Subsonic question

[Buckoman]

loading subsonic 308's here's what I came up with in 60 degree weather:

grains
Trailboss
9.5gr - 960 - avg960
10gr - 965- 973- 1009- avg983
10.5gr - 1041- 1023- 1014- avg1026
11gr - 1052- 1095- 1086- avg1078


The 11 grains gave me the tightest group but I'm conerned that I am just too close to the transonic border especailly in hotter weather. What's ya'll opinion?

 

[Hummer]

Re: Subsonic question

If it shoots for you and you like it drive on. Hits count misses are talked about.

 

[crumpmd]

Re: Subsonic question

I agree. I tried several bullets in my 1-12 twist 308 and with 168, 175, and 185 match bullets the better accuracy came with an occasional crack.
I am now shooting a 220 roundnose at 980-1000 and it shoots really well. The stability calculator says this is a nogo for a 12 twist but I have no keyholes and no baffle strikes. FWIW though I do have a 10 twist on hand now that i am going to switch to to lighten up the gun and make it my primary deer hunter. We seldom get a shot more than 150yards and I am sure that for 90% of my hunts kills will be inside 100.
So shoot what you are confident in. If you get an occasional sonic crack, no worries.

 

[ChadTRG42]

Re: Subsonic question

What bullet are you running?

 

[Buckoman]

Re: Subsonic question

I'm running a Sierra 180gr Round Nose.

My can is in the shop right now so I don't know if I'm below the sound barrier crack. Seems to me I am but my biggest concern is that I'm too close and am going to get the crack or at least transonic buzz. Is the 11gr at 1078fps within a good velocity range?
If I'm not too close to supersonic now, how about in 85 degree weather? I should expect an increase in velocity right?

 

[cwshooter]

Re: Subsonic question

Tried 10.8?
Maybe backing it off a couple of tenths will help with those rounds running too close to the sonic barrier.
CW

 

[Buckoman]

Re: Subsonic question

the question is what is the maximum velocity one should run subsonics at?

 

[bohem]

Re: Subsonic question

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Master_Blaster</div><div class="ubbcode-body">the question is what is the maximum velocity one should run subsonics at? </div></div>

The speed of sound...


I keep them at 1050 so that there's a little bit of leeway and they stay subsonic all year round.

 

[Witch_Doctor]

Re: Subsonic question

Did some research on the subject of the Speed of Sound for my own load development, and this website had the best information:

http://www.sengpielaudio.com/calculator-speedsound.htm

Using the calculator the following hold true:

@ 50 F = 1107 FPS

@ 60 F = 1117 FPS

@ 80 F = 1139 FPS

@ 90 F = 1149 FPS

@ 100 F = 1160 FPS

 

[Buckoman]

Re: Subsonic question

thanks gentlemen. Is there a "transonic" range that will give some sort of a report prior to supersonic?

 

[Witch_Doctor]

Re: Subsonic question

You are not going to get a Transonic signature, but what you will hear behind the gun is different than what another person will hear 10' feet away.