ACCURACY AND LOAD PERFORMANCE WITH MATTHEW CAMERON
left to cool to the ambient temperature before the next
three-shot group is fired. At the completion of the three or
four group detail, the barrel is cleaned in a specific manner.
Some research showed that perhaps one of the new
cleaners would result in a chemically clean barrel, not a bad
starting point for this series of tests. Thus Gunslick Foaming
Bore Cleaner appeared in my cleaning kit. I was not
surprised when it showed some residue after cleaning in the
normal manner. It was quick to use and certainly appeared
to clean rapidly without using a brush. Exactly where will the
first shot land out of a rifle when the barrel is not fouled?
Of course, this gives rise to the next two questions: firstly,
if a particular rifle does throw the first shot in terms of
distance, when does it become a problem? And secondly,
if it throws the first shot with a particular projectile, will it
throw any other projectile the same distance and direction?
As my good mate Graeme Wright says, “a ½" difference,
even for a varmint rifle, is one thing; a 4" difference is
another matter entirely.”
Under hunting situations, a fouling shot may not be
possible. Another point of interest is that I have noticed, over
time, that the first two shots on paper are quite often
touching while the third shot is some distance away –
although this still may be a suitable group. I finally thought
that this needed investigating. There is a nagging doubt in
my mind that possibly this third-shot aberration is caused by
barrel heating. All our family ammunition has individual
weighed powder charges. Thus for ammunition we can
control the following:
Different powders and primers
Neck tension-via annealing and dies.
Seating depth
Brass preparationI must admit to being careless with seating depth in
relation to most hunting cartridges. Perhaps it needed more
attention particularly in relation to some projectiles, as
some, including those with boat-tails are fussy, while others
with flat bases are not.
The speed at which we shoot groups is to me an
interesting subject and is something that I was prepared to
change if necessary and, hopefully, for the better. At present,
we normally shoot a three shot-group at a comfortable pace;
the change will be to shoot each shot with a specific time
interval between each.
I was of the opinion that the increasing barrel heat, when
shot at a comfortable rate, was interfering with the result
(i.e. the accumulated heat was possibly causing the third
shot to diverge, thus expanding the resultant group). This
appears to be a problem with cartridges with a larger powder
capacity and is compounded if the barrel is slim in profile. It
was entirely possible that the group was actually capable of
being smaller than the obtained results – in the past, this
situation has possibly caused some potentially good loads to
be abandoned.
There were four rifles available, in no particular order.
- Savage Axis in .25-06, topped with a 3x9 Bushnell
telescopic sight, new Winchester .30-06 brass converted to
calibre, 100gr Little protector point projectiles. Powder 51gr
of AR 2209 ignited with a standard Winchester primer. About
two years old. - Remington LRPV in .22-250 Rem, about nine years old
with a bull barrel; twist 1:9; topped with a Simmons 5x25
sight, it is a very good long-range varmint rifle. For this test,
we used Little 53gr hollow point projectiles in new S & B
cases, 34.5gr of AR 2206H and CCI BR 2 primers.- The oldest of the group is my Ruger 77V in .243
Winchester; bull barrel dating from 1982. It currently wears a
Weaver 2x10 Super Slam sight. The ammunition is new
Winchester brass and standard Winchester primers igniting
36.5gr of AR 2208, which propel 85gr custom rebated
boat-tail projectiles. - Finally, a Remington 700 with a fluted barrel circa late
1990s, .220 Swift, used Winchester cases and standard
Winchester large rifle primers, coupled with Speer 55gr soft
points, propelled by 45gr of AR 2213 SC powder.
»
http://www.rifleshootermagazine.co.uk 87ABOVE: All the
ammo used for this
test is common and
easily availableBELOW: The .243 and
.25-06 ammunition