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Old June 07, 2016, 02:02   #701
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Originally Posted by gunshooter View Post
I think as the rifle is fired, it heats up the upper receiver. The 3 different paths the heat travels through the upper receiver pulls the barrel axis out of alignment with any sighting system.
Sorry to say it but the fal will never be the savage 110 or variant accurate tack driver.
I do believe it will continue to be the joyous bullet launcher it was designed to be.
^

I think heat is the problem. I can make accuracy go away with heat, let the rifle cool off, and get the (previous) superior accuracy to show up again. I know other people have had this same experience.
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Old June 07, 2016, 06:41   #702
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The thing to remember is that these things can be individuals to an extent. I'm not going to say that there is _a_ root cause. That said, the rifle that shot that target was a free float izzy heavy barrel. One would have to get the receiver quite hot to induce enough thermal strain I would think.
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Old July 29, 2017, 12:11   #703
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After reading through most of this thread I see a lot of good advice and many people realize why their FAL is not a tack driver but do not know exactly how to fix it. Along with many other fixes that most have covered I want to add how I go about resolving the bolt issues and what the problem actually is.

Besides the basic downfalls of a semi auto and accuracy the FAL has a disadvantage of it's tilting bolt that does not fit the gun quite right. The bolt ends up in different locations in relation to the chamber each time it is cycled and has upward pressure on the chambered round from the next round in the mag and the chambered round is also not lined up with the bolt. On the FAL's I have owned the bolt is about 1/8'' lower than the chamber when in battery and also has wobble and pressure from the mag that puts tilted pressure on the rear of the chambered round. I resolve this by mating the bolt carrier and bolt to eliminate play and line the bolt up with the chamber.
The bottom of the bolt carrier's top surface has a ridge at the front (about 1/8'' wide that travels from left to right) that the bolt slides along. I remove the ridge and raise the flat surface above the ridge slightly. On the bolt I machine the top surface lower removing material. The top of the bolt gets machined a little at a time until it is able to lock into battery at the same height as the chamber.
The ''main'' problem with accuracy is that the chambered round sits into the chamber but is also attached to the bolt when in battery. The chamber is always in the same location so the bolt must be made to cycle into the same location each time and sit directly in line with the chamber without pressure twisting the round. This can be done by mating the bolt and carrier as I described.
If the front of the chambered round is sitting in the chamber but the rear is being forced upward by the bolt it makes the round sit with twisted pressure and differently each time. The bolt ''must'' be made to line up with the chamber and not be able to wobble when in battery.
I think the people with FAL's that are more accurate likely have bolt / chamber line up that is naturally closer to being correct than others. I also believe that the ridge on the upper carrier was not originally part of the design because it forces the bolt into the wrong location in relation to the chamber. The ridge was likely added to allow debris to have a place to hide and filter away not effecting the bolt and carrier as they slide for more reliability in full auto. Changing the bolt and carriers shape for reliability in full auto is likely the main reason the FAL bolt carrier does not fit the gun perfectly. With the proper shaping the bolt carrier can be made to fit perfectly again.

Another problem with the FAL and accuracy that is important is that many FAL's will cycle rounds into the chamber but the tip of the bullet will tap the bottom of the chamber and flatten or damage the tip. The bottom of the chamber mouth must be sanded and polished so that rounds slide into the chamber without damage but not to the point that to much of the casing is unsupported. This is more of a common sense fix than a big alteration.

Another big improvement is to use a handguard like a DSA railed handguard that locks everything in the front end snug and decreases vibration. By locking everything together the piston's movement has less effect on the barrel. Depending on barrel length this can make a difference. The handguard must not put force on the barrel that twists it out of it's natural position when installed. If using a bipod, a lock on handguard can also help with the upward pressure on the barrel causing as much of an effect on POI shifts.
There are several other improvements that need to be done to have an accurate / precise FAL but they have mostly been covered by others.

Last edited by bigjunk1; July 29, 2017 at 12:20.
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Old July 29, 2017, 13:07   #704
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As you said if everything lines up correctly you should have better accuracy, another if is if everything returns to the same place every time, when a barrel heats up (unevenly at that) it acts differently in rapid fire as opposed to slow fire. One way to try and fix that is to Cryogenic treat it, when you heat treat something it cools at different rates, allowing air pockets(microscopic) to form unevenly across say a barrel, thus allowing it to heat and cool unevenly while shooting throwing an unknown it to the mix. Cryogenic freezing a barrel will align the metal particles and eliminate the air pockets and you get a barrel that heats up and cools down uniformly eliminating stringing when you heat up a barrel by alot.
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Old November 27, 2017, 07:58   #705
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Bumping 1 of the best threads on the FILES!
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Old November 27, 2017, 12:03   #706
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best trick to get a 2 moa FAL is to buy one more.
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Old November 27, 2017, 19:34   #707
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Originally Posted by bigjunk1 View Post
Another big improvement is to use a handguard like a DSA railed handguard that locks everything in the front end snug and decreases vibration. By locking everything together the piston's movement has less effect on the barrel. Depending on barrel length this can make a difference. The handguard must not put force on the barrel that twists it out of it's natural position when installed. If using a bipod, a lock on handguard can also help with the upward pressure on the barrel causing as much of an effect on POI shifts.
There are several other improvements that need to be done to have an accurate / precise FAL but they have mostly been covered by others.
Not sure piston really plays a part in accuracy, hasn't the bullet already left the barrel by the time the piston starts moving?

I was reading an article explaining that a bigger factor on accuracy is the shock wave from the propellant igniting inside the cartridge moving down the barrel which affects the harmonics. Depending on the node of the vibration, there could be a very slight movement of the barrel/deflection just as the bullet is leaving the barrel. A barrel tuner or variations in powder charge can alter the harmonics by altering the node of the shock wave.
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Old November 27, 2017, 20:40   #708
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best trick to get a 2 moa FAL is to buy one more.
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Paco wins the internet today! Thanks for the bump and kind words -

I agree, harmonics play a big part here (and with any rifle barrel), especially for a skinny barrel FAL.

The question of the day is: when I turn a match-grade barrel blank to a profile that matches my heavier AR10 barrel and mount it on the FAL, why does it still vertically string with the gas on???
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Old November 27, 2017, 21:28   #709
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The question of the day is: when I turn a match-grade barrel blank to a profile that matches my heavier AR10 barrel and mount it on the FAL, why does it still vertically string with the gas on???
Cause when the round comes out of the magazine it is pointed up. If it was pointed right or left then you would have horizontal stringing.Just kidding

No really, didn't you do all that research on your adjustable bolt carrier to find the sweet spot that minimized/eliminated stringing by changing the angle of engagement with the locking shoulder. I know I welded up the top of my bolt and then filed it down until the camming surface would just let the carrier move to fully closed. Stringing wasn't eliminated, but reduced to around 2-3 inches at 100 yards.
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Old November 28, 2017, 09:00   #710
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Cause when the round comes out of the magazine it is pointed up. If it was pointed right or left then you would have horizontal stringing.Just kidding

No really, didn't you do all that research on your adjustable bolt carrier to find the sweet spot that minimized/eliminated stringing by changing the angle of engagement with the locking shoulder. I know I welded up the top of my bolt and then filed it down until the camming surface would just let the carrier move to fully closed. Stringing wasn't eliminated, but reduced to around 2-3 inches at 100 yards.
Yep. But this test was with the adjustable carrier tightened to have no slop. And the receiver face trued within 0.001". And a perfect 0.001" interference fit between the gas block and barrel. And the scope mount bedded to perfectly fit the receiver. And a free float handguard. And a tight upper/lower fit. And a tuned trigger.

Where is the "beating your head against a brick wall" smilie???
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Last edited by kotengu; November 28, 2017 at 09:27.
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Old November 28, 2017, 11:21   #711
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Good heavens this is to long to read.

I'll just throw in my two cents.

I have a new bare bones Voyager 21" SA58, as low grade as DSA offers. I got slightly under 2" MOA with iron sights off the bench last weekend.

Unfortunately, I can't tell you the ammo because I had a mixed mag, but I believe it's an old box of Privi I've had for about 8 years.

I was very pleased.
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Old November 28, 2017, 16:10   #712
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Clonehead is on the same page as I am, the thing is that the shock wave in the barrel acts through a hinge and catch.
kotengu, did u ever try tightening fit of the locking plunger?
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Old November 28, 2017, 18:52   #713
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Clonehead is on the same page as I am, the thing is that the shock wave in the barrel acts through a hinge and catch.
kotengu, did u ever try tightening fit of the locking plunger?
I installed an oversized locking body to tighten the upper/lower fit, but I never hard-connected the two together as we discussed. It's on my never-ending list, but I have a few things ahead of it to try when I get a spare moment to play again.
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Old December 02, 2017, 04:53   #714
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I must be incredibly lucky. I picked up a DSA para, 18" bbl, six years ago and the thing shoots 1-1.5 MOA consistently.

It did take THREE trips to DSA for it to run correctly but, hey, they EVENTUALLY got it right. Like, REALLY right.
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Old December 04, 2017, 06:57   #715
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Why is the latch thingie underneath the receiver not wide enough to rub against the sides of the trigger housing when closed?
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