Tag Archives: g7l

Nose Cone Design or Projectile Ogive Design

So here is a link to download the original MS Excel spreadsheet for Nose Cone Design.

I use a modified version myself to plot shapes that resemble long range target projectiles. If I can do it I’m sure those of you some knowledge of spreadsheets can come up with their own modified version. Follow the instructions and enjoy!

Example of a secant 338 calibre design I did using the Excel program.
Example of a secant 338 calibre design I did using the Excel program.

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.

 

7mm.com.au – Antipodean Industrial

Here is the link to an interview by Craig McGowan with me discussing Antipodean Industrial, G7<sub>L</sub> projectiles and bullet swaging.

Antipodean Industrial

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

 

Notes:

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

(2) Based on ICFRA Tech Rules & Regs for Fullbore TR 2008 Ed. 3 – Jul 2008 rule T2.19.2.1.

(3) Based on ICFRA Tech Rules & Regs for Fullbore TR 2008 Ed. 3 – Jul 2008 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.

FAQ

So why is the first projectile series called – ‘G7L‘?

The ‘G7‘ part of the name refers to the preferred standard of drag curve, used to compare the form factor of a long range boat tail projectile, to estimate its ballistic coefficient (BC) at various velocity (and atmospheric conditions). Traditionally a G1 drag curve was used to perform various ballistic estimates based on the Mach number measurement (velocity including atmospheric conditions). The shape of the projectile used to create the G1 drag curve had a flat base and an ogive profile similar to a benchrest projectile. It has been found that the G7 drag curve more accurately predicted the various ballistic calculations (e.g. trajectory/velocity) at longer ranges. This is because the G7 drag curve was developed using a projectile with a boat tail and a more aggressive ogive profile; hence a closer representation to modern long range projectile shapes.Modern ballistic software is now available with BC calculations utilising the G7 drag curve as an option.

The subscript ‘L‘ is acknowledgement of my bullet mentor Mr Gary Little for his assistance in developing this first range of projectiles for Antipodean Industrial. Gary Little produced a wide range of hand made custom projectiles under the company name of Little Bullets for many year in Australia. There is no doubt that without Gary’s mentoring skills, experience, industry contacts, generosity and patient personality, I would not have made any progress up the steep learning curve that is swaging bullets by hand.