View Full Version : Why Free Float a Carbine Rail System?
Now don't get hostile folks!
I'm just curious why there are so many Free Floated Carbine Rail systems available. To me a FF is what you want on a precision gun or an SPR or whatever. Why go to the trouble and expense of a FF on a CQB/Mid range weapon?
They're generally more expensive and harder to install.
1) Better for the "gangsta" grip, front grips.
2) Good for ease of light mounting.
3) Barrel seems to cool faster.
4) Looks better on my guns.
Correct me if I am wrong ... and I may be ... but all the top quality rails are pretty expensive, and I think most of the top quality rails are FF. The one's that are not (SureFire?) are expensive anyway.
So why not free float the barrel if you are putting a rail on?
That said I wouldn't put a rail on JUST to free float the barrel, either. But if you're in need of a rail, why not free float?
Additonally longer bolt life and increased reliability.
*According to a telecon I had with Gus Taylor
Correct me if I am wrong ... and I may be ... but all the top quality rails are pretty expensive, and I think most of the top quality rails are FF.
To me the KAC RAS is at least one of the Top Dogs, and it's not FF. :confused:
So why not free float the barrel if you are putting a rail on?
All things equal, I agree. But if you have to take off the FSB (with most FF you have to) then all things are not equal.
Additonally longer bolt life and increased reliability.
I'm going to have to digest that one for a while. :eek:
I'm out the door for a mission - but I will add to it when I'm back.
I'm out the door for a mission - but I will add to it when I'm back.
Be careful!
Robb Jensen
09-24-07, 12:11
Additonally longer bolt life and increased reliability.
*According to a telecon I had with Gus Taylor
I'm going to have to digest that one for a while. :eek:
Here's the geek-speak.......most FF rails feature a different bbl nut (not steel) which works like a heat-sink which allows the bolt area of the upper receiver, bbl extension, chamber and thus the bolt as well to cool more quickly. It's been proven that adding rails like the LaRue and DD M4 type rails with non-steel bbl nuts have lower levels of 'cookoffs' when run hard and hot.
As the barrel heats up from firing parts like handguards, handguard caps, delta ring etc all expand and contract and different rates, the way you're holding onto those handguards will influence whats going on with the barrel. On a free floated barrel nothing but the gas tube is in constant contact with it and thus no influence from outside forces.
Ideally all ARs no matter the barrel length should be free floated for consistent accuracy (nothing messing with the harmonics of the barrel). Imagine someone like Joe Satriani playing his guitar which sounds great and then you go over and hold down some of the strings while he's playing, it's probably not going to work nor sound very good at all.
All things equal, I agree. But if you have to take off the FSB (with most FF you have to) then all things are not equal.
I think that's relative. With the right tools, removing the FSB is a non-issue. Even without the right tools, it varies from minor annoyance to just paying someone else to do it.
The first DD rail I bought I got from ADCO. I just sent them my upper and back it came with the FSB shaved and the rail installed. Pretty damn painless! :D
I also just plain find the free-floats like the DD and LT to be more secure and stable. I've owned a RAS (or was it a RIS?) and didn't care for the attachment method. Do I NEED a FF rail and the better attachment method? Probably not. But either with a minor investment of time or cash it's worth it to me.
Primarily, free-floating allows secure attachment of accessories without play or movement. Vertical fore grips are secure, optics remain zeroed, bipods won't have any effect on accuracy. Most carbines with non-free floating handguards are still more accurate than their owners/shooters. Depends on your usage and what level of 'cool' you aspire.
Yeah. If you were running an Eotech way out front I could see wanting a FF.
But as far as VFGs and Lights, the KAC mounts up really tight. I know some of the Cheapo 2 piecers wiggle though.
toddackerman
09-24-07, 13:54
For me, it allows me to "Quick Change" barrels on my LMT MRP upper. Release two "TorX Screws" and off it comes, and on goes the other. Nothing is touching the barrel other than the gas tube.
Tack
I also like the free floated set ups. My rails of choice are DD.
Although I do admit that my latest build KISS (my version of it) has standard handguards.
Basically LMT 16" upper with troy buis on stag lower.
back,
I beleive that even a steel bbl nut affixed onto the rail will act as a heatsink to some extent.
The advantages to the FF system (depending on mount type) can allieviate the pressure on the barrel from a vert grip etc.
All weight on the barrel will contribute to forcing the barrel/barrel extension slightly out of alignment - thus forcing more pressure on one side of the bolt - especially on unlocking the locking lugs of the bolt will have unequal pressure exterted upon them - and thus lead to reduced bolt life.
With a more uniform pressure/lock, this then decreases wear and inturn leads to great life and reliability. Additionally this is another place where thin barrels with suppressors suffer greater bolt failure than thicker barrels.
Crane had a metric ton of data on this stuff for those with access who are curious.
For me - popping a FSB is a minor issue - and I feel the added benifits of a FF rail are worth the few extra dollar for the rail, and the few minutes to pull the FSB and barrel to replace the nut etc.
Yeah. If you were running an Eotech way out front I could see wanting a FF.
But as far as VFGs and Lights, the KAC mounts up really tight. I know some of the Cheapo 2 piecers wiggle though.
The KAC RAS is a very good rails system. The thing to remember though is that it is more money then most of the 1 piece FF rails on the market and they don't give you the benefit of less stress on the barrel.
C4
I know the Crane geek speak and it all really applies to full auto carbines.
Even burst fire guns don't have near the problems the full auto guns do and those problems are mainly caused by operators insisting on using the carbines as light machine guns.
The excessive heat with bolt failures rarely occurs with semi auto guns.
Bolt failures on semi auto guns are generally associated with out of specification bolts.
I have yet to see a semi auto carbine pop a barrel and I do repairs an many match used rifles and carbines.
Free float forearms generally make an accurate rifle even more so by relieving the already noted stresses on the barrel.
If you aren't trying to make a Match gun out of a semi auto version of a burst fire/full auto battle carbine then a standard, tight fitting, delta ring mounted rail forearm will work just fine and you have the advantage of switching the forearm out for standard handguards anytime you desire to do so.
AR15barrels
09-24-07, 19:44
I'm just curious why there are so many Free Floated Carbine Rail systems available. To me a FF is what you want on a precision gun or an SPR or whatever. Why go to the trouble and expense of a FF on a CQB/Mid range weapon?
Grant already beat me to the point, but here are some real numbers...
Knights RAS from Operation Parts: $316
LaRue 7.0 from about Anywhere: $250
DD M4 7.0 from about anywhere: $275 (includes 3 rail covers)
Installation of a freefloat handguard by a gunsmith: $25 to $50
So, you can buy a LaRue or DD handguard AND pay someone to install it cheaper than you can buy the Knights RAS that you install yourself.
The dedicated freefloat will be more solid than any system that snaps-on with the delta ring.
I have had allot of "play" with every Knights RAS I have had. My PEQ2 was always messed up. I only go with FF rails now.
To me the KAC RAS is at least one of the Top Dogs, and it's not FF. :confused:
All things equal, I agree. But if you have to take off the FSB (with most FF you have to) then all things are not equal.
I said "most" were free floated - there certainly are good, non-free floated rails. I never said there weren't so I am not sure what's confusing.
Personally, if I were spending that kind of money for a rail having someone remove the FSB wouldn't matter to me to get exactly what I wanted. But that's just me.
I like the ease of the Troy FF Rails.
Plus it is not very expensive IMHO.
The foremost reason for me has always been the increased cooling factor. As GotM4 and KevinB have already pointed out, the better ones act as pretty good heat sinks. They also allow better airflow around the barrel. How much of each of these they do can be debated, but I personally can tell a difference.
I got to be part of a informal test where we ran 3 mags full auto through various uppers, with an industrial grade digital thermometer. We noted the handguard temps at their highest point, the barrel temps, and the time it took the barrels to cool back down to a specific point. Free floated ones with good quality systems consistently had lower handguard temps, and faster barrel cooling rates.
Excellent info...
thanks, guys.
Turbo Supra
09-25-07, 13:00
Wow! :eek: Great responses, guys! I love the insightful info gained here as opposed to the mindless BS at the "other" AR website. :)
TheGhostRider
09-25-07, 16:49
I'm out the door for a mission - but I will add to it when I'm back.
Remember...
When all else fails...
Duck!
;)
cover your 6 and bring back some stories.
Kevin is my fookin hero, really:D Kev stay safe man!
All this FF for non-precision stuff confuses me,
I understand it is more solid for lasers/optics, but some non FF systems are pretty damn solid.
Cooling? Perhaps, but is it going to REALLY keep you from getting a cookoff or bbl meltdown?
Without destruction testing its all just talk on the internet.
For me, as an engineer, I am hesitant to put a big ass lever needlessly on a critical part.
The part about different expansion rates interests me, need more info on that guys!
Just talking out my ass here, as you can tell:D
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