G1 or G7 drag on Strelok?

[evetseel]

Hi folks

What drag function does everyone use on Strelok, for say a hornady 50gr v-max?

I’ve been doing some range work today and now have an itchy head.

with my Strelok settings set to G7 drag function (as it always has been) I’ve been shooting MOA at 300yds quite happily.

Today I pushed the range out to 400 yds and things got strange. Same weather and loads as previous though this time I’m hitting 16 inches low. I checked my zero at 100yds straight after - bang on!

So off home for a head scratch and brew and start playing with my ballistics app. I flick my Strelok drag function to G1 (apparently outdated) and low and behold my vertical clicks requirements go from 23 clicks to 32 clicks. (Somewhere I would probably say is about close to the vertical correction required after seeing today’s POI.

What’s everyone thoughts and what do you tend to use?

For your info I’m using:

Remington 700 24” 1:9 with a vortex ps-t viper 6-24

Lapua fresh brass with cci 4 primers, Alliant rl10 powder, hornady 50gr v-max with a 22.3 gr charge. Putting out at 3050fps.

 

[evetseel]

Hi folks

What drag function does everyone use on Strelok, for say a hornady 50gr v-max?

I’ve been doing some range work today and now have an itchy head.

with my Strelok settings set to G7 drag function (as it always has been) I’ve been shooting MOA at 300yds quite happily.

Today I pushed the range out to 400 yds and things got strange. Same weather and loads as previous though this time I’m hitting 16 inches low. I checked my zero at 100yds straight after - bang on!

So off home for a head scratch and brew and start playing with my ballistics app. I flick my Strelok drag function to G1 (apparently outdated) and low and behold my vertical clicks requirements go from 23 clicks to 32 clicks. (Somewhere I would probably say is about close to the vertical correction required after seeing today’s POI.

What’s everyone thoughts and what do you tend to use?

For your info I’m using:

Remington 700 24” 1:9 with a vortex ps-t viper 6-24

Lapua fresh brass with cci 4 primers, Alliant rl10 powder, hornady 50gr v-max with a 22.3 gr charge. Putting out at 3050fps.

Further info

 

[User00044]

BC (G7) 0.116 for 50 grain .224 vmax.
You appear to have the G1 BC entered.
Hope this helps .

FT

 

[Laurie]

I don't know or use Strelok, but the variance in its results are both wrong and strange. So, assuming you've used it correctly, there has to be something wrong in the program or its database values. As a rule, there is damn all difference between G1 and G7 at shorter distances, ie under 400-500 yards depending on bullet and calibre, with most bullets if the initial average BC values are reasonably close to actual.

Bryan litz gives the two average BC values for the 50gn Hornady VMax based on actual range tests as 0.110 G7 and 0.215 G1 covering the speed range of 3,000 to 1,500 fps Ballistic Performance of Rifle Bullets 3rd edition. (That's actual speed from muzzle to target.) Run those through Berger's Ballistic Calculator selecting the appropriate BC G1/G7 metric at 3,020 fps MV and the results say for 400 yards:

G1 ................... - 8.89 MOA / 37.22 inches

G7 .................. - 8.73 MOA / 36.5 inches.

So, only 0.7 inches between them at this distance and less than a single click on a 0.25-MOA click value scope adjuster.

The estimated retained speeds at 400 yards for this bullet are interesting too - 1,498 fps G1 and 1,508 fps G7 again very close. However, note that if accurate, they have now reached the lower figure for the average G7 speed measurement range. After there (not that many people will want to shoot a 50gn 224 beyond this distance) the calculations will become noticeably less reliable, especially for G1 whose values change considerably depending on bullet speed.

As you were shooting ~16 inches low at 400 that's 4-MOA 'out' and is almost exactly what my ballistic program says is the difference between 300 and 400 yard settings for either BC metric. ie G7 come-up from 100 = 4.75-MOA for 300 yards increasing to 8.73-MOA for 400 yards. Are you sure you entered 400 yards into Strelok?

 

[evetseel]

I think I may have discovered the error. I was using a G1 BC with the G7 drag function applied in my ballistics app. I didn’t realise that you need to enter the BC and then the drag function separately. What even is ‘drag function’?

 

[User00044]

Just run your imfo through Strelok Pro using their data . I suspect Laurie 's BC will be more accurate as manufacturers tend to be a little optimistic. Even correcting the BC doesn't appear to account for the extra drop .

 

[Eric the Red]

G7 is a better coefficient to use, certainly for longer ranges.

There are a number of tweaks that will need to be applied to get it mirror your real data. Truing your data is by far the most important thing. Accurate weather, DA etc all make a difference.
The biggest assumption I have seen made is either with velicity or true zero range. These need to be tweaked so you get data that matches your real world experience.

 

[User00044]

Drag Factors are the bullets ability to punch through the air . The 2 models used for these calculations are G1 and G7 .The G7 model is nearer to the Vmax bullet shape . The higher the figure the better the bullets ability to maintain velocity . This is a bit of a simplification.

As Eric the Red has pointed out you need to input accurate information .