I've read on some other forums that muze devices shouldn't be taken into account using OBT method for load development. Has anyone noticed any difference specifically with suppressors? In my mind if the pressure wave is traveling down the barrel it should continue down the muzzle device before returning toward the receiver. Wouldn't this effectively change the OBT node??
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Re: Obt and suppressors/muzzle brakes
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Frogman77</div><div class="ubbcode-body"> In my mind if the pressure wave is traveling down the barrel it should continue down the muzzle device before returning toward the receiver. Wouldn't this effectively change the OBT node?? </div></div> I would agree with you that the p wave will continue down the the muzzle device. So yes , the barrel times will change. How much it will effects your nodes i dont know.
I have a pressure trace machine which shows me my exit times, when i put a tuner on my gun it completely changed the results on the pressure trace. So, i just developed a load without the tuner, then put it on and adjusted the tuner. I could shoot 7 shot .5in groups at 200y before i burnt out my 6.5mm. So i cant really say if adjusting charge weights would have improved group size from there. When my tuner was on the worst possible setting i shot 1 moa groups at 200y. Since you probably cant make adjustments with a brake or can like you can a tuner, i would suggest developing your OBT/OCW load without your can, then put the can on and try tweaking the charge weights, see what you get on paper. Unless you'll never take the can off.
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Frogman77</div><div class="ubbcode-body"> In my mind if the pressure wave is traveling down the barrel it should continue down the muzzle device before returning toward the receiver. Wouldn't this effectively change the OBT node?? </div></div> I would agree with you that the p wave will continue down the the muzzle device. So yes , the barrel times will change. How much it will effects your nodes i dont know.
I have a pressure trace machine which shows me my exit times, when i put a tuner on my gun it completely changed the results on the pressure trace. So, i just developed a load without the tuner, then put it on and adjusted the tuner. I could shoot 7 shot .5in groups at 200y before i burnt out my 6.5mm. So i cant really say if adjusting charge weights would have improved group size from there. When my tuner was on the worst possible setting i shot 1 moa groups at 200y. Since you probably cant make adjustments with a brake or can like you can a tuner, i would suggest developing your OBT/OCW load without your can, then put the can on and try tweaking the charge weights, see what you get on paper. Unless you'll never take the can off.
Re: Obt and suppressors/muzzle brakes
My experience with a Browning 30-06 with a BOSS was that the BOSS (a brake, but also an adjustable weight, if you're not familiar) dramatically altered barrel harmonics, and dramatically altered both POI and also group size & shape when it was on vs. off the rifle. This experience was one of many which has demonstrated to my satisfaction that, while OBTs may be useful to a degree, there are MUCH larger, more significant things to consider with respect to barrel harmonics and finding good loads for a rifle. Harold Vaughn's very well-instrumented work demonstrates this also.
So, the short answer to your question is: yes.
A longer answer is that I don't know whether it alters the shock wave that Mr. Long proposes, as that depends primarily upon how tightly-coupled the device is to the barrel. What I do know is that hanging things off the end of a barrel will dramatically affect POI, group size, and group shape.
My experience with a Browning 30-06 with a BOSS was that the BOSS (a brake, but also an adjustable weight, if you're not familiar) dramatically altered barrel harmonics, and dramatically altered both POI and also group size & shape when it was on vs. off the rifle. This experience was one of many which has demonstrated to my satisfaction that, while OBTs may be useful to a degree, there are MUCH larger, more significant things to consider with respect to barrel harmonics and finding good loads for a rifle. Harold Vaughn's very well-instrumented work demonstrates this also.
So, the short answer to your question is: yes.
A longer answer is that I don't know whether it alters the shock wave that Mr. Long proposes, as that depends primarily upon how tightly-coupled the device is to the barrel. What I do know is that hanging things off the end of a barrel will dramatically affect POI, group size, and group shape.
Re: Obt and suppressors/muzzle brakes
I didn't thoroughly read the paper, but I believe the answer is NO, it will not affect the OBT as described by Mr. Long. It may affect the bullet in other ways, such as the harmonics of the barrel. Consider this quote from the "Optimal Barrel Time Paper" by Chris Long:
"The pressure pulse from the gasses in the chamber<span style="font-weight: bold"> cause a traveling wave of stress</span> that bounces back and forth along the barrel between receiver and muzzle, slightly changing the bore diameter in the process. Minimum dispersion of the shots will result <span style="font-weight: bold">when the rate of change of the bore diameter is at a minimum</span>, and this dispersion will present the least sensitivity to load variations (charge, seating depth)."
It isn't the pressure wave itself which we are worried about, but rather the accompanying stresses in the barrel. Once the bullet exits the muzzle, these barrel stresses can no longer act on the bullet. The pressure wave will follow the bullet until it exits the muzzle device, but the stress wave stays in the barrel itself.
I will also note that I have been using the OBT method with QL with my AR, which is wearing a brake. My primary testing is done with an OCW test, and I verify my results with OBT/QL. Both my current loads (55gr, 77gr) landed dead nuts on a predicted OBT node.
I didn't thoroughly read the paper, but I believe the answer is NO, it will not affect the OBT as described by Mr. Long. It may affect the bullet in other ways, such as the harmonics of the barrel. Consider this quote from the "Optimal Barrel Time Paper" by Chris Long:
"The pressure pulse from the gasses in the chamber<span style="font-weight: bold"> cause a traveling wave of stress</span> that bounces back and forth along the barrel between receiver and muzzle, slightly changing the bore diameter in the process. Minimum dispersion of the shots will result <span style="font-weight: bold">when the rate of change of the bore diameter is at a minimum</span>, and this dispersion will present the least sensitivity to load variations (charge, seating depth)."
It isn't the pressure wave itself which we are worried about, but rather the accompanying stresses in the barrel. Once the bullet exits the muzzle, these barrel stresses can no longer act on the bullet. The pressure wave will follow the bullet until it exits the muzzle device, but the stress wave stays in the barrel itself.
I will also note that I have been using the OBT method with QL with my AR, which is wearing a brake. My primary testing is done with an OCW test, and I verify my results with OBT/QL. Both my current loads (55gr, 77gr) landed dead nuts on a predicted OBT node.
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