My Berger 7mm hybrid BC test

[elmerdeer]

Hi guys I bought some berger hybrids 180gr bullets with a G7 BC of .345 and I decided to run some tests on them at semi lomg range 625 yards to see if they would get that BC. I have a Hoover metplat trimmer and poining die, so I sort 150 bullets and there is .002" variance at the ogive, pretty good so far. I start to metplat trim them about .005" and then point them. So if theory is correct I should loose about 2% BC and gain lets say up to 8% BC, so were 5% gain on BC which would bring the BC of this bullet up to G7.362 BC.
Well I shot them out to 625 yards and was low about 1.5 MOA, so I come back look at my speeds from my chrono at 12ft and decide to put a chrono at 200 yards to see what speed I am getting out there. Then I run those numbers with my 2 average velocities and I come up with my ne BC for these 180gr hybrid Bergers and I am a little off Bergers numbers.
The BC I got was .327, so it seems they are not as high as I thought.
Has anyone seen the same thing with these bullets?
But as far as acurracy they are pretty good if I do my part and the conditions are good, i get Half MOA or less at 200yards.
And when I shot at 625yards the bullets went through a quarter inch of steel like it wasnt there. So I think it should be a good hunting bullet. I shoot a 7mm Dakota caliber, Stiller predator action, with a 24.5" Rock barrel 8.73 twist and my load is 74.5grs Retumbo seated .015" off the lands and I am getting 2979 fps avg with low es and sd numbers.
Let me know if what I did was the right, as I am pretty new to long range shooting.
Thanks
Elmer

 

[bohem]

Re: My Berger 7mm hybrid BC test

I tested them without touching the bullet, just sorting the first run that was sold as seconds.

My test got the BC to be very close to original. Keep in mind that if don't get everything exactly right in the calculator you will get what appears to be an error in the BC when it really could be

Slight MV variation, pressure differences, shooting uphill/downhill a little bit, scope height measurement discrepancy, etc.

Also, you can't take an average MV and then move the chrono out to 200yd for a proper test. You need a second chronograph so that you know how fast it was going at the muzzle and then also at 200yd. Also, keep in mind that if the chrono you use is repeatable to +/-0.5% on a 3000 fps MV you are only reading reliably to +/- 15 fps.

My average results shooting them at 2780fps (measuring 20 rounds through the chrono) gave me pretty close dope to 1000yd, less than 1 MOA difference which was acceptable to me.

 

[elmerdeer]

Re: My Berger 7mm hybrid BC test

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: bohem</div><div class="ubbcode-body">I tested them without touching the bullet, just sorting the first run that was sold as seconds.

My test got the BC to be very close to original. Keep in mind that if don't get everything exactly right in the calculator you will get what appears to be an error in the BC when it really could be

Slight MV variation, pressure differences, shooting uphill/downhill a little bit, scope height measurement discrepancy, etc.

Also, you can't take an average MV and then move the chrono out to 200yd for a proper test. You need a second chronograph so that you know how fast it was going at the muzzle and then also at 200yd. Also, keep in mind that if the chrono you use is repeatable to +/-0.5% on a 3000 fps MV you are only reading reliably to +/- 15 fps.

My average results shooting them at 2780fps (measuring 20 rounds through the chrono) gave me pretty close dope to 1000yd, less than 1 MOA difference which was acceptable to me.</div></div>
Thank you for the info, i will try that and see.
Elmer

 

[mcfred]

Has anyone else played with this? I seem to remember reading somewhere that the 7mm hybrid used a larger punch in the die, so the meplats were larger than the VLD. This made them benefit more by tipping.

I'd be interested to hear from anyone who has tipped or pointed these. I'm guessing around a 0.35 G7?

 

[HodgdonExtreme]

Just gotta try it and see, I think.

"They" say smaller [diameter] bullets benefit more from pointing than bigger ones, because the meplat cross-sectional area constitutes a larger percentage of the total frontal area.

Well, at 1000 yards, I saw zip.shit difference in elevation for the 105 hybrid, tipped vs non.

Mind you, I saw an honest to goodness .1-.2 (call it .15) mrad improvement on the 142smk at 1000 yards. The 7mm 175smk improves nicely too, from a ~.635 BC to ~.655.

 

[TimeWillTell]

Didn't Bryan Litz test these bullets? Think I remember seeing their data in his Applied Ballistics book... He also goes into good detail on testing BCs yourself.

 

[[email protected]]

Good info guys, in going to be shooting 180 hybrids pretty soon if I can find them!
-any leads where I can get 1000 same lots?
-what pointing system do you use, and do you find it a Pain in the ass?

 

[kombayotch]

I did a number of BC tests (not for the 7mm Hybrid) a few years back, here is one of the threads:
http://www.snipershide.com/shooting...ed-new-155-palma-155-5-berger-155-scenar.html

Note the comments from Bryan in post #7 about the common mistakes people make when trying to determine the BC from drops.