D.R.D. Posted May 30, 2014 Report Share Posted May 30, 2014 This may not be a 308 specific question, but I thought I'd ask... On an AR15 with a 16" or 14.5" barrel, will using a free floating vs, non-free floating handrail really make much of a difference in accuracy within 100 yards? Quote Link to comment Share on other sites More sharing options...
98Z5V Posted May 30, 2014 Report Share Posted May 30, 2014 Depends on how you shoot it. If you use a 2-point sling, and usually sling up tight, you'd see an accuracy difference between freefloated and non, at 100 yards. Beyond 100 yards it does make a difference. Freefloat it. Quote Link to comment Share on other sites More sharing options...
planeflyer21 Posted May 30, 2014 Report Share Posted May 30, 2014 Just to add to that, the longer the barrel is the more noticeable the flex will be. Quote Link to comment Share on other sites More sharing options...
survivalshop Posted May 30, 2014 Report Share Posted May 30, 2014 (edited) The whole point of a free float hand guard is just the same as with free floating a bolt action or any other rifle , it is to eliminate or reduce any contact points between the hand guard & barrel . Letting the barrel free float or not interfere with the barrel flexing /whipping, so as to let the barrel respond naturally to pressure waves upon cartridge ignition & behind the bullets travel down the barrel . So, the answer is , yes , any barrel length & any range . Edited May 30, 2014 by survivalshop Quote Link to comment Share on other sites More sharing options...
D.R.D. Posted May 30, 2014 Author Report Share Posted May 30, 2014 Thanks Quote Link to comment Share on other sites More sharing options...
planeflyer21 Posted May 30, 2014 Report Share Posted May 30, 2014 The whole point of a free float hand guard is just the same as with free floating a bolt action or any other rifle , it is to eliminate or reduce any contact points between the hand guard & barrel . Letting the barrel free float or not interfere with the barrel flexing /whipping, so as to let the barrel respond naturally to pressure waves upon cartridge ignition & behind the bullets travel down the barrel . So, the answer is , yes , any barrel length & any range . Right...for dynamic flexing. Remember too that free floating was originally an answer to the problem of wooden stocks expanding and contracting with temperature and humidity. Sight in your 24" barreld rifle at 5% humidity on a cold day, then hunt in the rain 15° warmer and zero is gone. "Static flexing" if you will. Bedding was the other answer to static flexing. Not much call for bedding anymore with metal forearms and stocks. Quote Link to comment Share on other sites More sharing options...
D.R.D. Posted May 30, 2014 Author Report Share Posted May 30, 2014 (edited) The build is a lightweight AR platform. Lower - New Frontier Arms LW15 Polymer (complete) Upper - Lightweight S&W stripped w/o forward assist or port cover BCG - Ares Armor NiB CH - BCM Gunfighter mod 4 BUIS - Magpul rear MBUS PSA or BCM A2 Front sight block Barrel - 16" AR15 Performance Melonited CMV lightweight mid-length in 223 Wylde 5R hybrid 1:8 twist Muzzle device will be either a GoGun (NoTalon) SupperComp or a Griffin Armament M4SD II FlashComp (Which ever shoots better) Then, I may have the barrel cut down to 14.5 and pin on the muzzle device So,...that leaves the handguard. It's either gonna be: Magpul MOE Mid-length (8.7oz., 9", $30, non-free float) http://store.magpul.com/product/MAG418/184 or Strike Industries Mega Fins keymod rail (under 7 oz., 11", $130, Free-float) - they will be coming out with one in a month that is cut out for A2 front sight posts. http://www.strikeindustries.com/shop/index.php/rifle-accessories/ar/handguard/ar-mega-fins-key-mod-handguard-rail-9-black-448.html While trying to keep this as light as possible, I'm also wanting to keep the cost down as much as I can without sacrificing performance (tactical training CQB - to 200 yards max / maybe 3-gun) and put the saving towards my 308AR builds. So, for and extra $100, the Strike Mega FIns rail gives be a savings of about 2oz, 2 more inches of rail (nice for certain holds) and free-floating. Is the Mega Fins over the MOE worth it? Edited May 30, 2014 by D.R.D. Quote Link to comment Share on other sites More sharing options...
FaRKle! Posted May 30, 2014 Report Share Posted May 30, 2014 A lightweight FF tube is worth it over the MOE + FSB if weight is a primary concern. The less weight further away from you the better. I'd personally grab a MI SSK tube though. Quote Link to comment Share on other sites More sharing options...
D.R.D. Posted May 30, 2014 Author Report Share Posted May 30, 2014 (edited) Why MI if its heavier and more expensive than Stike Mega Fins? Edited May 30, 2014 by D.R.D. Quote Link to comment Share on other sites More sharing options...
FaRKle! Posted May 30, 2014 Report Share Posted May 30, 2014 Why MI if its heavier and more expensive than Stike Mega Fins?Because it's a known quality company. For instance, you know the total weight with MI's 10.5" rail is 7.7oz (including barrel nut and mounting hardware) while the Megafins 11" rail really weighs 9.5oz total (since they don't include the weight of the barrel nut and mounting hardware). Quote Link to comment Share on other sites More sharing options...
D.R.D. Posted May 30, 2014 Author Report Share Posted May 30, 2014 "since they don't include the weight of the barrel nut and mounting hardware" Are you certain about that? Quote Link to comment Share on other sites More sharing options...
survivalshop Posted May 31, 2014 Report Share Posted May 31, 2014 From what you plan to use your rifle for & you want to keep cost down , just go with the MOE . You can always change it later if it doesn't work out . Quote Link to comment Share on other sites More sharing options...
D.R.D. Posted May 31, 2014 Author Report Share Posted May 31, 2014 Farkle, I checked...you are correct! Thanks for pointing that out. Survivalshop, yes...I think that's what I'll do Quote Link to comment Share on other sites More sharing options...
shibiwan Posted May 31, 2014 Report Share Posted May 31, 2014 (edited) Or buy a cheapo float tube from eBay. Won't hurt the wallet that much and they aren't bad at all. Check out the monstrum tactical free float quad rails. Their FDE anodized ones are a good color match if you're looking to go FDE. I had stuck one of them on my old beater (which I later sold) and was really happy with the fitment. Edited May 31, 2014 by shibiwan Quote Link to comment Share on other sites More sharing options...
D.R.D. Posted May 31, 2014 Author Report Share Posted May 31, 2014 Great price, and a good option. I'd put that on a heavier build. I think I'll start with the MOE. If I wanted to upgrade, it would be cause low price was no longer a goal, and probably see if I could find a deal on the BCM Keymod since that's the lightest one out there I've seen that still has an integrated top rail. Tangent: What's the difference in heat transfer between something like the MOE and a keymod rail? Which one gets hotter more quickly? Quote Link to comment Share on other sites More sharing options...
shibiwan Posted May 31, 2014 Report Share Posted May 31, 2014 Great price, and a good option. I'd put that on a heavier build. I think I'll start with the MOE. If I wanted to upgrade, it would be cause low price was no longer a goal, and probably see if I could find a deal on the BCM Keymod since that's the lightest one out there I've seen that still has an integrated top rail. Tangent: What's the difference in heat transfer between something like the MOE and a keymod rail? Which one gets hotter more quickly? It's actually pretty darn light. There are also other Chinky clones of that FF quadrail pattern for around the same price. I believe they all started as clones of the YHM type FF tubes. They all use the same type of barrel nut mounting. Heat transfer? The keymod will warm up faster but will dissipate heat faster. The MOE, being polymer, will take a little longer to heat up but will retain the heat in the barrel for a longer time. Quote Link to comment Share on other sites More sharing options...
D.R.D. Posted May 31, 2014 Author Report Share Posted May 31, 2014 Given I'll be using a lightweight profile barrel, do you think heat will be a big issue with the MOE? (affecting performance....even if I wear gloves;-) Quote Link to comment Share on other sites More sharing options...
shibiwan Posted May 31, 2014 Report Share Posted May 31, 2014 Just how many rounds are you looking to put downrange at a time? Quote Link to comment Share on other sites More sharing options...
blue109 Posted May 31, 2014 Report Share Posted May 31, 2014 I had a MOE on the dissy. I never ran it really hard but it seemed to stay pretty cool. my old clark customs carbon tube sucked. it got uncomfortable after 2 quick mags. Quote Link to comment Share on other sites More sharing options...
gnatshooter Posted May 31, 2014 Report Share Posted May 31, 2014 Copper is more effective than aluminum at moving heat -- so I gotta wonder if there are any copper handguards/float tubes out there. It may not conduct well enough to make up for the heavier weight with the copper, though. Quote Link to comment Share on other sites More sharing options...
shibiwan Posted May 31, 2014 Report Share Posted May 31, 2014 Copper is more effective than aluminum at moving heat -- so I gotta wonder if there are any copper handguards/float tubes out there. It may not conduct well enough to make up for the heavier weight with the copper, though. Copper is too soft for structural parts. Quote Link to comment Share on other sites More sharing options...
gnatshooter Posted May 31, 2014 Report Share Posted May 31, 2014 (edited) Copper is too soft for structural parts. Yeah, I can see that. They use copper for heat sinks on high-end computers where aluminum can't transfer heat fast enough. Even so, aluminum is known for being pretty soft, too. This makes me wonder if the aluminum gun parts out there aren't actually alloys. When they say "crafted from aircraft aluminum" that's probably not a claim that the gun is made from recycled airplanes. If an alloy is a permissible solution to the problem of ductile metals, then maybe brass or bronze forearms/handguards/floaters should be eligible for consideration. Although, weight for weight, even aluminum alloys might still come out ahead. Edit: As we've drifted on this topic into questions of heat management, it might be good to look at: JP Enterprises Thermal Dissipator™ - http://www.jprifles.com/1.4.5_hs.php There's also a discussion of the JP unit athttp://www.brianenos.com/forums/index.php?showtopic=129410 P.S. If we stick to the free-float issue, here's the research paper that I've found to be best about the mechanics of barrel movement and harmonics: Barrel Tuner Analysis: Esten's 6PPC Rifle With and Without a Muzzle Tuner: FEA (Finite Element Analysis) compared to Test Data: Rifle Barrel Dynamic Pressure Analysis http://www.varmintal.com/aeste.htm Varmint Al has likely done more quantitative analysis of firearms, barrels and bullets than anyone else. Edited May 31, 2014 by gnatshooter Quote Link to comment Share on other sites More sharing options...
NTXshooter Posted May 31, 2014 Report Share Posted May 31, 2014 Copper would be too soft. Anyone familiar with Dan Wesson pistols? They were unique in that they were threaded on the end. The barrel shroud slipped over the barrel. And then a barrel nut was torqued against the shroud putting the barrel in tension. I had one and it was very accurate. I wonder how that concept would work on an AR with a free float tube? Quote Link to comment Share on other sites More sharing options...
survivalshop Posted May 31, 2014 Report Share Posted May 31, 2014 Those older DW revolvers , the barrel screwed into the frame , then with a feeler gage ( 0.002" ) you gaped the barrel to cylinder & replaced the shroud & tightened the outer nut onto the barrel to tighten down the shroud , so the barrel & shroud were anchored at both ends , not exactly free floating. I'm still trying to get my .44 Mag DW back , has both an 8" ( ported )& 6" heavy shrouded barrels . Quote Link to comment Share on other sites More sharing options...
D.R.D. Posted June 1, 2014 Author Report Share Posted June 1, 2014 (edited) However many rounds the trainer at the tac courses tell me to put down range :-) Edited June 1, 2014 by D.R.D. Quote Link to comment Share on other sites More sharing options...
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