85.5gr Hybrid in 1-8T
- Thread starter Quickoz
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Ned Ludd
Silver $$ Contributor
A predicted Sg of 1.29 is not so low that I would expect any gyroscopic stability issues whatsoever. However, you're getting close to where the BC you'd be giving up almost puts the 85.5 back down in the range of pointed 80.5 Fullbore bullets, or other similar ~80 gr offerings. If that isn't an issue for you, I think you'll find the 85.5s shoot acceptably well in an 8-twist at the velocities you are likely running.
What cartridge, speed and altitude?
Im going to be looking for around 3200 to 3250. I get 3280 to 3300 with 80gr VLD and they shoot very well indeed. The 85.5gr is a experiment. What are you calling acceptable accuracy?
Ned Ludd
Silver $$ Contributor
In my hands, until the estimated Sg gets down to around 1.1 (or below), you don't typically see slightly oblong holes in the target (keyholing) or any other obvious signs of gyroscopic instability. So by acceptable accuracy/precision, I mean comparable accuracy/precision to what you would observe with the same bullet out of a slightly more optimal barrel twist rate, whatever that may be. Having a sufficient twist rate for a given bullet is no guarantee that it will shoot with good accuracy/precision. At some point, you can only test them and see what you get out of your specific setup. Nonetheless, a predicted Sg of 1.29 simply hasn't been low enough in my experience to cause accuracy problems. I've loaded several different bullets with predicted Sgs in the 1.25 to 1.35 range and they performed just fine. Although it may mean giving up a noticeable amount of effective BC, a slightly slow twist rate typically doesn't necessarily indicate horrendous accuracy/precision issues.
I've loaded both the 85 RDFs and 88 ELDMs referred to in the earlier post out of 7-twist barrels. The 85 RDFs shot "ok", meaning occasional fliers were the norm. I suspect that is an issue intrinsic to the design/production of the bullet, rather than an instability issue. The 88 ELDMs have a much longer bearing surface and OAL than do the 85.5 Hybrids, typical of Hornady bullets. Running those out of an 8-twist barrel would not be a good idea, even at a velocity of 3200 fps. It's simply not a sufficiently fast twist rate for that bullet, and I'm not surprised they didn't fare well. According to Berger's Twist Rate calculator, the 88 ELDM would have an Sg of approximately 1.06 at 2850 fps, and only 1.10 at 3200 fps (59 degrees F, 0 ft elevation). Those values fall into the range I mentioned above where gyroscopic stability starts to become noticeable on the target. I think you'll be ok with the 85.5s, but you'll only know for sure how well they work when you load and test them. If it's a big concern, you might try to get a few to test first if you know a fellow shooter using them, or start with a single box until you are certain they are performing acceptably in your setup.
Ned,
Thata my plan. I only have 1 box for now. Unfortunately theres only myself and one other mate who have similar setups so I'm the test case this time.
I wont be trying the Hornady ELDMs, have seen too many jackets blow up in them with fast twist rifles so I dont touch them.
The BC drops to about a G7 of .252 with the 85.5gr which is still an improvement on the 80gr VLD. Hopefully get some testing down inside the next week before I go back to work.
Thata my plan. I only have 1 box for now. Unfortunately theres only myself and one other mate who have similar setups so I'm the test case this time.
I wont be trying the Hornady ELDMs, have seen too many jackets blow up in them with fast twist rifles so I dont touch them.
The BC drops to about a G7 of .252 with the 85.5gr which is still an improvement on the 80gr VLD. Hopefully get some testing down inside the next week before I go back to work.
I made it to 3300fps in a 22BR: https://forum.accurateshooter.com/threads/my-new-22br.3981971/page-3#post-37729524
That was leaning on it, but they go about the same speed as the 80s and have a similar bearing surface. They are much faster than the 90gn class. I think you'll have the boiler room and then some with a 22-250AI to go as fast or faster than your goal.
Got a box yesterday going to try 39.5 grains of superformance in my 22” 8t 22x47 lapua. 3200 would be nice and would out run the 80hpbt sierras.
I made 3200 with superformance with the 80grain pretty easy and accuracy is good.
but got 3300 with Rl 15.
hope tomorrow is clear enough to shoot!
I made 3200 with superformance with the 80grain pretty easy and accuracy is good.
but got 3300 with Rl 15.
hope tomorrow is clear enough to shoot!
Konrad.INc
Silver $$ Contributor
They’ll shoot clean at 600 out of a service rifle. The range is about 250-300ft MSL. Not my best looking string but a clean is a clean. This is an old 1-8 twist 223 Wylde barrel, 24gr Varget loaded at 1.923” base to ogive.
I've shot them from 1:7 WOA service rifle with fair enough accuracy to work with. Not so much with 1:8 223 Rem AR w/24"bbl; 1:8 223 Rem Target bolt rifle which is to say "very poor." Absolutely horrible in 1:7 24" bbl 224 Federal. 739 ft altitude in Central Texas. Going to try them from a 6.5 twist next...
Post your results. I'm looking for that info also. 22-250 AI in 30" 8 twist barrel. Getting 3550 with 80Amax bullets. Awesome accuracy. I have 200 - 85.5 Berger's. The 80.5 full bores shoot excellent also.
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