Lapua Subsonic Bullets in 300 BLK???

[Dr.Phil]

Has anyone messed around with the Lapua 200 Grain Rebated Boat Tail Subsonic Bullet in 300 BLK or 300 Whisper®/300 Fireball?

With its rebated boat tail design, would it be more efficient than the 220 SMK in subsonic performance?
From what I understand, the RBT design gives you the best of both worlds. (Flat Base & Boat Tail)
http://www.swage.com/ftp/rbt.pdf
They also have a cannelure for crimping, but I haven't heard any good arguements for crimping in 300 BLK other than to prevent the bullet from being set back in the case while cycling.

Due to the cost ($.44 each), I'm trying to decide whether or not to even play with these.
The 220 SMKs aren't much better as far as price goes (~$.36 each), but they have a proven track record with this cartridge.

[DKDravis]

I have used the Lapua bullet both in Lapua factory .308 and reloaded in my wildcat .30 based on a .30 carbine case.

The factory .308W subsonics were accurate from a suppressed Steyr Scout, groups in the 2" region at 110 yds.

Im my wildcat they never performed nearly as well, perhaps due to the twist rate, even though I saw no keyholing at 110 yards (100 m)

Generally Lapua bullets perform very well... only the heavy Berger VLD's outperform the Scenars in my 6.5 calibre rifles.

(And I have to pay around $1.1 each.....)

[Notar]

If you try them, please share your results. The 300 Blackout should see much larger exposure than the 300/221 fireball, experimenter's will find lots of different and good loads.

At 300 BLK speeds, I would guess not all the bullets high tech features would be used to full extent, but if they shot really well, it would be a keeper.

If the crimp groove was in the right place, I would use it in a AR.

[300Blk]

The best thing about that bullet is that it works in a 1:10 twist barrel most of the time. If you have a 1:8 twist barrel, I am not sure of any advantages.

I will say the shape does not seem optimal for AR magazines as to work in the magazine, it will have to be loaded to about 2.000 inches, which is on the short side. I prefer bullets that end up being a longer OAL.

[DKDravis]

One of the things that seems to be largely ignored in experimenting with subsonic velocities and low drag bullets is the fact that most VLD bullets are constructed to have a very high BC at supersonic velocities.. the ideal shape for low drag in subsonic flight is not the same as in supersonic flight. The Lapua bullet seems to be a very good compromise between shape and bullet length to allow stabilisation in subsonic flight. Given high enough twist rate (1:8) this advantage is probably a lot less.
Most of what we "can-makers" call "subsonic" is actually "Transsonic" that is close to the speed of sound. This means that we should actually look for a bullet shape that is ideal for dealing with a shockwave connected to the projectile (minimum shock shape) This means that "tangent Ogive" nose shapes and tangent/circular (Roundnose) with flat bases are the worst performing shapes in transsonic flight. The best performing shapes are the complex LV-Haack, Von Karman shapes and power-curves. The "rebated boattail" of the lapua projectile is a good tail-shape since it will lock the shockwave to the rear of the projectile over a wide transsonic range.
If you look closely the Lapua bullet has an ogive nose shape, as a compromise of projectile length. It also has distinct, but shallow drive bands, to minimize friction, i presume.

As to the placement of the crimp groove, I personally did not use the very shallow "cannelure" on the bullet, but crimped it in the front "driving band"

[Kublah]

Well... I think I understood half of that..

[DKDravis]

That may just be because it IS actually rocket science

Theodore von Kármán was a hungarian physicist who worked on rocket nose cone design (supersonic and hypersonic aerodynamics)
(He was one of the founders of JPL, Pasadena Jet Propulsion Labs)

Wolfgang Haack worked on the same stuff (WW2), and came up with a mathematical solution to a minimum drag body design that is used on any supersonic vehicle to this day (the Sears-Haack body)

This work applies directly to the design of bullet shapes to get high BC values. And to balance lenght and bullet weight with the drag on the bullet.

The highest BC bullets available today are auto-lathe turned bullets from a german gentleman called Lutz Möller ... He makes .375 bullets for the 375Cheytac with a G1 BC of around 1.2 to 1.4 These bullets use the Haack minimum drag shape.

Care for more Rocket Science??

[300Blk]

Someone can test the BC from 300 BLK. I am having that done with the Sierra 220.

[Dr.Phil]

It would be sweet if Lutz designed a subsonic bullet for the 300 BLK...
Hell, I bet he already has one for 7.62x39 in his military only line.

I can only imagine the expense though.
It would probably make the Lapua look like a bargain...

[DKDravis]

@"Silencertalk" That's the way to go, real world data beats all the theoretical mumbo-jumbo

@"Dr.Phil" Lutz Möller already has a pretty good "frangible" copper bullet for .308 caliber, but it is not a low drag design. His VLD designs are brass solids and are VERY long and optimized for supersonic use.. they require steep twist rates..

I'm working on several Low drag bullet designs that will be produced in my own country.. unfortunately the law here says "you can't export that sort of stuff"
prices in volume production are low enough to make it a viable option, even auto-lathe turned (CNC)