8.45 mm LM-Class Brass sport bullet in the .343" Lapua Magnum

LM-107

Very high BC Bullet for windy long Ranges

LM-Class LM-107 mm MSG | 59 mm long, 19.3 g Mass, 298 Grains, BC 1,02 for 107 mm long
for .343 Lapua Magnum in 900 mm long Barrel | 180 mm Twist length | Bore 8,72 mm, Groove 8,45 mm

History

You may want to read some the History in Kummersdorf. Then to understand the Concept behind Drive band bullets is easier. In the latter third party Measurements, intiated by Arrowtech Associates for the NDIA, shew, when pushed into the Throat, my Drive band bullets exhibited 38% less engraving Force and, rather important for the Precision shooter, the Force distribution standard deviation was more than a Magnitude smaller. The researched full metal jacketed Lead bullets just couldn`t compare. Well, this also holds for the Price. In Friendship You have to give, when You ongoing want to take.

You will see, such cheap pressed Bullets with not so slender shape and rather rounded Noses, compared to the CNC turned LM-Class very high BC Bullets for windy long Ranges cannot compare in Flight as well. Superior Design and Manufacturing yields superior Quality. Such Quality has to be made, it cannot be inspected into some lousy Junk pile, You might get from inadequate DEsign, Tooling, Machinery and Fabrication. Meanwhile, after some Years Research and Experience, Faults and Fallbacks included,  we use the best up to Date Soft- and Hardware available. I know, what we do and it's good. I know of no better Bullet than the LM-Class available on the Market for windy long Ranges. Early Predecessors, like the copper LM-105, won the Lapua Sniper Cup and still outperform other international Military Matches, where no Publicity is allowed and about I will not talk any further. Bu I know, what goes on, and it's good.

I will take any Long Range Challenge with my Bullets against Competition, provided some public an credible Control exists about the Circumstances under those such Competition shall happen.

Below Pictures will later be updated. In the Moment those are just principal Illustrations, actually LM-119 .  

LM-107 Pressure, contour, click to enlarge

 LM-107 900 m/s Pressure, iso, click to enlarge

 LM-107 900 m/s Velocity, contour, click to enlarge

 LM-107 900 m/s Velocity, iso, click to enlarge

 LM-107 900 m/s dynamic Pressure, click to enlarge

 LM-107 900 m/s Pressure, click to enlarge

Reamer

See the .343" Lapua Magnum Case and Reamer Specification. Bore is 3,45 mm, Grove is 3,72 mm = .343 Inch, hence the Name for this .338" LM Progressor

Overall Length

LM-107 LM-Class Brass sport bullet in the 107 mm long .343" Lapua Magnum Cartridge

Throat

The Throat is a 2° Cone (measured full angle, not just to the Rotation Axis)

Haack Nose

This LM-107 bullet use the 1941 Haack shape to minimize Wave drag nose. 

Adams Tail

Helped by drive band induced Micro turbulences in the middle Surface layer, the Tail uses the 1950 Adams (other Source)shape flow for the cut  Haack body to minimize back drag and reduce Surface friction (by reducing the Surface in a shorter Bullet). Adams tailed Bullets are shorter than a Viking, which helps to economize Mass production with less Rod length to procure. 

Gas exhaust

Unlike older rounder Bottoms (LM-105) or Viking shapes, the Adams tail introduces powerful Macro turbulences on the Muzzle. So the LM-Class very high BC Brass bullets for windy long Ranges need a specific Gas exhaust like the hdp Recoil brake, to control the Gas exhaust flow not to chaotic kick the flat Adams bottom and induce unwanted Yaw, leading to disperse the Hits on the Target.

Threaded hdp-Gas exhaust for LM-Class very high BC Brass bullets for windy long Ranges half mounted

Stability

With s_800m/s = 1,29 the LM-107 will fly stable from 20,6 Cal. long Twist or 180 mm even as low as 800 m/s Muzzle velocity, meaning mild Loads. Faster is better!

 Estimated Drag, BC and Gyroscopic Stability at Standard ICAO Sea Level Conditions
 -----------------------------------------------------------------------------------
  Möller LM-107 Cal. 8.700 mm, 19.3 g
  Ballistic Coefficient Calculated for Drag Function G1
 -----------------------------------------------------------------------------------
      Velocity       Drag Coefficient       RPM and Stability      maximum Twist-
                      Factor of Form        at a Twistlength         lenght
                         and B.C.             of 21,3 Cal.          for s = 1.3
   Mach  m/s   fps    Cw      i    B.C.       RPM        s        Cal.   in.    mm
 -----------------------------------------------------------------------------------
  0,441  150   492  0,073  0,360  1,008      48649      1,03      18,9   6,5   165
  0,514  175   574  0,072  0,360  1,009      56757      1,02      18,8   6,4   164
  0,588  200   656  0,071  0,355  1,020      64865      1,00      18,6   6,4   162
  0,661  225   738  0,071  0,343  1,057      72973      0,97      18,4   6,3   160
  0,735  250   820  0,071  0,317  1,143      81081      0,93      18,0   6,2   157
  0,808  275   902  0,071  0,279  1,302      89189      0,87      17,4   5,9   151
  0,882  300   984  0,075  0,237  1,530      97297      0,75      16,2   5,5   141
  0,955  325  1066  0,113  0,274  1,323     105405      0,52      13,4   4,6   116
  1,000  340  1116  0,229  0,484  0,749     110366      0,57      14,0   4,8   122
  1,102  375  1230  0,205  0,354  1,025     121622      0,64      14,9   5,1   130
  1,175  400  1312  0,248  0,399  0,909     129730      0,73      16,0   5,5   139
  1,763  600  1969  0,215  0,348  1,041     194595      1,14      19,9   6,8   173
  2,351  800  2625  0,181  0,331  1,095     259459      1,29      21,2   7,3   184
  2,939 1000  3281  0,155  0,304  1,192     324324      1,37      21,8   7,5   190
  3,526 1200  3937  0,134  0,271  1,339     389189      1,42      22,2   7,6   194
  4,114 1400  4593  0,119  0,241  1,505     454054      1,46      22,5   7,7   196
  4,702 1600  5249  0,106  0,216  1,678     518919      1,49      22,8   7,8   198
  5,290 1800  5906  0,096  0,196  1,852     583784      1,52      23,0   7,9   200
 -----------------------------------------------------------------------------------

.343" Lapua Magnum

The .343" Lapua Magnum progressed from the .338" Lapua Magnum, that offered slightly too much Powder for the Bore. So I opened up the Barrel from 8,38 mm Land and 8,58 mm Grove Ø to 8,45 and 8,72 mm or .343", hence the. Next the Neck grew from 8,31 to 8,5 mm to support the bigger bullet. The Should angle steepened from 40° to 60°, less than possible, as we know from Ackley, but a Limit in Mass production, we hope to see, or at least do not want to out design right from th Start. Good Cases balance Volume and Extraction with 1° Body Taper. Speed, pressure and precision friendly Throats are  2° Cones, so I changed that too.

The last Parameter set cannot so easily be generalized, as it mostly stems from the Mother Case, here the .338" LM, the Neck dimensions. One Day I will translate the "Halsrechner". Assuming not perfectly round Necks as well up to 0,1 mm undersized ones, I only could opt to ream the sized Necks round, then turn them on a bullet sized Mandril to an outer Diameter accommodate the usual Tolerances and get concentricity. How to save this Work for long? Well add a tight Chamber neck, almost with in the Elasticity limits of the Brass, so it will not much, or even not at all, permanently yield, when fired. This is the Recipe to first stuff the Bullet concentric before the Bore to get Precision (if the Bullet is also coaxially aligned, yaws not) and second gratify long Case life.

Obviously this Design rules (reform, blown out Case, turn Neck) generate quite some up front Work, but reward with both Precision and long Case life, so the Sporter will over the long Run be better of than without those. The Results also warrant the Effort, or let's say ask there for - if Bench rest type precision is wanted also on the long Ranges down to the Horizon.

The from .338" LM to .343"LM changed Cartridge propels the longer Brass LM-107, compared to its Copper Predecessor LM-105 as fast, but with a slightly higher BC (from 0,93 → 1,02) at a possible lower Price. So I call that Progress.

Lutz Moeller, 23^rd February 2008, l.moeller@online.de

Aerodynamic advise

Hello Lutz,

I have some news for you. Professor told me that from the aerodynamics point of view the LM-107 is more promising compared to the LM-105. The Viking is not (has been tried and rejected as no beneficiary to your other designs). The LM-105 nice as a basis for development. He suggested the following for the further development of the LM-107.

The Adams tail should begin from the 6th band the 7^th remains as is

All the bullet must be mirror shinned, except from the parts between the bands. These is beneficial to leave the fine tool marks on it creates a micro turbulence effectively eliminating drag at this section (as he told me this idea is also applied to the SR-71 Blackbird).

At the end of the Adams tail a small truncated cone must be added. The cone is calculated each time with the exact speed but for a speed of 800 - 1.100 m/sec it is advisable that the angle should be about 140-150 deg and height about 1.2 to 1.5mm (see picture).

Cone

The imprint of the rifling on the drive bands should be as smooth as possible so a rifling with no edges must be selected.

Yours, Aristidis, Montag, 29. Dezember 2008 16:01

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