Tag Archives: secant

OpenRocket – now we’re talkin’

For something a little bit different here is a link to the OpenRocket source download. It’s a Java based program. Don’t expect exact ballistics software but you cna construct your own designs and use the Component Analysis function to see how changes affect the drag etc.

Example I've done using OpenRocket
Example I’ve done using OpenRocket

Measuring the ogive’s radius.

So if you’ve managed to magnify the outline of your ogive, effectively you can calculate the radius by measuring the meplat to the shank/ogive intersection. This will become your chord length W.  

The  Sagitta of the arc or height (H), is measured perpendicular from the midpoint of the chord W.  

For double or multiple radius ogives there will be multiple chord lengths measure. Note also this method only works with ogives using a tangent and secant radius. The larger your outline is magnified the more accurate your measure will be, useful for those of us without an optical shadowgraph comparator or other such metrology equipment. Remember though you may have to contend with the parallax error depending on how you capture your image outline.

Radius of an arc or segment 

(link to Math Open Reference.)

To calculate the radius

Given an arc or segment with known width and height:

Segment of a circle.  A horizontal base line with an arc on the top.  Its height is H and width of the base W
The formula for the radius is:

Circle.  One vertical line through the center, one horizontal across the upper part, each half labelled 'a' 			     Vertical line labeled B in top part, c in bottom where:
W  is the length of the chord defining the base of the arc
H  is the height measured at the midpoint of the arc’s base.


G7L series projectiles

Calibres, Weights and Pack Sizes

Please confirm pricing at the time of order. Shipping not included, please confirm when ordering.

If you don’t see a particular weight listed in the calibres below, send an enquiry via email or the contact form.

Calibre Mass(gr) Est. Mach Averaged BCG7(1) Min Twist per 100 per 500 Code
224 80(2)  0.216 1:8” $50.00 $241.56 G7L-224-80
243 105 0.242 1:8” $70.00 $338.17 G7L-243-105
257 135   1:8.5” NA NA NA
264 130  0.258 1:8” $84.00 $405.79 G7L-264-130
264 140  0.278 1:8” $85.00 $410.63 G7L-264-140
284 168  0.319 1:10” $87.00 $420.31 G7L-284-168
“The Norm”
284 175   1:9” $88.00 $425.12 G7L-284-175
284 180  0.342 1:9” $88.00 $425.12 G7L-284-180
308 150   1:14” $61.00 $294.69 G7L-308-150
308 155(3)  0.239 1:13 $86.00 $415.47 G7L-308-155
308 168   1:13” $86.00 $415.47 G7L-308-168
308 175   1:13” $87.00 $420.31 G7L-308-175
308 185   1:12” $88.00 $425.12 G7L-308-185
308 190   1:11” $89.00 $429.94 G7L-308-190
Calibre Mass(gr) Est. BCG7(1) Min Twist per 50 per 500 Code
308 210  0.334 1:11” $46.00 $444.50 G7L-308-210


(1) Based on the “G7 form factor prediction” as described by Litz (2011, 573)

(2) Based on ICFRA Technical Rules for TR Shooting (2019 Edition)  rule T2.19.2.1.

(3) Based on ICFRA Technical Rules for TR Shooting (2019 Edition) rule T2.19.2.2.

Introducing the G7L series of projectiles

  • Precision gilding metal match grade target jackets
  • +99% Lead (Pb) cores
  • Hand swaged in Australia

The G7L series of projectiles is Antipodean Industrial’s entry into the hand swaged projectile market. In principle, the G7is a traditional long range (300y+) projectile designed for high levels of accuracy while maintaining supersonic velocity levels.


Another batch of G7L-284-180gr's ready for packing.