Primer data & accuracy

Apologies in advance for the long article here, but wanted to back up some of my previous statements with actual shooting results. 

To illustrate my previous posts regarding the accuracy capability of the No. 4 Lee Enfield shooting prone unsupported with the aid of a sling and aperture sights, I shot this 800 yard target shown below this past June.  This was with my Dominion of Canada Rifle Association (DCRA) 7.62 Conversion of a Fazakerley No. 4 Mk 2 with a Long Branch made 7.62mm barrel (of normal .303 service weight).  The conversion was done by Canadian Arsenals Ltd in Long Branch, Ontario for the purposes of SR(b) target shooting sponsored by the DCRA.  Barrel is bedded in the forend at the sling swivel band with 12-14 lbs pressure and at the chamber reinforce and has 2,300 rounds thru it.  The rifle is fitted with a Parker Hale 5C ¼ MOA click adjustable rear sight with standard six hole eyepiece and A.J. Parker “Matchmaker” front sight. 

The Load:

   Lapua .308 Win case - neck sized

   CCI BR-2 benchrest primers

   44.0 gr Varget (ADI AR2208) – all charges weighed

   Sierra 168 gr Tipped MatchKing seated to 2.95 inches for 0.020 inches off the lands. 

At this distance (800 yds) you can expect significant lateral dispersion due to wind drift and the challenge to identify and adjust (in advance of each shot) for the small shifts in wind direction and strength.  Vertical dispersion is a good indicator of how accurate the rifle and load is when fired off the elbows in the prone position.  I shot 12 rounds here, shot #11 was in the 8 ring at 9:00 caused by an undetected wind strength change.  The target monitor is zoomed in to show the full 10 ring and part of the 9 ring.  A 1 MOA grid line overlay can also be seen on the target photo. 

This load gives 5 to 9 fps standard deviation in velocity, the best I have recorded in .303 and 7.62/.308 handloads.  I attribute this to careful attention to reloading steps, quality of components and the consistency of the BR-2 primer.  Substituting CCI #200 primers or WRL primers gave more than double the velocity standard deviation. This consistency in muzzle velocity is what helps maintain a reasonably small vertical spread at long range: 12 inches (1.5 MOA) for the 12 shots. Excluding shot #11, the windage spread is 16 inches (2 MOA).

At 200 yards, I have equaled this 1.5 MOA group with ten shots shooting prone with my Fulton Regulated Long Branch No. 4 Mk I/3 (with standard as issued Mk 1 rear sight and blade foresight) in .303 using my standard .303 match load: PPU case, WLR primer, 40.0 gr Varget (charges thrown directly from measure into case) and 174 gr SMK seated to 3.05 inches.  200 yards is more forgiving of the small variations in case dimensions/weight, primer, powder charge weight, etc. than they are at 800 or 1000 yards.  

I’ve not yet been able to get a standard bedded (3-5 lb muzzle bearing) No. 4 rifle to shoot quite as good as those with center or mid-band bedded forends.  Some of this could be barrel condition.  I’ve gotten close, but not quite as good.