.308 High Velocity at 500 yards.

[waco]

All I can really tell you is it was not too long after sun up. We were shooting pretty much to the West, and it was cold. Just at or below freezing.

[oldblinddog]

All I can really tell you is it was not too long after sun up. We were shooting pretty much to the West, and it was cold. Just at or below freezing.

Early morning with cool temperatures and (relatively) high humidity will do it everytime.

[Larry Gibson]

I think there was a bit more going on there. Looks like smoke to me. We have another video shooting at the same target, same place, same time of day with very similar weather conditions. We were using jacketed bullets in the 6.5cm.
Check it out and see the difference.
https://www.youtube.com/watch?v=uEzMdXuC4O4

What was observed with the 6.5 was the "bullet trace", very well known among high power shooters. It's simply the disturbance in the air behind the bullet.........similar to the "wake" behind a boat in the water. When you see pictures of long range HP coaches behind the shooter with those large spotting scopes they are not looking at bullet holes in the target. They are watching the trace of the bullet to see how the wind is affecting the bullet and where the bullet goes into the target. The observed trace will end a short distance before the target and just a little above point of impact.

In the first video I suspect what is seen also in that trace is lube vapor condensing. The bullet is very hot when it comes out of the barrel and the bullet and lube are further heated by air friction, especially the fast the velocity is. The lube melts, vaporizes and then condenses in the cold air (it seemed like a fairly cold day in that video?) and is observed in the trace. I used to see the same thing all the time shooting in cooler weather in NE Oregon with cast bullets. Exact same load in warmer weather would not show any "smoke vapor" in the trace.

[Larry Gibson]

500 yards is a long way off. The longest range I have access to is 300 yards and that is about as far as I feel I can make an ethical shot........!

I'm watching the weather forecasts for the next low wind day and will be back out at daybreak. I have the last 75 XCBs of that last weight sortment loaded in 30x60 XCB cases. They are 2900 fps out of my 30x60 XCB rifle with the 16" twist barrel. I'm going to shoot that rifle "DAWN" at 600 yards.......should prove interesting.

Attachment 215397

Left to right; my 308 CBC, .308W, 30 XCB (30x57), 30x60 XCB and the 30-06 all with the 30 XCB bullet.

Attachment 215398

[tomme boy]

You can slow the speed of playback down to .25 and you can clearly see the smoke or vapor. You can also see that on some of the shots the bullet is clearly unstable.

[Larry Gibson]

tomme boy

The bullets are still stable. What you're seeing (pretty neat isn't it...)..is actual evidence of bullets in flight that exceed the RPM Threshold and go off on a tangent to the flight path. Notice, once Waco had the elevation correct, the 3 shots that hit steel flew straight on their trajectory. The misses all took off on a tangent beginning very early in the flight path as the bullet was ascending to apogee. It is especially noticeable with that last shot which started out on the same flight path but then really went high and away. That is exactly what I describe as occurring when a load is borderline exceeding the RPM Threshold. The 3 shots that hit did not exceed the RPM threshold and the others did, which is why they missed the steel.

Waco may want to re-chronograph that load and perhaps drop it back to 2200 fps. He was getting was getting 2260 fps with a faster burning powder than I used in a 5.4" shorter barrel with a softer alloyed XCB bullet. I know the 2267 fps load I tested is right under the RPM threshold for the powder and alloy I am using. Obviously he is pushing the bullet harder to obtain the same velocity. Some of the bullets he shoots with that load exceed the RPM threshold. That would also explain the apparent 2 separate groups he got on the 100 yard target in the video.

I don't know how many times I was asked, if not demanded of, to get a camera and film cast bullets in flight exceeding the RPM Threshold. Well, here it is.

tomme boy, thanks for pointing out the obvious with a reduction in video speed.

[waco]

Larry. I think it's a velocity thing. We saw the same results only worse when I was testing the Saeco 315 copy and the 312299. They were only doing 2180 and 2040 respectively. These loads were going sub sonic long before they reached the target causing them to start to yaw and become unstable.

The XCB was doing 2260. This is BARELY staying super sonic out to 500. These were showing better, yet not stellar results. I really think another 100-150fps would greatly improve the hit ratio.

I have about the cheapest tool to measure speed. A Chrony. This was set up 6 yards in front of the muzzle. Next time out with the same load I'll use my brothers new Magnetospeed chronograph.

Before this test the loads I was shooting were only doing 1600 fps. These looked like they were shot from a sling shot! They were going sub sonic just past 200 yards or so. That transition between super and sub sonic does very strange things to bullets.

I'll try for 2350-2400fps if accuracy holds. I believe these will prove to be more consistent.
Walter

[tomme boy]

To me what I see is the rotation of the bullet. Then there is another rotation that is larger that the bullet path is following. Don't know if I am explaining it right??

Pretty cool seeing the lube burning/vaporizing off the bullet as it goes down range then stops. Wonder if the lube that does not fly off may create some of the imbalance or whatever it is called?

I have shot to 500yards with my 308 with the Lee 155gr and never seen the smoke. Pretty funny as the drop at 1000 for 168amax was almost the same as the lee at. 500. Hit the 12" plate almost every shot. We had very gusty winds that day and was the reason for 5he misses.

[waco]

To me what I see is the rotation of the bullet. Then there is another rotation that is larger that the bullet path is following. Don't know if I am explaining it right??

Pretty cool seeing the lube burning/vaporizing off the bullet as it goes down range then stops. Wonder if the lube that does not fly off may create some of the imbalance or whatever it is called?

I have shot to 500yards with my 308 with the Lee 155gr and never seen the smoke. Pretty funny as the drop at 1000 for 168amax was almost the same as the lee at. 500. Hit the 12" plate almost every shot. We had very gusty winds that day and was the reason for 5he misses.

Tomme. How fast were you pushing that Lee 155gr?
Waco

[geargnasher]

Remember the MagnetoSpeed will affect barrel harmonics to some degree, try your groups with and without.

Gear

P.S. I have the sane question for Tomme.

[waco]

Remember the MagnetoSpeed will affect barrel harmonics to some degree, try your groups with and without.

Gear

P.S. I have the sane question for Tomme.

Gear. Yeah. We saw that on my brothers 6.5CM. It printed about 4 inches high at 100. Groups looked identical minus the height difference....

[Larry Gibson]

so why didn't yours do it again.
I must have missed it.

The velocity for Waco's and my 30 XCBs were essentially the same out of the 10" twist barrels; 2260 fps for his and 2267 fps for mine. The devil is in the details as to the bullets and how they got there;

Waco's bullets were softer than mine.
My 30 XCBs were WQ'd #2 alloy at 21 - 23 BHN.
My 30 XCB s were weight sorted differently than Waco's with mine at the top end of the "plateau" instead of the usual bell curve.
The barrel on my rifle is 2" longer, might not seem like a lot but it is.
Waco used IMR4831 which is a faster burning powder than the RL22 I used thus I used a slower time pressure curve to reach the same velocity.

Using a measured BC for the 30 XCB bullet obtained from the time of flight actually measured across 100 yards and inputting the data into the Applied Ballistics program (obtained with Bryan Litz's very fine book on long range ballistics) the remaining velocity at 500 yards is 1065 fps.....just beginning going subsonic.

Waco's load with his components were borderline at the RPM threshold. That was evident because 4 of the 9 shot traces followed the flight path and went into probably 14 - 16" (based on the 12" size of the steel). The other 5 shot were obviously above the RPM threshold because they left the flight path in a tangent prior to the bullet reaching the apogee of the trajectory. Those bullets continued to fly point forward so stability was not the issue. Thus we see 4 shot were slightly under the RPPM Threshold and 5 shots were over. That was very evident watching the bullet traces and from the 4 - 5 + moa group for the 9 shots.

All 10 shots of mine appeared to stay under the RPM Threshold for the components I use which is why I put 10 shots into 11 1/4" at 500 yards. However, my load also may have been borderline with the 2 wide shots that just creased the edge of the frame having been very slightly above the RPM threshold. The 8 shots on target were basically what the linear dispersion should have been had the load been under the RPM Threshold as was the case with the 14" twist load which was 335 fps faster yet of a considerably less RPM. That's why I think my load in the 10" twist barrel at 2267 fps (163,224 RPM) was borderline at the RPM Threshold for that load. Not quite as much as Waco's but still borderline. It was the subtle differences in the alloy/bullet hardness, barrel length and time pressure curve (powder burning rate used) that made that subtle difference.

[Larry Gibson]

Waco

"Larry. I think it's a velocity thing. We saw the same results only worse when I was testing the Saeco 315 copy and the 312299. They were only doing 2180 and 2040 respectively. These loads were going sub sonic long before they reached the target causing them to start to yaw and become unstable."

Go back and look at the bullet traces in your video of those 9 shots once you got on target with the speed reduced to .25. Five of those shots veered off on a tangent away from the flight path before the bullet reached the apogee of the trajectory. That means they were off on that tangent well before the velocity dropped below 1500 fps, well before going sub sonic. I think increasing the velocity will only exasperate the accuracy. Go ahead and try it but the proof your load is borderline at/above the RPM Threshold is right there in your video. It is not a "stability thing" as your bullets remained stable through out their flight.

We understand you have test fired the 20 rounds you loaded in the second video....how did those shoot?

[Larry Gibson]

BTW, geargnasher is correct. The use of the MagnetoSpeed will not only affect the barrel harmonics but I've found it most often affects the point of impact (zero) to some degree.

[waco]

Larry. No. I have not shot the next 20 rounds yet. I'm not sure where you came up with this info? I will post results when I do though.
I have 20 rounds of the exact same load in the 500 yard video to retest, and some of the same bullets from Fiver loaded with RX15 to try and attain more speed.
This weekend's weather looks dismal. Might be another week or so, but I'll post results as soon as I can.
Waco

[Larry Gibson]

Larry. No. I have not shot the next 20 rounds yet. I'm not sure where you came up with this info? I will post results when I do though.
I have 20 rounds of the exact same load in the 500 yard video to retest, and some of the same bullets from Fiver loaded with RX15 to try and attain more speed.
This weekend's weather looks dismal. Might be another week or so, but I'll post results as soon as I can.
Waco

Waco

geargnasher posted this in post #97; "Waco has already videotaped what those 20 rounds, loaded the same way, have done a few days ago."

Perhaps I misunderstood...."have done"......?

Those weather fronts that role through your area often end up down here a day or two later.....it isn't looking good for a wind friendly day here for a week either......

[waco]

Larry. Not really sure what Ian meant when he said that. I just loaded these rounds up on Feb.24th
The only time I have shot Fivers bullets were on film. I do have the remaining ones loaded and ready to go.
I will post the VIDEO results when I get a chance to go shoot them. The good, bad, and the ugly.
Waco

[waco]

Larry. You really should get a video camera. In this day and age they are SO cheap. The Sony I got zooms in to 500 like you saw in the video.
This would remove all doubt on your testing. Nobody can call me out on what I have done because it's right in front of you in real time.

I have been accused before of false results from pics I have posted. Some people think run of the mill products won't reach out to a mile. They are wrong.

This summer will produce some great videos of extended long range shooting. Jacketed of coarse.

Please don't use MY video to try and prove YOUR results here. You NEED to prove this for yourself. Film it in real time. Nobody can call you out then. Good, bad, or indifferent, your results will speak for themselves.

I look forward to seeing your future results with the .308 at high velocity with a 10" twist.

Thank you very much for your input and contribution to all who are following this thread.
Walter

[runfiverun]

okay, okay.
so your saying he needs to go faster.

I really think his 2 group results at 100 are from barrel harmonics.
some of the 500yd shooting results is from those same harmonics.

if he sighted in on a low shot and hit the target with only low shots that would explain the couple straight over the top.
the one that fell out was flat out a flier, ignition, neck tension, or a flaw [maybe the thin check come off?]
I really think his results are encouraging.
I would have to find something like a 30-40 moa scope rail to get my 308 out that far.
those are not all that common, and just about any of the older scopes would run out of clicks long before they could screw that much drop in.
I'm pretty surprised yours had that many clicks.

[waco]

Pretty sure Larry said I need to go slower.