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I just had a realization. When you are working towards precision rifles you are trying your hardest to make everything you can on that rifle one unit. When you're working with a bolt action rifle you want to make sure the stock is bedded into the rifle properly, lap the bolt, and then make sure that barrel is 100% free floating. If you are using a gas piston rifle like the Massound, XCR-M,(I'm assuming these will be gas piston) or any other gas piston rifles it will never be free floating. So wouldn't a traditional AR have more potential to be more accurate than any gas piston rifle ever would?

The reason I say this is I was holding out for the Massound to make a 7.62 semi-auto precision rifle. But then getting off the phone with Noveske about 300 BLK barrels he brought up an interesting point that a gas piston rifle will never be as accurate than a barrel than a free floating barrel.

With that in mind, who's the best option for DMR stye rifle? DPMS? Knight? Noveske? POF? FAL? Anyone I'm missing? I'm interested in your opinions.
 

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I'm not a firearms expert by any stretch of the word;

But I was always under the impression that a free floating barrel is one that is connected directly to the reciever and nothing touches it from that point. The original AR15/M16, M4 and any varient that has a hand guard that uses the front handguard ring for support is not free floating. Putting pressure on the handguard will shift the point of impact. (unless the pressure is exactly the same everytime)The newer railed handguards that are available, (Troy, KAC, etc) dont use that ring for support and attach by the barrel nut. (nothing touches the barrel after that point for support) and they are in practical terms free floating.

By this definition, the ACR has a free floating barrel. The FAL with a standard handguard would not. Anything that could put pressure on the barrel, other then it's attachment to the reciever would not be free floating. I am not saying Noveski is wrong, (not at all, they know alot more about rifles then me) but maybe they are using a much tighter definition then the one I just provided.
 

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I'm not a firearms expert by any stretch of the word;

But I was always under the impression that a free floating barrel is one that is connected directly to the reciever and nothing touches it from that point. The original AR15/M16, M4 and any varient that has a hand guard that uses the front handguard ring for support is not free floating. Putting pressure on the handguard will shift the point of impact. (unless the pressure is exactly the same everytime)The newer railed handguards that are available, (Troy, KAC, etc) dont use that ring for support and attach by the barrel nut. (nothing touches the barrel after that point for support) and they are in practical terms free floating.

By this definition, the ACR has a free floating barrel. The FAL with a standard handguard would not. Anything that could put pressure on the barrel, other then it's attachment to the reciever would not be free floating. I am not saying Noveski is wrong, (not at all, they know alot more about rifles then me) but maybe they are using a much tighter definition then the one I just provided.
But does it still count as a free floating barrel with the piston and gas operating components?
 

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from what i understand, the piston reduces accuracy, but from what i've seen it does not. according to the internetz the piston is not a true free float system because there is direct contact between the bolt and piston/op rod or some bs like that and D.I. doesnt have that contact

if thats true or not i have no clue, honestly i can usually pull very similar groups (ish) out of either type of rifle with no issues considering they are set up similarly


I could see how the free floating handguard helps, especially after the barrel starts heating up though since everything starts heating up at different rates
 

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But does it still count as a free floating barrel with the piston and gas operating components?
I would say yes, as long as the piston assembly is placing the same pressure on the barrel at all times and not influenced by outside forces. (upper reciever and handguard)

Using the ACR as an example, the gas block / piston are attached to the barrel, but they move with the barrel and are not restricted in that movement. You would think that maybe where the pistion goes thru the upper reciever to impact the BCG would be an issue. But there is enough clearance so it moves freely. So after you zero the rifle, the pressure you place on the barrel is the same everytime, no matter how you hold the it.

Now with all that said, free float in the strictest sense would be nothing attached to the barrel past it's attachment to the reciever to allow it to whip on its own and not effect barrel harmonics. (not to many semi-autos out there like this) Even a DI rifle with a gas block won't meet this definition. All this should be taken into account when designing a semi-auto rifle and if it's is, won't be an issue when using a "free float" system like the ACR.

Again, this is my humble opinion and when sitting down with engineers, could be argued both ways. (splitting hairs)

ETA: op, a sincere thanks, (Im serious) for starting this thread. I havent excersized the grey matter like this in awhile. (very refreshing really :) )
 

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Here's another good one, when people tell me the SCAR is free float. Huh?

SCAR owners, what does the bottom rail attach to?
It actually is free floating, (using the definition: nothing is touching the barrel forward of the trunnion) The lower part of the handguard looks like it is touching the barrel forward of the trunnion, but actually acts as a bridge / attachment for the front "lower barrel support." The lower rail connect the lower barrel support and trunnion, but never touches the barrel. (FNH calls the trunnion "barrel extension") If you also examine where the barrel and gas block meet the front of the upper reciever, (lower barrel support) they do not touch anywhere. It's a weird setup, but for all intents is a free floating design. If you have the opertunity to see the barrel assembly out of the rifle, you will see it truely is "free floating" in the sense that nothing is touching the barrel forward of the trunnion. (where it is fasten to the upper reciever) I am only refering to a SCAR 16s, I have never seen a Mk16 up close, but assume they are the same.

It's very deceptive, but innovative design really :D
 

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I'd say that when dealing with any semi-auto, you can't really go by the strictest of definitions that would fit the bolt actions. I'd say that under that definition, any free floated handguard is just that. Meaning that the handguard itself is free floated. Which is still nice. It just means that any pressure against the handguard won't affect the barrel.
 

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...................................... It just means that any pressure against the handguard won't affect the barrel.
I wish I could that, It took me three long post to say that....

:eek: Sometime I just get too technical :eek: (dipping his head in shame...........:( )
 

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While I think the ACR wins over the SCAR at 5.56 (and supposedly 6.8), I'd go SCAR-17S for .308/7.62 NATO
 

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Discussion Starter · #11 ·
I had not realized my initial post would go this deep.

So is there any semi auto rifles out there that are truly free floating like a bolt action rifle? I don't feel as though a barrel attached to a gas tube is free floating. It would restrict the barrel from doing it's natural whip motion. However it does seem though that usually the gas operated rifles are the more accurate rifles.

I just started looking at everybody, doing research... Knights, Noveske, Adcor, Patriot Ordinance, Armalite, FNH, HK, Fulton, Stag, Wilson, Les Baer, Rock River, Bushy, Remington, Daniel, Spikes, Panther, JP Enterprises. All of them look like they have something eventually attached to the barrel but I could be wrong. JP and POF looked close to being fully free floating.

I think where it comes down to is buying a Krieger or Lilja barrel (hopefully for a Massound someday) and making it the best out of what you got.
 

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This discussion does make me a bit interested to have a 20"+ barrel and PRS stock on my list of modularity.

My ideal ACR:

10.5" CQB with enhanced foregrip and folding stock
14.5" carbine with polymer foregrip and folding stock
20" rifle with polymer foregrip and and fixed stock
24" DMR with bigdog foregrip and PRS stock

Living in California will nix the first but the others are doable. Department of redundancy would nix the 20" rifle so reasons of economy would leave me with a 14.5" barrel, polymer foregrip and enhanced stock with the bigdog and/or enhanced tri-rail foregrip and PRS stock.
 

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Hold on, so you're elling me the gas block and barrel never touch? As I recall (from dealing with the SCAR back in 2007) the lower rail bridged up to the gas block,
and the gas block was attached to the barrel.
 

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The only semi-autos with nothing attached to the barrel would be a blow back gun. (like the old hk91, 93 etc. nature of the beast) that is why the old HK PSG-1 was such an accurate semi-auto rifle. But alas, they are bout 8-15k if you can find one in good shape.

If the manufacter of the semi-auto takes into account all the varibles of the barrel dance, they can get very close to the accuracy of a bolt gun. But in my opinion never surpass it head to head.
 

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Hold on, so you're elling me the gas block and barrel never touch? As I recall (from dealing with the SCAR back in 2007) the lower rail bridged up to the gas block,
and the gas block was attached to the barrel.
Yes sir,,,,,,The lower rail does not touch the barrel or gas block. The lower rail is a bridge, connecting the barrel extension and front support. The front support does not touch the barrel. The barrel and gas block dont touch it, but are very close. There ia about an 1/16" - 1/8" clearence. (don't have calibers handy to measure it) It is very deceptive unless you really look closely.
 

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You can tell which guns are really free floated by the skinny barrel option

You don't see M16A1 style skinny barrels on the ACR or HK416 because the piston-on-barrel design exerts force on the barrel, which affects accuracy, so they beef up the barrel so it can resist the piston forces.

The SCAR, and XCR both use pistons, but the pistons aren't affixed to the barrel like the ACR or HK416
 

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Interesting observation
 

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On a side note, there is a good chance Canadians will get the first shipment of XCR-M's a few weeks or so before we do.

The USA model will have the new stock which requires a little more time, while the Canadian model will only have the old style fixed stock due to USA export regs so it can be launched sooner.
 
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