nralifer
Well-Known Member
The jump to the lands was the same in both cases. If the jump on one wss greater than the other the one with the greater jump would be marginall slower.
Badlands Precision Bullets thread - From BC to terminal ballistics
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akmtnhnt
Well-Known Member
Well, like I said, having different seating depths can vary the pressure by a significant margin, which will change the velocity as well. The software is rather close on predicting the amount slower you saw out of bullet #1 from this pressure difference. I think if you had equal pressure from both, you'd have a very similar result in muzzle velocity.
nralifer
Well-Known Member
Possibly so. We looked at this issue many years ago and tried the Nosler E tip, Barnes TTSX and Hornady GMX against our bullets and in general lower bearing surface bullets could be pushed a little faster but it wasn't much, and certainly not enough to make up for large BC differences. We decided that greater improvements in bullet performance and range could be achieved by improving BC and working on hollow point design.
akmtnhnt
Well-Known Member
I think if you seated Bullet #1 a little deeper to get the same seating depth, the speeds would be the same, or really close to it.
This one?Hopefully someone else can help. I don't recall the thread title or what the original intended thread topic was. So many hit the ditches and no one remembers where it started or was headed in the first place.Should have flagged it. My apologies. (Not sure we want to reopen that can of snakes anyway.)
The pressure factor is for sure an interesting dynamic. It can give some seemingly counter-intuitive results. I would love to get some equipment and do some pressure testing comparos on my own, but this stage of life doesn't give me the time.
I appreciate what you do in developing and bringing a product to the market. The inputs of $$$$$, effort and stress are significant for sure.
Why Hammer Bullets Are Always Faster
Compared 69gr Sierra bullet to a 71gr Hammer Hunter with same load data. Done this with different calibers. Same results. Hammers are always faster. This time I recorded it.
Yep. And you gotta pay attention to guys like @Fiftydriver who have been on the cutting edge of the shooting industry for enough time to have weathered a few doubters along the way. (post 20, 65, 69, etc)This one?
Why Hammer Bullets Are Always Faster
Compared 69gr Sierra bullet to a 71gr Hammer Hunter with same load data. Done this with different calibers. Same results. Hammers are always faster. This time I recorded it.www.longrangehunting.com
C.O. Shooter
Well-Known Member
It's not about being a doubter. Unfortunately, there's always going to be a better mouse trap.
nralifer
Well-Known Member
It's the jump to the lands that has the most influence on speed, that is why I kept the jumps the same. Repeated the test with increasing powder charges to the point that the case was full to the neck shoulder junction and for every charge Bullet #1 was slower. At least in this example the ridges don't add velocity. As iterated in this style of bullet the ridge dedign fails to add velocity,
That's not been our experience over a broad swath of trials. Did you read Fiftydriver (Kirby Allen's) posts on this? His observations mirror what we've found. (or rather vice versa)
You need more/faster powder to get to the same pressure with bullet 1...and the velocity will pick up considerably.nralifer
Well-Known Member
I am going to try StaBall-Match which is slightly slower than Varget but considerably faster than LVR. Have already reached 3242 fps with the BD2 bullet using 53 gr of LVR in the 24" barrel and the LRP brass with no apparent overpressure signs yet. Have not been able to do that with Bullet#1. Max speed so far is 3178 fps with 52 LVR. 53 gr gave only 3129. Not sure what is going on there but I was very careful to measure our 53 gr and it was clearly compressing with bullet seating like in the BD2. Have you been able to safely get 3200 fps from a 308Win? Like to see that recipe and see how it compares with what I am using.That's not been our experience over a broad swath of trials. Did you read Fiftydriver (Kirby Allen's) posts on this? His observations mirror what we've found. (or rather vice versa)
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nralifer
Well-Known Member
The COAL are 2.860" for Bullet#1 and 2.900 For the BD2 which has a longer ogive.
RH300UM
Well-Known Member
What are the minimum velocities for expansion of the BD-2 and the SBD-2?
nralifer
Well-Known Member
1700 fps for both the BD2 and SBD2. The longer and thinner ogive on the SBD2 in fact gives them a lower impact velocity of 1650 fps. Customers have harvested Elk at 4500 ft elevation at 1225 yds with 195 gr .308 BD2 bullets where the expected impact velocity was 1780 fps with one shot DRT kills.
nralifer
Well-Known Member
Here is the data for the SB-Match as promised
Gun: 24"1:9 Bartlein barrel, 308 Win.
LRP Lapua brass, BR-2 primer,
COAL: Bullet #1=2.860", BD2 150 gr =2.900" (0.025" jump for both).
SBM gr Bullet#1151gr 150gr BD2
47.5 2918 2957
48.5 2948 3004
50.0 3002 3073
51.0 3060 3110 some flattening
52.0. 3105 ——
52.5. 3133 some flattening ——
G7BC: Bullet#1=0.184
BD2 = 0.266
The Bullet #1 with many ridges intended to reduce barrel/bullet friction (at the point I started seeing early pressure signs) only had a 23 fps advantage in speed over the BD2. This speed advantage is more than made up by the large difference in G7BC between BD2 and Bullet#1. The multiple ridges detract from BC likely to a greater extent than they increase MV. All charges 50 gr or more were compressed charges. The powder level in the 52.5gr charge was more than half way up the case neck.
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