The question before this august body is this: is there some kind of add on part, wrap, weight or other material that I can add to a New York state legal AR barrel to improve group size with commercial ammunition?
The rifle is a stock JP rig with a 16 inch, 1:8 twist street legal barrel with no threads at the muzzle. New York, so threads no bueno. No threads means no commercially available tuner can be added to it. The rifle in all particulars shoots great... except with respect to group size.
I only shoot commercial rounds in it, and have tried Black Hills 55gr, 69gr, 77gr, PMC Bronze 55gr, Fiocchi 55gr and HSM 77gr rounds. The groups across that sample vary from 1.25-1.75 MOA, and it isn't uncommon to print a few rounds out at 2 MOA in a 10 round group at 100 yards. That isn't an exhaustive sample, but sufficient to tell me the harmonics on those loads at least are not aligned.
And to pre-empt the obvious question, I have another AR15 that will shoot sub .75 MOA at 100 yards. So, there is always shooter error, but the problem rig is a problem in its own way.
So, I am going to mechanically tune the barrel with something wrapped around or attached to the exterior of the barrel at the muzzle. The rig has a 12 inch hand guard, so there is a little room to maneuver in terms of "at the muzzle" or slightly behind it, but I don't want to remove the hand guard if possible, just for convenience.
My experience with the Eric Cortina tuner on a bolt gun is that adjusting it less than a quarter turn takes group sizes way down. That tells me that the harmonic adjustment necessary for the AR shouldn't have to be too drastic. Maybe wishful thinking.
Thus far, I have shoved some O rings over the muzzle end, but that wasn't sufficient to get to the right harmonic node for any of the commercial rounds I mentioned.
I realize this post suffers from at least two shortcomings. One: just develop a custom load for the rig and quit bothering us. Two: you live in New York, so you get what you deserve.
Still, interested in any suggestions.
The rifle is a stock JP rig with a 16 inch, 1:8 twist street legal barrel with no threads at the muzzle. New York, so threads no bueno. No threads means no commercially available tuner can be added to it. The rifle in all particulars shoots great... except with respect to group size.
I only shoot commercial rounds in it, and have tried Black Hills 55gr, 69gr, 77gr, PMC Bronze 55gr, Fiocchi 55gr and HSM 77gr rounds. The groups across that sample vary from 1.25-1.75 MOA, and it isn't uncommon to print a few rounds out at 2 MOA in a 10 round group at 100 yards. That isn't an exhaustive sample, but sufficient to tell me the harmonics on those loads at least are not aligned.
And to pre-empt the obvious question, I have another AR15 that will shoot sub .75 MOA at 100 yards. So, there is always shooter error, but the problem rig is a problem in its own way.
So, I am going to mechanically tune the barrel with something wrapped around or attached to the exterior of the barrel at the muzzle. The rig has a 12 inch hand guard, so there is a little room to maneuver in terms of "at the muzzle" or slightly behind it, but I don't want to remove the hand guard if possible, just for convenience.
My experience with the Eric Cortina tuner on a bolt gun is that adjusting it less than a quarter turn takes group sizes way down. That tells me that the harmonic adjustment necessary for the AR shouldn't have to be too drastic. Maybe wishful thinking.
Thus far, I have shoved some O rings over the muzzle end, but that wasn't sufficient to get to the right harmonic node for any of the commercial rounds I mentioned.
I realize this post suffers from at least two shortcomings. One: just develop a custom load for the rig and quit bothering us. Two: you live in New York, so you get what you deserve.
Still, interested in any suggestions.
