[Jack Monteith]

Hi, Mr. Gates:
  I'm afraid you've got a goof in your Tech Note. The 100 yard velocity with a muzzle velocity of 1000 fps should be 870 fps, assuming a G1 BC of .125, not 670 fps. In turn, this gives a .652" wound channel, not .503". Now if I never made a mistake!!!!!!!!!!

Bye
Jack

 

[Jack Monteith]

Hi, Mr Gates:
  Being Scottish, I was too tight to buy one, so I wrote my own in dBase III+ (no, you old hackers, that is not a misprint). It read in the Ingalls tables and did the necessary math. I got the tables and formulae from Hatcher's Notebook. Later I converted it to QuickBasic so it would be easier to give copies to my friends and firearm safety students. It uses the G1 table now so it matches the ammo company's tables.

  It now corrects for non-standard atmosphere, prints ballistic charts, finds the ballistic coefficient given velocities at two ranges, and finds the muzzle velocity from Chrony data. I spent a lot of time making keyboard entry easy. You can crank out tables all day with one hand on the number pad. Try that with a Windows program. Anyhow, it was a lot of work.

  It's pretty close to McTraj and the Oehler program untill you get out to long range. I'll try to fix that some time. It's strictly DOS, but it will run in a DOS window under Windows 3.1 and 98 SE.

  I found a copy of PCB and I wasn't getting your numbers, so I ran them through McTraj. It looks like PCB is using the Ingalls table and ICAO atmosphere, while I'm using the G1 table and Standard Metro.  Therefore, PCB needs a BC of .134 and my program needs a BC of .125 to get numbers that match your data. Another case of apples and oranges. Dear Reader, if I've lost you, check out page 499 of the Speer #11 manual.

  I might be violating copyright laws if I distribute it.

  I always look forward to your postings.

Bye
Jack

 

[Jack Monteith]

Hi, Mr. Gates:
  It looks like your BC of .151 equals my BC of .144. If your refiguring of the form factor raises your BC from .134 to .151, that extends the effective range by 15 yards. In other words, the bullet slows to 870 fps at 115 yards instead of 100 yards.

  Getting back on topic, I've heard about slower bullets being more effective because they act for a longer time a number of times. There's a lot about "killing power" we don't understand yet.

Bye
Jack