Badlands Precision Bullets thread - From BC to terminal ballistics

[JTH]

BC clearly matters. A friend of mine helped a buddy harvest this Bull Elk at 1225 yds. One shot and fell dead right there. Used a 300WM. The data for the load is seen in the table. Bullet penetrated fully and not recovered was a 195 gr BD2 hitting at an estimated 1761fps. For shooter it was his introducton to Bulldozers. Needless to say, he was impressed. Clearly these BD2 pills are designed for long range with a high BC for its weight giving it a very effective long range terminal performance

I'm curious about the twist recommendations for the 30 cal options.

Having shot quite a few different monolithic bullets, I tend to err on the side of caution with twist rate to ensure proper stability and generally look to get a gyroscopic stability factor above 1.5 and preferably closer to or above 2.0. I am convinced this plays a role not only in accuracy, but also in terminal performance.

I was interested in the 205 sbd2 which recommends a 9.5 twist, (my barrel is a 9.0 twist) but instead chose the 195 sbd2 which still has a phenomenal G7 bc value of .345 (personally verified by drops out to 600 yards). The 195 with my load data is getting a stability factor of 1.57 and grouping great, but I feel this is on the lower end for stability with a monolithic bullet.

I'm thinking the bullet length with the lighter aluminum tip included may be throwing off the calculation for gyroscopic stability. Can you provide some insight on this? Can a 205 truly be stabilized in a 9.5 twist? Very interested in your thoughts on this. Is there a way to adjust the bullet length in the ballistic program to account for the lighter weight of the aluminum tip?

 

[akmtnhnt]

I'm curious about the twist recommendations for the 30 cal options.

Having shot quite a few different monolithic bullets, I tend to err on the side of caution with twist rate to ensure proper stability and generally look to get a gyroscopic stability factor above 1.5 and preferably closer to or above 2.0. I am convinced this plays a role not only in accuracy, but also in terminal performance.

I was interested in the 205 sbd2 which recommends a 9.5 twist, (my barrel is a 9.0 twist) but instead chose the 195 sbd2 which still has a phenomenal G7 bc value of .345 (personally verified by drops out to 600 yards). The 195 with my load data is getting a stability factor of 1.57 and grouping great, but I feel this is on the lower end for stability with a monolithic bullet.

I'm thinking the bullet length with the lighter aluminum tip included may be throwing off the calculation for gyroscopic stability. Can you provide some insight on this? Can a 205 truly be stabilized in a 9.5 twist? Very interested in your thoughts on this. Is there a way to adjust the bullet length in the ballistic program to account for the lighter weight of the aluminum tip?

The JBM stability calculator allows you to put the tip length in there.

And yes, it does effect the calculation. You cannot assume the tip is copper.

 

[nralifer]

I'm curious about the twist recommendations for the 30 cal options.

Having shot quite a few different monolithic bullets, I tend to err on the side of caution with twist rate to ensure proper stability and generally look to get a gyroscopic stability factor above 1.5 and preferably closer to or above 2.0. I am convinced this plays a role not only in accuracy, but also in terminal performance.

I was interested in the 205 sbd2 which recommends a 9.5 twist, (my barrel is a 9.0 twist) but instead chose the 195 sbd2 which still has a phenomenal G7 bc value of .345 (personally verified by drops out to 600 yards). The 195 with my load data is getting a stability factor of 1.57 and grouping great, but I feel this is on the lower end for stability with a monolithic bullet.

I'm thinking the bullet length with the lighter aluminum tip included may be throwing off the calculation for gyroscopic stability. Can you provide some insight on this? Can a 205 truly be stabilized in a 9.5 twist? Very interested in your thoughts on this. Is there a way to adjust the bullet length in the ballistic program to account for the lighter weight of the aluminum tip?

Your instincts about gyroscopic stability are well placed. The recommended twist rates for the 205 SBD2 actually is 8.5. Both the aluminum tip and lower atmospheric pressure add stability, the former because the light tip makes the bullet behave more as a bullet of shorter length (usually about 0.100" shorter), and high altitude, causing lower station pressure (gyroscopic stability increases with lower station pressure). We quote a twist rate that will stabilize the BD2s at sea level, so that at higher altitudes stability will increase. Your idea of over stabilizing the bullet is sound. Stability factors above 2 are icing on the cake since at the over stabilization aids in the transitioning of the bullet to subsonic speed, something not necessary for hunting since the BD2s are are designed to open at 1700 fps impact velocity.
As to whether the added angular momentum (increased rpm of the bullet) adds to the terminal performance, a faster spin at impact certainly can't hurt, and may cause more liquefaction by the sharp petals after expansion aiding in penetration to some degree, how much though I can't tell you. Excellent question though.

 

[JTH]

Thanks for the reply. I just made the adjustment of reducing the length by 0.100 and the stability factor for the 195 jumps from 1.57 to 1.88 in my 9.0 twist, which is great.

When I plug the 205 in with the same parameters and drop 100 fps to account for the extra 10 grains of weight the stability comes in at 1.42, confirms I made the right choice in going with the 195.

 

[codyadams]

Thanks for the reply. I just made the adjustment of reducing the length by 0.100 and the stability factor for the 195 jumps from 1.57 to 1.88 in my 9.0 twist, which is great.

When I plug the 205 in with the same parameters and drop 100 fps to account for the extra 10 grains of weight the stability comes in at 1.42, confirms I made the right choice in going with the 195.

Yup, in planning a build for the 205, I had my barrel made with a 1:8 twist. The 195 is about right in your twist, I personally aim for 2.0 stability like you.

 

[jasent]

Yup, in planning a build for the 205, I had my barrel made with a 1:8 twist. The 195 is about right in your twist, I personally aim for 2.0 stability like you.

Is that the 30 nosler you were doing?
I also prefer a 2.0 or better. Thinking I may go 1:7 on my next barrel so I can play with the 241 Seneca as well possibly in a rum

 

[codyadams]

Is that the 30 nosler you were doing?
I also prefer a 2.0 or better. Thinking I may go 1:7 on my next barrel so I can play with the 241 Seneca as well possibly in a rum

Yup, 20" 30 nosler.

 

[jasent]

Yup, 20" 30 nosler.

Have you verified bc in your setup yet

 

[hunter87]

Comparing them to Berger 215s, are you able to reach comparable velocity's with them? The 205s at 3100 have some sweet ballistics

 

[jasent]

Comparing them to Berger 215s, are you able to reach comparable velocity's with them? The 205s at 3100 have some sweet ballistics

They are 100fps slower than Berger's in my rifle. Doesn't matter well worth it even at 200fps less. Bc and accuracy more than makes up the difference

 

[SheepShapeAK]

Well, I finally got done processing all the meat from the trip.

Here are some pictures. I did have a snafu with my rifle and didn't catch it until after I downed my fourth caribou. Rear screw on my action came loose. Made me think it was just my crappy shooting, but after I tightened it, the shots on my moose were right where I was aiming.

195 BD2's performed great. My furthest shot was only 656 yards. Closest was 300.

Four caribou and a dandy bull moose for me on the trip. We ended up with 8 caribou and 2 moose total. Two of my caribou were for two families back in town.

Exit wound on one of the caribou.

Exit Wound

Internal Carnage

Entrance

Internal

 

[SheepShapeAK]

Some pictures from the moose. He measured out at 59".

By the time we decided who would take him, he got wise and started to run off. I cow called and he turned back to look at us, stopping right at about 300 yards. He was facing towards us slightly quartered to my left. I put the shot in between his front shoulder and neck. Second shot he was broadside and finished him off.

Entrance

Inside entrance

Second entrance

Internal

 

[cbuck516]

Here is a more detailed report of the 0.257" 95gr BD performance on pronghorn. Again, MV of 3550, impact @ 200y with velocity of 3217fps and energy of 2183ft*lbs.

Below: Bullet entry is the red little blood stain on the front quarter. Entry hole is a 0.257" hole as seen in later photos. On impact, the front quarter that the bullet enter through was slightly rearward so the bullet didn't pass through the chest cavity as far forward as this photo might indicate.

Below: Bullet exit was several inches back of the entry as the animal was slightly quartered to me. This is the exact position that I found the animal in. There are actually two exit holes, a larger one and a smaller one. This leads me to believe either a large section of a petal separated from the bullet shank and exited or a large fragment of bone was ejected through the body. I think a petal fragment is more likely myself.

Below: Here is a photo of the hide where the bullet entered showing a very small entry hole, approximately the diameter of the 0.257" bullet.

Below: Here is a closeup of the two exit holes previously descrbied.

Below: Bullet tip was found in between front quarter where bullet entered and the chest cavity. It never entered the chest cavity.

Below: This is the front quarter that the bullet entered and expanded inside of. This is a view of where the bullet exited the front quarter travelling only through soft tissue. After processing, it appeared that the bullet began expansion within 1-2" of travel trough this front quarter and left a ~1.5" path of destruction in the tissue that it passed through.

Below: Entry into chest cavity shows the same ~1.5" path of destruction as well as a few broken ribs.

Below: Exit from chest cavity shows slightly smaller ~1" path of destruction and less rib damage.

Below: In the top of the photo there is obvious damage to the heart, but the lungs appeared mostly intact overall. There is damage to the lungs seen just to the left of where the heart is damaged, but the lung tissue was not liquified.

Below: Upon removal of the hearty and lungs, the extent of heart damage was more obvious. The heart was butterflied open and nearly cut in two pieces. The lungs were mostly in tact other that the small areas where the bullet passed through. Again, nothing appeared liquified.

Overall, I was very pleased with the performance of this bullet. Like I said before, he ran maybe 30 yards then tipped over. As said by @codyadams in previous posts, the blood seen here is mostly between muscle groups and connective tissue. Bloodshot meat was very minimal which was my goal in switching to copper bullets. I hope to use this load on some Whitetails here in Missouri this fall. I will likely set up my family heirloom 1959 Remington 760 Gamemaster in 270 Win for my nephew launching the 0.277" 128gr. BD2. My 270 Win load wasn't developed for that gun, but hopefully it shoots well enough that I can just load and go.

 

[Reemty J]

Boy oh boy, thank you fellows for the detailed photos, well done! Sheepshape, what a successful hunt!