meters. Again I'm not trying to start a fire, I'm just really trying to understand the accuracy difference & what it all boils down to in a cqb situation that we might expect to face given shtf time. I personally believe one should not have a rig that is blameable for loosing in a life & death situation, because the cost of a good weapon,& gear just means nothing when facing the last frontier. Respectfully the Searcher.

A good Marksman is always highly disciplined.

Look at who shot well in Boot Camp, and who didn't.

Learning to shoot on the Marine KD course is about discipline.  Hell, a WEEK of "snapping in"??
That's about discipline.

Is having extremely disciplined Marines a good thing in a CQB type engagement?
Damn right it is.

Oh, how I HATED that week of snapping in!

Oh the memories! Snapping in drove me crazy when I was at Parris Island. Just give me some damn bullets so  can shoot something! I thought for sure the DI's were just trying to torture us. Remember how they made you hold your scuz brush? Just like you were pulling the charging handle on the M16(which had so much slop between the upper/lower you could see daylight through it).

Although I didn't know it back then, I too was puzzled to find out that a tight sling could deflect bullet impact. It makes sense, but they sure as hell didn't tell us that in bootcamp. And at the School of Infantry they dropped the sling technique as far as I can remember. Kinda hard to shoot and scoot with a sling like a noose around your arm. I was a SMAW and Dragon gunner anyways.

I was never in the service. But I think they teach shooting with the sling, As a way of teaching the fundamentals of good Marksmenship.  Yeah the whole sling thing goes out the window in combat but you still have to teach the fundamentals.

Allthough I've never been in combat, I can still see how getting into a sling arm could be aplicable in open comat at longer ranges. In some instances I'm sure it has happened that at long range & I'm talking 500 yards or better a rifle squad has met a rifle squad. Mono e Mono, & I bet the guy using a tight shooting position was able to make a lot more dead guys than the guys that just did their shooting willy nilly like a bunch of numnuts. Yes, dahh, I know that getting into a sling pos is hard, but not impossable, but like a deer hunter in ambush on open ground, so is a soilder that knows that the enemy is approaching, "prepared". Again don't read to much into this coment as I was in the Corps, & I know that part of being prepaired is to have a fighting hole. Yes it is basic rifle tech, but that is the Marine standard, That every Marine is a rifle man when it comes down to shtf time. At 500 meters the front site post on a  M-16 covers the target about 99% so to make a hit in these sircumstances is difficult, on paper. I'm sure it must be harder on a living, moving human target at that distance. I've seen alot of Army dogs in the news that have Trijicon equiped weapons, any one know if the Marines have them yet? & if so is it now a standard issue thing for the grunts? I was a machinegunner in a heavy machinegun plt. Those SMAWS were louder than hell. Glad it was you & not me. I loved my .50 cal.

...known in the Corps as "Sling Palsy".

During my Army days (83-95), the sling was just a way of carrying the rifle at shoulder arms.  There was no talk of using the sling during shooting.

Hey Redleg, what was the distances for rifle qual in the army when you were in? When I was in the Corps we shot from 200,300,& 500 meters in a variety of positions. I would like to see someone hit a torso sized target consistantly at 500 meters with no rifle point of contact with the ground , & open standard sights with no sling lock down. I would be extreamly impressed to see it done with any consistancy, I wouldn't doubt there are some who could, but their busy with the olypmics, Or with being my new heros!

Army qualification consisted of popup targets at 50, 100, 150, 200, 250, & 300m - half from a standing foxhole position and the other half from the prone position.

In singles combat rifle competition, it was 10rds (8/2 w/ a mag change) at 100m rapid-fire from an offhand standing position, 10rds (8/2) sustained-fire at 200m from a seated position, 10rds (8/2) sustained-fire at 300m from a prone position, and 20rds (single shot) slow fire at 400m from a prone position.

Thanks for the reply Red-leg. I would love to have tried shooting something moving. All the Marine Corps targets were stationary, & all our shooting was from level ground. We never got to shoot from a fighting hole. I have shot about 1/2 dozen running deer with my AR, & I found the ones running full tilt were much easier to hit than the ones that lope.I Missed 5 shots at a deer that was loaping at a slight angle towards me. It was imbearasing as all heck. I stoped because I was schocked I hadnt hit it. I got a shot at the same deer at 3 times the distance a few minutes later at a dead run & got my, "hum" 1 shot 1 kill ratio back on track