Ballistic calculator problem

[azhunter86]

Hi, y'all. This is my first post. I've been reloading for quite sometime. Just purchased a ruger m77 mkII, in 6.5x55 swede. Mounted a Burris Fullfield II E1 in 4.5x14-42mm with the ballistic plex reticle. Shooting a 140 gr Hornady sst, Winchester case, Winchest lr primer, and RL 17.

Anyway, went to sight her in for the first time. Used my info of the loaded ammo and weather at the current time in my ballistic calculator(Strelok). I first shot at 25 yards to make sure I was on paper. The calculator said to be high .59" to be zeroed at a hundred. first three shots happened to be 1.25" high. So, I moved the target back to 100 yards, figured it was close enough. The problem is the grouping at 100 yards ended up being 8-9" high. Great grouping but the calculator left me puzzled as to how far off it was.

The info inputted into the calculator is as follows and was my starting load, but the bullet being seated .02" away from lands to ogive. So, the printed fps would be faster due to the less pressure in the case. Anyway, about 2300 fps (no chrono due to being shot, earlier this year), .52 bc(g1 by hornady), 2349 elevation, 65 degrees, and scope mounted 1.66" from bore.

Any suggestions as to what happened? Is this a common problem? I'd be happy to answer any questions. Just been researching like crazy and couldn't find anything.

Thanks for the time, Justin

 

[TexSavage]

azhunter86, I plugged your info into my shooter app and based on the info you gave and me guessing your twist at RH 1:9, 0% humidity, 1.25" high at 25 yards, velocity at 2300, etc. I show you should have hit 7.4" high at 100. When trying to input a 100 yard zero, I actually see your 25 yard shot being -6 (below, not high). Maybe that was a misprint in your post.

I am guessing your velocity is above 2300, more in the 2,800 to 2,900 range. Your energy would be in the 2350 to 2375 ft-lbs range at 25 yards based on the 2,800 to 2,900 fps. Just my two cents worth.

The above is not intended to be used as anything other than what I am seeing. Do not use the information for any other purposes other than as a reference and possible source for double checking your original data.

 

[azhunter86]

It's a 1:8" twist and 22" barrel. That would be scary fast since it's the starting load from hornady.

 

[azhunter86]

The calculator said .59 low to be zero. But in actuality the bullet hit 6" high. Sorry went back and used calipers to measure the difference. What calculator do you use? I'm thinking it's an error with the one I'm using.

 

[TexSavage]

I use Ballistic AE and Shooter. Have been mainly relying on Shooter. AE says with 6" high at 100 yards that is a Zero of about 275-280 yards and you would be 1.03 high at 25 yards.

Shooter shows 275-280 yard zero and .9 high at 25 yards.

I also saw some Red Box data on 129 grain that is between 2,850 fps and 3,100 fps, but I think they were max loads (Real Guns - The 260 Remington Versus the 6.5x55 Swedish Mauser Part 1). Just one of the sites I looked at. All loads should be started at least 10% below and watch for signs of high pressure.

The following works for me and me alone in my rifle and is not shared for duplication purposes, just as FYI.

I have a Savage Model 12 heavy barrel 26" in 300WSM and I am pushing a 185 Berger at 2988 (Chrono), but I am at max powder load. Did a lot of extensive load workup with H4831SC. Also shot JLK 190VLD's out of same gun at 3004 fps and AMAX 185s at 2995. It was also a max load, but no pressure signs at all. I have been reloading for 34 years and have some experience. It works for me and I have seen no signs of pressure excess. Of course I could see it tomorrow, if so we back down to no signs and settle in. I have roughly 650 rounds through the rifle.

 

[azhunter86]

Cool, I'll have to check those out. I was just curious as to why my calculator was so far off. To say .59" low at 25 yards and zeroed at 100 yards. Although, it says the same calculation for 200 yards as yours. So, I guess the calculator I use is inaccurate for sub 100 yard ranges.

I'm starting to work up some loads for my 300 weatherby mag, Berger 200 gr hybrid target with IMR 4828ssc. Says max load is 2966 fps, that'll make my jaw hurt for sure, lol. Shooting out of a Weatherby mark v.

Thanks for the info, I appreciate it