LOAD DEVELOPMENT AND SUPPRESSORS...

[JarHeadTim]

Good morning...

OK, I am entering uncharted territory here and looking for experienced advice. I have been precision hand loading for 37 years so I understand the process. What I have no experience with is loading for a suppressed weapon and some initial base questions come to mind such as:

How much does the addition of a suppressor affect / alter barrel harmonics?

1. Will ACCURACY, not POINT OF IMPACT (POI) change if load development is done without the suppressor being used during the process? (I have my gut feelings, but I don't want to express my opinions here yet).

2. Does the addition of the suppressor change the Nodes?


Lets start there, based on your comments I'm sure the conversation will evolve. THANK YOU for your anticipated responses...

S/F

[a_canadian]

On your second question; it is not possible that adding mass to a vibrating body will not change node location and spacing. The additional mass added to one end of the barrel is the same sort of exercise as adding length to a tuning fork. The pitch drops to a lower note with the fork. How could it not with a barrel? So it seems that this answers the first question as well. Loads developed for accuracy without the suppressor will not deliver matching results when the suppressor is fitted. Perhaps you could simulate the suppressor while developing the loads however. If you knew the exact mass (and mounted change in length, which might also be a factor) you could add a dummy weight of the same mass to the muzzle and test with that in place.

[T-Rex]

For reference, I have a 308Win (1:12, 20") that I use only for target shooting (100-600yds). I developed loads for it, w/o a suppressor, and was consistently seeing <.5moa. Once I got a suppressor my groups enlarged. I went through kind of the same thought process as you. I ended up chronographing w/ the can on and found my velocity was about 150fps higher than w/o. I developed new loads, to drop the velocity and tighten the groups. With a little effort I got my groups back to where they should be and the velocity was close (accuracy being more important).

Each case will be different. Barrel length and profile will alter the data as well as suppressor length, weight, center of gravity, material, etc, etc. You need to remember that the suppressor you intend to use may not be the best choice for precision shooting. Using a weight, to represent the can, wouldn't be effective. Forget about harmonics, it may be the beast of how the internals are designed. The gases can and will have a direct effect on the bullet, regardless of barrel length, suppressor weight, etc.

These points aside, I'd just go about developing a load as you normally would, just w/ the suppressor attached.

[JarHeadTim]

On your second question; it is not possible that adding mass to a vibrating body will not change node location and spacing. The additional mass added to one end of the barrel is the same sort of exercise as adding length to a tuning fork. The pitch drops to a lower note with the fork. How could it not with a barrel? So it seems that this answers the first question as well. Loads developed for accuracy without the suppressor will not deliver matching results when the suppressor is fitted. Perhaps you could simulate the suppressor while developing the loads however. If you knew the exact mass (and mounted change in length, which might also be a factor) you could add a dummy weight of the same mass to the muzzle and test with that in place.

OK, Canadian, good point, I hadn't really thought it through (I'm recovering from the Flu so I'm not hitting on all eight cylinders mentally yet)... Once the bullet exits the rifling the effect of the nodes are cancelled so any weight hung on the barrel after that does not effect bullet flight. I was looking at it like the suppressor was "extending the barrel there by adding time to the resonance, so to speak.

Does the additional weight of the suppressor change the harmonics of the barrel there by influencing change, like adding a tuner to the barrel?...?

[a_canadian]

Exactly. One weight or another doesn't make a lot of difference as far as harmonics are concerned. It's like the question 'what's heavier, a ton of feathers or a ton of lead?' Stick a suppressor-equivalent mass of any sort on the muzzle and your nodes and peaks are going to shift significantly. Of course with the right suppressor weight you could match nodes, just shifting it down an octave for example. But figuring that out and nailing it exactly in your suppressor build could be quite a nightmare. Probably better to test with the suppressor, as T-Rex talked about, since it's not just weight becoming a factor here. Then if you need a barrel tuning weight add that as well.