Home Forums Reloading Reloading Software Why doesn't Sierra Infinty software use the G7 BC?

Which ones do use G7, vs, don't

Here are three examples of Sierra's multiple BC values.



Looking at the above examples it's clear that no single drag function can best match those three bullets, which is why Sierra is sticking to their multiple BC technique. In a way they are giving you a custom drag function for each of their bullets. Unfortunately, most apps can't accommodate Sierra's multiple BC values, at least not correctly.

As for other software, Ballistic Explorer does all the drag functions including Sierra's multiple BC technique, and it also has by far the most accurate conversion of BC's from one drag function to another drag function of anything I've found. Likely that's because the conversion is based on research published by Ken Oehler. It can even convert Sierra's multiple G1 BC values to any other drag function including back to a single G1 value. Here are some examples.

Assuming a MV of 3000 fps the equivalent single G1 BC value for bullet #2145 is 0.408 and the G7 value is 0.208. Relative to the multiple BC value, drop relative to LOD out to 1000 yards is within 0.08 MOA for the single G1 BC value and within 0.39 MOA for the G7 BC value. G1 is a better match for this bullet than G7.

The same experiment for bullet #2140 gives an equivalent single G1 BC value of 0.359 and an equivalent single G7 BC value of 0.186. Relative to the multiple BC value, drop relative to LOD out to 1000 yards is within 0.01 MOA for the single G1 BC value and within 0.68 MOA for the G7 BC value. G1 is a better match for this bullet than G7.

The same experiment for bullet #2200 gives an equivalent single G1 BC value of 0.442 and an equivalent single G7 BC value of 0.224. Relative to the multiple BC value, drop relative to LOD out to 1000 yards is within 0.27 MOA for the single G1 BC value and within 0.10 MOA for the G7 BC value. G7 is a better match for this bullet than G1.

This all assumes Sierra's measurements of BC are accurate.

This article lists some software that uses the G7 ballistic coef.

http://02b0516.netsolhost.com/blog1/2009/06/17/a-better-ballistic-coefficient/

Sierra came out at end of last year with Version 7. I purchased a copy. In all my years purchasing software I have never seen a bigger piece of junk. It had bugs that crashed the program, and my computer at time. All I can say it was the most screwed up program I have ever seen. I could not believe a company like Sierra would ship that kind of junk. I called and emailed them about how that reflected on all of their products. After around two months, they emailed me a link to download to fix on the program. Today it is 100% better than V-5 0r V-6. Then about month latter they had a pdf “User Guide” it is free download. You need not have the Infinity software install to use it. But it will give you a very good idea on what the program can do. It keeps track of all your guns and load date. It is not a reloading manual, you use what ever reloading date that you have used over the years. It does have a list of all or most bullets mfg. If you purchase the Suite you do get the Sierra reloading manual. I highly recommend that you purchase the suite version. If you know bullet BC and velocity you can make and save a custom bullet. When you save a custom bullet it can include powder type, grains of powder, bullet mfg. and velocity, if you have a chronograph. If you don’t have chronograph, you can use the program to calculate bullet velocity. No it is not as accurate as a chronograph, but it will get you very close. Velocity calculator is not listed in the guide. If you what to know how calculate velocity, send me private message. You can also make custom cast bullets if you want. If you are not willing to read and try to under stand the “User Guide” I would not download it. But you can use the “Delete Key” any time. Don’t think you can learn all the capabilities in one afternoon.

Link to Guide

https://www.sierrabullets.com/products/infinity-software/

Thanks for the link. I was looking at the Infinity 7 video on the Sierra website two months ago and my impression was that they were using a phone app interface. Great on a smart phone, but on Windows I want a windows interface where I can open the parts of the program I need and go between them in any order rather than paging back and forth to get what I want.

I'll go through the user guide and see if I was mistaken and if 7 is improved enough over Infinity 6 to justify the price.

I can not tell you about phone apps. I would call them, I have not seen anything on apps. Go thru the user guide two or three times. When you start to use the program, all your loads should be put in as "Custom Bullets Editor" page 39 of guide. This is what I did. The box custom Bullets I us name of Sp CZ 453 22 RL. Then Sp CZ 527 221 Fireball. Next Sp Ruger 10-22 LR. Next Sp Ruger KM 77 VT .223. Did that with ever gun I have. When you start the program and go to the "Bullet Selection" page the default "Manufacturer" is Sierra. When you click on Sierra all manufactures are in alphabetical order. With Sp in front of your firearms name they are the next line down from Sierra. Then in list of bullets every bullet you use in that gun is listed. You can see on page 39 all the information you enter is listed. This is not even close to what V-5 and V-6 were. Just make sure you get the suite verison, and down load up-grade.