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Free floating M1A barrel

This is a discussion on Free floating M1A barrel within the Modern M14 forums, part of the M14 M1A Forum category; This is a design question for the experts. I'm wondering if it would be feasible to free float an M1A barrel? Assuming that the receiver ...


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Old November 29th, 2011, 11:29 AM   #1
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Free floating M1A barrel

This is a design question for the experts. I'm wondering if it would be feasible to free float an M1A barrel? Assuming that the receiver were securely locked into a chassis type stock like the JAE or Sage, would the barrel mounting method and op rod gas system of the M1A keep it from realizing the benefit's of a free floated barrel as the AR does? I understand that the cycling action of the gas system imparts deflective forces on the barrel, but doesn't a piston operated AR's piston do the same thing? I know that the JAE stock offers an optional barrel tensioner which preloads the barrel, but I'm thinking that a free floated barrel would be superior to that. Perhaps the receiver would need to be lugged/double lugged in order for it to be rigidly locked into the stock?

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Old November 29th, 2011, 11:39 AM   #2
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Short answer, no. By securing the barrel with an op rod guide you allow less movement from the gas system and control the barrel whip as well. A gas piston gun can never be truly free floated. The gas system adds weight and stress on the barrel. This a leading reason why ARs are generally more accurate, they dont have moving parts hanging off the barrel. The biggest benefit imo of free float for semis and autos is no zero shift because of accessories on the rail system. Gas piston ARs see a decrease in accuracy from direct gas as well.

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Old November 30th, 2011, 05:10 AM   #3
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I would beg to differ, with the M14-06/Valkyr platform, we have free floated both an M14 and M1 barrel and gas system with great results. The key is the receiver, it has to be stiff enough to handle the weight, and locked in by design to handle it. I will do some experimenting over the next few months with both M1 and 14 receivers in various stocks as I get time, to see the differences between them and the new receiver, but from just the preliminary comparisons, the new M14-06/Valkyr receiver seems to be the key to the floating barrel and gas system.

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Old November 30th, 2011, 08:31 AM   #4
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In the '70's the U.S. military experimented with a "product improved" M14 at Aberdeen and Leavenworth. Fat, heavy floated barrels in fat stocks, similar to the heavy bolt-action benchrest rigs common to the era. But there was no way to shake the gas system - hole in the barrel dumping gassified fuel to a cylinderized piston to push the spinning wheel. The experiment was abandoned because the heavy, bulky rifle didn't shoot any better than a M21 or NM M14.

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Old November 30th, 2011, 09:30 AM   #5
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Originally Posted by losok View Post
I would beg to differ, with the M14-06/Valkyr platform, we have free floated both an M14 and M1 barrel and gas system with great results. The key is the receiver, it has to be stiff enough to handle the weight, and locked in by design to handle it. I will do some experimenting over the next few months with both M1 and 14 receivers in various stocks as I get time, to see the differences between them and the new receiver, but from just the preliminary comparisons, the new M14-06/Valkyr receiver seems to be the key to the floating barrel and gas system.
Youve changed the receiver too though. I dont think you would get good results from a normal m1a.

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Old November 30th, 2011, 02:31 PM   #6
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The Marines free floated barrels on their double lugged guns with great success. One was used to win the overall National Championships at Camp Perry several years ago.

During the course of a match at the USMCAGCTC 29 Palms, CA my rear lugged SEI rifle experienced a problem failing to extract a couple of times during the 1000 yard stages. A Marine armorer checked the rifle over and told me I should rebed it and float the barrel. I followed his advaice even though I thought it wouldn't work well on a rear lug gun. Turned out i was right. The groups opened up. After rebedding again using front ferrule pressure my groups shrank down to 3/8 inch (one of the better rifles I've built).

I have since built a few double lug guns and free floated the barrels with good success, but I only do this with double lugs.

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Old November 30th, 2011, 02:38 PM   #7
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Ted,

How is the free floated scheme? Does it mean there is no contact between the stock ferule and the lip if the front band? If that were the case, how much gap is typical with McM stock to ensure the two do not make contact when the rifle is slung up?

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Old November 30th, 2011, 02:57 PM   #8
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Originally Posted by losok View Post
I would beg to differ, with the M14-06/Valkyr platform, we have free floated both an M14 and M1 barrel and gas system with great results. The key is the receiver, it has to be stiff enough to handle the weight, and locked in by design to handle it. I will do some experimenting over the next few months with both M1 and 14 receivers in various stocks as I get time, to see the differences between them and the new receiver, but from just the preliminary comparisons, the new M14-06/Valkyr receiver seems to be the key to the floating barrel and gas system.
I think the term "free float" is not the term to be used here. To me it means to isolate the barrel from the receiver forward from any thing that may impinge or touch the barrel...thus allowing it to oscillate without any outside influence. In the case of a garand or m14, by the above definition, "free float" is not possible. So, I assume that your term "free float" is to isolate the barrel with the gas system attached from everything else that is happening when you pull the trigger...and the real goal is to have everything happen exactly the same as the shot before it....to include all the clickty clacks, vibrations and reciprical movements that occur have to happen exactly the same way shot after shot.... call it accurizing or something else, but by definition, imho it is not free floating.

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Old November 30th, 2011, 03:34 PM   #9
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Perhaps "freefloat" is not an accurate term for what I was referring to. What I meant was, isolating the barrel, and by functional necessity the gas cylinder, from the stock and any influence by the shooter. My original question was one of, was the barrel/receiver interface, rigid enough to handle it, and was the receiver itself rigid enough that it could be fixed into the stock. I find it interesting that Ted mentioned that in his experience it didn't work well with a single lugged receiver, and required the added stability of a front lug. That leads me to believe that the receiver may not be very rigid on it's own. I am just looking at the platform from a design aspect here, I understand that sometimes, even if an accurizing modification works, the minimal accuracy improvement doesn't justify the amount of work/expense, required to achieve it. It just seems to me, that expense/complexity aside, if you were able to rigidly fix the receiver )at front, rear and both sides, in a rigid, chassis type stock, You might possibly get the maximum accuracy that the M1A design is capable of. Of course, sometimes when you make a structure too rigid, and it's not able to distribute shock forces through flexing, you end up with a situation where you could end up with premature failure due to localized fatiuge.

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Old November 30th, 2011, 04:09 PM   #10
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Originally Posted by Mocos View Post
I think the term "free float" is not the term to be used here. To me it means to isolate the barrel from the receiver forward from any thing that may impinge or touch the barrel...thus allowing it to oscillate without any outside influence. In the case of a garand or m14, by the above definition, "free float" is not possible. So, I assume that your term "free float" is to isolate the barrel with the gas system attached from everything else that is happening when you pull the trigger...and the real goal is to have everything happen exactly the same as the shot before it....to include all the clickty clacks, vibrations and reciprical movements that occur have to happen exactly the same way shot after shot.... call it accurizing or something else, but by definition, imho it is not free floating.
I guess then by that standard even the common use of free float as it applies to AR type rifles would not apply since the gas block is connected to the tube, which in turn runs back in to the upper. I applied the term to the barrel and gas system as a unit. The goal your are correct, as you would be in bolt guns, is to have the harmonics be the same every time you pull the trigger, along with all the harmonics from the op rod movement and gas pulse.

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Old November 30th, 2011, 05:24 PM   #11
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I would think an extremely heavy barrel would handle damping any vibrations the gas system had. I mean so large diameter that the op rod guide would would have a figure eight hole, the op rod would ride against the bottom of the barrel. I think you could get about 1" diameter there. The barrel would weigh about three times the slender GI ones. Then a special gas cylinder, we want to keep the huge diameter all the way forward to the FS. Might as well make the GC a billet, not two rings on a pipe. And a double lugged receiver. An aluminum billet stock would only need to go forward to the front lug. Oh, maybe a fore end to hang on to, with a bipod rail? Oh awright, composite stock.

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Old November 30th, 2011, 05:34 PM   #12
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With a rifle that draws at the front-end and a medium to heavy barrel you can use bedding compound to build a pillar under each side of the front of the receiver. Not as firm as a torqued-in front lug but pretty good. I don't think the pillar adds anything with a standard contour barrel.

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Old November 30th, 2011, 05:49 PM   #13
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This originally started as more of a design/engineering pursuit for me than anything else. I was just wondering if it was feasible to "freefloat" an M1A barrel in order to get greater accuracy. But at some point, with extensive/drastic modifications, I think it starts to become a question of if it's still an M1A, and if it becomes so heavy that it becomes like one of those rail guns, it becomes so specialized that it has little practical value, then you get to that place where that accuracy improvement is outweighd be the loss of functionality.

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Old November 30th, 2011, 06:15 PM   #14
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Quote:
Originally Posted by Jgun View Post
This originally started as more of a design/engineering pursuit for me than anything else. I was just wondering if it was feasible to "freefloat" an M1A barrel in order to get greater accuracy. But at some point, with extensive/drastic modifications, I think it starts to become a question of if it's still an M1A, and if it becomes so heavy that it becomes like one of those rail guns, it becomes so specialized that it has little practical value, then you get to that place where that accuracy improvement is outweighd be the loss of functionality.
throughout this forum there have been anecdotal instances of rifle out of the box does moa with "good" ammo....what it means is that all the parts are working in some harmony shot after shot....including the shooter. Anything you do to your piece should be with the intent to make it repeatable on a consistent basis. "freefloating" however applied is just another technique that may or may not work in harmony with the other parts. At one point it may become a point of diminishing returns.

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Old November 30th, 2011, 07:44 PM   #15
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Quote:
Originally Posted by Jgun View Post
My original question was one of, was the barrel/receiver interface, rigid enough to handle it, and was the receiver itself rigid enough that it could be fixed into the stock. I find it interesting that Ted mentioned that in his experience it didn't work well with a single lugged receiver, and required the added stability of a front lug. That leads me to believe that the receiver may not be very rigid on it's own...
I don't think it's a question of rigidity, but of torque. As there's no clamping force at the front of the receiver without the double lug feature, the barreled action will try to rotate up during recoil, pivoting somewhere around the back half of the action. Some flex of the action occurs due to the unbalanced nature of the clamping point, as well.

For most M14 types, the front band lip is a rough equivalent of the front action screw.

The easy disassembly designed into the M14 works against trying to refine it into a benchrest accurate rifle. Not a fatal flaw, but annoying to some.


Last edited by jmoore; November 30th, 2011 at 10:06 PM.
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