Drop chart for RUAG GP90?

[scottm]

Bought 2 200 round packs:

I found real velocity data ( 2811 fps at 15 feet from a 16" barrel AR ) and manufacturer supplied G1 data ( .331 ).

Plugged G1 = 0.314 ( 95% of RUAG value ) and velocity of 2811 fps (I have a 16.5" AR) into Bulletflight app:

10 degrees C, 80 meters elevation, 50 yard zero
100m +1.4" +1.2MOA
200m -1.4" -0.6MOA
300m -12.6" -3.7MOA
400m -34.5" -7.5MOA
500m -70.3" -12.3MOA

Using AE223N (62gr bullet). I got real drops of 16MOA at 500m from a 16.5" barrel. The above GP90 chart seems too good.

Questions:
-Does anyone have a field generated drop chart for GP90?

-As a first approximation, would you dial down the ballistic coefficient of .314 some more? The first time I shoot this past 200 yards will be in a match, so I'd like to be as close as possible.

 

[carbonrod]

I haven't shot GP90 in a while, but this was my drop chart out of an R15

100m +1.5
200 0
300 3
400 7
500 10

 

[scottm]

I haven't shot GP90 in a while, but this was my drop chart out of an R15

100m +1.5
200 0
300 3
400 7
500 10

Thanks very much Carbonrod. I checked the velocity source I used originally and it was acquired at 94 degrees F (34.5 Celsius)! Not a likely temp at Vokes in the spring. I was able to shoot 5 rounds over a chronograph last weekend. The average velocity at 10 Celsius was 2725 fps out of my 16.5" barrel. I also am going to go with the published G1 of .331. Maybe RUAG doesn't exaggerate the ballistic coefficient. They would be about the first.

Slower velocity, higher BC than my previous assumptions and a 200m zero =
100m +2
200 0
300 -3.2
400 -7.3
500 -12.4



Very close to your real data through 400m. The R15 has a slightly longer barrel than mine so I'll try -11 at 500m.
100m +1.5
200 0
300 -3
400 -7
500 -11

I can post what I find here to 500m after May 7 in case anyone else wants to try GP90 in the future. I know handloading is the way to go for best effect, but the GP90 isn't *too* expensive to use for a few matches a year and has a reputation for decent accuracy. Works well up close in mine anyway.

 

[Longshot]

Will you be shooting your HK again mate?

 

[scottm]

I am. Are you going to come out and school us May 7 at Vokes? Guess it partly depends on when Longshot II decides to arrive

 

[Longshot]

Well he just arrived and I'm still hoping mom will let me outta the house for a day

 

[diopter]

Your barrel is 4.78" shorter than what GP90 is tested with. Bound to be major differences.

Here's some original specs with the Sig. Just convert the drop from meters to inches and then the distance from meters to yards to see the difference from your barrel to the Swiss standard.

http://theswissriflesdotcommessageboard.yuku.com/topic/8664/STGW-90-Sight-question

 

[diopter]

2811 ft/s is about 856 m/s, about what GP90 is listed on the chart at 50m(860m/s)