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Posted: 9/8/2006 6:10:12 PM EDT
[Last Edit: 9/9/2006 7:54:33 PM EDT by Molon]
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.




Link Posted: 9/8/2006 6:14:17 PM EDT
Science... it's not just for geeks...
Link Posted: 9/8/2006 6:19:34 PM EDT
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.
Link Posted: 9/8/2006 6:34:16 PM EDT
[Last Edit: 9/8/2006 6:54:52 PM EDT by Molon]

Originally Posted By Obskur:
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]

Link Posted: 9/8/2006 7:28:36 PM EDT
Link Posted: 9/8/2006 7:31:13 PM EDT
[Last Edit: 9/9/2006 10:53:44 PM EDT by Vapor-Trail]
Molon,

Thank you for doing these tests and posting them here.

Your posts have answered so many questions that I have been too lazy to find out myself.

Members like you are the reason I like this forum.

Link Posted: 9/8/2006 7:44:34 PM EDT
Link Posted: 9/9/2006 8:31:36 AM EDT
Paul's partner, Wes Grant, put me onto this concept four years ago: FF RAS for Colt 16" LW barrels; RAS for Colt M4 barrels. Looks like, once again, MSTN is GTG.

Today, the choices for FF handguards are much better.
Link Posted: 9/9/2006 7:52:14 PM EDT

Originally Posted By Vapor-Trail:
Molon,

Thank you for doing these tests and posting them here.

Your posts have answered so many questions that I have been to lazy to find out myself.

Members like you are the reason I like this forum.



You're welcome and thank-you.

Molon
Link Posted: 9/9/2006 11:03:33 PM EDT
Excellent reading and nice Pic's.
Link Posted: 9/10/2006 2:24:43 PM EDT
Excellent!!
Appreciate you taking time to do that, Molon.
Link Posted: 9/10/2006 3:14:01 PM EDT
Molon, you are the man. You are a real asset to this community. I was going to mention the test should have used the same barrels in each type of set up but of course you already knew that and posted it.
Link Posted: 9/10/2006 3:26:02 PM EDT
[Last Edit: 9/10/2006 3:32:31 PM EDT by PaperStreet]
Thanks for the test Molon.

EDIT: Thanks Jack. Reading too fast...



Link Posted: 9/10/2006 3:29:12 PM EDT
He said in the first post that it was Colt.
Link Posted: 9/10/2006 4:22:17 PM EDT
52grn in a 1:7 bbl? am i missing something?
Link Posted: 9/10/2006 9:43:11 PM EDT

Originally Posted By lobsterman:
52grn in a 1:7 bbl? am i missing something?


Maybe not missing anything, but it sounds like you have bought into internet myths.
Link Posted: 9/12/2006 9:21:55 AM EDT
Nice thread thanks for all the information
Link Posted: 9/12/2006 9:26:56 AM EDT
Good work.
Link Posted: 9/12/2006 11:38:27 AM EDT
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...
Link Posted: 9/12/2006 12:39:25 PM EDT
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.
Link Posted: 9/19/2006 9:05:36 AM EDT
BTT waiting on next test.
Link Posted: 9/19/2006 11:13:48 AM EDT

Originally Posted By Baldmonk:
BTT waiting on next test.


I've been busy working on tests for my ammunition thread. I'll probably be busy with that for a while.

Molon
Link Posted: 9/19/2006 12:52:22 PM EDT
Link Posted: 9/20/2006 8:35:27 PM EDT
What an informative test and displayed very well, if I might add. This thread has cemented my desire to purchase a FF handguard.
Link Posted: 9/20/2006 8:59:51 PM EDT
Good practical info. Thanks
Link Posted: 9/20/2006 9:38:44 PM EDT
[Last Edit: 9/20/2006 9:44:35 PM EDT by magnumb]
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.
Link Posted: 9/20/2006 9:40:22 PM EDT
Wow .... now how cn you argue with that! Thanks!
Link Posted: 10/10/2006 9:55:10 PM EDT
Bump for a really great thread.
Link Posted: 10/11/2006 10:52:48 AM EDT
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?
Link Posted: 11/12/2006 11:05:43 AM EDT
bump
Link Posted: 11/12/2006 9:03:43 PM EDT
Whoa, I guess I missed this the first time (and when it was bumped).

Makes me feel good in knowing I just ordered my first FF last night (MI FF).

WIZZO
Link Posted: 11/12/2006 9:56:22 PM EDT
I am switching to an SDI barrel and a DD rail at the same time. Do not know which will help more - but I will attribute it to whichever compoany sends me a free hat first
Link Posted: 11/13/2006 8:26:53 AM EDT
Link Posted: 11/13/2006 1:09:23 PM EDT

Originally Posted By LaRue_Tactical:

Originally Posted By Molon:
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.


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 . . .




Link Posted: 11/19/2006 8:31:05 AM EDT
Hey Molon,

I don't mean to pester you, but do you have any more photos of the free floated build (the one with the PRI hand guard)?

Thanks.

Justin
Link Posted: 11/19/2006 9:45:28 AM EDT
The pic's on page 1 mirror my before/after free-float groups w/ BH 52 gr. ammo in my MT6721.
Link Posted: 11/19/2006 10:00:29 AM EDT

Originally Posted By CitySlicker:
Hey Molon,

I don't mean to pester you, but do you have any more photos of the free floated build (the one with the PRI hand guard)?

Thanks.

Justin


Here you go.











Link Posted: 11/19/2006 2:39:15 PM EDT

Originally Posted By Molon:

Originally Posted By CitySlicker:
Hey Molon,

I don't mean to pester you, but do you have any more photos of the free floated build (the one with the PRI hand guard)?

Thanks.

Justin


Here you go.



img58.imageshack.us/img58/3014/16lwfreefloat21resizedrqd7.jpg

img58.imageshack.us/img58/3500/16lwfreefloat05bresizedln0.jpg

img58.imageshack.us/img58/8296/16lwfreefloatrecessedfrlf6.jpg

img58.imageshack.us/img58/6122/miniacogwallpaper06resicc1.jpg



Right click, save as.

Thanks Molon, you rock!
Link Posted: 11/19/2006 5:22:07 PM EDT

Originally Posted By eye_spy:
Wow .... now how cn you argue with that! Thanks!


Very easily with a sample size of one for each test group, no blinding, and few rounds fired.
Link Posted: 11/21/2006 4:31:32 AM EDT
Link Posted: 11/22/2006 4:33:00 PM EDT
Link Posted: 11/22/2006 5:57:13 PM EDT
Link Posted: 12/5/2006 5:52:06 AM EDT
[Last Edit: 12/5/2006 5:53:00 AM EDT by Baldmonk]





Swap the two barrels around.
See if the accuracy follows the barrel or the handguard system.
Report back.



+1
Link Posted: 12/5/2006 6:04:38 AM EDT
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.

Link Posted: 12/5/2006 8:23:34 AM EDT
Link Posted: 12/21/2006 7:38:51 AM EDT
Molon, did you ever see if the accuracy followed the barrel or float tube ??
Link Posted: 12/21/2006 5:25:49 PM EDT
Link Posted: 12/23/2006 4:42:40 AM EDT
+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
Link Posted: 1/4/2007 6:12:16 AM EDT

Originally Posted By SoldierBilly1:
Wasn't free float designed to improve sling shooting?

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.
Link Posted: 1/4/2007 9:37:49 AM EDT
Tag for the swaping float tube for the barrel to see if the accuracy follows the barrel or the tube.
Link Posted: 1/18/2007 9:05:09 PM EDT
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