Dot Net Presents
Sighting In a
Mosin-Nagant "Sniper" Rifle
Arguably the most popular, if not
most prevelant, rifle currently on the military surplus
market is the Russian Mosin-Nagant bolt action rifle
in 7.62x54R. A combination of interesting history,
low price, reliable design, and many variations make
it an ideal rifle with which to begin a military
One of the more interesting variants
of the Mosin-Nagant is the 91/30 sniper rifle. A
major surplus distributor has imported many thousands
of 91/30 rifles, along with a boat load of PU scopes.
Their "wizards" (calling them gunsmiths
is a bit of a stretch) have cobbled together these
rifles and scopes, which are now being sold as collectible
sniper rifles. The easiest way to tell if you have
one of these cobbled rifles is by the price. If you
paid around $300, you can be sure it's one of these,
as a genuine MN sniper rifle goes for about $700.
Fig. 1 - The PU scope and mount.
Now don't get me wrong - I love
MN rifles, and with a little TLC, these "sniper" models
can be made to shoot quite accurately. The problem
with them is that since the scope mount was not machined
to match the rifle at the time of original manufacture,
some misalignment problems with the scope, particularly
with the windage (horizontal) adjustment can occur.
While a genuine sniper rifle would have had any variations
between the scope and receiver machined out, these "wizard" jobs
have not. Also, unlike modern rifle scopes where
the reticle stays centered and the entire field of
view moves for sight-in purposes, the PU scope's
field of view is fixed and only the reticle moves.
The drawings that follow illustrate the problem.
Fig.2 - The ideal sight picture
on a properly adjusted scope. The red cross represents
the point of aim, and the red dot is the bullet impact.
The 3 line reticle of the PU scope centers on both.
Fig.3 - Typical sight picture of
an unadjusted "wizard" sniper rifle. The
bullet impact is high and left of the point of aim
at the red cross indicating both elevation and windage
Fig.4 - The windage and elevation
adjustment knobs on the PU scope actually have enough
play to move the reticle to center the crosshair
on the point of impact as shown in here. (Remember
what I said earlier that adjusting the PU scope moves
only the reticle, not the entire sight picture as
on a modern scope.) However, this is a really poor
sight picture. We're looking for the sight picture
shown in Figure 2.
Fig. 5 - The elevation adjustment
screws on the mount (see Fig. 1) can be adjusted
to give the sight picture shown in Figure 5 by loosening
the bottom screw and tightening the top screw. If
your bullet impact was low in the sight picture,
loosen the top screw and tighten the bottom. Use
very small adjustments on these screws. A 1/4 turn
of these screws causes about a 6 inch change on the
target. Now the elevation picture is correct, as
shown here, but the windage still leaves much to
be desired. Once the elevation has been adjusted,
it would be useful to put some locktight on the BOTTOM
SCREW ONLY. The top screw must be able to loosen
if you ever want to remove the scope base from the
Fig. 6 - Once your elevation is
adjusted properly, you now must decide whether to
grind or shim the scope base in order to adjust the
windage. If you have a sight picture similar to that
on the left, grind it. If something like that on
the right, shim it. When grinding, again use SMALL
increments, so as not to grind off too much.
Fig. 7 - Photo of how much I had
to grind off my scope base in order to get the ideal
sight picture shown in Figure 2.
Now that you have the ideal sight
picture, it is now time to calibrate the scope. By
loosening the 2 small calibration screws on the windage
and elevation knobs (see Figure 1), the top portion
of the knob can be turned without moving the reticle.
Set the windage to 0 and the elevation to whatever
range you were firing at (in meters). Tighten the
calibration screws, and you're done.
Fig. 8 - One of my better groups.
With a well tuned in hand load,
you should be able to achieve sub MOA groups with
your Mosin-Nagant. The group shown in Fig.8 is at
100 yards with my pet load of 44.5gr of IMR 4895
and 165gr Sierra BTSP (.308 diameter). I'm sure the
one flyer was me, not the rifle! But this target
does show one of the downfalls of the PU scope, which
is it's lack of fine adjustment. When you move the
dial what you think is just a slight adjustment can
actually move the group several inches. Oh well -
Tuco's postal match was going for group, not accuracy!
Dot Net Presents
Fine Tuning of
the PU Scope
I have seven PU snipers now and
have examined a half a dozen others. I regularly
shoot a few of them and have learned a few things
through observation and practical use that I thought
I might share with some of you fellas picking up
a PU sniper for the first time. I test my rifles
off the bench at a 100 yard indoor range, regularly
shoot at a 100-300 yard military style range, and
shoot long range precision target/tactical at a 1000
yard facility. All parts of the PU rifle setup work
together to give its optimal accuracy and any part
not given the proper setup attention can detract
from its performance
First on accuracy:
I have found a good PU 91/30 sniper
will shoot 3 shots out of 5 touching at a 100 yards
fairly consistently indoor or outdoor with good ammo.
(That may sound unreal but this is a common occurrence
with MOA rifles-it is almost assured that 2 or 3
shots will be touching when you put 5 .30 caliber
bullets into an inch at a 100 yards) I don't hand
load yet, so the best I use is new production S&B
FMJ and I have had excellent results with silver
tipped Czech green lacquered steel case, head stamp
63 (through 67)/bxn. The challenge is usually trying
to hold the thing on target through the trigger pull!
I found the following accuracy standards on the Russian Sniper Page:
a 91/30 PU rifle was expected to shoot 10 shots into
3.5 cm (1.38") at 100m, 7.5 cm (2.96")
at 200m, 18 cm (7.09") at 400m, and 35 cm (13.79")
at 600m. I would imagine this would be done off of
some kind of mechanical vise type rest.
PU scope use:
1. Sighting through the PU scope,
if you look to the lower portion of the field of
view you will see a small circle with a vertical
bar - this is the front globe and post iron sight.
Move your eye/head position right or left until the
bar (front sight post) superimposes over the bottom
of the vertical reticle element. When it is aligned
it will "split" into two thin lines that
bracket the lower portion of the vertical reticle
element. Then put your pointer on target. This will
help you to consistently align your eye to the scope.
Note: You may or may not be able
to see the full globe and post in your field of view.
This depends on how you have set up your mount using
the vertical adjust screws on the base. All four
of my Russian snipers came to me with at least one
of the vertical adjust screws punched in place. As
configured I can see the full round of the front
globe and post sight. This image sits at the bottom
edge of my field of view-the bottom of the globe
touching the bottom of the field of view. This image
was so consistent with my first four PU rifles I
thought I was actually seeing a "rear lens alignment
reticle" within the scope! Also with the vertical
adjust screws punched in place the horizontal bars
are up at the top quarter or third of the field of
view sighted in at 100 yards. This gives the reticle
enough range of travel to still be comfortably in
the field of view out to 1300 meter elevation setting.
2. Get your eye up close to the scope so you have optimal field of view. It
is not too comfortable but you will have more light and a more consistent scope
picture. You won't really have a cheek weld more of a chin weld. I have found
that a major factor in achieving consistency with these short length scopes
is a consistent scope picture, i.e. you can move your head/eye placement and
the pointer will move slightly on the target. This is very apparent when holding
on small long range targets. The trick is to again use the image of the front
sight as a lens alignment reticle: position your head/eye so that you can (1.
See full field of view through the scope, and (2. See the full circle of the
globe sight hood-this is a must so you don't have to move your head, only your
eye-from pointer to front sight alignment image to target. If you consistently
achieve this scope picture your head/chin placement will be more consistent
and you should be able to achieve better groups and POI repeatability at different
elevation settings. If you hold your head to far back in a more comfortable
position you will 1) lose the full field of view 2) increase parallax effect.
Note: I don't know if these rifles
were intentionally set up to take advantage of seeing
the front sight in the scope field of view or not.
All I know is that I can see it and have used it
with good results. Consistent stock weld is a fundamental
taught even today in precision shooting. Even with
today's modern equipment with parallax focus adjustment
consistent stock weld is considered a basic building
block essential to making these finer tuning adjustments
effective. It is critical with the very basic short
focal length PU scope and is a challenge with the
scope set so high above the receiver and with the
stock comb as low as it is.
3. Hold the horizontal reticle bars consistently level.
4. I takes some practice to get used to the horizontal bars and pointer reticle.
With only 3.5 power you have to concentrate hard on the tip of the pointer
and how you hold it on your target, and then repeat the hold for all the shots
in your group. It is easy to find yourself just plastering the tip over a 2
inch square piece of tape at 200 yards, not really trying to place the tip
of the pointer on it in a consistent manner. The rifle should be capable of
shooting within about 2 inches at that distance, but on one shot if your pointer
is at the bottom of the 2 inch square and the next shot your pointer is at
the top of it. You may find that you have a group that is spread over 6 inches
or more and you will be scratching your head wondering why. These PU's are
about as far from a target scope as you can get and still be looking through
two pieces of glass. It is a real challenge to get the best out of your rifle
using one. It is more of a precision optical sight, a couple steps above iron
sights, rather than what you think of in terms of a modern day scope.
5. The Ordinance Corps manual states the windage adjust knob calibration marks
are one mil (milliradian) which is 3.6 inches at 100yd and I have found this
to be a practically correct.
6. Tighten the thumb screw down with a screw driver. I have found that finger
tightening will allow the scope to move after a couple of shots.
Notes on scope setup:
1. These things were sighted in
by a pro and the base lower vertical rough adjust
screw may be punched and immovable. Or at the very
least there are usually some punch marks that put
pressure on the screws to keep them from falling
out. Try to keep these screws aligned to their original
struck positions (or at least note their position
down if you are inclined to move them). Keep in mind
that though the horizontal bars may be further towards
the top of the scope than you like when sighted in
at 100 yards, at 600 to 800 yards they will be at
or near center scope-right where you like them to
be when trying to make the long shot. If you want
to center the horizontal bars at a 100 yards and
your bottom screw is movable be sure to note down
where it was originally set.
2. If you aim through the iron sights and hold them level to the horizon and
then look through the scope and notice that the horizontal bars are not level
there is probably a purposeful reason for this. It has to do with alignment
of the scope longitudinal centerline to the bore longitudinal centerline. When
you rotate the rifle along its longitudinal axis to bring the scope horizontal
bars level, you are probably bringing the scope and bore longitudinal centerlines
into alignment by centering the scope over the barrel. There may have not been
enough room for adjustment on some of these re built, re used scope mounts
and bases to get the scope over the barrel through means of filing the tabs
on the mounts. Though it may seem awkward or unnatural to not hold the rifle
in a perfectly vertical position, these fellas knew what they were doing when
they set these things up. This alignment is critical in precision long range
shooting or precision shooting at varying ranges.
Think about it: with scope CL right or left of bore CL you have to aim the
scope (adjust windage) left or right to converge with the bullet at any given
distance. You will be fine for a single distance, say 100 yards, but when you
aim out to 200 or 300 you need to adjust windage to hit point of aim to compensate
for the built in error caused by the difference in scope and bore longitudinal
CL. Depending upon how far out this alignment is and if shooting at shorter
ranges, this effect can be negligible. It will be much more pronounced at longer
ranges but can be compensated for by preemptive windage settings in addition
to the normal elevation settings as you sight in for each range. There will
be more consistency and less room for error though, if you just rotate the
rifle so the scope is over the barrel-that is why these guys set them up that
way so you will aim over the bore CL.
1. Consider taking the time to
break in your barrel just like you would a brand
new rifle. Properly breaking in should greatly reduce
or eliminate fouling and greatly improve accuracy
2. Re-check all screws on scope/mount and rifle for tightness after first 5
shots. Check again after 20 shots and periodically there after. If groupings
were good then spread for no apparent reason-- check for loose take down screw
or scope screws. These little used snipers have not really been "shot
in" yet with the actions seating snugly into the stocks as on a well used
rifle. Bring a white or yellow grease pencil to the range and mark all the
screw slot locations on the scope, mount and action. Check them occasionally
to monitor working screws. I have found the tang takedown screw has always
been the first to move on most of my rifles, then the forward takedown screw.
I have found backing the tang screw out even an eighth turn will make a difference
3. Sighting in to point of aim is quick and easy with the PU scope. After your
5 shot barrel warm up, off rests pick an aim point and shoot a three shot group.
Keep the rifle aimed at the aim point and don't move it while adjusting the
windage and elevation knobs until the pointer is centered on the group you
just shot. In this way you are aligning the scope to where the bullets just
hit (POI), so next group will probably be darned close to point of aim. The
toughest part is the fine adjustment of the knobs-it is hard to move them in
the small amounts necessary to pin point a bull at 100 yards so you may want
to try it at 50 yards first to make it easier. There are two screws on top
of the adjusting knobs that hold the silver elevation and windage calibrated
rings in place. Loosening these screws slightly will allow you to turn the
calibration rings to zero your settings. Be sure not to move the adjusting
knobs while doing this. Be careful not to over tighten these screws as they
will strip easily. There is plenty of clamping surface area holding the calibrated
ring in place and it does not require a lot of screw pressure.
4. Don't let the barrel get too hot! Shoot 3x5 and then give it a rest. Bring
another rifle or two and rotate through them. This lets you get the most out
of your range time but doesn't burn up one rifle.
5. Get to know your rifle. Record elevation settings for varying ranges and
ammo. Note where the first few cold shots hit so you can compensate for it
next time out and impress your buddies by screwing the mount on and hitting
a first shot bull. These things are that predictable and will hold zero that
6. Or you can not shoot it and let it just sit there and admire its ungainly
beauty. That is fine, too.
Suspect your scope knobs are moving between shots and spreading your group
but don't want to take the risk of disassembly and trying to tighten up the
knobs? Try this:
Once you sight the rifle in for the distance you wish to shoot, instead of
zeroing the calibrated rings, turn them so the calibrated ring stop tabs move
forward to the stop pin then tighten the screws. Between shots you can check
to make sure the stop tab is making contact with the pin and can be pretty
much assured that your reticle will be in the same position for each shot.
This is a fool proof way to eliminate the possible knob movement factor from
poor grouping problems.
Problem Group Patterns and Things
How are your 5 shot group patterns
using the scope? Are they random spread, couple flyers
but otherwise tight, signs of tight or loose stringing
diagonally or vertically. I have seen all of these
in my PU shooting.
Things to check for:
- Loose thumbscrew-- even though
it is a ""thumb"" screw you
have to use a screwdriver to tighten it down or
it will let the mount start moving only after a
couple of shots. Will cause a rapidly expanding
string with increasing distance between impacts
as you progress through the five shots. Make sure
to crank it down using the full force of one hand
on a screwdriver.
- Moving base vertical adjust
screws. Will cause vertical stringing or diagonal
in conjunction with an overly loose thumbscrew.
- Moving scope adjust knobs--may
be imperceptible at first and drive you nuts. Usually
will make a tight stringing pattern vertical or
horizontal depending on which knob is moving or
diagonal if both are moving. May make sudden post
first shot change in POI and then string the next
four shots tightly. This is because after the first
shot one or both knobs may move or jump to the
next friction point and then start creeping imperceptibly
- Scope knob backlash. Where you
move scope knob but don't see immediate corresponding
movement of reticle. This condition could allow
reticle to move freely with shot to shot recoil
although having apparent fixed knob position. Check
that the tiny scope knob locking screw is in all
the way and tight for the affected knob. I this
doesn't tighten the backlash problem up you could
have some loose internals.
- If you are doing well open sight
then I won't tell you to check your take down screws--
but check them anyway and often. Use a white or
yellow grease pencil and mark the slot positions
to see if the are working. Do this on all of the
screws on the scope mount, too, and on the thumbscrew
and base vertical adjust screws (one which may
be punched immovable anyway).
- Maybe your base is loose? This
is not something I have run across with my collection
but it is something to check.
- How I tighten my mount to base.
Bring thumbscrew to light finger tight. Lightly
tighten vertical adjust screws. Bring thumbscrew
to full finger tight. Tension vertical adjust screws
to final position. Torque thumbscrew in with single
hand on screwdriver.
Following is a tip on eliminating
scope knob movement on recoil as a cause for poor
Suspect your scope knobs are moving
between shots and spreading your group but don't
want to take the risk of disassembly and trying to
tighten up the knobs? Try this:
- Once you sight the rifle in
for the distance you wish to shoot, instead of
zeroing the calibrated rings, turn them so the
calibrated ring stop tabs move forward to the stop
pin then tighten the screws. Between shots you
can check to make sure the stop tabs are making
contact with the pins and can be pretty much assured
that your reticle will be in the same position
for each shot. This is a fool proof way to eliminate
the possible knob movement factor from poor grouping
Have fun and safe shooting,