Badlands Precision Bullets thread - From BC to terminal ballistics

[nralifer]

I was hoping for a BC improvement more similar to the 195gr VS 205gr 0.308" BD2 (G1 of 0.675 vs 0.785 respectively). With the 0.277" BD2 comparison of 140gr vs 150gr being G1 0.650 vs 0.680, there isn't much of a ballistic advantage from my simulations. I simulated both bullets in GRT using the same approach and then plugged into my ballistics calculator. At 800 yards (50F @ 7,500ft), the 150gr is moving 50fps slower, has 50ft# more energy and 0.1" less wind drift than the 140gr. That is nearly identical performance in my opinion.

Is the 150gr 277 being designed to accommodate some specific problem that 6.8 Western shooters have with the current 140gr?

 

[nralifer]

Not really. People like heavier bullets and the 6.8 Western will push that bullet considerably faster and with a better BC than the Berger 170 gr out of the commercially available twist barrels. Penetration on game with either the 140 or 150 bullet should be much better than the Berger especially at high impact velocities.

What cartridge did you use in your simulation and what muzzle velocity did you predict for the 150? My guess from the 6.8 W a 3200fps should be achievable. The 140 from a 270 Win should be around 2900-3050 fps. Depends on the powder a lot. Superformance is quite good in the 270Win.

I was hoping for a BC improvement more similar to the 195gr VS 205gr 0.308" BD2 (G1 of 0.675 vs 0.785 respectively). With the 0.277" BD2 comparison of 140gr vs 150gr being G1 0.650 vs 0.680, there isn't much of a ballistic advantage from my simulations. I simulated both bullets in GRT using the same approach and then plugged into my ballistics calculator. At 800 yards (50F @ 7,500ft), the 150gr is moving 50fps slower, has 50ft# more energy and 0.1" less wind drift than the 140gr. That is nearly identical performance in my opinion.

Is the 150gr 277 being designed to accommodate some specific problem that 6.8 Western shooters have with the current 140gr?

Weather cleared enough that I was able to actually measure the BC with my lab radar. G1 came out at 0.71, so clearly better than the 140 gr. We wanted to keep the bullet stable in the 1:7.5 twist range to accommodate the commercially available rifles but still have a higher BC than the 170 Berger. The 140gr SBD2 would be an excellent choice for a 1:8 twist 270Win though. These days of component shortages you can still find 270Win brass fairly easily. McGowan and Preferred Barrels make 1:7 twist barrels in .277 caliber though.

 

[FEENIX]

Weather cleared enough that I was able to actually measure the BC with my lab radar. G1 came out at 0.71, so clearly better than the 140 gr. We wanted to keep the bullet stable in the 1:7.5 twist range to accommodate the commercially available rifles but still have a higher BC than the 170 Berger. The 140gr SBD2 would be an excellent choice for a 1:8 twist 270Win though. These days of component shortages you can still find 270Win brass fairly easily. McGowan and Preferred Barrels make 1:7 twist barrels in .277 caliber though.

X-caliber does too.

 

[Bghunter338]

Weather cleared enough that I was able to actually measure the BC with my lab radar. G1 came out at 0.71, so clearly better than the 140 gr. We wanted to keep the bullet stable in the 1:7.5 twist range to accommodate the commercially available rifles but still have a higher BC than the 170 Berger. The 140gr SBD2 would be an excellent choice for a 1:8 twist 270Win though. These days of component shortages you can still find 270Win brass fairly easily. McGowan and Preferred Barrels make 1:7 twist barrels in .277 caliber though.

I got one of the McGowan one's.

 

[jacob_strass]

What's minimum expansion velocity on these bullets generally?

 

[jacob_strass]

Really like the idea of these bullets and have a couple different cartridges and builds in mind to use them. But I was curious how these bullets act terminally on average? Are they closer to a Barnes where they peel back and maintain 90-99% weight or are they more like a hammer bullet where the petals shed and the base continues through? I'm mainly interested in the 100 grain .243 and the 150 grain .277.

 

[nralifer]

What's minimum expansion velocity on these bullets generally?

1700 fps. May be less for the SBD2's because ogives are longer and a little thinner giving them higher BCs

 

[Copper Basin]

Why a 8 twist when the manufacturer says a 7 twist for the 160?

Doesn't this skew all results?

Also the terminal ballistics part of the ballistics trio are negative affected?

I was running the 160's in a 7 Sherman short, 8T, proof barrel. They BC's held up at my altitude I shoot at. At 6000 ft and above I gain a twist. I was running them just at 3000 with 64g of H1000. I ran paper targets at 800 and no keyholing. JBM ballistics had the stability factor of 1.90. I know people like to run mono's at 2 or higher if they can. At 1000 yards this bullet is still going 1937 fps with 1384 ft lbs of energy. I have not had a chance to hunt with this bullet yet as that rifle was sold before the season.

While I agree on the face of it it would negatively impact the results. In shooting it, even at cedar hills (elev 4473 approx), the bullet has been performing well.

So far, the JBM data has been accurate and I will look for some hunting opportunities to test terminal performance.

Wilson did not offer a 7T for the .284 so I wanted to see what the 8T did with this bullet.

Sorry for answering out of sequence. Since you are in my neck of the woods, if you would like to shoot my setup with the 160's at cedar hills just PM and we can work out a time to do it.

 

[nralifer]

I was running the 160's in a 7 Sherman short, 8T, proof barrel. They BC's held up at my altitude I shoot at. At 6000 ft and above I gain a twist. I was running them just at 3000 with 64g of H1000. I ran paper targets at 800 and no keyholing. JBM ballistics had the stability factor of 1.90. I know people like to run mono's at 2 or higher if they can. At 1000 yards this bullet is still going 1937 fps with 1384 ft lbs of energy. I have not had a chance to hunt with this bullet yet as that rifle was sold before the season.

While I agree on the face of it it would negatively impact the results. In shooting it, even at cedar hills (elev 4473 approx), the bullet has been performing well.

So far, the JBM data has been accurate and I will look for some hunting opportunities to test terminal performance.

Wilson did not offer a 7T for the .284 so I wanted to see what the 8T did with this bullet.

Sorry for answering out of sequence. Since you are in my neck of the woods, if you would like to shoot my setup with the 160's at cedar hills just PM and we can work out a time to do it.

At a station pressure of 25.00 inHg the 160gr .284SBD2 is stable from an 1:8 twist at a muzzle velocity of 3100 fps. I chose that station pressure from a chart of atmospheric pressure that equates altitude with uncorrected atmospheric pressure. If you already have shot those bullets at that altitude and the BC and accuracy are holding up then I would say you are good.

 

[Copper Basin]

At a station pressure of 25.00 inHg the 160gr .284SBD2 is stable from an 1:8 twist at a muzzle velocity of 3100 fps. I chose that station pressure from a chart of atmospheric pressure that equates altitude with uncorrected atmospheric pressure. If you already have shot those bullets at that altitude and the BC and accuracy are holding up then I would say you are good.

I am using 23.98 corrected pressure for 30 degrees and 6000 ft. I am using .150 for the platic tip on JBM trajectory model. I know I have asked you before on the proper tip length for the SBD-2's. I might be using the wrong one. When I shot at my range, elev 4473, the corrected pressure has been around 25.30 for 30 degrees. The 160's have been spot on.

 

[RH300UM]

View attachment 426989
Round #2 ready

Just as I thought. Rl26 is my rifles choice to continue. 90.5 grains

 

[RH300UM]

I'm liking it!
30 off the lands with 3kfps a BC of .410 ( to be validated soon) and great accuracy
Should make for a great combo

 

[RH300UM]

I ordered some more 250 SBD-2's to work (have fun) with!
Just need this snow to stop piling up so I can stretch it out and validate this load.
I've got 50 new fire-formed brass ready and waiting.
Lots of time to practice before Guide season starts in august.
Hmmm. Elk season is 10 months away……

 

[Aloeus]

I know a lot of people were having good luck with staball in here, but I just can't get it to shoot consistently. Its not accurate and its not really consistent velocity wise either.