Bullet Design

[pjifl]

I have been wasting time writing a computer program to help
with my understanding of bullet design.

Some aspects need a lot of work but others I am quite pleased with.
There is a lot more work required - but this will have to wait.

There are undoubtedly bugs etc - and I would like to hear about any you find.

A zipped version with some examples is downloaded at

http://www.users.bigpond.com/PJIFL/bullet-shapez.zip

Unzip and arrange the entire directory to hang off C:\

Then run the program in that directory.

Any feedback is very welcome.

Peter Smith.

[CEW]

Peter a mutual friend has asked me to post this info for him.

Dia 7.62 mm
Tail dia 7.00 mm
Tail length 0.5 mm
Bearing length 10.5 mm
Front length 22.0 mm
Secant ogive
Sharpness ratio 1.12 (possibly 1.15)
Tip dia 2.0 mm
Hollow length 4.5mm
Pressure at 1020
Altitude of 100 ft
Humidity of 80%
Temp 80 degrees


These are the dimensions of the bullet he used to shoot the Aus record 1.35" group in a recent 600 yard BR match. The calculated BC was about .480 at 2500 fps where his was calculated on V and drop at just over .500 at 3350 fps using 6.6 minutes total drop to 600 yards.
SF of 1.5 given at 13 twist where he used 14 and SF of 2.06 and a possible theoretical twist rate of 20.1 to achieve a 1.0 SF. The calculated weight was 162.9 grains where the actual is a neat 162. Calculated ogive of 9.4 cals where the actual is 10.
All in all he reckons the program is quite useful even with the likes of the flat based bullets but the SF numbers are questionable. Possibly they may be based on G6 or G7 not G1 which is more suitable for FB bullets. Can this setting be altered? He will ring you soon to speak to you about such things.
Peter.

[pjifl]

Thanks to CEW and friend for useful comments and data.

Program predicts BC of very close to 0.5 at 3300 as shown in the BC_V graph so thats not too bad. Close enough to be useful;

The twist rate is the least reliable at the moment and is not modified for different atmospheric conditions so is a loose estimate.

This all originates from McCoys old basic programs and the version I have is incredibly difficult to transfer to another computer language - needs a lot more work here to check everything which will not happen overnight.

Peter Smith

[pjifl]

The Bullet Design program I have written has been significantly improved.

Feedback is welcome.

A section on required twist rate has been added which shows stability at different velocities and ranges.
This alows the user to make intelligent choices.

The previously reported required simplistic twist rate has been deleted.

A more intelligent meaning to bearing length has been implemented. Plus a few other small improvements.

The program does give a good feel for all of the interactions between parameters when one input is changed.

See below for original post.


>I have been wasting time writing a computer program to help
> with my understanding of bullet design.
>
> Some aspects need a lot of work but others I am quite pleased with.
> There is a lot more work required - but this will have to wait.
>
> There are undoubtedly bugs etc - and I would like to hear about any you
> find.
>
> A zipped version with some examples is downloaded at
>
> http://www.users.bigpond.com/PJIFL/bullet-shapez.zip
>
> Unzip and arrange the entire directory to hang off C:\
>
> Then run the program in that directory.
>
> Any feedback is very welcome.
>
> Peter Smith.

[pjifl]

Further to my program on bullet design

1/ I have now entered 34 real life bullets. If anyone is interested I can
send a zipped file of all of them. There will be more added when I have
time.

2/ I have a much newer and more capable version of the program. For some
reason I cannot upload to my web site but can send a zipped file to anyone
interested.

Please contact me if you want any of this material

Peter Smith

[pjifl]

I have placed a copy of my program on the web so I do not have to send it individually to people. I may expand this web page to some other shooting stuff. It includes about 50 real world bullet files and the latest version of the program.

Probably worth it for people who are using the program to get the latest version and extra bullet files.

Its at

http://www.users.bigpond.com/pjifl/shooting.html

Peter Smith.

[pjifl]

There was a corrupted file on my website which is now fixed. You can now download the Group Analysis program OK.

http://www.users.bigpond.com/pjifl/shooting.html

Peter Smith.