Ballistic coefficient and velocity for SW 175gr.

[Clamber]

Hey guys, I need to make a new profile on Bullet Flight for the Southwest 175 grain Sierra Matchking .308, but I'm not sure what the ballistic coefficient or velocity is.

Can you guys help me out?

Thanks,
Coby

 

[geometro]

Re: Ballistic coefficient and velocity for SW 175gr.

http://www.sierrabullets.com/index.cfm?s...mp;bullettype=0

Exact velocity is something you have to use a chronograph: the load maps for 175g SMK ranges anywhere from 2200 to 2600 fps.

The guys at Southwest sould be able to give you their load information to at least make a educated guess.

 

[Driftwood]

Re: Ballistic coefficient and velocity for SW 175gr.

http://www.snipershide.com/forum/ubbthreads.php?ubb=showflat&Number=1998987
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: MikeSWammo</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: cajunshooter</div><div class="ubbcode-body">Mike
What velocity are you getting with your 175 in 308
I've got a 20" sps looking for a good load.
What are you thoughts of using the 155s
I've got a 1 in 10 twist </div></div>

Our 19" test barrel is shooting 2585 and the 24" is shooting 2648. I would expect you to get just under 2600 fps in your 20 SPS.

As for using the 155s, I guess it would depend on your application, and preference. They have a bc close to the 175s, and are about 200-250 fps faster. However, they appear to be more sensitive to wind.

We still have some of both in stock at the SH price. Also, they are available with either large or small primer Lapua brass.

</div></div>
Variable <span style="text-decoration: line-through">G7</span> G1 BC for 175 SMK
.505 for 2800fps
.496 for 1800fps - 2800fps
.485 for 0 - 1800fps

 

[Clamber]

Re: Ballistic coefficient and velocity for SW 175gr.

Okay thanks guys. I don't have access to a chronograph at the moment, but that estimate from Mike at SW should be alright for now.

So I put the velocity as 2590fps and in the first BC spot I put .496, but is that all I need to do? Do I need to change the G1 to G7?

 

[mavrick10_2000]

Re: Ballistic coefficient and velocity for SW 175gr.

.496 is a G1 BC not a G7.

 

[Redmanss]

Re: Ballistic coefficient and velocity for SW 175gr.

Good catch by Mavrick.

175gr SMK has an average G1 of .475, and a G7 of .243.

For your program, you'll get more accurate modeling from the G7.

 

[DirtDart]

Re: Ballistic coefficient and velocity for SW 175gr.

Clamber,
Go into utilities, go to bullet libary, find the sierra section, scroll down to 175 and hight light the 175 smk with BL G-7 than import that to your new weapon profile. I did this from memory but you should be able to figure it out

 

[Clamber]

Re: Ballistic coefficient and velocity for SW 175gr.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: DirtDart</div><div class="ubbcode-body">Clamber,
Go into utilities, go to bullet libary, find the sierra section, scroll down to 175 and hight light the 175 smk with BL G-7 than import that to your new weapon profile. I did this from memory but you should be able to figure it out </div></div>

Oh wow thanks. I didnt know it had the 'projectile database".

 

[RonboF117]

My average muzzle velocity out of my 18" OBR shooting Southwest Ammo's 175g is 2550 fps. Conditions were 88F, Sta. Press. 28.13, Density Alt 4200, 1600 MSL, and 39% humidity. This was using a V2 Magnetospeed chrono.