Choosing Bullet Weights, specifically for long distance shooting

[joelogic]

I am shooting a .308 and speed is a bit fast because the primers are flattening out a bit. I will dial my loads down.

What are the usual expected speeds for 168gr and 175gr bullets?

Seems WC846 is hotter than BLC-2 which is the data Hi-tech recommends.

BLC-2 168gr Min 44.0 FPS 2569 39,400 CUP Max 47.0 FPS 2754
WC846 168gr 46gr FPS 2861

BLC-2 175gr Min 43.0 FPS 2517 39,200 CUP Max 46.0 FPS 2706
WC846 175gr 45gr 2840.

[GeoffLinder]

In pretty much any caliber the heavier a bullet is the higher it's BC will be. Heavier bullets are longer because they have more material in a fixed diameter. This increases SD (Sectional Density) and this increases BC (if the bullet shape is correct). This is why VLD's in any caliber are always at the heavy end of the available bullet weights. Their long tapered shape is why they fly so far, so well.

There are 3 BC drag models to choose from. If you use flat based bullets, use G1, regular boat-tails use G5 and heavy VLD's use G7 drag model.

If the Mfgr doesn't supply G5 or G7 BC info you will need to calculate it. G5 is usually about 62-63% of the Mfgr's BC1 and G7 about 50%. Example, mfgr BC1 = .362 - G5 corrected = .229 - G7 corrected = .181

[Seesm]

Geoff on my reloading I have been doing 62 and 69 grain.. My thinking was it will shoot good in my Mini 14 and ok in the Kel tec and my Ar style rifles... Yes no maybe?

[ocabj]

The Ballistic guy at Berger, Bryan Litz, wrote a recent article about BC. I'm sure it can be found on the Berger website.

Article? The guy wrote a 500+ page book on ballistics two years ago. It's a must read.

[ronas]

Article?

Here's a May 16, 2011 article he wrote. Form Factors: A Useful Analysis Tool
Link below.

http://02b0516.netsolhost.com/blog1/?p=186

[17+1]

Are you shooting a 300 WM? Because the velocities you give are awfully high for a .308.

This is exactly what I was thinking...

I haven't chrono'd my SMK 168 load yet but judging by the drop out past 500 yards, it should be up around 2500-2550.

[Sub95]

44gr of varget 168gr bullet gets me 2700+ on the Chrony, it was set 15 feet in front of the muzzle.

[30Cal]

I am shooting a .308 and speed is a bit fast because the primers are flattening out a bit. I will dial my loads down.

What are the usual expected speeds for 168gr and 175gr bullets?

Seems WC846 is hotter than BLC-2 which is the data Hi-tech recommends.

BLC-2 168gr Min 44.0 FPS 2569 39,400 CUP Max 47.0 FPS 2754
WC846 168gr 46gr FPS 2861

BLC-2 175gr Min 43.0 FPS 2517 39,200 CUP Max 46.0 FPS 2706
WC846 175gr 45gr 2840.

Flattened primers are an indication of pressure, but don't necessarily mean that you're too hot. This is where the chronograph comes in real handy. Mine are definitely flat and even slightly mushroomed at nominal velocities. Depends on who's primer your using.

Also, I don't know about WC846, but BLC-2 is one you have to watch out with. The hotter the day is, the hotter the load becomes. This is pretty typical of ball powders in general.

[RobG]

Those speeds are measured from your gun? What barrel length? Lots of shooters use the 175 smk, 178 amax, or 155 scenars for a reason. They work.