Ballistic coefficient question

[dc8cappie]

Shooting NSA 31 gr slugs in my FX Impact PP 700mm Slug ”A” barrel with CF liner and CF outer tensionEd. Here is what is happening and then my quandary. Shooting 1000 fps zeroed @ 50 yards. I’m using Sterlok Pro set for the NSA 31 slug, G1. Reset scope (Element Nexus) for target@170 yds. Take shot and slug lands 0.9 MRAD high. Shot again, same impact point, so JFTHOI changed factor to GS. The next slug landed slightly lower but still high. I new G7 would never work, so I set RA4 and shot. This slug landed almost exactly where I was aiming. I should add that this was early morning shooting with no wind, mid 80’s Florida humid day.

Question, has anyone else tried using RA4? What were your results?
Otherwise, opinions on why I have these results!
Thanks before hand, all thoughtful thought welcomed.

 

[Ghostranger169]

Yes, RA4 agrees with predicted POIs for slugs(especially at longer distances) more than any other Strelock choice.
GA for narrow waisted pellets. G1 for MRDs and King Heavies

 

[dc8cappie]

Thanks ghoststranger169, it’s interesting that StrelokPro loads the .22 NSA 30 slugs with G1 as the coefficient index for them. I also wonder why nobody has taken the time to mention it here?

 

[Ghostranger169]

StrelokPro defaults to G1 for most slugs that I have entered. G1 works fine at closer distances. A couple of years ago, someone posted a similar thread and said that RA4 works better for longer distances. Some people may not know and others aren't that particular.
You should also verify the to find the best BC to use for the speed and distance and conditions you are shooting in. At longer distances, the "multi BC" function will give improved results.

 

[MEC17670]

Sorry, guys but what is RA4, another ballistic program?

 

[shootermeb]

Sorry, guys but what is RA4, another ballistic program?

RA4 is a drag model for a specific shape of projectile, more specifically a heeled 22LR bullet shape. G1 and G7 are other drag models commonly used for bullets; G1 is the flat base bullet shape, and G7 a boat tail bullet. A different BC (Ballistic Coefficient) value is defined for each different drag model. A BC value is typically not interchangeable between models. For example, you should not use a G1 BC in a G7 model, it will result in an incorrect ballistic solution. Also, it is best to choose the ballistic model that best represents your projectile shape.