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View Full Version : has anyone ever actually tested freefloat vs standard?


justinlemieux
07-04-2012, 8:28 AM
has anyone ever actually tested freefloat vs standard on an ar 15. I use ff rails all of the time, but i wonder if it makes a lot of difference. in a bolt gun with no gasblock it makes sense. just wondering if any saw big accuracy improvements after swapping rails.

CIV Tactical
07-04-2012, 8:38 AM
I have heard of of people increasing there accuracy by a factor of 2 when they switched to a free float. This means they cut there grouping size in half. It does make a difference.

Hoop
07-04-2012, 8:42 AM
I find rifles group a little better and shoot much more consistently free floated vs. not.

Gunfighter420
07-04-2012, 8:47 AM
I use free float rails because I use two point slings. When I shoot slung, I shoot with a lot of tension to keep the rifle tight and don't want my sling torquing on the barrel at all. Even a slight bend when slung is inches at 100yds if you're shooting for accuracy. That's the only reason I use freefloat. No matter how you shoot with a freefloat, you'll never put any tension on your barrel and will always be in line with your optic or ironsights. That brings me to another topic. Sometimes I'll see pics of optics mounted on the rail and for me thats a big no-no. Optics should always be on the upper receiver because the barrel is attached to the upper receiver and they will always be in line. If the optic was on the rail, any tension on the rail will throw off your zero. I tested just how much force is required by pinching the barrel and rail together near the muzzle and it doesn't take much to see how much it bends. If you really pinch it hard, the barrel and rail will almost touch if you have a 12" rail like I do. If you have to sling with a standard drop in rail, I would highly reccomend the sling attachment is as close to the barrel nut as possible so it doesn't torque as much on your barrel if it was attached near the muzzle. Anyway, thats my $.02.

has anyone ever actually tested freefloat vs standard on an ar 15. I use ff rails all of the time, but i wonder if it makes a lot of difference. in a bolt gun with no gasblock it makes sense. just wondering if any saw big accuracy improvements after swapping rails.

tuna quesadilla
07-04-2012, 9:05 AM
No, it's completely untested an the only reason the military uses it is because it looks cool.

Come on, what did you expect with a question like that? ;) Of course there's a benefit to free float. It may or may not shrink your groups, but it WILL allow you to be more consistent from shot to shot when resting the rifle on different types of surfaces.

starsnuffer
07-04-2012, 9:06 AM
^
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Gunfighter has it right. If you're just shooting from a bench and the only torque on the barrel is the weight of the weapon, you're fine either way. If you're using a sling properly then you will be putting a lot of torque on the barrel and it will bend enough to matter an MOA or so depending on how hot you get.

Either is fine for hitting minute of watermelon at 100 yards, so it really depends on your use and what you're going to be happy with.

-W

tuna quesadilla
07-04-2012, 9:10 AM
^
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Gunfighter has it right. If you're just shooting from a bench and the only torque on the barrel is the weight of the weapon, you're fine either way. If you're using a sling properly then you will be putting a lot of torque on the barrel and it will bend enough to matter an MOA or so depending on how hot you get.

Either is fine for hitting minute of watermelon at 100 yards, so it really depends on your use and what you're going to be happy with.

-W

When I went to my first Appleseed I took my basic, non-free-float, AR-15 carbine, because the idea is to use a standard off the shelf military rifle. The carbine had been sighted in on a benchrest but of course, when we do the Appleseed we shoot from sling-supported positions.

My first few groups were 3 inches low at 25 yards. Extrapolate that out to 100 yards and I would have missed the target by A FOOT. I now know that I was putting way too much tension on the sling and I could have used less tension and still been just as stable, but with a free float that wouldn't have even happened in the first place.

starsnuffer
07-04-2012, 9:20 AM
Are you sure it was a carbine and not a rifle? That's a pretty severe bend when you consider the gas block/sling mount is not that far from the bolt. Rifle length gives you more leverage and more barrel to bend.

Any comments on the profile and construction of the barrel? If it was a pencil barrel and not CHF then it would be easier to bend then a full profile cold hammer forged barrel. A 12MOA deviation from bending the barrel is pretty insane, even pig-iron Chinese PSL's don't bend that much.

-W

tuna quesadilla
07-04-2012, 9:24 AM
Are you sure it was a carbine and not a rifle? That's a pretty severe bend when you consider the gas block/sling mount is not that far from the bolt. Rifle length gives you more leverage and more barrel to bend.

Any comments on the profile and construction of the barrel? If it was a pencil barrel and not CHF then it would be easier to bend then a full profile cold hammer forged barrel. A 12MOA deviation from bending the barrel is pretty insane, even pig-iron Chinese PSL's don't bend that much.

-W

16" Sabre Defence government profile with midlength gas.

I'm just telling you what I and others personally observed that day. :cool:

justinlemieux
07-04-2012, 3:54 PM
tuna quesadilla...."because the military uses it" does not mean its the best. there as much victims of "guchi" stuff as civilians are. the military using it...to me..isnt proof that its awsome

OutlawDon
07-04-2012, 4:03 PM
This is old news. Search on ar15.com for plenty of info.

http://ar15barrels.com/tech/freefloat.jpg

Merc1138
07-04-2012, 4:11 PM
tuna quesadilla...."because the military uses it" does not mean its the best. there as much victims of "guchi" stuff as civilians are.

There's nothing "gucci" about a freefloated barrel.

As people have tried to explain to you, the entire point is to make sure there is nothing affecting the barrel. Applying pressure in any direction, and any changed in that pressure applied can affect accuracy. That pressure can be from a sling, a bipod, a rest, even a wood stock changing shape slightly due to heat/humidity.

You could bed a barrel to stabilize it as well if you could get it rigid enough, although I couldn't tell you which would be better after the fact. But the thing to consider with the bedding option, is that it takes more time, more material, adds more weight, more cost, and is probably a heck of a lot harder to get as consistent as simply not touching the barrel if you don't have to.

justinlemieux
07-04-2012, 4:44 PM
thanks outlawdon. exactly what i was looking for

kendog4570
07-04-2012, 8:01 PM
has anyone ever actually tested freefloat vs standard on an ar 15.


I believe the US Army Marksmanship Unit did around 20+ years back. They found that isolating the barrel from irregular sling tension made for rounder, tighter groups. It was also found that constant sling pressure in the A2 configuration, while it would move the group, would produce tight round groups as well, just not too many shooters can hold that constant pressure for a sustained period of time.

docsmileyface
07-04-2012, 9:39 PM
its not tighter groups you get, its less deviation from point of aim to point of impact. With non freefloating barrels like Kendog explained outside forces can change your POI - ie using sandbags or other barrel support will make your impact higher then when you are shooting off hand. Free floating helps mitigate that.

tuna quesadilla
07-04-2012, 9:47 PM
tuna quesadilla...."because the military uses it" does not mean its the best. there as much victims of "guchi" stuff as civilians are. the military using it...to me..isnt proof that its awsome

Try reading my post again... don't overthink it. ;)

The final, undebatable answer is that FF removes human inconsistency from the equation. I facepalm every time somebody says "are you even a good enough shooter to take advantage of free float?" It's NOT about accuracy, it's about POA vs POI. After my own personal experiences with FF vs non-FF, I refuse to own a non-FF AR. On a non-FF AR you are forced to never use any kind of rest or barricade and always use a magwell grip if you are concerned with shot-to-shot consistency.

FMJBT
07-04-2012, 10:19 PM
Are you sure it was a carbine and not a rifle? That's a pretty severe bend when you consider the gas block/sling mount is not that far from the bolt. Rifle length gives you more leverage and more barrel to bend.

Any comments on the profile and construction of the barrel? If it was a pencil barrel and not CHF then it would be easier to bend then a full profile cold hammer forged barrel. A 12MOA deviation from bending the barrel is pretty insane, even pig-iron Chinese PSL's don't bend that much.

-W

12 moa is only a deflection of .2 or 1/5 of a degree, not hard to believe at all. Hammer forging has very little to do with a barrels resistance to bending. Heat treatment and the resulting rockwell hardness will have a much greater impact on flexibility than barrel construction or material. Pencil barrels will of course be more flexible than medium or bull profile barrels, but two barrels of the same profile will show very little if any difference in bending strength provided they are both treated to the same hardness level.

USAbodypilot
07-04-2012, 10:45 PM
If you're using a sling properly then you will be putting a lot of torque on the barrel and it will bend enough to matter an MOA or so depending on how hot you get.


You are on the right track but what you see happening and what you think caused it are a little off. You can't reasonably 'bend' a barrel with your sling pressure, not even a pencil barrel. That said what you can do is dramatically change the harmonic resonance of any barrel, the thinner the barrel the more easily you can mess with it with small pressures and contacts.

You might get lucky if your sling or other barrel pressure point such as a rest or stock contact is consistant such that it will just shift your POI - that does not mean you have BENT your barrel to aim at that new point. It just means that the additional mechanical input has changed the natural harmonics of the barrel and it will spit the bullet out a little different than the same barrel without that same contact/pressure.

Free floating is often more predictable as it allows the barrel to resonate naturally with minimal variation from shot to shot as the barrel contact/pressure is more constant.

It does not follow that free floating is always worth the effort/cost though!

docsmileyface
07-05-2012, 6:10 AM
here is my experiment to you doubters - shoot 10 rounds from a prone position using a sandbag under the barrel, then shoot 10 rounds using the weapon supported by the magazine with no force at all under the barrel and use a magwell grip like Tuna said and see where your two groups land on paper. No doubt the size will be the same, they'll just be in very different places.

mif_slim
07-05-2012, 7:32 AM
FF vs non-FF doesn't matter much. If your nonFF is tuned right it'll shoot just as good or even better. Same is true to FF. Some gets worst groups putting FF on because they've changed the harmonics of the barrel.

All FF does is make the barrel more consistent because different pressure from nonFF can and will change POA/POI.

HighLander51
07-05-2012, 12:45 PM
Derrick Martin figured it out back in 1976 and made his own free float handguards from lefter M16 parts to isolate the barrel from the handguard sling attach. The barrel is the same as always, it's the handguard that is 'floated'

I use the PRI carbon fiber handguard myself, it is indexable.

http://www.accuracyspeaks.com/bio_on_derrick.htm

Donk310
07-05-2012, 2:02 PM
FF vs non-FF doesn't matter much. If your nonFF is tuned right it'll shoot just as good or even better. Same is true to FF. Some gets worst groups putting FF on because they've changed the harmonics of the barrel.

All FF does is make the barrel more consistent because different pressure from nonFF can and will change POA/POI.

^^ This guy has it right. All of my rifles are free floated except for one. The one that is not, my DDM4, used to be but I switched it back to its original configuration to preserve the "M4 look", since the free float system did not better my shots. This rifle is so tuned that I out-shoot the guys with the free floats. The best thing to do is conduct your own testing. You may be better with one than you are the other. Both systems need a marksmen to apply them accurately.

USAbodypilot
07-05-2012, 4:32 PM
Rifle length gives you more leverage and more barrel to bend.


Have a read of the posts above, you really are not bending the barrel to alter the POI.

AfghanVetOrcutt
07-05-2012, 4:58 PM
No, it's completely untested an the only reason the military uses it is because it looks cool.

The military doesn't normally use a free float. M4s and M16s have the 2 piece drop in hand guards in either the old plastic or the newer railed versions.

tuna quesadilla
07-05-2012, 5:37 PM
The military doesn't normally use a free float. M4s and M16s have the 2 piece drop in hand guards in either the old plastic or the newer railed versions.

Yes, that's very common knowledge.

Look at rifles such as the SDM-R, SAM-R, and M4A1 Block II SOPMOD, Mk. 18 Mod. 1, Mk. 12 Mod 0/1, etc etc.... to see why my implication that the military uses and has used free float is 100% factually correct.

justinlemieux
07-05-2012, 5:42 PM
thanks everyone for clearing this up. makes a lot of sense. thanks tuna for all you input.

Yugo
07-05-2012, 5:44 PM
I dont know but what I do know is one time watching American Guns there was a video SLOW MOTION of a free float AR and when it was shot you can see how the barrel moves before the rest of the gun so judging by this if you have a standard hand guard your barrel will be affected by the solid hold VS. a free float where it can travel naturally. So it seems that a non skilled shooter will have a better "score" using a free float.

phish
07-05-2012, 5:53 PM
^^ This guy has it right. All of my rifles are free floated except for one. The one that is not, my DDM4, used to be but I switched it back to its original configuration to preserve the "M4 look", since the free float system did not better my shots. This rifle is so tuned that I out-shoot the guys with the free floats. The best thing to do is conduct your own testing. You may be better with one than you are the other. Both systems need a marksmen to apply them accurately.

funny, because that post contradicted itself and made absolutely no sense

not to mention it contained the much parroted word "harmonics" with no explanation as to what it really means in this particular context

"tuned", wtf does that really mean? like tuning forks used for pianos?

mif_slim
07-05-2012, 6:50 PM
Tuning means the whip of the barrel has less whip causing the bullet to fling less. Freefloat basically lessens the chance of inconsistent pressure on the barrel. For example, wood flexes and bends during cold/hit weather. This bend puts pressures on the barrel causing the barrel to be fling differently from the last range trip the gun was sighted in. So, that changes the POI from POA.

When the barrel is tuned (glass bedded, freefloat, etc) it gets better consistency therefore the term "tune". The reason why reloading makes more accurate ammo is because they tune it to fit the barrel. Factory load is to shoot and cycle majority of the guns so their more on the highend velocity/pressure. My reload ammo maybe subMOA but because your barrel has different harmonics it can be less or more accurate then mines.

USAbodypilot
07-05-2012, 9:17 PM
.... it contained the much parroted word "harmonics" with no explanation as to what it really means in this particular comtext
"tuned", wtf does that really mean? like tuning forks used for pianos?

Ok so there is a LOT of stuff on the net explaining how the different order harmonics mix in a barrel to give unpredictable results. Perhaps this tuning article covers some of the more practical things YOU can look at to make a rig more consistant for your shooting use...

http://en.wikipedia.org/wiki/Accurizing

Some people 'parrot', others study and learn.

phish
07-05-2012, 9:38 PM
oh oh! Wikipedia so it must be true! yeah, love the little disclaimer at the top of that "article", try again

http://www.sinclairintl.com/.aspx/pid=35166/Product/Rifle-Accuracy-Facts-Soft-Cover

this one's written by an accomplished and legit rocket scientist, not some anonymous interweb jockey

USAbodypilot
07-05-2012, 9:51 PM
oh oh! Wikipedia so it must be true! yeah, love the little disclaimer at the top of that "article", try again

Did you read it? While light on detail there is some very good stuff on the wiki page.

Donk310
07-06-2012, 4:53 PM
funny, because that post contradicted itself and made absolutely no sense

not to mention it contained the much parroted word "harmonics" with no explanation as to what it really means in this particular context

"tuned", wtf does that really mean? like tuning forks used for pianos?

Pay more attention to the last 3 sentences. Hardly worth my time to explain what you can be figuring out on your own.

phish
07-06-2012, 6:58 PM
well by all means, enthrall me with your acumen professor...

DBR
07-06-2012, 8:23 PM
Do a search on receiver flex. Yes, you can bend the barrel on an AR with sling tension if the sling is attached to the barrel. Actually you are most likely changing the barrel's harmonics.

However, when you use a free float fore end the float tube is attached at the barrel nut and any bending moment on the fore end will flex the receiver. This results in barrel angular displacement. Without a sling on the fore end or a forward grip being pulled back a free floated barrel is probably not influenced by the shooter's hold. But, the free float does not isolate the barrel from anything that flexes the receiver.

http://www.m4carbine.net/showthread.php?t=58