Accuracy Problems With M1917

[Patrick Chadwick]

I think that one day I should get around to making a properly thought-out decision tree for this, but here goes with a first approximation... Updates and corrections are to be expected!

Precondition: make the usual checks of the rifle for head clearance, damage-free crown, barrel fit in channel, plausibly tightened system screws etc. These have been described several times in these forums.

1) Pick a range, preferably 50 meters/yards for a very first trial, since you have no idea of the relationship between POA and POI and want to be reasonably sure that the shots will be on the paper!

2) Take some standard 30-06 commercial ammo, nothing exotic. On an M1917, put up the backsight leaf and set the slider as low as it will go. Shoot off a sandsack or good rest, and use a 6 o'clock aim. This will put the shots on target in a typical 8" black at 50-100 yards/meters. Shoot five shots.

3) Are all bullets on paper? At this stage, it does not matter where!
YES – go to 4)
NO - the rifle has a defect. Not an "issue". A defect. Go to 6)

4) Are the bullet holes round?
YES – go to 7)
NO - this indicates keyholing or marginal bullet stability. But some bullets take a short distance to stabilize. If the POI is central enough to permit it, increase range to 100 and try again.

5) Are the holes round now?
YES - it was the bullets taking a while to stabilize. Go to 7)
NO - You have a problem. Go to 6)

6) The cause could one or more of
a) Seriously worn throat
HELP: reloads with the thickest flat-base bullets that will chamber, set out as long as they will go.
b) Damaged or bell-mouthed muzzle and/or crown.
HELP: recrown worn/damaged crown. Counter-bore worn muzzle (already doen in this example).
c) Bullet diameter too small for rifling – since you are using commercial 30-06 ammo, the rifling must be seriously worn.
HELP: reloads with the thickest flat-base bullet that will chamber.
d) Bent (i.e. damaged) barrel or barrel being bent by hard bearing on the barrel channel (warped stock)
HELP: Straighten barrel. Ensure correct fit and/or float of barrel in channel. Correct or replace stock.
- All of the above must be fixed or at least mitigated before it makes sense to continue to 7)

7) Do you have what may be called a group at 50?
a) Diameter 3” or more. Not good enough. Return to 6) and check carefully.
b) Less than 3”. Not brilliant, but usable. Go to 8)
c) Less than 2”. What I would expect from an M1917 before optimization. Go to 8)

8) Horizontal POI
Is the group within the black at 50%.
NO: Go to 6) d)
YES: Drift the foresight blade (if required) to correct the horizontal position.
If the correction puts the blade more than 1/16” from the center line, then you may still have a slight problem under 6). Go to 6) and repeat
If the correction requires less than 1/16”, go to 9)

9) Vertical POI
After any necessary correction as under 8), the group should be entirely within the black at 50. But only if you are using the sighting and aim as in 2).
Group is now in the black?
YES – go to 10)
ABOVE – the foresight blade may be too short. Replace with a higher blade. Go to 2)
TIP: Lee Enfield blades fit!
BELOW – I have never experienced this with a military rifle. A bent barrel is a possible explanation.

10) You have a rifle that groups sensibly on target at 50.
Go to 100 and repeat!


Note: The above may seem complex, but if you perform all the steps in sequence and carefully, you will reach 10) much faster than if you just dive in and plink away!


Good luck with your rifle!

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