Sako Upward Pressure in 1979 AV

[Deleted member 14372]

I read as many old posts as I could before posting this. If it already answered let me know.

It seems the older Sakos were built and bedded with upward pressure. My AV has small gaps along the sides of the barrel but none under the tip. It allows la .001 shim under it that gets a little sticky near the tip suggesting some pressure there. When I tap the underside of the forearm there it “rattles” a bit indicating the tip is not so tight against the barrel. When I squeeze the stock and barrel together the “rattling” is deadened.

I opened her up and there is no obvious pressure bump. Smooth barrel channel back to front.

It shoots pretty good but had some vertical stringing yesterday. Wondering if this is supposed to be floated (given the gaps on the sides ) or if it needs a bump / shim near the tip.

I don’t want to alter this rifle but might add a shim if it is indicated

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[Deleted member 14372]

Here are the groups yesterday. Larger group first .070 off the lands. Smaller group second .050.

Vertical stringing on both. Horizontal seems rock solid.

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[Deleted member 14372]

The bottom shot on the left group was me. I remember that pull.


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[stonecreek]

It wouldn't hurt to try a shim in the barrel channel just to see how it reacts.

 

[bloorooster]

BD
You could be dealing with a few different factors. Tho it is said that some rifles are built with forearm pressure at the tip, it’s not mentioned anywhere as to how much pressure is involved. Or…was involved in 1979. Things could have changed, as far as wood shrinkage over time. A test shim won’t hurt anything I suppose. I’d imagine that the amount of upward pressure needed is slight.
The next factor could be your rings, tho they are vintage Sako rings. If the rings are not squared and true (they can be warped by over tightening) this could be your problem. I’ve had that happen before.
Next could be your scope, sometimes the elevation turret is not holding the adjustment set. Try a different scope that you are certain about.
Next is factory ammo, and with the vertical strings you’re getting it almost stands to reason that the ammo could be your problem. Try some different ammo.
Make sure you are getting the action screws snug each time you put the rifle back together, paying close attention to how snug, not over tightening and compressing your bedding even more each time you disassemble. Wood is softer than steel as we know, but if it’s slightly compressed a little more each time, eventually the bedding will suffer from it. It could turn out that you’re going to need a shim at the tang instead of the barrel channel
My thoughts only.
Good luck
Edit: just noticed that you are shooting hand loads..the second group is just over an inch at .050” off the lands. That’s a pretty good jump , maybe try .007-005” off the lands.

Bloo

 

[Deleted member 14372]

Thanks. At the range now. .030 today. Getting closer. Gonna do 5 w a shim and five without. Will send pics.


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[Deleted member 14372]

Ok so the goal here is to see if the rifle needs more upward pressure since it rattles a bit when you tap it. My shim was .0035 and thick enough to eliminate the rattle.

I shot 3 with the shim then 3 without then 3 with.
This was with:

This without

First shot 1.4” low

This was with

Vertical range 1.0”

I know it’s not a lot of data but added to yesterday it seems like this rifle wants a bit more pressure at the tip of the forend.

The action screw is as tight as I can get it.


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[Deleted member 14372]

Conditions were ideal. 70 f. No wind. 5 minutes between shots. Barrel cool.


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[icebear]

A couple of comments. First, sometime during A-series production, Sako changed from upward pressure at the tip to free-floating the barrel, so the barrel may or may not originally have had tip pressure. The photo of the barrel channel appears to show that the last inch or so at the tip is finely finished, suggesting that the barrel was floated at the factory. This doesn't mean it won't shoot better with a shim. Every gun is different.

Second, manipulating the barrel and forend for "rattle" is not the best way to check barrel fit. The standard gunsmith's tool for this is a dollar bill. If the barrel is floated, the paper should slide freely all the way back to where the barrel starts to widen out for the chamber. A non-floated barrel should float between the chamber and an inch or two behind the tip. The wood, or a shim, should exert only upward pressure. Any side contact anywhere along the barrel channel will degrade accuracy. Back in the day, a lot of gunsmiths would full-length bed the barrel into the stock. I disagree with this practice as it leaves the barrel vulnerable to warping of the stock. Side pressure does not appear to be an issue with this particular rifle, but I am addressing the general case.

The rifle in the photo is a Tikka M55. I believe Tikka has always built their sporting arms with fully floating barrels. All of mine (2x M55, 1x M65, 1x M695) have floating barrels, apparently from the factory. The M55/M65's are all tack drivers with factory ammo. The M695 is a bit less consistently accurate, but performs well with the right handload.

 

[stonecreek]

he standard gunsmith's tool for this is a dollar bill.

I see by the photo that inflation has increased by 5X since the standard gunsmith's tool for checking a floating barrel was established.

 

[Deleted member 14372]

Without any shim it will not allow a dollar bill to go under the barrel at the tip. It will allow it further back but not at the tip. That is why I thought it was meant for upward pressure.


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[Deleted member 14372]

Can I float it by shimming at the front action screw? What was the manufacture’s intent?


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[stonecreek]

Yes, you can make the barrel float by shimming under the recoil lug, but that was not how the manufacturer meant it. That doesn't mean that it wouldn't work. Floating a lightweight barrel usually doesn't do well, but the barrel on the A-V is fairly beefy, so it might be worth a try.

 

[Deleted member 14372]

So you think it was intended for the forend tip to touch the barrel even though it is smooth (no hump)?


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[bloorooster]

I kinda think your gun is ok. How much load development have you worked with? The shim in /shim out shows no real evidence of change aside from the lateral change of the group spread.
These are the same type of results I have with some of my rifles when I have the wrong loads , and even more so the wrong mind set. Shooting handloads can be very satisfying when it all comes together. When it doesn’t , and I sit there at the bench adjusting and readjusting the set up, my form and everything else I can blame for poor performance, I get the same groups as you .
Whether you use a $5 gauge or $100 . Nothing will come together until you find the right load or at least get closer than you are. Be patient, be calm, let the results come, before you wear yourself out and wear the blueing off of the action screws.

Bloo

 

[Deleted member 14372]

Thanks! [emoji6]


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[Deleted member 14372]

I am having fun with this. Just would like to know the Sako part of this: meaning is that rifle built for upward pressure or to float. My new 85 is definitely a floater. My 1972 FinnBear is not. Interested in Icebear’s comment about the A series going to free floated. Seems like another Sako mystery!


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[bloorooster]

Whether your Sako is a floater or sinker..poor accuracy , does not make it a turd!
Does your Finnbear shoot better? I’d almost bet it does.
Bloo

 

[Deleted member 14372]

I haven't really put it through its paces yet and haven't loaded for it. This damn full time job of mine is keeping me too busy! I shot some Sako factory ammo through it recently and I recall it liked it.

 

[Bucktote]

Hi Bernie's Dad,
I have an AV30/06 that Ijust restocked and am zeroing for the deer season. I have a FAT Wrench and it says the torque on a #6 screw should be torqued @ 20 inch pounds Max. so that's what I did on the recoil lug screw & #18 for the trigger/tang screw. Most of our guys don't need a Fat Wrench to torque the action screws (bolts). As for a hunting rifle I see two of the 3 shots are really close, so could it be you? rather than the rifle, scope, bullets, powder load,free-bore, lands distance??? Just my thoughts, if your barrel is not touching the sides of the barrel channel, you might try the shim under the recoil lug as Stonecreek suggested. That is where I would start, but your shots show two very close hits and well within killing acuracy. My AV targets are very similar to yours, (see fouling shots thread). Have fun & best wishes!! B/T