View Full Version : Can different handguard mounting methods affect accuracy?
ZipZopBoop
08-10-15, 19:53
I think it's well enough established that a free float handguard can improve on the precision of an AR because it reduces the number of factors that can affect the barrel, thus reducing variability in "barrel harmonics." In other words, it reduces the amount of contact the barrel has on other objects which can change the way the barrel vibrates and moves. These minor changes affect the path of the bullet and reduce the precision of the rifle.
Is it possible that different handguards and different methods of mounting them affect precision as well? If such minor effects on the barrel change precision significantly (statistical significance, not practical), it seems probable that differing methods of mounting a handguard as well as the physical properties of the handguard itself can affect precision. Has any testing been done on this matter?
rcoodyar15
08-11-15, 09:37
I think it's well enough established that a free float handguard can improve on the precision of an AR because it reduces the number of factors that can affect the barrel, thus reducing variability in "barrel harmonics." In other words, it reduces the amount of contact the barrel has on other objects which can change the way the barrel vibrates and moves. These minor changes affect the path of the bullet and reduce the precision of the rifle.
Is it possible that different handguards and different methods of mounting them affect precision as well? If such minor effects on the barrel change precision significantly (statistical significance, not practical), it seems probable that differing methods of mounting a handguard as well as the physical properties of the handguard itself can affect precision. Has any testing been done on this matter?
I am sure it does. Many precision upper builders only want to use their hand guards for that very reason. I am sure they have learned through experience what worked for them. I would like to see that testing if you find it.
another thing precision upper builders recommend is a clamp on gas block because the stress is evenly distributed around the barrel. Set screw and pinned gas blocks create point stresses. In fact I have read that set screws can even make a bulge in the bore of the rifle. You know that would effect accuracy.
another thing precision upper builders recommend is a clamp on gas block because the stress is evenly distributed around the barrel. Set screw and pinned gas blocks create point stresses. In fact I have read that set screws can even make a bulge in the bore of the rifle. You know that would effect accuracy.
I'll buy #1 and #2, but #3? Deform a 1/4 inch thick tube with a set screw, no.
SniperOverwatch
08-11-15, 11:46
I'm no expert, but as I understand it the barrel nut is more of a factor in accuracy. So to answer your question...technically, yes. But only insofar as they use different barrel nuts.
A nut that doesn't require timing for the gas tube will allow you to achieve more favorable torque values. I can't find any non-anecdotal evidence, but it's generally accepted that tighter barrel nuts decrease accuracy, albeit marginally. Most shooters probably wouldn't notice.
On my accurized rifles I went with an Aero Precision M4E1 upper so I can torque the barrel nut to any number I choose and don't have to mount the handguard to the barrel nut. I'm probably not a good enough shot to notice though.
another thing precision upper builders recommend is a clamp on gas block because the stress is evenly distributed around the barrel. Set screw and pinned gas blocks create point stresses. In fact I have read that set screws can even make a bulge in the bore of the rifle. You know that would effect accuracy.
I've read this as well, though I really wonder how you could apply enough torque to such a small set screw do to this. Perhaps this is one of the reasons some builders use green loctite on the surface where the gas block meets the barrel... so less torque is needed to keep the block in place (i'd also read something about loctite dampening different harmonics between the block and the barrel).
rcoodyar15
08-11-15, 14:23
I've read this as well, though I really wonder how you could apply enough torque to such a small set screw do to this. Perhaps this is one of the reasons some builders use green loctite on the surface where the gas block meets the barrel... so less torque is needed to keep the block in place (i'd also read something about loctite dampening different harmonics between the block and the barrel).
Damn! Now you are going to have me bedding my gas block when I put this thing back together. Is there ever an end to this stuff?
I think it's well enough established that a free float handguard can improve on the precision of an AR...
More correctly, a FF tube can improve the consistency of an AR by isolating the barrel from external influences and letting the barrel vibrate naturally.
Pinning a gas block with a pin too large for the hole can cause bulges inside the bore. It's also a problem when driving tapered cross pins in too deeply. This is why I prefer cutting an FSB without removing it from the barrel. Installing tapered cross pins does swell the hole a bit. That's what holds the pins securely in place. Remove the pins and the holes will be lightly larger than when the pins were originally installed. To get the re-installed pins tight again, the pins have to be driven in a little deeper, increasing the possibility of causing a bulge. Set screw can also cause bulges when the barrel is dimpled too deep and the screws installed too tight. One has to be particularly careful when the barrel is only .625" at the gas block.
Barrel harmonics is a whole other subject. There are three ways to get a rifle to shoot good-
1) Find ammo that matches the harmonics of the barrel
2) Tune the barrel harmonics to match the ammo
3) Deaden barrel harmonics so it shoots well with nearly all types of ammo
rcoodyar15
08-11-15, 16:40
More correctly, a FF tube can improve the consistency of an AR by isolating the barrel from external influences and letting the barrel vibrate naturally.
Pinning a gas block with a pin too large for the hole can cause bulges inside the bore. It's also a problem when driving tapered cross pins in too deeply. This is why I prefer cutting an FSB without removing it from the barrel. Installing tapered cross pins does swell the hole a bit. That's what holds the pins securely in place. Remove the pins and the holes will be lightly larger than when the pins were originally installed. To get the re-installed pins tight again, the pins have to be driven in a little deeper, increasing the possibility of causing a bulge. Set screw can also cause bulges when the barrel is dimpled too deep and the screws installed too tight. One has to be particularly careful when the barrel is only .625" at the gas block.
Barrel harmonics is a whole other subject. There are three ways to get a rifle to shoot good-
1) Find ammo that matches the harmonics of the barrel
2) Tune the barrel harmonics to match the ammo
3) Deaden barrel harmonics so it shoots well with nearly all types of ammo
a stopped barrel is a wonderful thing. Wonder when they will make a tuner for an AR
I wonder when people are going to get back Planet Reality and focus on the stuff like shooting and forget the minutia?
I wonder when people are going to get back Planet Reality and focus on the stuff like shooting and forget the minutia?
Never. Haven't you heard that M4 barrels are inherently more inaccurate because of the M4 cutout for the grenade launcher? That weak point causes the barrel to flex unnaturally at that point, throwing the bullet off trajectory :suicide:
rcoodyar15
08-13-15, 04:04
I wonder when people are going to get back Planet Reality and focus on the stuff like shooting and forget the minutia?
I certainly have not quit shooting
I do like to shoot small groups and to do that you have to concentrate on the minutia
if all you want to do is blast zombie targets with surplus military ammo have at it
if all you want to do is blast zombie targets with surplus military ammo have at it
Surely, you speak of the collective "you", to include anyone out there shooting.
Ken Hackathorn once made a comment in a newsletter directed towards the membership of this forum and the type of shooting in which is emphasized here, that goes like this....
Practicing at the range from a bench rest or prone is great for zeroing or testing loads. Otherwise, shooting from a bench or prone is just like masturbating, you get the rounds off, but not the real thing.
ZipZopBoop
08-13-15, 11:05
I wonder when people are going to get back Planet Reality and focus on the stuff like shooting and forget the minutia?
Right. Because the two are mutually exclusive and depth of knowledge is bad.
rcoodyar15
08-13-15, 13:21
Surely, you speak of the collective "you", to include anyone out there shooting.
Ken Hackathorn once made a comment in a newsletter directed towards the membership of this forum and the type of shooting in which is emphasized here, that goes like this....
Now I can understand how three gun and pistol competition could be a lot of fun. My problem is I am old and fat and certainly not nimble and quick.
I have been shooting all my life and never owned an AR till a couple of years ago. Bought one on a whim. That gun is a blast. I was like a kid with a new .22 rifle.
After reading a bunch about them I decided to build me one. I am hooked for life.
that said for me the only really interesting gun is an accurate one! Lots of details have to come together to create small 5 shot groups consistently. Now that is a challenge to me. Believe me compared to a bolt gun getting an AR accurate is challenging.
I really don't understand the fascination many have for the M4 battle rifle. Not very useful for hunting, not very accurate and I doubt very many of the people buying them will ever take them into combat. Guess like I did when I was a kid its fun to dress up and play army.
Now I can understand how three gun and pistol competition could be a lot of fun. My problem is I am old and fat and certainly not nimble and quick.
I have been shooting all my life and never owned an AR till a couple of years ago. Bought one on a whim. That gun is a blast. I was like a kid with a new .22 rifle.
After reading a bunch about them I decided to build me one. I am hooked for life.
that said for me the only really interesting gun is an accurate one! Lots of details have to come together to create small 5 shot groups consistently. Now that is a challenge to me. Believe me compared to a bolt gun getting an AR accurate is challenging.
I really don't understand the fascination many have for the M4 battle rifle. Not very useful for hunting, not very accurate and I doubt very many of the people buying them will ever take them into combat. Guess like I did when I was a kid its fun to dress up and play army.
When you say that they are not very accurate, what does this actually mean? Also, how they are not useful for hunting? Can I not kill a coyote with an M4???
C4
I think it's well enough established that a free float handguard can improve on the precision of an AR because it reduces the number of factors that can affect the barrel, thus reducing variability in "barrel harmonics." In other words, it reduces the amount of contact the barrel has on other objects which can change the way the barrel vibrates and moves. These minor changes affect the path of the bullet and reduce the precision of the rifle.
Is it possible that different handguards and different methods of mounting them affect precision as well? If such minor effects on the barrel change precision significantly (statistical significance, not practical), it seems probable that differing methods of mounting a handguard as well as the physical properties of the handguard itself can affect precision. Has any testing been done on this matter?
When I am doing a precision build, I seek out barrel nuts like those from Geissele and BCM where the barrel torque value is set at 40LBS. Squeezing the receiver is never a positive thing IMHO. With that said, there are more important aspects to accuracy than the barrel nut torque value.
C4
I really don't understand the fascination many have for the M4 battle rifle. Not very useful for hunting, not very accurate
It is a mistake to believe accessories define the rifle or configuration determines accuracy
I doubt very many of the people buying them will ever take them into combat. Guess like I did when I was a kid its fun to dress up and play army.
Seriously?!?
rcoodyar15
08-13-15, 14:05
When you say that they are not very accurate, what does this actually mean? Also, how they are not useful for hunting? Can I not kill a coyote with an M4???
C4
I would say the average m4 grouping at 100yrds is 2 to 3 inches. Oh I am sure I am going to hear about all those .25" AR's but they sure aren't posting targets in the MOA Challenge.
Makes a fun varmint rifle
Not for whitetails and mulies and elk and other medium and large game.
The AR15/M16/M4 family of weapons wasn't designed to be a hunting gun. It was designed to kill people, just like the AK47. It doesn't mean that it can't be used as such. I am not a hunter, and don't care about hunting at all. One thing I can tell you is that when people are hit with a bullet and fall down incapacitated and or die, they could give a shit less if that group was .025 MOA or 3 MOA.
If you think that is ineffective, you would be surprised to learn that there are a lot of dead people no longer breathing oxygen that will attest to it's effectiveness. As for people dressing up and playing Army, it might also surprise you to learn that there are a lot of legally armed civilians who use them for personal and home defense. When I am on the road I carry an M4 of sorts in my vehicle ready to go. Quite simply I want something practical and more effective at putting down people than a handgun. YMMV
I would say the average m4 grouping at 100yrds is 2 to 3 inches. Oh I am sure I am going to hear about all those .25" AR's but they sure aren't posting targets in the MOA Challenge.
Makes a fun varmint rifle
Not for whitetails and mulies and elk and other medium and large game.
I certainly have not quit shooting
I do like to shoot small groups and to do that you have to concentrate on the minutia
if all you want to do is blast zombie targets with surplus military ammo have at it
This is m4carbine, not bughole benchrest... Emphasis on hard use, working guns.
Accuracy is of interest to all of us. But the never ending diminishing returns discussions I find a bit silly, and borderline out of scope. (My view)
Free float handguard started due to the significant and observable effect of camp Perry type slings on pre A2 AR's.
2-3 moa type variance.
Do different types effect barrel harmonics? Could be, but you already have your big factors in torque, etc.
There are some common sense things. But the threads of late are getting tiresome. (Facing receiver, loc-tite RE, then loc-tite nut, then gasblock...)
I would say the average m4 grouping at 100yrds is 2 to 3 inches. Oh I am sure I am going to hear about all those .25" AR's but they sure aren't posting targets in the MOA Challenge.
And you would be mistaken to make a generalized assumption like that on all m4 form factor carbines.
You admit you are a Johnny come lately to AR's, then start to lecture and somewhat insult people with decades of experience in the platform?
This is about the 10th time you have referenced the moa challenge
We all have our interests. I'll not make fun of yours, and please leave your condescending comments away from mine
rcoodyar15
08-13-15, 17:08
The AR15/M16/M4 family of weapons wasn't designed to be a hunting gun. It was designed to kill people, just like the AK47. It doesn't mean that it can't be used as such. I am not a hunter, and don't care about hunting at all. One thing I can tell you is that when people are hit with a bullet and fall down incapacitated and or die, they could give a shit less if that group was .025 MOA or 3 MOA.
If you think that is ineffective, you would be surprised to learn that there are a lot of dead people no longer breathing oxygen that will attest to it's effectiveness. As for people dressing up and playing Army, it might also surprise you to learn that there are a lot of legally armed civilians who use them for personal and home defense. When I am on the road I carry an M4 of sorts in my vehicle ready to go. Quite simply I want something practical and more effective at putting down people than a handgun. YMMV
yep
I have an AR-15, stock PSA, Under the back seat of my truck and about 500 rounds for it. I also have a .45 between the front seats a a couple of hundred rounds for that. I have another fighting ar strapped to my bailout pack.
that said I have had a pistol toters, didn't have concealed carry back then, license since I was 18 years old and I am now 60. Haven't had to kill anyone yet. In fact I have never been in a situation where I felt the need to draw. I am a construction superintendent and have built stuff from Miami to san Francisco. Been in the good areas and the bad areas. We often do our concrete placement in the wee hours of the morning. What I am getting at is I have not lived a sheltered life.
I have no illusions about what might happen. I have a years stockpile of food and a way to defend it but I believe there is about a 99.9% chance that I will never need it.
I have plenty of fighting AR's and ammo. I also have bolt guns for hunting and my play guns for the range. Each has its place.
for me only accurate guns are interesting.
I have plenty of fighting AR's and ammo. I also have bolt guns for hunting and my play guns for the range. Each has its place.
for me only accurate guns are interesting.
I know you mentioned a 6mm AR, but you might find 65grendel forum interesting for accuracy. Some very serious long range/accuracy shooters there. (Not there are not some here as well)
About half the Grendel types are chasing accuracy. Then another chunk optimizing for hunting. And others interested in optimizing the infantry carbine for mil use defense use. (Approach 7.62x51 pwrformance in ar-15 form factor)
I'm interested in all three, just get bored with bench shooting and heavy guns.
rcoodyar15
08-13-15, 18:08
I know you mentioned a 6mm AR, but you might find 65grendel forum interesting for accuracy. Some very serious long range/accuracy shooters there. (Not there are not some here as well)
About half the Grendel types are chasing accuracy. Then another chunk optimizing for hunting. And others interested in optimizing the infantry carbine for mil use defense use. (Approach 7.62x51 pwrformance in ar-15 form factor)
I'm interested in all three, just get bored with bench shooting and heavy guns.
this is the technical forum. Seems that would be the place to discuss the technical aspects of making an AR accurate
only other places I post are reloading and precision AR's and bolt guns
I read all of those forums. Benchrest central, Accurate shooter, long range hunter, snipershide the grendel forum bunches of them
What I like is load development. Finding that combination of powder, charge, bullet, COL that the rifle likes best. After that I kind of lose interest in that gun.
Sometimes l like to take one of my fighting ar's out and run a few clips through it. Put up some steel knockdown targets and raise hell but I quickly get bored with that.
I guess what you are really saying is to find me another forum
In fact I have read that set screws can even make a bulge in the bore of the rifle. You know that would effect accuracy.
The Lija AR24 barrel I just installed has a machined flat for the purpose of installing a set screw style gas block.
Three set screws blue loctited and properly torqued are not going to deform a barrel.
They give you an Allen wrench just for the purpose of not being able to over torque it.
When the little Allen wrench torsions, it is tight enough.
I guess what you are really saying is to find me another forum
Not at all my intent. Just that there are many people interested in the topics you've been raising there.
Myself, I like accurate carbines. Which are sort of self limiting. Have less interest in the unicorn tears treatments, but do try to follow the common sense things that help accuracy. (Shooter, Ammo, glass, barrel, trigger, freefloat, etc)
Put another way, I'd rather have an uber reliable, reliably sub moa carbine I can shoot well than a bughole bench queen. (Did that for a bit as well). But that's just me.
Rcoddyar, here the kind of thing the Grendel AR crowd and similar are focusing on:
https://www.m4carbine.net/showthread.php?p=2163506
We've found seating depth / jump / coal to be a very big factor in the AR's relative to bolt guns.
Some of this is throat/caliber dependent, but is just an example of how some very serious and experiences accuracy/distance shooters focus their efforts.
I would say the average m4 grouping at 100yrds is 2 to 3 inches. Oh I am sure I am going to hear about all those .25" AR's but they sure aren't posting targets in the MOA Challenge.
Makes a fun varmint rifle
Not for whitetails and mulies and elk and other medium and large game.
Interesting. Have you read any of Molon's posts??
Typically speaking, a well made M4 barrel will produce 1.5" groups (with good ammo, glass and shooter).
While I agree that the M4 profile is not the best option, it can certainly do the job.
C4
This is m4carbine, not bughole benchrest... Emphasis on hard use, working guns.
Accuracy is of interest to all of us. But the never ending diminishing returns discussions I find a bit silly, and borderline out of scope. (My view)
Free float handguard started due to the significant and observable effect of camp Perry type slings on pre A2 AR's.
2-3 moa type variance.
Do different types effect barrel harmonics? Could be, but you already have your big factors in torque, etc.
There are some common sense things. But the threads of late are getting tiresome. (Facing receiver, loc-tite RE, then loc-tite nut, then gasblock...)
Disagree. If one builds and precision AR and it does not achieve expected results (MOA goals or vertical stringing) then these things (loctite, facing, etc) are discussions worth having. This isnt a debate about magic snake oil - these are techniques used by major players (AA, JP, etc) and I don't think its without merit trying to discern the reasons. You may find searching for that hypothetical extra 1/4 MOA silly, but remember that amount may make the difference for a shooter at 600m. And this is coming from a guy who thinks bench rest shooting is boring.
ClassIIIGunsmith
08-14-15, 14:43
You're only going to get soooooooo much accuracy out of a AR-15 Pattern because it's a Semi automatic rotating bolt rifle which means the bolt might not always be in the same spot every shot which will effect accuracy. The most accuracy you can get is from a super high quality heavy barrel (X>.750") with a good tight bore according to a .223 Go Gauge and only if the go gauge is the only one you can close the action with. Also I have gotten 1" groups Iron sighted with a Colt SP1 at 100 yards and that's not free floated but my free floated DMR gun I used on my last Prairie Dog Hunt at 600-800 yards distances gets a .75" 10 round group when I am shooting at my best at 100 yards. But a .224 diameter bullet is buffered by the wind easily so a larger round would be a better choice because my best Marksmen rifle is my Winchester M70 Pre-64 with a Heavy barrel and a Night Force 12-42 x 56 Scope can get .5" groups at 100 yards if I really try but that rifle is hand loaded with ammo tuned to the barrel. Ammo is 90% of accuracy after a barrel and scope because my M70 only likes 155gr Sierra HPBT Match King with 51.2gr of 748 powder (which is a hot load for 748). My DMR likes 28.0gr of 748 (also a hot load for 748) with 90gr Sierra HPBT Match King bullets. So ammo is most bench rest shooters issues but if your happy with 1" groups at 100yds using only a free float be my guest because my old Colt can shoot that using Irons (I can't anymore cause my eyes got old but the gun can)
Disagree. If one builds and precision AR and it does not achieve expected results (MOA goals or vertical stringing) then these things (loctite, facing, etc) are discussions worth having. This isnt a debate about magic snake oil - these are techniques used by major players (AA, JP, etc) and I don't think its without merit trying to discern the reasons.
I don't disagree in general. It's the idea that somehow hard use carbines cannot be accurate, and if not going to extreme measures (unicorn tears) that you are wasting your time.
I listen very closely to anything Bill Alexander says, as I know he has a huge amount of experience making accurate AR's that are also reliable even in full auto. I use Some JP parts, etc.
Bill was pretty specific on his views for things like receiver facing. Forget the exact quote, but it was something like "which do you think will give, the Aluminum receiver nose, or the steel flange backed by a large barrel nut well torqued". I've built one carbine with an AA upper/barrel, and I saw no need for it. If I could have measured a gap, I probably would have asked for an exchange. Did follow his advice on torquing. Did not do the 2xx blue loctite bedding, but probably would on a DMR type build.
But you also see the internet experts argue with him. Like necks. He did a bunch of testing, as did AMU. Found tighter necks in Grendel pretty much made no difference in accuracy, but negatively impacted reliability. Huge debate. Same for throats. BA went with a compound throat that shoots well with many bullets and jumps. And will admit that one of the alternate throats (LBC) might work better with two bullets, but won't across the full range. And most of our grendel experience has backed up these positions. So I tend to listen when Bill talks.
I also find it telling what the AMU, Whiteoak, and similar feel are important, vs what they do not offer or do.
But for M4 type carbines??? My priority is: technique, ammo, barrel, free float, glass, trigger. Beyond that we are getting into diminishing returns for most things.
I'll shut up, and we go back to set screw barrel bulges and what loc-tite to bed your gas block with. :-)
So what does one do, when all of the stupidity doesn't work? Do you start tossing barrels until you find the right one? The AR15/M16/M4 is a combat rifle. The fact that most of the quality ones will out shoot the MILSPEC standard is a testament to the rifle and design. But, at some point people need to be grounded in reality.
Disagree. If one builds and precision AR and it does not achieve expected results (MOA goals or vertical stringing) then these things (loctite, facing, etc) are discussions worth having. This isnt a debate about magic snake oil - these are techniques used by major players (AA, JP, etc) and I don't think its without merit trying to discern the reasons. You may find searching for that hypothetical extra 1/4 MOA silly, but remember that amount may make the difference for a shooter at 600m. And this is coming from a guy who thinks bench rest shooting is boring.
So what does one do, when all of the stupidity doesn't work? Do you start tossing barrels until you find the right one? The AR15/M16/M4 is a combat rifle. The fact that most of the quality ones will out shoot the MILSPEC standard is a testament to the rifle and design. But, at some point people need to be grounded in reality.
Well, I think "stupid" might be a little brash... but if your goal is to achieve a specific MOA with factory ammo, and your current setup/barrel with snake oil isn't achieving that, then yeah it might be time to junk it and find something better. That is, unless your trying to achieve 1/4 MOA... then it might be time for a reality check :D
From what I see on a regular basis people spend money looking for the elusive Leprechaun and after they spend a small fortune on their magic wand, they buy some crap ammo. Or worse, they buy some garbage scope and mount and then some crap ammo. I wonder how much would be gained by actually going out and shooting their basic set up.
Well, I think "stupid" might be a little brash... but if your goal is to achieve a specific MOA with factory ammo, and your current setup/barrel with snake oil isn't achieving that, then yeah it might be time to junk it and find something better. That is, unless your trying to achieve 1/4 MOA... then it might be time for a reality check :D
From what I see on a regular basis people spend money looking for the elusive Leprechaun and after they spend a small fortune on their magic wand, they buy some crap ammo. Or worse, they buy some garbage scope and mount and then some crap ammo. I wonder how much would be gained by actually going out and shooting their basic set up.
I don't disagree at all. I was making an ASSumption that anyone trying such techniques would already bee using quality components.
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