This article appeared in the July/Aug 2005, #176 issue of the Fouling Shot and was written by CBA member, Karl Bosselman.
Occasionally letters arrive to me and magazine articlescontinue to be published revealing similar depressingaccounts of major-level disappointments in cast bulletaccuracy. Virtually none of these individuals mentionhaving slugged their barrel bores. Consequently, they’reusing a “stab-in-the-dark” approach which seldom worksout well. As most readers of this publication realize, ahuge mass of good cast bullet data is available for those who search. After all, cast bullet shooting has beenongoing for centuries, and we do know a great dealabout it.
Accurate cast bullet shooting is based upon threethings: knowledge, using common sense, and beingmethodical.
Occasionally letters arrive to me and magazine articlescontinue to be published revealing similar depressingaccounts of major-level disappointments in cast bulletaccuracy. Virtually none of these individuals mentionhaving slugged their barrel bores. Consequently, they’reusing a “stab-in-the-dark” approach which seldom worksout well. As most readers of this publication realize, ahuge mass of good cast bullet data is available for those who search. After all, cast bullet shooting has beenongoing for centuries, and we do know a great dealabout it.
Accurate cast bullet shooting is based upon threethings: knowledge, using common sense, and beingmethodical.
The primary component in top levels of consistentaccuracy in both cast bullet and jacketed bullet shootingis excellence in barrel quality. In addition, be it either19th Century single-shot and repeating firearms, or 21stCentury precision benchrest/target and autoloaders, slugthat bore, be it either factory-produced or handloadedammunition that’s involved. You must know the exactgroove diameter and you must know the exact riflingtwist rate. This latter most certainly for the Importantdecision(s) of helping to select your useable if not idealbullet weight(s). As most serious shooters and hunters know, as realizedthroughout the centuries,the heavier-weight projectilesalmost alwaysproduce best results forhunting performance(optimum trajectories totopmost and quite consistentterminal ballistics)to competition matchaccuracy especially asconcerns trajectory aswell as remaining powerat extreme range distancework. Another benefit exists in the tendency for the
With straight-grip butt stock and .45-70 chambered 22” round micro-grooved barrel,this is Marlin’s ‘recreation’ of their original Model 1895 that was discontinued in1915. This model has the round breech bolt and no asinine hammer-block ‘safety’which poses a definite danger for dangerous game hunters using such a rifle. Thismodel was produced from 1972 to 1979.
From left to right, (1) .416 (Frank C.) Barnes wildcat -the .45-70 U.S, Govt. case bottlenecked from .457” to.416” caliber. A very nice optional chambering forhunters using cast bullets and/or jacketed handloads.(2) .40-82-260 W.C.F. (circa 1885) - REM-UMC manufacture,This 260-gr. FNSP I consider too light for thecaliber (.406” bullet dia.), a 300 gr. is light enough(3) .40-72-300 W.C.F. (introduced 1895) - W.R.A.Co.manufacture. Optional factory loading was .40-72-330 with a blunt RNSP bullet. This cartridge is aclose relative to the subsequent .405 W.C.F (1904)using a 300 gr. RNSP bullet. HUNTINGTON, ofOroville, GA, lists in their catalog .40-72 W.C.F. barrelgroove diameters running from .403" to .412" SingleShot Rifle Journal staffer, Connor Duncan, states thiscartridge's bores as running from .403" to .408". heavier-weight projectiles almost always produce best results for hunting performance (optimum trajectories to topmost and quite consistent terminal ballistics) to competition match accuracy especially as concerns trajectory as well as remaining power at extreme range distance work. Another benefit exists in the tendency for their longer shanks to be slightly more forgiving of minorbore imperfections, thus (slightly) enhancing levels ofconsistent accuracy over the lighter, stubbier bullets.As has always been the case throughout firearmsmanufacture, tooling constantly wears on an ongoingbasis and thus tolerances vary. Couple this with occasional,but, in present-day times more common, haphazardcraftsmanship and on-purpose barrel quality compromises(usually to reduce production cost) and you havean ideal recipe for disastrous levels of inaccuracy. The old statement (paraphrased), likely first grumbled in print many decades ago by some unqualified and/or biased gun writer, that “Micro-groove rifling will not shoot cast bullets accurately” is as patently ridiculous as the statements, “two-piece-stocked rifles are inaccurate,” and, “the only accurate rifles are turn bolts” (this rifle type this writer considers superbly ugly, an ergonomic monstrosity, and a type which over 95% of their owners cannot ideally stock for proper fit due to length of rearward bolt travel).
Not very long ago I built a unique Mid-Range “Creedmoor type” rifle based upon an early-production Ruger No. 1 action I finely tuned, fitted special stocks of my designs, and installed a top-of-the-line Match Grade chrome-moly Shilen “micro-groove” (8 lands, 8 grooves) barrel chambered in a one-of-a-kind wildcatted somewhat obscure vintage black powder cartridge not known for superb accuracy or high power. Case necks I expanded from .406” to .4l6” caliber which is today’s world standard .40 caliber dimension - .416”x.40-72 W.C.F. With shortened and fire-formed strong, modern cases (9.3x74R, RWS and Norma manufacture), and muzzle velocities running from about 1300 fps to about 2100 fps with 355-grain to 400-grain, custom bullets of different styles - all gas checked, painstakingly tailored handloads produce one-hole 100-yd. groups (5- to 10-round clusters) under ideal range conditions from my specially made quarter-ton bench. So…
1. Slug that bore
2. Be specific with your bullet(s) design(s) and weight(s)
3. Be exacting with your bullet alloys as to purpose(s)and velocity(ies), and exacting as to your bullet lubechoice(s) - which is also governed by your purpose(s)
4. Barrel bore dimensions must be consistent... hand-lapor fire-lap to achieve it. Mass-produced factory barrelsdefinitely tend to vary in internal dimensions
5. If your rifle is of production-grade, for top accuracydefinitely have it well tuned by a knowledgeable gunsmith familiar with its type and inherent idiosyncrasies.
The above five points constitute only the beginningapproach to fine cast bullet accuracy pursuits. •
1. Slug that bore
2. Be specific with your bullet(s) design(s) and weight(s)
3. Be exacting with your bullet alloys as to purpose(s)and velocity(ies), and exacting as to your bullet lubechoice(s) - which is also governed by your purpose(s)
4. Barrel bore dimensions must be consistent... hand-lapor fire-lap to achieve it. Mass-produced factory barrelsdefinitely tend to vary in internal dimensions
5. If your rifle is of production-grade, for top accuracydefinitely have it well tuned by a knowledgeable gunsmith familiar with its type and inherent idiosyncrasies.
The above five points constitute only the beginningapproach to fine cast bullet accuracy pursuits. •
