Speed of sound ?

[Bull 228]

Morning,
As a Class 3 dealer I feel like I have had a better than average exposure to suppressors. (no intent on being a smart ass, just qualifying) I have always figured that between roughly 950 to 1000 fps one should expect to be safely sub sonic. I had not had any prior experience with the "Whisper" and it is quite possible that I had exaggerated expectations. But it sure seemed to me that I was still getting the sonic crack. In hind sight I should have video taped the shoot so that I could listen to the shots from a different perspective. I think I will mix up another batch of ammo at slightly lower fps and see what the results are. Thanks for the input, I am always happy to hear from others with more experience than I. I am definitely still inexperienced in the Whisper department.
NT

[TCCrewchief76]

were you shooting indoors or under the cover of a roof? That always makes things WAY louder...

[Bull 228]

I was outdoors and in the wide open. Anyone have any more load data for their "favorite" pet sub loads? Any input and or advice is always welcomed and appreciated.
NT

[TCCrewchief76]

A few 10.5" AR's I've built are running 1000 FPS with 8.5 grains of Ramshot Enforcer with 220 MKs.

Kevin

[Bull 228]

After speaking with a source yesterday he advises me that if I am getting 995 ish fpa that I am for sure sub sonic. I think that I figured that it was going to be much more quiet. Thanks for your load info also though.
NT

[alorton]

Originally Posted by Bull 228

Morning,
As a Class 3 dealer I feel like I have had a better than average exposure to suppressors. (no intent on being a smart ass, just qualifying) I have always figured that between roughly 950 to 1000 fps one should expect to be safely sub sonic. I had not had any prior experience with the "Whisper" and it is quite possible that I had exaggerated expectations. But it sure seemed to me that I was still getting the sonic crack. In hind sight I should have video taped the shoot so that I could listen to the shots from a different perspective. I think I will mix up another batch of ammo at slightly lower fps and see what the results are. Thanks for the input, I am always happy to hear from others with more experience than I. I am definitely still inexperienced in the Whisper department.
NT

You are correct that if you are under 1000fps you should be subsonic. That's why I was curious as to the possibility of having a chrono that reads a little low. I've heard of shooting across two chronographs side by side and having them read 100fps different than each other.

I asked about experience with suppressors because some folks think what they see in the movies is how their gun should sound. A Whisper is quiet as far as suppressed guns go but it isn't "movie quiet" so to speak. I would do exactly what you plan, lower the velocity just a bit and see if you get better results. You might also try different powder combos.

My rifle likes 2400. I use 8.5gr for a 240SMK or 8.0gr for a 208 A-Max. They both come in at just over 1000fps.

[Bull 228]

I think the chrono is good, but have never thought of that being the problem. Will try to find a way to test it. Who manufactures the 2400 powder you mentioned, I am always open to try out womething new. I have a box of the 240gr. SMK in route as we speak.
NT

[alorton]

Alliant 2400, listed in most reloading manuals as just "2400".

A few other popular choices are Lil Gun, Viht N110, or AA1680.

[Expatriot]

At near 6000 ft elevation you may well be running up against the transonic range. The speed of sound is lower at higher elevation. Get your velocities down below 950 fps and you should know for sure.

[Bull 228]

thanks for the help. always appreciated.
NT