7mm or .308?

[lancetkenyon]

I would love to send some downrange out of a .300RUM at about 3300fps too.

 

I would assume these are a VLD type bullet design to get that BC? Long ogive, small meplat, long boat tail? Are they going to be for hunting (softer copper), or target?

[nralifer]

nra, where can I buy some? I'd like to do an objective evaluation of these.

 

I would love to send some downrange out of a .300RUM at about 3300fps too.

 

I would assume these are a VLD type bullet design to get that BC? Long ogive, small meplat, long boat tail? Are they going to be for hunting (softer copper), or target?

Thanks guys for your interest. We are waiting for a response from the ATF regarding a manufacturers FFL before we can sell anything. Also the 180 gr bullet should be stable out of a 1:10 twist barrel down to an ambient temp of 20F. At temperatures below this the stability factor goes below 1.3. Would be happy to send you some bullets as soon as we settle the FFL issue. The bullets are solids intended for target shooting. You could shoot Coyotes, Prairie Dogs or Pigs for fun. They are not expanding bullets.

[308Nut]

 

 

nra, where can I buy some? I'd like to do an objective evaluation of these.

I would love to send some downrange out of a .300RUM at about 3300fps too.

 

I would assume these are a VLD type bullet design to get that BC? Long ogive, small meplat, long boat tail? Are they going to be for hunting (softer copper), or target?

Thanks guys for your interest. We are waiting for a response from the ATF regarding a manufacturers FFL before we can sell anything. Also the 180 gr bullet should be stable out of a 1:10 twist barrel down to an ambient temp of 20F. At temperatures below this the stability factor goes below 1.3. Would be happy to send you some bullets as soon as we settle the FFL issue. The bullets are solids intended for target shooting. You could shoot Coyotes, Prairie Dogs or Pigs for fun. They are not expanding bullets.

I have a solution to the ATF issue. Just send 50 as a gift. Free evaluations never hurt.

 

M

[nralifer]

Well, today my partner and I went and tested the 170 gr .308 bullet for a BC. We used a 308Win and a 300Wby Conditions were cold: temp 18 degrees, pressure 30.25 and wind 10-12mph with a wind chill close to 0. We had tried twice before with 2 Superchronos but this did not work. Turns out to get readings that correspond closely with the Oehler 35 the Superchrono has to be perfectly parallel to the bullet path. This complicates things at the target end since the trajectory is now arced so that you can actually get readings at the target chrono higher than the muzzle velocity. We decided to calibrate the Oehler with the Superchrono at the muzzle and then used the Oehler at the target. We were able to get them to read within 8-10 fps of each other 12 feet from the muzzle. We determined the velocity drop for the 300Wby and got bullet drop data for the 308Win. Both sets of data correlated and indicated a BC of 0.65 over the 308 yd spacing between the chronos. The MV for the 308Win was 2725 from a 20 in barrel, and the 300Wby 3188 from a 26 in barrel. It is a lot of work to do this especially in the winter. We plan to do this for three other bullets, weather permitting. I will keep you posted.

[308Nut]

Are you shooting near sea level?

[nralifer]

Are you shooting near sea level?

Elevation here is 1309 ft

[lancetkenyon]

.650 BC for a .308" 170gr. bullet is phenomenal!

 

You don't hit that BC with a Berger until you pass the 210gr. VLD @ .631. The 215gr. Hybrid is just over that @ .696.

A 210gr. SMK is only .645 G1 BC, and the 240gr. SMK is only @ .711.

 

Post a photo of the bullet. What is the overall length of the bullet? It has to be at least 1.5-1.6" long, right?

[STOMP442]

I'm guessing BC numbers will be revised much lower once longer range testing is completed. For the BC to be that high with a bullet of that weight the form factor will have to be in the 0.77 range. Meaning that these bullets are roughly 23% more aerodynamic than the G7 standard projectile. The best match bullets with the highest BCs have form factors somewhere around 0.97-.98 the math is not working out for me on this.

[308Nut]

+1 on STOMPs reply ^^^^^^^^

 

It is not physically possible for a 170 grain 30 cal bullet to reach the .6G1 mark let alone .65. The BC evaluation process used has a flaw somewhere. It can be hard to find which component is flawed or which combination of items.

 

The 177 GS bullet proves this. 177 mono metal shaped like a 208 AMAX and is advertised at .638G1 by GS bullets. Actual firing tests prove that they're not even close to .6 let alone the .638 they advertise.

 

Something that should always be done when using the double chrony method to evaluate bullets with unkown BCs is to shoot another bullet that has a proven BC side by side so you know if there is a major fubar. I have done this in the past for a side by side comparison. You know if you're shooting a 175 SMK over two chronies and you come up with .580G1, you know you screwed up somewhere because you know that the 175 SMK does not have a BC anywhere near .580. It gives you a reference to compare against. You will also know if you're higher or lower than the reference and either way you'll know what percentage higher or lower it is. For example, when the 210 ABLR came out and had a published value of .73, it didn't take a rocket scientist to know that there is no way for a 30 cal 210 grain class bullet to hit the .730 mark. What was the first thing I did when I received some? A little load development and then the double chrony test. I had a 208 load that was within a few FPS of the 210. I shot them side by side. Knowing that the 208 has an accepted average .633G1 BC and a .66+ G1 at 2900'sec I had an accurate reference point to compare against the 210ABLR. After calculating .647G1 for the 208, I knew for a fact that my components were set up properly and that my calculations were correct. At lease very close. Then having shot the 210 over the same two chronies minutes apart from the 208, I knew the calculated value would be very close to reality. It showed me that it was slightly lower than the 208 between 0-200 yards. Out to a grand, it showed that it was slightly higher. I'm assuming that it is because it's BC decays slightly less than the 208 over distance but who knows? At least I know that these two bullets are very close in BC.

 

One red flag I see is your statements of barometric pressure. I'm assuming your using your stated pressure values in your equation. If you are and those are corrected for sea level values while you are shooting at > 1300' elevation, that is part of the problem.

 

Like I said before, the ATF will allow you to donate a handful...It'd be good to get another opinion.

[Havasuhunter]

+1 on STOMPs reply ^^^^^^^^

 

It is not physically possible for a 170 grain 30 cal bullet to reach the .6G1 mark let alone .65. The BC evaluation process used has a flaw somewhere. It can be hard to find which component is flawed or which combination of items.

 

The 177 GS bullet proves this. 177 mono metal shaped like a 208 AMAX and is advertised at .638G1 by GS bullets. Actual firing tests prove that they're not even close to .6 let alone the .638 they advertise.

 

Something that should always be done when using the double chrony method to evaluate bullets with unkown BCs is to shoot another bullet that has a proven BC side by side so you know if there is a major fubar. I have done this in the past for a side by side comparison. You know if you're shooting a 175 SMK over two chronies and you come up with .580G1, you know you screwed up somewhere because you know that the 175 SMK does not have a BC anywhere near .580. It gives you a reference to compare against. You will also know if you're higher or lower than the reference and either way you'll know what percentage higher or lower it is. For example, when the 210 ABLR came out and had a published value of .73, it didn't take a rocket scientist to know that there is no way for a 30 cal 210 grain class bullet to hit the .730 mark. What was the first thing I did when I received some? A little load development and then the double chrony test. I had a 208 load that was within a few FPS of the 210. I shot them side by side. Knowing that the 208 has an accepted average .633G1 BC and a .66+ G1 at 2900'sec I had an accurate reference point to compare against the 210ABLR. After calculating .647G1 for the 208, I knew for a fact that my components were set up properly and that my calculations were correct. At lease very close. Then having shot the 210 over the same two chronies minutes apart from the 208, I knew the calculated value would be very close to reality. It showed me that it was slightly lower than the 208 between 0-200 yards. Out to a grand, it showed that it was slightly higher. I'm assuming that it is because it's BC decays slightly less than the 208 over distance but who knows? At least I know that these two bullets are very close in BC.

 

One red flag I see is your statements of barometric pressure. I'm assuming your using your stated pressure values in your equation. If you are and those are corrected for sea level values while you are shooting at > 1300' elevation, that is part of the problem.

 

Like I said before, the ATF will allow you to donate a handful...It'd be good to get another opinion.

So, 308? Wait, what's this post about?

[308Nut]

 

+1 on STOMPs reply ^^^^^^^^

 

It is not physically possible for a 170 grain 30 cal bullet to reach the .6G1 mark let alone .65. The BC evaluation process used has a flaw somewhere. It can be hard to find which component is flawed or which combination of items.

 

The 177 GS bullet proves this. 177 mono metal shaped like a 208 AMAX and is advertised at .638G1 by GS bullets. Actual firing tests prove that they're not even close to .6 let alone the .638 they advertise.

 

Something that should always be done when using the double chrony method to evaluate bullets with unkown BCs is to shoot another bullet that has a proven BC side by side so you know if there is a major fubar. I have done this in the past for a side by side comparison. You know if you're shooting a 175 SMK over two chronies and you come up with .580G1, you know you screwed up somewhere because you know that the 175 SMK does not have a BC anywhere near .580. It gives you a reference to compare against. You will also know if you're higher or lower than the reference and either way you'll know what percentage higher or lower it is. For example, when the 210 ABLR came out and had a published value of .73, it didn't take a rocket scientist to know that there is no way for a 30 cal 210 grain class bullet to hit the .730 mark. What was the first thing I did when I received some? A little load development and then the double chrony test. I had a 208 load that was within a few FPS of the 210. I shot them side by side. Knowing that the 208 has an accepted average .633G1 BC and a .66+ G1 at 2900'sec I had an accurate reference point to compare against the 210ABLR. After calculating .647G1 for the 208, I knew for a fact that my components were set up properly and that my calculations were correct. At lease very close. Then having shot the 210 over the same two chronies minutes apart from the 208, I knew the calculated value would be very close to reality. It showed me that it was slightly lower than the 208 between 0-200 yards. Out to a grand, it showed that it was slightly higher. I'm assuming that it is because it's BC decays slightly less than the 208 over distance but who knows? At least I know that these two bullets are very close in BC.

 

One red flag I see is your statements of barometric pressure. I'm assuming your using your stated pressure values in your equation. If you are and those are corrected for sea level values while you are shooting at > 1300' elevation, that is part of the problem.

 

Like I said before, the ATF will allow you to donate a handful...It'd be good to get another opinion.

So, 308? Wait, what's this post about?

It's about bullet BCs having limitations. If a 30 caliber 170 grain bullet could hit or exceed the .600G1 mark, the 7mm would be obsolete all together. But the 7mm isn't obsolete and for good reason. Neither are obsolete. They just shine in areas the other doesn't. Having 170 class grain bullets in .6+G1 BCs is one of the 7mm shining qualities. 170 class grain bullets is not the 30 cals strong suit regardless of shape, material or any other factors.

[nralifer]

+1 on STOMPs reply ^^^^^^^^

 

It is not physically possible for a 170 grain 30 cal bullet to reach the .6G1 mark let alone .65. The BC evaluation process used has a flaw somewhere. It can be hard to find which component is flawed or which combination of items.

 

The 177 GS bullet proves this. 177 mono metal shaped like a 208 AMAX and is advertised at .638G1 by GS bullets. Actual firing tests prove that they're not even close to .6 let alone the .638 they advertise.

 

Something that should always be done when using the double chrony method to evaluate bullets with unkown BCs is to shoot another bullet that has a proven BC side by side so you know if there is a major fubar. I have done this in the past for a side by side comparison. You know if you're shooting a 175 SMK over two chronies and you come up with .580G1, you know you screwed up somewhere because you know that the 175 SMK does not have a BC anywhere near .580. It gives you a reference to compare against. You will also know if you're higher or lower than the reference and either way you'll know what percentage higher or lower it is. For example, when the 210 ABLR came out and had a published value of .73, it didn't take a rocket scientist to know that there is no way for a 30 cal 210 grain class bullet to hit the .730 mark. What was the first thing I did when I received some? A little load development and then the double chrony test. I had a 208 load that was within a few FPS of the 210. I shot them side by side. Knowing that the 208 has an accepted average .633G1 BC and a .66+ G1 at 2900'sec I had an accurate reference point to compare against the 210ABLR. After calculating .647G1 for the 208, I knew for a fact that my components were set up properly and that my calculations were correct. At lease very close. Then having shot the 210 over the same two chronies minutes apart from the 208, I knew the calculated value would be very close to reality. It showed me that it was slightly lower than the 208 between 0-200 yards. Out to a grand, it showed that it was slightly higher. I'm assuming that it is because it's BC decays slightly less than the 208 over distance but who knows? At least I know that these two bullets are very close in BC.

 

One red flag I see is your statements of barometric pressure. I'm assuming your using your stated pressure values in your equation. If you are and those are corrected for sea level values while you are shooting at > 1300' elevation, that is part of the problem.

 

Like I said before, the ATF will allow you to donate a handful...It'd be good to get another opinion.

We used the BC calculator on the JBM ballistics site. Notice that under the conditions tested the atmospheric pressure was higher than the standard 29.92. Also, the temperature was 18F. The air under our test conditions was considerably thicker than under standard conditions and creates more drag on the bullet. If you go to the trajectory calculator on Shooters Calculator site and plug in the muzzle velocity of 3188, use 175 gr for the bullet weight, and use a BC of 0.5 (a little higher than the advertised BC for the 175SMK), at 308 yds ( the distance separating the 2 chronos in our test) the predicted terminal velocity under standard atmospheric conditions is 2604. Our measured terminal velocity for our 170 gr bullet in atmospheric conditions where the air was thicker was 2748. If you plug in the lower temperature and higher barometric pressure at the altitude we did our test and use the SMK BC of 0.5 you find that the SMK bullet terminal velocity goes even lower to 2580. We plan to do more testing not only on the 170 gr bullet but also on a 180 gr and 208 gr 30 cal bullets as well as a 265 gr 338 cal bullet. We are also planning on having independent tests by a professional ballistics lab verify our findings. We are also seeking funding to get a new professional chrono that Oehler is promoting that uses their Model 35 at the muzzle and a series of acoustic microphones that broadcast a wireless signal up to a kilometer. The chrono costs $18,000 and can measure the average velocity of a projectile over any distance up to 1000 yds. Data capture should be a lot more efficient than the setup we are using, and so direct comparisons with conventional bullets will be much easier.

 

As far as posting pictures of the bullets, I will need to see if my partner in this venture has any objection. If not, I will post them.

[308Nut]

Did you actually shoot the 175 SMK to gain a reference for an accurate comparison?

 

Tell us a little more about your set up. IE how you measured 308 yards, how you measured barometric pressure, temperature, humidity and determined the altitude.

 

Did you test the new chronographs together front to back to ensure they're both the same?

 

How did you enter your data into JBMs engine?

 

Thanks for sharing,

 

M

[nralifer]

I've already mentioned that the two chronos were correlating within 8 to 10fps of each other. We made sure that the Oehler 35 and the Superchrono were less than 2 feet apart with the start detector of the Oehler 12 feet from the muzzle. That put the Superchrono about 17 feet from the muzzle. Distances were measured with a Leica laser rangefinder. Temp was measured directly with a thermometer and the barometric pressure and humidity were obtained from a weather app that gets data from the weather station at the local airport 6 miles away. The 300 Wby was used for the bullet velocities. The Oehler was placed at the target, and the window that the bullet had to pass through to get a reading was about 4X4 inches. We were fortunate that we did not hit the Oehler. The bullet drop data was obtained using the 308 Win. The muzzle velocity for that test came from the Superchrono. The bullet drop at a MV of 2725 fps was 13.5 inches at 309 yds. since the Oehler was 1 yard from the target. So the chronos were separated by 308 yds, and the Superchrono itself was 309 yds from the target. The actual muzzle of the 308Win was probably around 312yds from the target. As mentioned the temp was 18, the pressure 30.25 and the humidity 58%. We were shooting south and the wind. which was variable, was coming generally from the northwest. We did not shoot the 175SMK. We believe our results are accurate since the velocity data correlated with the drop data. We are encouraged, and want to get more reliable equipment to capture velocity data more efficiently. I plan to compare the 168 and 175 SMKs to our 170gr copper bullet using bullet drop data since this is a lot easier to get and does not run the risk of blowing up my Oehler 35. I think a more accurate comparison will be between the 168SMK and our bullet since I can get the MVs to be the same and the bullet weights are only 2 grains apart.

[STOMP442]

Why was velocity only measured with the 300 and drop with the 308? Why not both tests for each cartridge to compare results. Also how are you measuring bullet drop? Are you shooting a group and measuring to the center or only one shot? How accurate are these test rifles with the bullets in question? Are these rifles fired from a machine rest or is there a human element to be accounted for as well?