Badlands Precision Bullets thread - From BC to terminal ballistics

[akmtnhnt]

I was talking to George about the 135s and we think I can get away with a 1:7.5". That's going off the jbm calculator.

The jbm is difficult to use unless you have bullets in hand.

 

[akmtnhnt]

I have 125s and 135s but have not have a chance to try them yet. At my altitude of 3300', I'll need 3300 FPS to get SG of 1.5 with 1:8." At sea level, you'll need a ridiculous velocity, i.e., 4900 FPS for an SG of 1.5. I was using Berger's twist calculator.

Have you considered 122 Cayuga? https://patriotvalleyarms.com/flm-6-5mm-122gr-cayuga-hunting-bullets-50ct/. It is meant for 1:8" twist. Good luck!

Ya, I run all my stability at SL, standard, just to be sure, as I do hunt in even denser air than that condition.

 

[FEENIX]

I was talking to George about the 135s and we think I can get away with a 1:7.5". That's going off the jbm calculator.

I think he is right ...

 

[Ed AO]

I think he is right ...

View attachment 318238

Yes. He had me put .100" for the tip. But maybe he just gave me a number to put in.

 

[FEENIX]

Yes. He had me put .100" for the tip. But maybe he just gave me a number to put in.

I think you will be OK.

 

[akmtnhnt]

Yes. He had me put .100" for the tip. But maybe he just gave me a number to put in.

That does make a pretty big difference.

 

[Pdvdh]

Aluminum and plastic tips allow a lesser tip length than their actual lengths when determining stability. Courtney and Miller conducted tests, and came up with a modified model for tipped bullets, for tip material much lighter than copper/lead.

Patagonia Ballistics ColdBore 1.0 software includes that model in their ballistics software, for tipped bullets.

The Courtney & Miller model only considered stable flight for precision in flight. It didn't address higher stability that might be needed to improve terminal performance in game animals.

 

[highdrum]

What's the twist of that rifle? The 135's need at least a 1 in 7, ideally 1 in 6 from my calculations.

I'm sorry I was shooting the 125s, I edited my original post. I'm running 8tw.

 

[Monkeygoat]

I've got 50 of the 135's and going to try them in my 7.5 twist, 28", 6.5 Max.

Looks like COAL to the lands is 3.1500 - will start with seating depth test .010-.100, considering 55.5 gr 8133 for the seating depth test, since my load for 145 Matchburners is 63 gr.

Welcome any input though - loading them up tomorrow and shooting Sun. Also have N570.

 

[Monkeygoat]

^Updated the seating depth test, went 15, 30, 45, 60, 75, 90 off, all over 57 grains 8133.

 

[Monkeygoat]

Looks like I'm going to be close to the lands! Control group with Bergers first. Then I shot 45, 60, 75 off, then back to 30 and 15 last.

 

[Mike D Texas]

Looks like I'm going to be close to the lands! Control group with Bergers first. Then I shot 45, 60, 75 off, then back to 30 and 15 last.

View attachment 322052View attachment 322053

Very nice. They told me to start at .050 and work in/out from there. Looks like .015 is going to be best for you.

 

[Northkill]

Looks like I'm going to be close to the lands! Control group with Bergers first. Then I shot 45, 60, 75 off, then back to 30 and 15 last.

View attachment 322052View attachment 322053

What velocity were you running on these? That is some tight shooting.

 

[Monkeygoat]

What velocity were you running on these? That is some tight shooting.

I didn't even set up Magneto since 57 grains 8133 was just a shot in the dark. I'll work up from there and take some velocity readings, and buy some more 135's!