Tikka T1x

[Tony Z]

I got to do the 22 Magnum barrel today. Fairly straight forward machine jobbie. The factory shank is considerably undersized at 17.65mm where the action bore is 17.75mm. That is 0.1mm or 4 thou clearance for you dinosauruses. So i cut the shank to 17.73mm and machined a flat where the set screws lock. This will prevent any burring locking the barrel in the action. This should be mandatory if this rifle is to be made to switch barrels. Replaced the set screws as their socket is oversized and they are 2mm short as well.
The OD of the stock barrel is 22.8mm at the knox. I cut the 22 Mag barrel to 23.5mm for around 0.25mm radial clearance of the forward action sleeve.
I got hold of a 17 HMR magazine last week and after setting the barrel in place today i cycled a few rounds. A bit sticky at first when chambering but after cutting a slight ramp at 6 o'clock it cycled through the action flawlessly. The barrel profile is considerably heavier than the 22 LR barrel so the action has been transfered to a T3 varmint stock. Hopefully i will get to fire it this weekend.

[Camel]

Nice neat job there Tony, anyone would think you had done that type of thing before.

[johno1]

Great job Tony can't wait for the range testing.

Would it be a proposition to simply re chamber a 22 lr to 22 mag or do you think the poor fit of the original barrel as described would make it not worthwhile?

Johno

[Tony Z]

Johnno 22 LR barrels are 0.222" to 0.223" groove diameter. A 22 Mag uses 0.224" jacketed bullets so 22 LR barrels are too tight and pressure will likely exceed case strength. The other issue is the twist rate. A 22 LR runs a 16 twist that works fine with a lead bullet. A jacketed bullet even at the same 40 grains would be borderline stabilization at 22 Mag velocities in a 16 twist. 14 is pretty standard.
Anyway i intend to use both barrels and am looking to modify things so the barrels can be switched without removing the action from the stock.

[johno1]

Tony, its a bugger getting old I knew that but must have been away with the fairies, I seem to be in constant contact with them lately, even buying the 5mm rem mag

Anyway a lovely job and looking forward to see how it performs

Johno

[Tony Z]

Update on the 22 Mag barrel. Shit conditions but the barrel shot well with a couple of ammo brands going under an inch at a 100 yards. Namely both CCI and Hornady 30 grain tipped bullets. Other ammo was not so hot like Win Power point which was best descibed as a pattern. Really awful actually but probably to be expected from an unjacketed lead bullet. The old style Win 40 grain HPs went into around 1 1/2".
I went on to shoot some other rifles and let the 22 Mag barrel cool.
An hour later i shot it again and noticed a subtle POI shift. About an inch higher then back to original POI as a few groups warmed up the barrel. Then i let it cool and shot it again to the same higher POI. Then i called it a day.

At some point i had decided i would dismantle the rifle and cut some clearance in the barrel tenon bore at 12 o'clock to create contact points only at 10 and 2 o'clock to create a more positive re zero between barrels. Sort of a upside down V block arrangement. Once i dismantled the rifle and had a far closer look and did some bore measurements that i had avoided to start with because of interference with the set screw locations at 6 o'clock, i discovered Tikka has done this from the factory. It is only around 0.1mm eccentricity but there is no doubt the T1x is set up to swap barrels but never informed anyone.
The tenon i cut on the Mag was straight, no step like the factory 22 LR barrel seen in the pictures above. The eccentric bore comes short of the overall tenon length, hence the reason for the step and hence the reason for my POI shift. When the barrel was inserted it was concentric at the rear, a perfect fit. The front is eccentric and when the set screws are torqued, there is uneven contact and flexing of the tenon. So as temp alters, so does flex and ultimately POI. Easy fix today with the step cut in.
This may not improve things much, if at all groups wise, but it will bring the barrel into a neutral set so POI should stabilize. Hopefully.

[lee_enfield223]

Nice pictures and a great update

[Tony Z]

An update with the 22 Mag barrel in the T1x at a 100 yards. Bit of right to left that caught me cold in the second group, but i got the window narrowed down to get some sense out of it.

I settled on 30 Vmax as a test bed for further ammo testing and replaced the 2-7 Burris with a 3-9 Conquest. I weight batched the Vmax ammo to see what would transpire after reading some yank forums where shooters are seeing 150 fps or more variation in velocity in many current batch lots of most all 22 Mag ammo.
You be the judge but to me there is a definite bullet impact shift as you shoot the different weights. Random selection with the first batch was a bit so so. Another batch shot at the end of the session looks to be somewhat better and somewhat worse but i put it down to fouling and barrel heat at the end. I tried some CCI and Fiocchi 40 HPs midway through and as expected they were indifferent as well as around 3 inches lower.
I think that with a clean barrel, weighed ammo and a set of flags as well as a bit more grunt in the scope, the T1x could do five consecutive groups under MOA. Pretty rare these days with the ammo quality that i am seeing since i sold my other magnum.

[lee_enfield223]

Do you think that since you machined the step at the back of the barrel shank that your groups have stabilized, also not bad accuracy from those 30gr Vmax

[Tony Z]

Lee, yes the climb i saw previously has clearly gone.

I did a search on tuners on 22 Magnum rifles that came up blank barring once instance of a Limbsaver.
Having done a lot of tuner development for 22LRs over a number of years, it seems incredible that no-one has screwed glued or pressed a tuner onto a single 22 Magnum barrel. Maybe it has been done but not reported. I can see why not as it really has never had a place in any form of organized competition.

[lee_enfield223]

Yes I was thinking of trying a tuner on my t1x in 22lr, but 22mag ?? now that's a great idea, or even on a 17HMR

[Tony Z]

So it's been raining a tiny bit up here in Townsville and i got a little bored.
Built two tuners. A Calfee style for the 22 Mag barrel and an adjustable type for the 22 LR barrel, not yet completed.

I have set the Calfee tuner at the 9th harmonic using the Rx formula. See if we can get some sense out of it after the not so great result with the 308.
No ranges open this weekend and all other access i have is saturated so it will be a couple of weeks away before i get to test. That is if the rain ever stops.
Here are the numbers for those wanting to check for me. (Old Trev)

Barrel length. 20.45"
Acoustic length 23.01"
Tuner bore of 0.819"
End correction 0.246"
Physical length 22.764"

[Old Trev-39]

Hi Tony,
I agree with the final figure.
How are you holding out with the flooding?
Cheers,
Trevor.

[Tony Z]

All good Trev. Golf is out for a few weeks though.
Thanks for running the numbers.

[Tony Z]

Just a couple of pics of the tuner on the 22LR barrel.
Just needs a bit of counterboring on the barrel adapter and some index markings and it's done.