I did utilize the BRL studies of the separate drag effects of various circular-arc headshape parameters, meplat size, boat-tail angle and length, and driving band size in designing my monolithic copper ULD bullet shape. However, any projectile design must be a compromise. My ULD rifle bullet design ended up being quite similar to a scaled-down version of the US Army M549 155 mm projectile which BRL designed from the same drag studies data. It has a 30,000 meter maximum range.
I selected a 3.2-caliber length secant-ogive headshape with RT/R=0.500, a 0.100-caliber Meplat, a 0.9-caliber wide, groove (+) diameter rear driving band, a 0.7-caliber boat-tail (length) with a 7.5-degree half-cone angle, and having a convex base with a 0.93-caliber radius of curvature. The small-diameter base-drilling has no aerodynamic effects, but does act to shift the CG forward, nearer to the aerodynamic CP, which minimizes overturning moments. The convex base helps prevent yaw destabilization while transiting the muzzle-blast zone by stabilizing the location of the aerodynamic stagnation point in reversed flight. The 4.5-degree surface break angle at the junction of the ogive and shank is machined sharp (not radiused) in order to force the tripping of the boundary layer flow-field from laminar flow into turbulent flow at that location. The rear corner of the boat-tail is similarly machined sharp to minimize alternating vortex shedding into the wake and, thereby, reducing base-drag in all forward flight phases and minimizing limit-cycle yawing in transonic flight. All other profile vertices are well radiused for aerodynamic smoothness and minimizing secondary shocking in supersonic flight. For best rifle accuracy, the dual-diameter bullet provides positive centering in the bore at two widely separated points to prevent in-bore yaw during rifling engravement. This design obviates the need for any hybrid ogive.
The ULD bullet design should demonstrate 74-percent of the aerodynamic drag of the G7 (VLD) reference projectile in hyper-stable flight; 12-percent improvement due to hyper-stable flight itself, and 14-percent aerodynamic design improvement. McDRAG agrees with the aerodynamic improvement, but does not know about hyper-stable flight. Having no access to a CFD design aid, I did not seriously consider using a rebated boat-tail. David Tubb has received 200 of my latest 245.3-gr 338-caliber copper bullets for test and evaluation. I anxiously await his BC measurement over 1,000 yards and his comments.
I edited-in a new estimator for initial gyroscopic stability (Sg) based on Herr Dr. Kneubuehl's cone-on-cylinder bullet model and adjusted for agreement with McCoy's McGYRO estimates for my monolithic copper ULD rifle bullets. It appears on page 12 of the attached updated CWAJ calculation paper. It does work better than Don Miller's VLD algorithm for modern monolithic copper bullets.
I would be happy to put any Hide members in touch with Mic McPherson if you would PM me. I am reluctant to publish his contact information without his permission. I believe he is ready to make his LAW muzzle brakes commercially after recovering from double knee replacement surgery. The prototypes certainly work well.
