• Watch Out for Scammers!

    We've now added a color code for all accounts. Orange accounts are new members, Blue are full members, and Green are Supporters. If you get a message about a sale from an orange account, make sure you pay attention before sending any money!

Flatline Transition

Dan Warner

Private
Full Member
Minuteman
Feb 11, 2017
205
195
Since the introduction of the Flatline bullets, we have always stood by the fact that they were never designed with transitional flight in mind. Achieving a marked 20% increase in supersonic flight performance and the extension of that flight has always and continues to be the primary intention with these. That said, we were never really concerned about what happens beyond the transition point. But the more folks push the limits and demand the best of both worlds, the more we started to pay it some attention. You all know that we have started adding the option of the Tubb nose ring to our bullets. Part of montra of this adaptation is that it is supposed to add stability into transition. But no one has really tested this option to see what happens at once it does transition... until now.
The test has been setup to run the traditional Flatline side by side with a Tubb ringed Flatline with the intention of finding out how much the ring aided transitional stability. The intention here is to exclude all other variables as possible variances in the test, so the ring was the only variable. Same gun, same load, shot subsequently so atmospherics are the same, etc. I won't bore you with the semantics of the test specifics (unless you want to hear them), but the gist is that the 256 Flatline is shot out of an extremely fast twist barrel at muzzle velocity just above supersonic. What we have found initially was surprising to say the least. 400 yards beyond the point of transition, both bullets were still stable and showed no signs that they were even beginning to wobble. There is really nothing difinitive to say about the ring addition at this point, but we still do not know if there is an advantage. But we do know for a fact that we have transitional stability with the Flatline on its own.
The next steps will be to push back even further; keep moving back until we find both the breaking point in stability of the un-ringed Flatline and to determine if the ring modification actually provides assistance at that point and beyond.
Again, the take away here is that there is more sub sonic stability in the Flatlines than even we expected. It has long been thought that they simply tumbled out of the sky once they hit transition, but that is simply not the case.
 
What twist did you run? I’ve been thinking about switching to that bullet for my next build. I realize your shooting much slower than my goals

I guess I’m really wondering what the stability factor was for the load you tested?
 
Any difference in the shot to shot variations in the BC with and without the nose ring?

I'm probably not the only one that's interested in the test specifics.
 
The testing is being done with a 5.4 twist, shot at 1660fps. With the rate of decay, this closely mimics the conditions of transition at much shorter distance. The load was proven; less than 1/2 minute variance even at the 1100 yard mark, so I'd have to say that shot to shot BC variation is negligible. The only difference was a slight elevation shift between the ring and un-ringed. This is expected given the slight decrease in measured BC of the ringed bullet.
Jasent- If you want to run these, I'd consider 8 to 9 twist for optimal results.
 
  • Like
Reactions: jasent
I’m thinking about doing up a 6.5 twist and test Jim Boatrights ideas on hyper stability. Running a 9 twist now so I can compare. Thank you
 
I'm going to clarify one thing that Dan said. The 1,660 fps muzzle velocity used in the fast twist was not randomly selected. The velocity produces a known RPM at the muzzle, and that specific RPM was identified by using the known RPM decay rate on similar size, weight, and shape projectiles and matching the decayed RPM for a 256 shot from a standard twist (9.3") barrel at 3,100 fps. Makes sense right? By matching the after decay RPM rate from the standard twist with a muzzle velocity RPM in the fast twist, we could dramatically shorten the distance that the pills would be shot, also significantly enhancing our ability to see what, if any, stability difference there would be between the 256 Flat Line and the 256 Flat Line w/ Tubb ring. Stated differently its easier to see what is going on at the target site from 1,100 yards away than it is at 2,200+ yards. More testing is planed and will be done to verify our initial stability results and to push back even further and see what our results will be with an even slower muzzle velocity (lower RPMs).

Given our findings so far, I think is safe to say that faster is better when it comes to turning solids - Berger acknowledged this a few years ago when they identified optimum twist which were considerably faster than previously published minimum twist for their jacketed pills.

All said an ddone my next .338 barrel will likely be 1:8.5 certainly no slower than a 9.0.
 
Last edited:
If these bullets end up performing well in the subsonic region, I would be interested in them again. Thanks for the update!
 
Frank-
Not as of yet, but we'll compile some sort of 'official' report to release once we've seen results of further distance comparison. It will include all to the pertinent, associated data of the test conditions along with the results. Aside from hits on target, what would you like to see as far as imagery goes?
 
  • Like
Reactions: Bravo6niner
Definitely interested in all this myself, keep us updated

I'm planning on getting a .338 NM barrel soon so I am anxiously awaiting any results
 
Funny. We had posted results on our web page years ago, but that post didn't come along with the website update. Obviously results were not posted here.
Now that solids have been out for some years, most are aware of the general rule that they do transition but lose energy rather quickly once they do. But if driven at speeds to utilize the high bc, the transition point is much further out in distance to that of the jacketed lead projectile.
The additional of the Tubb nose ring extends and improves transition but it does so at the expense of about 25 points of bc; a rather equal trade.