M39: *** RESOLVED *** First shot in 5 shot groups @ 100yd are 4-6" high

[sakosf]

Which model of the M39 do you have? Also, WW2 or post war stock?

[kouye]

Which model of the M39 do you have? Also, WW2 or post war stock?

It's a '42 Sako/SKY with a wartime stock. Very nice bore.

[CDFingers]

It's possible you don't have full contact at the nose cap. I have gone by the Finn practice of having about 5 lbs of pressure on the barrel by putting oiled felt or cork at the nose cap, either on top or beneath the barrel. If your barrel floats through there, it might bend when it gets hot and then make contact.

Interesting problem.

CDFingers

[kouye]

It's possible you don't have full contact at the nose cap. I have gone by the Finn practice of having about 5 lbs of pressure on the barrel by putting oiled felt or cork at the nose cap, either on top or beneath the barrel. If your barrel floats through there, it might bend when it gets hot and then make contact.

Interesting problem.

CDFingers

I'll give that a shot. I also might add the tang shim back in. Looking at some older targets, the groupings were more consistent with the shim in place, except for the first shot anyway.

[sakosf]

It's possible you don't have full contact at the nose cap. I have gone by the Finn practice of having about 5 lbs of pressure on the barrel by putting oiled felt or cork at the nose cap, either on top or beneath the barrel. If your barrel floats through there, it might bend when it gets hot and then make contact.

Interesting problem.

CDFingers

Yes, about 5lbs of pressure sounds about right. I have a 1941 SAKO that did not seem to shoot right. I altered the number & placement of shims on this rifle with very positive results. I spent time evaluating how the barreled action set in the stock on this rifle. The bottom rifle in the photo is the 1941 SAKO. I bought it about 10 years ago

[kouye]

My first M39 was a '44 Sako. I was disappointed to find that it was glass bedded and it didn't even shoot well. Then one day, I picked up some Russian Match ammo, and BANG! it shoots very close to my M1A NM...for $1500 less...shoot horribly with Russian and Hungarian heavy ball, or any light ball.

[TRAP55]

Is the barrel floated from the hand guard? Next time out, remove the bands and hand guard, then try it.

[kouye]

Is the barrel floated from the hand guard? Next time out, remove the bands and hand guard, then try it.

Dang! I meant to do that today but I forgot. I'll try that too. Thanks.

[CDFingers]

The tang shim raised the action just a tad. If you took out the tang shim, there's one problem solved. Then go for the downward pressure.

Best of luck.

CDFingers

[kouye]

Okay, so I took the M39 out again with the barrel channel corked at the muzzle. Results are about the same, maybe marginally better.

I removed the handguard (still with the cork under the barrel at the muzzle) and all of a sudden, 1.5" groups. All were high groups, but I didn't making any adjustments after the first shot.

This worked for Russian heavy ball, Russian match, and PPU match.

So now all I have to do is do a better job of sanding the handguard and test with and without the cork.

So glad this is resolved, it was driving me nuts. The rifle is great in all other aspects but was not shooting well.

[sakosf]

Do you need that cork under the barrel? I would think if you adjust the amount & placement of the shims, it might not be necessary to have the cork there.....I would do that before sanding the handguard on a M39 SAKO/SKY.

[kouye]

The cork under the barrel at the muzzle didn't help. However, I had been shooting it w/o the cork but with the handguard on and it had the problem.

I've done a quite lot with the shims and nothing changed until I removed the handguard.

I can try swapping handguard with another M39 at least temporarily to test the theory more.

[Flyin Brian]

The cork under the barrel at the muzzle didn't help. However, I had been shooting it w/o the cork but with the handguard on and it had the problem.

I've done a quite lot with the shims and nothing changed until I removed the handguard.

I can try swapping handguard with another M39 at least temporarily to test the theory more.

If you ever get up this way, I have quite a few spare M39 handguards, and a new M39 stock that you could try it on. I also have some ammo that would rule out any issues there

[TRAP55]

Told ya so.
Had one do that to me too, it's those little things that'll make ya pull your hair out trying to guess what it is.
Steal some Play-Do from the neighbors kid. Roll up a piece into a long real thin string, and lay it on top of the barrel the length of where the handguard sits. Set the HG straight down on top of it, and put the bands on tight. Reverse that process, and sand where the Play-Do string is smashed flat. Repeat until the PD is only smashed about 1-2mm thick. Then give the kid his Play-Do back.

[kouye]

If you ever get up this way, I have quite a few spare M39 handguards, and a new M39 stock that you could try it on. I also have some ammo that would rule out any issues there

Thanks Brian! I have 5 handguards to try...and I can swap stocks with 2 other M39's that I have, the 4th one has the bedded action so I don't know if that one would work...

As for the ammo, the behavior was the same with 3 types of ammo and it happened with every group, 6 groups each range day, 5-6 range days...until today...

Trap55 - I won't give the Play-doh back...