Okay, I admit it. I'm getting older. I'm not old, yet, but just older. For those of you who have been through this,
you will already know that, for the most part, the change is very subtle. One day you wake up and you realize that you
cannot do something you could do before. Right?
This same sort of subtle change affects one's shooting as well.
|
The sight radius
of an AR-15 service rifle is only 20 inches |
And, now for
another admission; I've never been a great prone 600 yard shooter.
I have always been an adequate 600 yard
shooter (I do hold a Master classification in high power rifle), but it was
mastery of the other three stages (200 yard standing slow fire, 200 yard
sitting rapid fire, and 300 yard prone rapid fire) that really got me that
Master card.
For many who cannot master
the 600 yard line, the blames lies in the inability to call the wind; however,
that was never my problem.
In fact, I've
called the wind the last four years for the Louisiana State Service Rifle Team
at the National Matches at Camp Perry in Ohio.
For me, the
problem lately has been that by the time I get back to the 600 yard line, my
older eyes are worn out.
The short sight
radius of the service rifle, combined with my tired, old eyes, leads to the
front sight disappearing sometime around shot eight of the 22 shot string (two
sighting shots and 20 shots for record).
A disappearing sight is not conducive to high scores, as I tend to
string shots high and low because I cannot seem to get the post front sight on
my service rifle to be centered in the target mass.
For those of you who have never fired an
AR-15 service rifle, the sight radius (the distance between the rear sight and
the front sight) is a mere 20 inches.
And, although in the picture below the post and target are both
in clear focus, in fact it is quite impossible in real life to get both the
post and target in focus.
|
The
sight picture through the rear peep sight of the AR15 with the post front sight
centered underneath the target is called a "6 O'clock Hold."
|
Indeed, one of
the most difficult lessons for a high power rifle novice is to convince him or
her to let the target blur and to keep the front sight in focus.
Although it sounds simple, in reality it is
really hard.
One's mind wants to see
that target, but keeping the target in focus is a sure way to lose points as
the front post wanders out of the center of the target.
|
The
shooter can either keep the target in focus (left) or the front sight in focus
(right). The preferred sight picture is
the one at right, which is hard for older eyes.
|
A lot of time, money, and effort
has gone into shooting glasses and lenses that insert into the rear sight hood
of my service rifle (yes, the CMP does allow one to insert a lens into the rear
sight hood). Although I'm not giving up
on shooting my service rifle, a recent incident at the monthly mid-range prone
match at Palo Alto Rifle & Pistol Club convinced me it was time. Time for what? Read on.
The format for the mid-range prone match is three separate strings of 22
shots (two sighting shots and 20 shots for record) all from the prone position
at 600 yards. To say the least, my first
two strings of fire with my service rifle were downright horrible. I was just about to give up and not waste the
ammunition shooting the third string when my good friend, Buck Kliebert,
suggested I shoot his Palma rifle. I
greedily accepted his offer and fired a very respectable score with a rifle I
had never shot before!
Palma is another discipline of
high power rifle that involves shooting matches at 800, 900, and 1,000
yards. There are several major differences
between a Palma rifle and a service rifle, but for the sake of this article,
the main difference between the service rifle I was shooting and Buck's Palma
rifle is the sights. The facts are that
(1) the service rifle sights are battle sights that have been
"improved" for use in shooting matches, and (2) the Palma sights are
pure target shooting sights by design.
The difference in the sights is dramatic, particularly for anyone over
40 years of age!
|
The
sights found on the service and match rifles are shown. In panel A, the standard service rifle
front sight is shown with a narrow post.
In panel B, the modified rear sight is shown with a corrective lens
in the hood. Panel C and D show the
Stallings Machine "Rightsight."
The iris is adjustable. In panel E, the Phoenix side-mount rear
sight is shown. |
|
After firing
Buck's Palma rifle, I immediately decided, "I've got to build one of
these."
I discussed this with Buck
and friends, Bob and Bill Jenkins, who are both high master high power rifle
shooters.
Bob and Bill both urged me not
to build a Palma rifle, but instead to build a "space gun," which
would allow me to shoot both the mid-range (600 yards) and long range (800,
900, and 1,000 yards) prone matches, and also to shoot
"across-the-course" matches (XTC matches are shot at 200, 300, and
600 yards).
Perfect!
The three outstanding shooters had solved two
problems for me: (1) I would be able to shoot the longer range prone matches
and (2) continue to shoot the XTC matches I love so much.
Further, the rifle would be built on the very
familiar AR-15 platform.
Although it is easy to say,
"I'm going to build a space gun," in reality there are so many
choices that the process can be overwhelming.
In my case, I wanted a rifle that I could use XTC, so many of the
decisions were easier. The first
decision was to determine which caliber I would use. The path of least resistance would have been
to use .223 Remington. I have shot tens
of thousands of .223 rounds through my service rifles over the last 15 years. I
have a progressive press set up to load short line rounds (200 and 300 yards)
with Berger 77 Gr. Match OTC bullets and 24.2 Gr. of Varget with Winchester Small
Rifle primers (cartridge overall length, COAL, of 2.260" to fit in the
standard AR-15 magazine). I have a Redding
.223 caliber competition die set to seat Berger 82 Gr. match BT target bullets
over 24.2 Gr. of Varget with Federal Premium Gold Medal Match GM205M primers for the long line (COAL of
2.445" in my service rifle). [WARNING! Both of these loads exceed recommended pressure
limits and the reader must not use these loads without first reducing powder charges
by at least 10% and working up to this load.
Note that my rifle has a Wylde chamber, and not a SAAMI .223 Remington
chamber. These loads are UNSAFE in a
standard .223 Remington chamber!]
But, Bob Jenkins recommended I go elsewhere. He recommended the relatively new 6 mm Hagar
round. Unlike the .233 Remington, which
has been a standardized cartridge for many years, the 6 mm Hagar has yet to be
recognized with SAAMI standardization.
|
Pictured
from left to right are empty cases for the 6 mm BR Norma, 6 mm Hagar, 6.8
mm Remington SPC, and .223 Remington.
The loaded cartridges are (left to right) .223 Remington loaded to
magazine length with the Berger 77 Gr. OTC Match bullet, .223 Remington
loaded with the Berger 82 Gr. BTHP bullet, 6 mm Hagar loaded to magazine
length with the Berger 95 Gr. Hybrid bullet, and 6 mm Hagar loaded with the
Berger 105 Gr. BTHP bullet. |
|
The 6 mm Hagar is built on the same case as the .30 Remington and 6.8
mm Remington SPC, with substantially more case capacity than the .223
Remington.
The .223 Remington holds 28.8
Gr. of water, whereas the 6 mm Hagar holds 37.5 Gr., an increase of 30% in capacity.
This additional case capacity allows one to
propel heavier bullets, with their concomitant higher ballistic coefficients,
at comparable velocities.
As mentioned
previously, most XTC shooters choose to shoot 75 or 77 Gr. bullets at the 200
and 300 yard lines.
These bullets are
designed to allow the shooter to seat the bullet into the .223 Remington case
to a COAL of 2.260, which is the maximum length that will fit into the AR-15
magazine.
Magazine length rounds are
necessary, as there are rapid fire strings at both the 200 and 300 yard lines,
and the rules of the game require the shooter to fire these rounds from a
magazine.
In my rifle, I get 2853 FPS from Berger 77 Gr. Match OTC bullets. With the 6 mm Hagar, I can load Berger 95 Gr.
Classic Hunter bullets to magazine length, and get the same velocity. However, the 95 Gr. bullet is 23.4% heavier
than the 77 Gr. bullet, with a 14% increase in ballistic coefficient from 0.376
to 0.427. In a 10 MPH full value
crosswind (blowing perpendicular from left to right or right to left across the
path of the bullet), the 77 Gr. bullet will drift 8 inches (2.5 MOA) at 300
yards versus 6 inches (2 MOA) for the 95 Gr. bullet. While this may not seem
like a lot to the uninitiated reader, the “X-ring” on the 300 yard target is
only 3 inches wide, and the shooter typically will not have time to make
adjustments to his or her sights during rapid fire shooting in which the
competitor must fire 10 rounds in 70 seconds with a mandatory magazine change
(when time begins, the shooter loads a magazine containing 2 rounds, fires
those two rounds, and then changes to a magazine containing the remaining 8
rounds, and then fires those). A small
change in wind velocity can have huge implications in one's score with lighter
bullets.
The difference is far more dramatic for the “long line” ammunition. All firing from the 600 yard line is slow
fire, where each round must be loaded into the rifle one at a time. This allows the competitor to fire long
bullets that are seated out much too far to fit into the magazine. My 600 yard load for the .223 Remington uses
the Berger 82 Gr. match BT target bullet seated to a COAL of 2.445 inches
leaving the muzzle at 2750 FPS. In the 6
mm Hagar, I can drive the Berger 105 Gr. BTHP to 2872 FPS. The 105 Gr. bullet is 28% heavier than the 82
Gr. bullet, with an increase in the ballistic coefficient of 27%. At 600 Yards with a 10 MPH full value wind,
the 82 Gr. bullet will drift 31 inches (5 MOA), whereas the 105 Gr. BTHP bullet
will drift less than 25 inches (4 MOA).
The "X-ring" on a 600 yard target is only 6 inches wide, so,
again, a small change in wind velocity can have a huge impact on the location
of the shot for small bullets with relatively low ballistic coefficients.
Okay, I see you scratching your head at this point and asking the
obvious question.
"If heavier
bullets and high ballistic coefficients are better, why did you build a rifle
in 6 mm instead of .30 caliber (7.62 mm)?"
That indeed is a fair question and the answer can be found in the
original requirements.
I wanted to build
a space gun based on the very familiar (to me) AR-15 platform.
The AR-15 platform is limited in the length,
diameter, and power of the cartridge that it can accept, and any .30 caliber
cartridge is going to have a seriously short case to caliber ratio, and be
vastly underpowered.
The 6 mm Hagar is
an excellent compromise, using a heavier bullet in a standard, necked-down .30
Remington case.
|
This
10-shot group was fired at 100 yards using the Berger 105 Gr. BTHP bullet
with 29.1 Gr. Hodgdon Varget and a GM205M primer in Hornady cases. Note that the single high left shot in
the group was called "out" by the author as soon as it was fired. |
So far, my tests with my new 6 mm Hagar space gun have proven that the
Berger 105 Gr. BTHP bullet is extremely accurate using 29.1 to 29.7 Gr. of
Hodgdon Varget, and anyone would be more than satisfied to use this load at 600
yards.
However, Berger has an even
better 105 Gr. bullet than the BTHP.
Berger's
new 105 Gr. Hybrid bullet has a ballistic coefficient of 0.547 versus 0.493 for
the 105 Gr. BTHP bullet.
As can be seen
in the accompany table, the Hybrid bullet is longer and the ogive has been
pushed forward; however, the longer bullet has a longer nose length.
These features result in a much improved
ballistic coefficient in a bullet of the same weight.
Although the bullet promises better long
range accuracy, so far my tests have been completely unsatisfactory.
I have not been able to find a load that
results in acceptable accuracy.
For
instance, the 0.36 inch spread at 100 yards with the 105 Gr. BTHP would result
in an expected spread of 2.2 inches at 600 yards, which is more than adequate
to keep the bullet in the 6 inch X-ring.
On the other hand, the best accuracy I have achieved with the 105 Gr.
Hybrid bullet is 0.80 inches at 100 yards, which would result in an expected
extreme spread of almost 5 inches at 600 yards.
The extreme spread is almost as big as the X-ring!
But, fear not!
I will keep on trying until I either get the
105 Gr. Hybrid bullet to shoot well, or I'll accept the slightly lower
ballistic coefficient of the 105 Gr. BTHP bullet and use it for all of my 600
yard shooting.
So, what are the components used to build the new space gun?
The upper assembly was purchased from
accomplished gunsmith and high power rifle competitor John Holliger of White
Oak Precision.
As of the writing of this
article, John was selling his 6 mm Hagar upper assembly exclusively through
Creedmor Sports.
The upper is built by
John with a 28-inch stainless-steel Criterion match barrel with a 1 in 8
twist.
I decided that I wanted an even
longer sight radius, so I extended that 28-inch barrel by attaching Norm
Houle's 6-inch "bloop" tube onto the end of my barrel.
The tube assembly has a clamp-on locating
ring plus a clamp-on "bloop" tube that positively indexes off a
tapered pin that protrudes from the locating ring. The locating ring is light
but very strong and absolutely stays put when one clamps it on the barrel end.
The "bloop" tube part of the assembly has two clamp-on screws. With
the "bloop" tube installed, the sight radius becomes a whopping 37.5
inches (take that 50 year old presbyopic eyes)!
|
The
"bloop" tube is attached to the barrel. |
If the barrel of a rifle is its heart, then surely the trigger is the
brains of the entire operation. A good
trigger cannot be understated on a match rifle.
I've been using the Geissele (pronounced guys-lee) service rifle trigger for several years and am ecstatic
with its performance. In service rifle
competition, the trigger must be able to
Bullet
|
COAL
|
Powder
|
Charge
|
Muzzle Velocity
|
No. Shots in Group
|
Group Size
|
Berger 105
Gr. Boat tail Target
|
2.445
|
Varget
|
28.5
|
2754 ± 12
|
5
|
0.37
|
(#24428) BCG1 = 0.493, BCG7
= 0.253
|
Varget
|
29.1
|
2792 ± 8
|
10
|
0.36
|
|
|
Varget
|
29.4
|
2812 ± 8
|
4
|
0.37
|
|
|
Varget
|
29.7
|
2834 ± 10
|
10
|
0.36
|
Berger 105
Gr. Match Hybrid Target
|
2.445
|
Varget
|
29.4
|
2760 ± 19
|
10
|
0.84
|
(#24433) BCG1
= 0.547 BCG7 = 0.278
|
|
Varget
|
29.4
|
2801 ± 11
|
3
|
0.75
|
|
|
IMR8208XBR
|
28.2
|
2815 ± 6
|
3
|
0.87
|
|
|
H4895
|
28.6
|
2851 ± 4
|
3
|
1.47
|
|
|
AA2495
|
28.0
|
2794 ± 6
|
4
|
0.77
|
|
|
AA2520
|
29.7
|
2897 ± 9
|
10
|
0.87
|
|
|
Reloader 15
|
29.7
|
2867 ± 4
|
10
|
0.80
|
|
|
IMR4320
|
29.8
|
2893 ± 6
|
10
|
0.91
|
|
|
BL-C(2)
|
30.7
|
2885 ± 18
|
3
|
0.99
|
Berger 95 Gr.
Hybrid
|
2.285
|
Varget
|
29.0
|
2803 ± 17
|
10
|
1.25
|
(#24570) BCG1
= 0.427 BCG7 = 0.219
|
|
Varget
|
29.0
|
2751 ± 17
|
10
|
1.61
|
|
|
Reloader 15
|
29.4
|
2849 ± 19
|
10
|
0.61
|
|
|
IMR4320
|
29.4
|
2848 ± 15
|
10
|
1.00
|
Hornady 87
Gr. V-MAX
|
2.285
|
Varget
|
29.8
|
2886 ± 5
|
3
|
0.91
|
(#22440) BCG1
= 0.400 BCG7 = 0.199
|
|
|
|
|
|
|
Hornady 75
Gr. V-MAX
|
2.285
|
Varget
|
31.7
|
3148 ± 28
|
3
|
1.37
|
(#22420) BCG1
= 0.330 BCG7 = 0.160
|
|
Varget
|
31.7
|
3148 ± 28
|
3
|
0.89
|
Abbreviations:
|
COAL, cartridge overall length; BCG1,
ballistic coefficient using G1 drag
|
|
function; BCG7, ballistic
coefficient using G7 drag function
|
|
Primers Used:
|
Long range loads with 105 Gr. bullets used
Federal GM205M
|
|
|
Short range loads with 75, 87, or 95 Gr.
bullets used Remington 7 1/2
|
|
|
|
|
|
|
|
|
|
support 4.5 pounds of weight without "breaking."
However, with a match rifle, any safe weight
is allowed.
I chose to install the
Geissele Hi-Speed Match Rifle Trigger in my new rifle.
The Geissele Hi-Speed Match Rifle Trigger has
a 1
st stage of 1.5 to 2.5 pounds and a 2
nd stage of 0.4
to 0.9 pounds. Because the trigger is designed for NRA High Power Match Rifle
competition with highly modified, match-grade AR-15 rifles, its adjustability,
lighter 1
st and 2
nd stage pull weights, and fast lock
time enhances trigger control and accuracy while the full-power hammer spring
provides uniform primer ignition for more consistent bullet velocity.
In my rifle, the trigger is set at 2.5
pounds, which is about as light as anyone would want for XTC matches where
rapid fire strings are shot.
|
The Geissele
Hi-Speed Match Rifle Trigger breaks at a crisp 2.5 pounds.
|
The trigger was installed into an
AeroPrecision lower receiver along with a White Oak Armament lower parts
kit. I know that many shooters get
completely "wrapped around the axel" about lower receivers. DON'T!
I have used lower receivers from dozens of manufacturers over the years
and I can tell you that I have not found a bad one yet. I have service rifles built on Bushmaster,
Rock River Arms, and Armalite lower receivers, and hunting/zombie rifles built
on other receivers. If you want to build your own space gun and you already
have a lower receiver, use it. If you
are planning to purchase one for your project, buy the cheapest alloy lower
receiver you can find and build away!
For the buttstock of my new rifle I
chose the excellent White Oak Precision adjustable buttstock for a right handed
shooter (yes, they make a left hand version as well). The stock has an easy to use thumbwheel adjustment
for the cheek rest, and reference marks machined on the buffer tube and
buttplate length of pull rod for repeatable adjustments.
The cheekpiece housing and buttplate hanger
are aluminum with an anodized finish and the buffer tube, length of pull rod
and buttplate backer are made of steel for added weight. The complete assembly, with buffer and spring weighs four
pounds. The cheekpiece does interfere with the operation of the standard
AR-15 charging handle, so a bolt carrier-mounted handle is necessary. The White Oak Precision upper assembly comes
with a bolt carrier-mounted handle. The
White Oak Precision Adjustable Buttstock is adjustable for:
- Buttplate Height
- Cast-Off/On, 0-2"
- Length of Pull 9-16" (AR-15 measured from trigger)
- Buttplate Yaw
- Camber
- Cheekpiece Height
Although I specifically chose this
buttstock because of the numerous possible adjustments, this has proven to be a
double edged sword. The learning curve
for getting all of the correct settings in the three positions of XTC shooting
(standing, sitting, and prone) was steep and it took quite a while to become comfortable
in all three positions.
Item
|
Manufactuer
|
Supplier
|
Cost
|
Upper
Assembly
|
|
|
$ 1,080.00
|
Bloop Tube
|
|
|
$
135.00
|
Trigger
|
|
|
$
279.00
|
Lower
Receiver
|
AeroPrecision
|
|
$
85.00
|
Lower Parts
Kit
|
Various
|
|
$
40.30
|
Adjustable
Buttstock
|
|
|
$
425.00
|
Front Sight
|
|
Stallings
Machine
|
$
379.00
|
Rear Sight
|
|
|
$
408.00
|
Rear Sight
Base
|
Lipski
|
|
$
64.50
|
Rear Sight
Iris
|
|
|
$
51.00
|
Anti-glare
Tube
|
|
|
$
14.00
|
|
|
|
$ 2,960.80
|
|
When choosing the front sight, I spoke
to Buck Kliebert about what he was using on his rifles. He suggested the Stallings Machine Rightsight. The Rightsight is built around a 30mm
front sight tube, and was developed for high power rifle competition to have
the best possible sight picture allowed by iron sight rules.
The Rightsight comes with an adjustable iris
made by Gehmann, and are available in 4 sizes: 2.4 - 4.4 mm, 2.9 - 4.9 mm, 4.0
- 6.0 mm, and 5.5 - 7.5 mm.
Given that
this was my first XTC match rifle, I called Wayne Fourche at Stallings Machine
and discussed my needs.
He suggested
that I use the 4.0 - 6.0 mm for XTC competition.
The adjustable iris is the same as the
Gehmann 520 iris in a larger frame made to fit the Rightsight and other 30mm
sights.
The Rightsight also includes a
30mm, 0.5 diopter Crizal Alize anti-reflective lens, which enlarges the target
when one looks through the sight.
The
base onto which the Rightsight is mounted has 50 MOA adjustment, allowing me to
move the front sight when moving from 300 yards to 600 yards, with only minimal
adjustments to the rear sight.
|
The Stallings Machine Rightsight was
chosen for its flexibility, as it may be used for XTC, Mid-Range, or Long Range
competitions.
|
For the rear sight, I used the Phoenix Precision rear sight with
adjustment knobs that rotate in the same direction as a service rifle
sight.
For the uninitiated, a brief
explanation is in order.
The standard
match rifle sights adjust just like a rifle scope.
To move the impact of the bullet to the
right, match sights and rifle scopes are adjusted counterclockwise.
However, on a service rifle, to move the
bullet impact to the right the shooter would adjust the knob clockwise.
For me, who has been shooting service rifle
competition for decades, the chose was a "no-brainer."
For me, turning the knob clockwise will
ALWAYS move the bullet impact to the right.
I'm far too old to learn the new trick of adjusting the other way, so I
purchased a match sight with service rifle adjustments.
The sight was originally purchased years ago
by me for a different project, and unfortunately is the side mount version.
For the space gun it would have been better
to have a top mount sight.
To turn the
side mount sight into a top mount sight, I purchased a Lipski rear sight base.
The rear sight comes without an iris so that the shooter can set up the
sight as he or she wishes. I chose to
install a Gehmann 0.5 - 3.0 mm iris on the sight. The Gehmann system of rear
sight irises is based upon their patented fixed-seat iris design constructed
with tempered stainless steel leaves attached to the iris body. All irises are
built upon this principle, and all additional features connected to and within
iris combinations benefit from this principle. As a result, the peephole seen
by the shooter is absolutely circular throughout the full range of
adjustments. The iris is very important
to the shooter, as it enables the shooter to achieve an extended depth of
optical field to clearly see both the front sight and the target picture at the
same time. All internal and external
black surfaces are manufactured to give absolutely minimal light reflection,
which is another cause of sight picture loss when shooting XTC in bright
sunlight. And, speaking of bright
sunlight, the final touch was to place a Gehmann 35 mm anti-glare tube on the
front of the rear sight.
So, now that the rifle is finished, the hard part has begun. As luck would have it, though, the hard part
is also the fun part! I'm slowly
climbing that learning curve to get familiar and comfortable with the rifle in
all three positions. So far, my standing
scores have gone up nicely, mainly because the long sight radius is so
forgiving as that front sight dances around the target. In contrast, my sitting position is a
freaking mess! My scores have dipped
dramatically, and will continue to be poor until I find that sweet spot. Finally, my all important prone position is
getting better each time I fire the rifle, and it
won't be long until I won't have an excuse for a shot out of the
10-ring.
|
The
completed rifle weighs 14.8 lbs. and is 57 in. long. |
Now, enter my 50 year old eyes. As evidenced by the racks of
"cheater" glasses at any Walmart or pharmacy, it gets harder and
harder to see things up close as one ages.
That target 600 yards away is a whole lot easier to keep in focus than the
front sight that is only 20 inches away.
So, my tired, old eyes give up and the front sight just disappears. And, as I work hard to try and see it, the
target disappears. I don't mean it fades
or blurs. I mean it freaking disappears! So, my new sight picture is a quite out of
focus target and quite out of focus front sight. Argh!