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Bush Chook

Hi All,

I've recently fore-end stabilized and bedded my Dad's Sako 85 Finnlight in .260 Rem. This significantly reduced group sizes overall - which was good -but hasn't fixed its flier problem - instead it appears more pronounced. However, this apparent worsening of the problem could be an illusion due to the fact that overall group size has reduced.

The Symptoms:

While this has been an ongoing issue, todays result was quite the best example of this problem.
I was doing a graduated load test of three shot groups about 1.5 grains over the maximum recommended, increasing in 0.1 grain increments (just being cautious) per group. Of this string, virtually every single group consisted of two shots touching and one flier. As the rifle neared a good load, this “flier” worked its way down to the other two (forming a nice triangle group) and then on the other side of the good load, it worked its way out again. Over about 0.7 grains of powder charge it came in and out twice – forming two good loads, and several also-rans. Group sizes ranged from about 1 – 0.5 MOA so the results aren't that shocking but even in the good load the flier started becoming noticeable at 200 yards. The flier shot was usually the first or third shot, but was sometimes the second.

A sweet spot that I investigated further down the powder charge scale also exhibited the same issue – two good shots and one lonely, unwanted little bullet hole than wandered in and out again.

Possible Causes Investigated:

One of the reasons for doing the bedding job in the first place was to eradicate these nomads so I was particularly careful to relieve all parallel wall metal and the front, bottom and sides of the Boss. (To those who are familiar with the 85 bedding system, the boss fits into a floating alloy lug which, in this case, had been thoroughly glued in by a somewhat-wanting gunsmith. I ground out the front, bottom and sides of the Boss recess. I also ground a triangular shaped piece of material from the lower rear of the Boss recess forming a “trap” for bedding compound behind the boss. The result of this was better than expected, with a thin line of alloy-on-Boss contact at the top rear of the Boss trapping a strong layer of compound against the Boss further down. This seems to have held up well as after 50 shots no signs of cracking have appeared.) I relieved virtually everywhere else with a layer of tape – the only areas with flush contact were the two beveled sides of the base of the action, the back of the boss, the flats and the knox. Maybe this single tape layer is insufficient at high risk areas like the back of the tang and the sides and front of the Boss? The action fits into and out of the stock very smoothly and doesn't need to be walked or wiggled out. I went over the fit of the action after my last round of fliers and found it was pinching in a few areas which I duly relieved. In my very limited experience it now feels spot on. Its also lightly greased except around the Boss. Are there any problem areas with the 85 action that need extra relieving?

The bore looks all good. I have been through it several times with a bore scope, most recently after cleaning after today's shots and apart from a little crazing at the throat and the odd scratch on the lands, I couldn't see anything untoward. However, I am no expert, so it's possible. The crown also looks sharp and undamaged. The barrel had been completely copper-de-fouled before today's shots so it wasn't copper buildup.

The extreme spreads of today's loads were mostly all under 20 so it wasn't wildly varying velocities.

It could be my shooting technique. Are there any habits which cause fliers? I'm fairly sure I wasn't flinching or jerking the trigger (most of the time) but it may have been some other subconscious habit.

Final Musings:

I was wondering if maybe this wasn't in fact a flier problem but just the result of the barrel harmonics of this particular rifle coming down to and going away from a good load. Looking at the groups of the good loads at 100 yards today, one wouldn't say there were fliers in the group. It was just on either side where the walkers appeared. However, as usual nothing in rifles is simple and at 200 yards the fliers appeared with the 2 good shots close together. It just strikes me as very curious that apart from the good loads virtually all groups had a flier.

So what do you guys think? Bedding problem and relieving required? Shooting technique issue? Natural barrel harmonics? Something else?

Thanks very much!!