It's only the 168 matchking that has the issue. It was designed as a 300m bullet and doesn't do well past 700m. All the other 168s work fine. If you are married to the 168 class bullets do yourself a favour and try the Berger 168 hybrid.
.308WIN Load development for long range *QUESTION*
- Thread starter Evil_Dark
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What kind of elevation are you using to get to 1000yards at that speed?
I'm assuming that's a typo or his barrel is about 10" long...
Or the typo is in the distance measurement.
Tried a OCW group testing with the 178gr A-Max. I found a node at 40.8gr 41.1gr 41.4gr with the IMR-4895, velocity around 2630fps. Have to fine tune the load, but in this range, this node seems to be forgiving a lot (very similar POI on these three groups, and these groups where pretty tight!).
At this velocity, 1000 Yards seems to be plausible as I'm still above the speed of sound... I have to test the 208gr ELD as soon as the weather is better.
Dark
At this velocity, 1000 Yards seems to be plausible as I'm still above the speed of sound... I have to test the 208gr ELD as soon as the weather is better.
Dark
It's also a question of availability. I've switched to Sierra (with the 168gr BTHP) because large qtys were hard to find with Hornady. I shoot more and more, so box of 100 are quickly spent... And sometimes box of 100 are also out of stock... Upsetting!
Dark
I believe the 168 SMK was unique in its boat tail angle degree.
Seems it was steeper than others at 11 or maybe 13 degrees. That angle caused shifts in the Center of Pressure and caused the bullet to become unstable from about 1340fps to subsonic. They seem to make it thru sometimes and knucle ball at other times and I can't predict when so I don't shoot them anymore past about 700m.
IIRC the other(s)? are around a 7 degree boat tail angle and don't become unstable thru the transition.
Seems it was steeper than others at 11 or maybe 13 degrees. That angle caused shifts in the Center of Pressure and caused the bullet to become unstable from about 1340fps to subsonic. They seem to make it thru sometimes and knucle ball at other times and I can't predict when so I don't shoot them anymore past about 700m.
IIRC the other(s)? are around a 7 degree boat tail angle and don't become unstable thru the transition.
Terry Perkins
CGN frequent flyer
- Location
- Bruce County
I will share my experience with 178 grain Hornadays. Your bullet is in trouble according to Brian Litz, the transonic zone starts below 1340 fps, if you're at sea level your bullet will yaw and pitch badly. If you're at 5000' ASL your bullet is above the transonic limit, you are good to go. I have shot 178 Hornady bullets that went transonic at 1000 yards. Sometimes they missed the 6' board, and came in quiet according to the marker in the butts.
Depending on Density Altitude, it may begin to transition towards subsonic @ around 1340 as TP mentioned as it decelerates. Depending on bullet design, the Center of Pressure moves similar to the CP moving on a plane's wing. It it gets out of relation to Center of Gravity a bullet can get unstable, which is yaw/pitch and then it sounds funny as it knuckle balls to wherever if you are near it as in the scoring bunker.
Over simplified but accurate. Some bullets transition well due to their design, some don't. Velocity and spin play a part also.
bluegrizz77
CGN Regular
- Location
- Fort Mcmurray T9K2K7
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bluegrizz77
CGN Regular
- Location
- Fort Mcmurray T9K2K7
1364 ft was the alt and the 10 shot average was 2801 fps from the chrono. Using your ballistic program will give you your 1000 yrd moa to work with. The alt at the 1000yrd target was 3579 feet, you just have to work the wind. The 1000 yrd speed is getting slow at 1260 fps so past its ideal range.
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I shoot 178 gr Amax (43.0gr Varget, PRVI cases, CCI BR2s, mv: 2540) and they go transonic around 850 yards. Last time I measured, I shot a 10 shot group at 870 yards that was a hair under 1 MOA, I believe. I've also made hits reliably at and past 1000 yards. In my experience, the 178s are pretty stable through the transonic range. Your mileage may vary
I have a difficult time sorting how a certain BC bullet will be stable in one barrel and not in another barrel and the issue being anything to do with the bullet.
I'd wager it's barrel twist, velocity and differences in DA.
I'd wager it's barrel twist, velocity and differences in DA.
We have been exposed to complicated ballistic data, beyond our basic comprehension. Physical properties such as Axial Moment of Inertia, Transverse Moment of Inertia and Centre of Gravity from Bullet Base are some factors determining why Sierra 168 and other bullets tumble in transonic zone. We have seen Dopplar Radar data indicating instability with "triangles" for this particular bullet.
Regards,
Peter
Regards,
Peter
For what it's worth, my data comes from shooting the 178 gr Amax in a 20" barrelled 1/10 twist with a mv around 2540 fps. As far as DA goes, I looked back through my notes and the 10 shot group I mentioned at 870 yards was shot Sept 29th, it was sunny with a temp of 15.7 C and a DA of 807m. In those conditions, the round would have gone into the transonic zone at approximately 815 yards.
I was told by a experienced shooter on this forum that when the bullet travels inside a barrel, the barrel will mark/scratch the bullets (the riflings, the chamber etc...) an then affect the bullet shape / aerodynamics. Not very much, but enough to make a difference from rifle to rifle. I have a 5R barrel, so it must engrave/mark the bullet differently than a standard one...
I tought that it was a good theory, plausible. And it also explain the little difference I had when I compared my results VS a ballistic program results, I had more drop that what was supposed, knowing all the environment variables, and fired through a chronograph. When I played around (lowering) the BC to fit the ballistic program results, I began to match every time my results with the ballistics program, even with different shooting conditions (different wind, temperature, velocity and angle of fire) now the program results where pretty dead-on. That's why I adopted this theory...
Dark
