Lapua 167-gr Scenar . . . an anomaly?

[David P. Herne]

Gentlemen,
Today I saw something truly notable while shooting three very similar loads through a new custom .300 WSM. While all three loads incorporated the same amount and type of propellant as well as projectiles of very similar design and weight, one of the three produced an initial velocity averaging roughly 150 fps faster than the other two!

The bullets in question here were: a) Sierra's 168-gr Matchking; b) Nosler's 165-gr Ballistic Tip; and c) Lapua's 167-gr Scenar, while the powder charge consisted of 69.0 grains of VV 560.

Of course, great care was taken to insure that the ojive was right at 20-thousandths off the lands in all three instances. Also, the brass was all new (Norma) and the primers were all Federal Gold Match 215M.

Still, the Sierra Matchking and Nosler Ballistic Tip loads both produced mean initial velocities of approx. 3150 fps, while the Lapua Scenar load was moving out at an astounding 3300 fps!!! To my delight, the Lapua load was also the most accurate of the three.

Now, I realize that B.C. and material consistency/density have a not altogether insignificant impact on such things as initial velocity. But gentlemen, I've never known them to account for such extraordinary variations when all other variables are held constant.

By the way, the barrel of the subject rifle is 28" and the ambient temp. in which the shooting was done was around 95 degrees F.

What dost thou think of such a phenomenon, gentlemen?

Dave

[ 06-13-2003: Message edited by: Houston Boy ]

 

[Brent]

Dave,
I found almost the same thing when comparing the 178gr A-Max, 180gr BT, 180gr Scirocco and 180gr Ballistic Silvertip. All except the A-Max were about the same in MV and PSI, the A-Max was faster, with less pressure... not exactly 150 fps but closer to 100 fps if I remember correctly.

Dads 300 WSM with the 27.5" bbl was pushing them at "ALL" 3275 fps.
With 76gr RL19 he was getting 3356 fps with the 168 SMK, pressure in his rifle was still only at 63,000 psi. The 180's were all running about 67k psi. I think he was getting full on powder with the 168gr if I remember right, not sure if he could even get any more powder in there. RL19 sure works sweet in his barrel.

How long is your barrel?

 

[texas]

Up kinda late arent you Brent

Did you get my e-mail?

HB I should be coming your way saturday will give you a call.

 

[Brent]

I think I shot one back at ya a couple minutes before you posted.

I think it's getting light out again.

I'm the late night type for sure. My wife "was" too, until she got called back to work yesterday morning. The boss called at 9:30am and said she needed to be in Talkeetna at noon! Two hour drive from here.

She's shocked back into work mode now.

 

[David P. Herne]

Brent,
It appears to be well established at this point that Reloader 19 is the very best propellant for the subject cartridge. But I had no idea such remarkably high initial velocities could generated with it in 180-gr VLD projectiles. The cartridge just isn't supposed to be capable of this level of ballistic performance, as is maintained in so many published evaluations thereof, which, incidentally, also tell us that it could never substitute for the .300 Winchester Magnum. With this, however, I firmly disagree. I mean, I've never see safe .300 WM loads drive 180-gr projectiles at over 3200 fps!

As to your question about the length of the barrel on this new rig, it's 28 inches.

Texas, I'm sorry I was working this past weekend. But call any time so we can just chew the fat and talk about hooking up to do some training for LRH of the elusive whitetail deer we have here in Texas.

Regards,
Dave

 

[texas]

Dave I didn't get to make it down waterpump went out on car before I got ready.

 

[Brent]

Dave,

I agree.

I would have had a hard time believing the MV had I not tested them and seen for myself. Dropping down from the 300 Ultra to the 300 WSM is really enticing now. I'm thinking that a longer bbl and opening my sons Win classic compact 308win up to 300 WSM with a brake is well worth the money now!! He's really getting into reloading now, and he's catching the LR bug too.

Wish I could get him to the range more often though, he's been busy with his fire fighting training as a junior all winter, which he really enjoys.

 

[Mysticplayer]

Houston Boy, try measuring the diameter of these bullets. I bet that the Lapuas are slightly smaller then the rest.

I had a 6BR that had a very tight bore. Alot of very accurate bullets wouldn't work at all, but when I found some "smaller" ones, the rifle really shone.

Bore friction has a large impact on pressures and if you reduced the bullet diameter just a smidge, the velocity increase would be possible.

I believe this is what Lazzeroni has done with his coated Barnes X bullets. They are just a little smaller to allow for higher muzzle vel. He can get away with this because as the rifle manufacturer, he can spec any barrel groove/land dimension he wants. If the same bullets were used in production rifles, they could be a dismal failure if the wrong size bore was used.

Jerry