Author Topic: 45/70BC RangeReport  (Read 268 times)

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Offline rifleman61

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45/70BC RangeReport
« on: April 04, 2006, 11:28:52 AM »
Date of test 01April06/1100
"Shooting in" stage 25 yards [Shooting in= rough adjustments on the sight, locking front sight element and printing a half dozen rounds]
Zero stage 100 yards
Range conditions at zero stage:
wind: intermittent at 5~7, right to left, occasionally quartering into the face at 12:00
light: high overcast flat grey
humidity greater than 70%, seen in the air, and felt on the face
temperature: <55deg.F
Departures from H/R specs?: Yes
Manufacturer's sights removed and Pedersoli/Soule sights installed, adjustable iris on the tang, and a front sight installed prior to fire with an aperture of~.100 ".  RATIONALE Manufacturer's installed sights not capable of giving or controlling declination sufficient to fire a course of 800 yards; while acceptable as an hunting sight they will not render a "long range" capability that is consistent and competitive.

Barrel from manufacturer rebored in chamber to render chamber conformal with brass specifications for nonstandard 535 gr. "Postell" and 500 gr. Lee "variant" rounds.  Chamber was rendered "straightwall" to accept handloadings for those mentioned rounds.  Chamber throat was moved forward .030 to accomodate new loadings.
Manufacturer's ejector was reconfigured to extractor, which is considerably less a distraction, for me.  Barrel was "not" bedded or glassed, fired as same from H/R.
ROUNDS: 40
Brass:
a. Starline, trimmed to -5mils of maximum spec to 2.100"
b. all primer pockets polished and buffed
c. minimally flared
d. tumbled to factory new condition
PRIMERS: all variables eliminated WW Large Rifle standardized.  This is in accord with National Match Specs, for M-14 loadings.  WWLR is very consistent in its burn.
POWDER CHARGES:
a. 3031IMR 38.5 grs. 1300fps
b. Hodgdon Varget 42 grs. 1300fps
All charges dropped +/- 0
LOADING GROUPS: 2 groups of twenty rounds each, of two ten round strings.  Each group being composed of [2] 10 round groups of 535 gr. "Postell" in 3031 and Varget loadings, and [2] 10 round groups of 500 gr. Lee "variant" in 3031 and Varget loadings.  All rounds cast from #2 alloy anc chill shocked at casting to 20 Brinnell hardness.
Lee is typed as "variant" because its geometry is neither "Postell" nor Schmittzer, but it has some of the outward  physical characteristics of each in its geometry.  It is a 500 gr. flat based bullet with four driver bands and three grease grooves occupying 60% of its body length terminating behind a short ogive with a short sharp point.  This renders it potentially a very accurate round with the proper loading.
No extraordinary measures were taken as to housekeeping for the barrel.
Barrel was dry swabbed with a clean cotton patch between fireing groups
Barrel was cleaned prior to "shooting in" with standard bore solvent, 12 passes from phosphor bronze brush and passes from cotton patch sufficient to render a clean dry patch with no "rifle".
RESULTS:
At 100 yards a six round group was fired from bench position only.  Extreme spread of group was ~<2-1/2 inches, with a mean radius of the group of 1-1/4 inches.  Center of any round from the center of the group was approximately not < than 1", nor more> 1-1/4" at 6:00 in the ten ring.
Rounds of 535 gr. Postell fired at random with previously mentioned powders, no appreciable difference noted between the two powders in terminal velocity or terminal accuracy at this stage.  Recoil was greater with 3031IMR but not uncomfortable;  felt recoil with Varget was noticeably smoother.  A check of burn rate comparison tables shows Varget to be a slower burning powder, which accounts for this.
Rounds of 500 gr. Lee "variant" show themselves to be potentially the most accurate of the selections with either powder loading. Three round groups were fired that measured less than 1" in extreme spread.
Problems encountered:
Cheek weld--there is a substantial difference between a modern smokeless military rifle [M-14] and a period weapon of this genre; establishing a good sight is a function of "time"
Pedersoli/Soule, well worth the investment, although it too takes some getting used to, but once mastered renders the rifle quite surprising in its actual accuracy.  45/70BC due the drop of its comb should be a very pleasant weapon to shoot off hand; it is barrel heavy but it is not pronounced and is not uncomfortably so.
Further tests to follow:
200 yard and 300 yard off hand and"stick" shooting


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