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Free float barrel

Discussion in 'Rifle Discussion' started by ripcity, Dec 26, 2011.

  1. ripcity

    ripcity Milwaukie Active Member

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    I'm just curious if a free float barrel is super critical for a rifle. I'm interested in getting a smaller caliber (.22-6mm) somewhere in that vicinity. I'm just trying to find out if a free float is that critical. What is the advantages and disadvantages to a free float? Any information would be great. Thanks
     
  2. parallax

    parallax eugene, or-gun Bronze Supporter Bronze Supporter

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    A free-floating barrel is a specific design technology used in highly accurate rifles, particularly match grade rifles, to increase the accuracy of the weapon.

    With normal rifles, the barrel rests in contact with the stock. If the stock is manufactured of wood, environmental conditions or operational use may shift alignment of the stock, which may cause the barrel to shift its alignment slightly over time as well, altering the projectile flightpath and impact point. Contact between the barrel and the stock also interferes with the natural frequency of the barrel, which can have a detrimental effect on accuracy in some cases. The interference of the stock with the barrel's forced oscillation as the bullet passes down the bore can cause the barrel to vibrate inconsistently from shot to shot, depending on the external forces acting upon the stock at the time of the shot. Micro-vibrations acting during the bullet's passage result in differences in trajectory as the bullet exits the bore, which changes the point of impact downrange.

    A free-floating barrel is one in which the barrel and stock are designed to not touch at any point along the barrel's length. The barrel is attached to its receiver, which is attached to the stock, but the barrel "floats freely" without any contact with other gun parts, other than the rifle's sights. This minimizes the variance in possible mechanical pressure distortions of the barrel alignment, and allows vibration to occur at the natural frequency.
     
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  3. civilian75

    civilian75 Hillsboro, OR Well-Known Member

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    My non-expert opinion, that depends on what kind of the application and accuracy you want/need. Most hunting rifles for deer and larger up to 200yd-ish you are fine with ~ 1-2 MOA accuracy and may not need a floating barrel.

    For varmint, target shooting and sending ordinance over to the next zip code, then you will be after the sub-MOA holy grail, and a floating barrel is just one of many things you will need. That's what I suspect you want to do with the 22 cal barrel burner you have set your sights on.

    More non-expert opinion. It is said that non-floated wood stocks sensitivity to humidity and temperature will affect POI to some degree. Humidity will have a negligible effect on synthetic stocks but I don't know about temperature. So, it would make sense to lean towards synthetic, right? Not in my experience; I once tried to "float" barrel with a synthetic stock; I so much wished it was wood! It is easier to sand/file barrel-to-stock contact surface on a wood stock.

    This I have noticed: when firing several shots consecutively, a thin floated barrel can exhibit some vertical stringing as the barrel heats up. Floated bull barrels will take many, many more shots before any vertical stringing is noticed.
     
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  4. ripcity

    ripcity Milwaukie Active Member

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    Thanks for the timely feedback. I'm learning a lot about floated and non floated barrels.
     
  5. mjbskwim

    mjbskwim Salmon,Idaho Well-Known Member

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    I read a lot about this earlier this year and don't believe I have seen it put so well.
     
  6. orygun

    orygun West Linn Bronze Supporter Bronze Supporter

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    There has been some good insight posted here. Also, usually a "free floated" barrel is bedded at the chamber, but not always.
    But, as in ballistics, barrels don't always react exactly the same. I've had more than one gun react positively to free floating the barrel but, not all. Some barrels like the upward pressure from the stock and shoot more accurately that way.
    The comments about the possibility of a wood stock being affected by humidity are true, or at least can be. Laminated wood stocks are much less prone to this problem. Synthetic almost immune.
    So, if you have a gun that shoots very well and is not free floated, you may not want to mess with it. If you do choose to free float it and it's not better, you can easily change it back with some of the bedding products.
     
  7. coop44

    coop44 Tacoma ,WA Well-Known Member

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    Bedding and freefloating is tricky, depends on the barrel, caliber (recoil) and the length. light barrels in moderate to heavy calibers have what is commonly described as "whip". this is when the barrel actually flexes as the gun is fired. Those barrels are served best by full length bedding. The same barrel in a light caliber (say .223) may do better with either free floating or a slight upward pressure on the barrel at the end of the stock (this is very old school and it works, prevents stringing). Of course heavy barrels in any caliber do well free floated.

    There is a reason there are full length stocks on military bolt actions, it helps add rigidity to the barrel without the extra weight of a heavy barrel. Some of these stocks actually incorporated a "saddle" and a spring at the tip of the stock to provide upward pressure (#1 SMLE's come to mind). Some springfields and mausers I have removed from the stocks have actually had shims of paper between the stock and barrel. Many currently manufactured rifles actually have this incorporated into the inletting of the rifle, a "bump" at the end of the barrel channel.

    As far as the mentioned warp of wood stocks, this is best prevented by sealing the exposed grain on the inletted portion of the stock (after any bedding) with BLO, polyurethane, thompsons, or anything suitable. This will also help prevent staining from any lubricants used on the surface of the gun. Remember not to remove the action from the stock more than needed, excessive removal and reinstallation can deform the bedding material and ruin the "fit".

    hope my experience helps

    As far as bedding products go after experimenting with lots of different epoxies, I stick with Microbed. Acraglass just turns into a mess for me. Actually had some pretty good results with some of the 5 minute epoxies (black) from the hardware store, the kind that comes in a two sided syringe.
     
  8. deadshot2

    deadshot2 NW Quadrant WA State Well-Known Member

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    Not much to add to coop44's post but I'll toss a few more that I've run across over the last half century.

    Some super accurate rifle makers will actually provide support for a lighter barrel about 2/3rds of the way from action to muzzle. Some incorporate support pillars about 30-45 degrees apart that form a cradle for the barrel actually pushing up on the barrel so it's pre-loaded with 10-15# of upward pressure. In some cases it's merely a saddle that is adjusted by removing the front sling swivel screw and adjusting a set screw. Trial and error finds the best "pre-load" for that barrel/ammo combination. I've actually seen a pair of fine thread drywall screws installed in the barrel channel to form support points. Removing the action and either screwing in or out the screws to adjust, then merely bedding a 1" band in the barrel channel when the optimum pre-load is achieved.

    All of my rifles are bedded at the action only with one exception, that being an old sporterized 1903. I continued the bedding forward to about the midpoint of the taper just forward of he action. It somewhat coincides with the forward end of the chamber. The rest of the barrel floats and even with the old original barrel (just turned to remove the old sight platform) with a date stamp of 10-42 it shoots nece 3/4" groups at 100 yards.

    As for bedding material I prefer Devcon 10110. It holds up under heat, cold, recoil, doesn't get soft, doesn't crumble, and can actually be machined if necessary, If you have a mill, it sure makes for some neat trigger and magazine inletting. It's pricey at about $45 for a 1# can but that's a lot of bedding. I even use it for bedding scope mounts/rails.