Accuracy change after adding hand guard retainer

[dust feeder 2]

I'm just wondering if anyone ever noticed an accuracy change after adding a hand gard retainer. Now, don't jump on me...I know these aren't percision target rifles and there's already a gas block clamped to the barrel, but I have to guess clamping the retainer on the barrel is just another point that effects barrel harmonics.

 

I there any legitimacy to this theory? I'm just a casual shooter, but wanted to hear from the folks who know a lot more than I do.

[pjj342 632]

I may not know much more than you do, but Ive heard of this kind of thing before.

 

To answer your question, yes, anything metal you attatch to your barrel will affect the harmonics and make it less accurate. How much less accurate, I dont know. Im thinking like 1/4" at 100yds, or maybe less. I cant imagine it would throw your projectile much more than that. Although, 1/4" will get bigger and bigger when you shoot out farther.

 

IMO, its really not anything to worry about, as this isnt a precision type rifle. Its pretty damn accurate under most any circumstances and made to be rugged. If it was made to hit bottle caps at 400yds, then I wouldnt attatch anything to the barrel. Since its standard form has the retainer, gas block, sight block, and cleaning rod on it, dont worry about the accuracy, just put it on if you want to. I dont think youll notice a difference.

[Scott Kenny 144]

It's not the retainer that messes with accuracy so much as a wood handguard pushing on the barrel. That's why a lot of normal hunting rifles went to synthetic stocks.

 

As long as a metal part is solidly attached to the barrel, it shouldn't change native accuracy. The rounds should all hit in about the same area. Adding a barrel damper (or a bayonet) can/will change harmonics, but that changes lot-to-lot consistency more than same-lot point of impact.

[opto_isolator 3]

I would think that if it does affect accuracy, you could adjust the front sight. Otherwise, it may affect grouping repeatability. But if that is a concern, than better ammo may help more.

[dust feeder 2]

Sorry, accidentally posted twice

Edited October 2, 2011 by dust feeder

[dust feeder 2]

From what I hear the issue with effecting barrel harmonics is that the accuracy change is not concistant from shot to shot so you can't simply adjust your sight. As your barrel, hand guard, retainer, etc. Heat up at different rates they all interact differently effecting the harmonics differnetly from shot to shot.

 

As I said in the first post I know this isn't a percision rifle. Just wondering if anyone noticed a measurable difference before and after converting their hand guarrd.

 

I was tthinking that Saigas factory hand guard design could be one of the reasons they have relatively good accuracy compared to other aks

[Scott Kenny 144]

If your rifle isn't consistent from shot to shot (assuming that the rifle itself isn't moving), something is loose. Anything properly secured onto the barrel will change point of impact ONCE, from where it hit before adding the part to where it hits after adding the part.

[sickness 89]

The harmonic vibrations of the barrel are not much different than the harmonics of, say, a guitar string.

 

At lengths of integer divisions of the string/barrel (1/2, 1/3, 1/4, 1/5, etc) those are the "node points". These are points where the barrel/string doesn't move while vibrating. For guitar, if you lightly touch a string at the the 12th fret (1/2 the length of the guitar neck) and pluck it, you'll get a noticably different sound than if you actually completely depress the string. What you're doing is canceling the movement of the string ("modes" of vibration) that don't have a node at that point.

 

You have to be pretty precise about it on guitar, otherwise the harmonic note won't sound right. Small deviations in position close to a node point change the sound significantly, ranging from a clear bell-like tone, to just a dead flat thump.

 

When you interfere with the vibration in any way, you have to do it PRECISELY the same way, every time. On a barrel, the extreme forces involved can shift your handguard retainer a tiny bit and make the barrel "sound different" - i.e. shoot differently. If you shoot fast, and the barrel heats up and linearly expands, now your node points are moving too.

 

So contact with your barrel can certainly affect accuracy.

 

On the other hand, there are platforms, like the M14 where for accuracy it is recommended to set the gun up so that the stock places downward tension on the barrel.

 

It all depends on whether it is repeatable from shot to shot.