AR Sponsor
[ARCHIVED THREAD] - FREE-FLOAT VERSUS NON-FREE-FLOAT (Page 1 of 2)
Posted: 9/8/2006 6:10:12 PM EDT
|
I frequently hear this question asked, “How much does a free-float tube improve accuracy?” It only seems logical that removing outside stressors on the barrel using a free-float tube would improve accuracy, yet I’ve never actually done a comparison to see what the difference is. I decided a test was in order. Having recently tested the accuracy of a free-floated Colt 16” light-weight barrel (with a PRI carbon fiber tube) and having the same make barrel in a non-free-floated configuration, I decided these two barrels would make for a good comparison. These barrels are chrome lined, NATO chambered and have a 1:7” twist. This is the same barrel that Colt uses in their model 6520 carbine.  All testing was done from a bench rest at 100 yards and consisted of firing 10-shot groups of hand-loaded 52 grain Sierra MatchKings. A Leupold Vari-X III set at 25X magnification was used during testing. The three 10-shot groups used for evaluation of the free-floated barrel measured 1.06”, 1.42” and 1.47’. The three groups were over-layed on each other using RSI Shooting Lab software to obtain a 30-round composite group. The mean radius for this composite group measured 0.36”. The three 10-shot groups obtained from the non-free-floated barrel measured 1.68”, 1.89” and 1.95”. The mean radius of the 30-round composite group from this barrel measured 0.56”. A difference of 0.20” in mean radius at 100 yards is equivalent to approximately 0.6” or 0.6 MOA.  So in this particular case (shooting from a bench with light-weight barrels) the free-float tube improved accuracy by 0.6 MOA. I imagine a high-speed-low-drag type torquing down on a vertical foregrip or a real-hard-holder sinching up on a sling would realize an even greater benefit from the use of a free-float tube. Here is a pic showing the best 10-shot group from each barrel.  |
|
Nice comparison. I can see where there could be some other variables, ie: rounds through each barrel, production differences between each, barrel-reciever fit, etc. But i think the difference in groups shows that it must make a pretty substantial difference. Thanks for taking the time to run the test and post the results. Very interesting. |
Agreed. An even better test would have been if I had tested the barrel that is now free-floated when it was still non-free-floated in order to have a before-and-after comparison of the same barrel. Alas, I didn't think of doing a comparison until after I had alreday installed the free-float tube. [Yoda voice] Hmmm. In the making, another test, I see. [/Yoda voice] |
|
Good basis for comparison. Another consideration or two, that simulate real world conditions... Sling up both guns. Shoot the same groups with each, and vary the shots within each group to include some with a hard sling hold, some resting solid on a bag only, and some off a bipod, monopod off the mag, etc.. You should find the FF groups to be hugely better than the ones with a non-FF setup. |
| Thanks for the work and the information sharing. I noticed right after I bought my first KAC FF-RAS that my groups shrank about 0.5" on average. I attributed it to the free float; but I've often wondered if just the free float alone could make that much difference when I wasn't using a sling. Looks like it can... |
|
Molon: Thanks for the comparison! The next time you think about running this kind of comparison, could you throw in another set of groups from the control rifle (the one with/out the free-float) but this time remove the handgards and use the spring loaded coupling point at the back of the barrel as the benchrest rest point? This would isolate the different guns/barrels* for only a triffling of added effort. not that there is any reason whatsoever to assume anything other than a fair test. |
I've been busy working on tests for my ammunition thread. I'll probably be busy with that for a while. Molon |
|
Very cool. Thanks for doing the work. My Varminter and 16 V-Match both came so outfitted and the purchases were made "thinking" your results all the way. I shoot alot of bolts and it is easy to see that IN MOST situations, free floating a barrel that came non-free floated (and shot so-so to crappy) can show a very remarkable spike in accuracy. Whether my AR's would show similar results....who knows? But it doesn't hurt the confidence level one bit. Thanks again. |
|
Just to put it on the table, I wonder if the .6" differance between the rifles could be attributed to trigger, more comfortable use of the HG, barrel & sight differances. Yes, a tight sling would make a big differance, but would .6" be in the range of a neglible variance? Considering different components or is it soley the HG design? |
Great stuff Molon ... a good one to tack ... answers the daily question.  M. LaRue |
The next time I do a free-float versus non-free-float test, I promise I'll use one of these  . . .  |
Right click, save as. Thanks Molon, you rock! 
|
Swap the two barrels around. See if the accuracy follows the barrel or the handguard system. Report back. |
|
Also, as suggested earlier, add sling pressure. Set up a hold where the forearms is rested on a hard object, both at the 6:00 and 9:00 positions. Get the barrels hot and see if shots start walking. Good thread. Pics are nice, it's good to see this experiment in action. |
use WHAT?? ARMS scope rings?????????? heretic! 
|
|
+1 have to swap barrels around and re-check results. furthermore, need to add a pressure point to something free floated to each to see if you can influence results for further proof. that is, de-ff the thing! Agreed, 1/7 with a 52 gr? Wasn't free float designed to improve sling shooting? I have seen reports of benched AR's non ff outshooting benched ff's. need much more data. Anecdotally, I know the ff using a sling shoots better vs non ff. holds zero day to day and precision better. hipwr rifle teams know this. in fact, if your ff goes bad so do your groups. Billy |
FF ensures that the harmonics of the barrel don't change when other things change. Such things might be the shape of the wooden stock on a bolt-action in different humidities, contact between the bipod and the ground, weight of lights, etc. on a rail, or sling tension. In the case of highpower shooters with tight slings it's very important to isolate the sling tension from the barrel. For a benched gun, it isn't such a big deal if the pressure on the HGs from the bags can be kept constant so that the pressure on the barrel is also constant. |
[ARCHIVED THREAD] - FREE-FLOAT VERSUS NON-FREE-FLOAT (Page 1 of 2)
AR Sponsor
Join the Community
Your next conversation starts here.
Create your free account to join discussions, share your experience, save topics, and connect with the AR15.COM community.
- Join discussions
- Follow topics and replies
- Connect with fellow enthusiasts
Already a member? Sign in
Stay informed by subscribing to our Newsletter