nralifer

Here is a photo of some of the 30 cal bullets we have made and are now testing. From left to right, the first is the 170 grain we have recently measured a BC on. The next is a 180 grain. The third is a 220 grain SMK for comparison. The fourth is a 208 grain. With the exception of the SMK of course, all the bullets were machined from copper bar stock on a Swiss lathe. Notice the grooved that reduce the bearing surface relative to the 220 SMK. Barnes swages their copper bullets and then cuts their groves in each bullet as a separate operation to reduce their bearing surface. The groves also reduce copper fouling in the barrel because the copper displaced by the rifling deposits in the recess of each groove. Also notice the ogive shape. It is slightly different from the tangent ogive on the SMK, and theoretically more efficient at Mach 2.5 and below than either the secant or tangent. The bullets also seem to be as tolerant of seating depth as tangent ogive bullets.

All things being equal the longer bullet will have a slightly lower BC because of frictional losses along the shank due to the extra length. However the copper bullet could actually be designed to have a significantly lower "bearing" surface contacting the rifling and be launched at a higher velocity because of lower frictional losses in the barrel. The largest effect on BC is actually the ogive profile and ogive length as well as meplat diameter. Copper actually is a better material for bullet design than lead. Lighter high BC bullets can be machined and launched at higher velocities. Machining can create profiles that are difficult if not impossible to swage into lead core jacketed bullets. That is the reason why the bullets on the market have basically only 2 types of ogive, tangent and secant. Berger has a hybrid where a portion of the ogive is secant and the part closer to the shank is tangent to reduce the criticality of the bullet seating depth in influencing group size, but they all have large bearing surfaces.

We ran out of light conditions that would allow the Oehler to work. The drop test was measured from group center. The rifles will shoot these bullets at sub minute of angle without a machine rest. By the way STOMP, did you ever try Superformance in the 7mag? Lancetkenyon, I apologize for not answering your question fully. The length of the 170 bullet is 1.435 inches. It is well stabilized by a 1:10 twist barrel. Stability factor under the conditions tested was >1.4 as fired from the 308 Win. The 220 SMK measures 1.505 by comparison.

It would be interesting to try Superformance powder. You potentially could get to 7 mag velocities. It has the same burn rate as H4831. Would look up the data in the Hodgdon Annual Manual and start out with the low charge weights specified for H4831 and increase by 1/2 grain increments from there. Watch carefully for pressure signs. Superformance works very well for me in the 270Win.

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.

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.

Elevation here is 1309 ft

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.

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.

Have you looked into the 129 grain LRX from Barnes? I've been having really good success with it in my 270WSM. I have not, but it looks interesting. The stated BC is good.

Got the chronographs, and started playing with them. Takes some practice, but for those of you interested in looking at the Superchrono acoustic chronograph, they are interesting little instruments. Be sure to follow the directions to the T and use them on flat ground. At the muzzle, be sure to put it at least 10-12 feet away to avoid recording the muzzle blast. Anyway, was able to get BC data for a 30cal 180gr bullet that we made from copper bar stock on a Swiss lathe. Conditions were 13 F, 30.16 BAR, and 100% humidity. I used a 300WSM, with 71.1gr Superformance with a muzzle velocity of 3120 fps. The range was 185 yds. The calculated G1 BC from the drop in velocity was 0.62. I was using my hunting rifle with a 1:11 twist 26 in Lilja barrel. Stability factor was 1.12 which is on the ragged edge of stability under the conditions tested, but nevertheless got round holes on the target and the 4 shot group size was 1.3 in. The drop at that distance corresponded with the velocity change. Both indicated a G1 BC of 0.62. For a first try these data are encouraging. I have now a 300WSM barrel with a 1:9 twist mounted on a Savage 110 action that should improve the stability factor to over 1.4 under those conditions. Weather is cold now in South Dakota but with better stability the BC may increase some.

Havasuhunter, did you try Superformance?

When talking about the the 7mm and 308 bores, one thing to remember, like cubic inches in engines, the bore cross sectional area determines the bullet energy potential, because the amount of accelerating force exerted on the bullet varies as the square of the radius. Thus a 308 bore has grater power potential than a 7mm, which is greater than a 6.5 which is greater than a 6mm. A good illustration of this concept is to compare the 7mm08, 308 Win and 338 Federal. All use the same parent case and almost equivalent powder charges, but a lot more muzzle energy is obtained by the 338 cal bullet (2500 ft-lbs for the 7mm08 vs 3220 ft-lbs approximately for the 338 Fed).

We have on order 2 acoustic chronographs that have larger detection areas. They seem to be well suited for determining velocity drops over long distances. If we can maintain minute of angle groups we should be able to get data on virtually every shot by placing the chronograph under and slightly in front of the target. Also the chronograph can be protected from a bullet impact since the detection area is above the chronograph, by placing it behind a sand bag. Measuring velocity drops over 300-400 yd should be readily doable.

We have made a 180 gr 308 bullet that by drop at 400 yds has a 0.65BC. The 170 has a similar profile.

It is a 308 bullet.

Would be interesting to get the specifics on your buddies load. Components can make a huge difference in performance. I have been testing CFE 223 and Leverevolution (LVR) in the 308Win although there are no published data using the latter in the 308. Both powders have similar burn rates. The gun has a 20 in. lapped Douglas Match barrel and a Savage short action. Best result so far is seen with 48.5gr of LVR using a 170 gr bullet. Muzzle velocity was a little over 3000 fps using a Magnetospeed chrono. A three shot group was 0.501 in. Ambient temp was 38F. This performance pretty well matches what is published in the Hodgdon 2012 reloading manual for the 7Mag and 7WSM. Had some pressure signs, with extraction being a little sticky. I think, though that 2900 fps is readily doable in this rifle. If anyone wants to try the LVR in their 308 or 7mm08, would start with 44gr and work up in 0.5gr intervals. Use a chronograph you have confidence in and be mindful of the ambient temperature. I do not know how temperature stable LVR is. I had a problem with throat fouling using CFE 223. Not sure why. Will need to need to look into this further. One note. Whether a 30 cal or 7mm bullet is better is sort of academic. Larger caliber bullets have greater performance potential than smaller caliber bullets. One problem 30 cal rifles have slow twist rates compared to 7mm rifles. Practically all production 30cal rifles have between 1:12 and 1:10 twist barrels, whereas 7mm rifles are 1:9.5 or faster. The twist rate has a big influence on the BC of the bullet design. BC is increased with weight, nose design and length and boat tail length. A faster twist barrel will stabilize longer, higher BC bullets. A friend of mine is designing 30 cal bullets that potentially have BCs exceeding any conventional 7mm bullet. His method of calculating BCs is probably accurate. He had doubts about the advertised BCs of the 190gr LRAB bullet, and calculated its BC at 0.550. Turns out that a measured BC by Bryan Litz for this bullet was 0.567. The bullet I mentioned above was a 170 gr solid copper bullet 1.43 in long that is stable from a 1:10 twist barrel, and machined from 110 copper bar stock. The calculated BC on that bullet is 0.6. Berger makes a 168 gr 7mm bullet with an advertised BC of 0.617. In a few weeks we will have the instruments to actually measure the BC, not only of that bullet but also other commercially available bullets under the same conditions. Looks like with the right components a 308Win can run with a conventionally loaded 7Mag.

There are basically four ways to measure projectile velocity. Using light (Chrony, Oehler), sound (Superchrono), magnetic field disturbances (Magnetospeed) or radar reflection (Mylabradar). The optical chronographs are the most familiar to all of us, and work by detecting a shadow as the projectile crosses 2 or 3 light detectors and measuring the time it to do that, then calculating the velocity. Optical chronographs would work for all bullets, shotguns and even arrows, but are finicky. There are now small radar chronos for arrows that will attach to the bow but are not useful for firearms. One of the newest chronographs (search Superchrono) is useful only for supersonic projectiles, but is extraordinarily versatile. It has two microphones spaced apart and as the bullet traverses that distance the crack of the shockwave the bullet generates as it travels over the microphones triggers a counter that measures the time it took the shockwave to go by both microphones. It will not work with arrows or bullets traveling at subsonic velocities. In December a low power Doppler radar chrono is scheduled to be released (mylabradar) that can measure arrow and bullet speeds over short distances. Probably the best value and greatest versatility is achieved with low priced optical chronographs, but these are finicky in terms of the intensity and quality of light needed to make them work, and are weather dependent. One thing you have to be ready for. Once you start measuring velocities it is hard to stop. It can be frustrating and fun at the same time. Have fun.

I think all of the forum viewers would be very interested if you developed some Superformance loads for the 7RM. It is a very popular cartridge but Hodgdon does not list a Superformance powder load in their 2012 manual. Since Superformance has a burn rate virtually the same as H4831, you could start out a couple of grains below the maximum for H4831 and work up in 0.5gr intervals until you either got pressure signs or reached the max grains listed for H4831. I have used this same approach to develop loads for the 330Dakota and 300WSM. For a 140gr 7mm Nosler Partition bullet, Hodgdon lists 64gr of H4831 as the max load. Unfortunately I do not have a 7RM or I would do it myself.

I guess you are missing the point I'm trying to make, and that is that Superformance powder in the 270 can really make it perform. It would be interesting if you tried it in the 7mag and see how much it improves its performance. It has a greater powder capacity and therefore more potential for higher velocities. We can look forward to improvements in powder technology largely because of the wars we have been fighting and the heavy use of special forces driving small arms development. That means as some of these powders make it to the civilian market, cartridges that were thought to be mediocre will be made to perform to levels that not thought possible. If you like hand loading , it can be exiting.

Barnes bullets admittedly have low BCs, but they nevertheless are excellent bullets. The Cape Buffalo you see me with in the picture was killed with a single shot using a Barnes TSX bullet, and it was not a 375 caliber. The bullet went clean through the Buff and liquified the heart. The BCs are adequate for clean kills out to 500 yds and the trajectories of these bullets over that distance are flat enough given the BC. The 140 TSX 270 bullet launched at 3200 fps with a BC of 0.404, will drop 39 in. at 500 yds. The Berger 140 gr 270 bullet with a BC of 0.487 will drop 36 in. at that distance if launched at the same speed. That is less than a minute of angle difference. Just one's heart beat will cause more variation in the aim point than that. At close range though the Barnes bullet will likely hold together and penetrate better than the thin jacketed Berger. If I was hunting Caribou and came across a 300 pound Black bear at 50 yds, I know which bullet I would rather have. But the long range target shooter would much rather use the Berger. It's all a matter of matching the bullet to the job at hand.

Barnes bullets have just about the worst BC possible especially in their 7mm offerings which are only flat base on top of that. Use any other bullet but Barnes in 168gr or heavier and the 7mm mag will walk all over the 270. heck even a high BC 140 in 7mm will out perform your 140 Barnes at 3200 fps. I have nothing but great things to say about a 270 but to call it the equivalent of a 7mm mag is just wrong. The point I was making was that the .270 Win with the proper barrel and powder and bullet can perform as well as the 7mm Rem Mag. If you use a Barnes 140 gr in a 7mmRM it is not likely that you will be able to propel it much faster than in the rifle I described. The fastest MV for the 7mmRM 140 gr bullet listed in Hodgdon Reloading magazine is 3138 using 63 gr of Hybrid 100V. The 270 can propel a bullet of the same weight at that speed. This indicates that the 270 case is actually more efficient in terms of the muzzle energy/grain of powder produced than the 7mmRM case which uses about 9% more powder. I'm not trying to make the case that the 270Win is better than the 7mmRM, but show that the 270 Win has a lot of untapped potential. Berger, who makes bullets with high BCs, lists a 0.487 BC for their 140 gr 270 and 0.510 for the 7mm 140 gr bullet. If propelled at the listed MVs (3138 for the 7mmRM and 3200 for the .270 Win) The drop at 500 yds is 1 inch greater for the 270 as compared to the 7mmRM.

Thanx for your comments. I would be very interested to see what results you get. I'm pretty sure the chronograph is reading the velocities correctly since I have tried factory ammo and the Superformance reloads in my Winchester with a 22 in barrel, and the factory loads were always substantially slower for the same bullet weight.

The 270 has great untapped potential. I have been using the Superformance powder and shooting Barnes TSX bullets. I got a 26in Benchmark barrel with a 5 grove 1:9 twist. Today explored the limits of velocity with the 140gr TSX. Has a BC of 0.404. Got it to shoot 3200 fps and at 500 yds this bullet still has 1364 ft-lbs of energy. It is still supersonic at 1000 yds. With this powder and the right barrel length the 270Win is virtually the equivalent of the average 7mmRem Mag. One can verify the trajectory using the trajectory calculator on shooterscalculator.com

Had a chance to test 140gr TSX bullets in my 26in Benchmark barrel. Got 0.7 in group and average velocity was 3202fps using 58 gr of Superformance. Also tried 59.5 grs behind 130gr TSX and got an average of 3296. Had some primer flattening but no problems with extraction. These are likely max loads, so approach with caution and work up to them in 1/2 grain increments.