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  #1  
Old 06-27-2007, 11:24 PM
Brooks Brooks is offline
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Default Sako vs. Cooper strength

From the Cooper 21 thread I see the consensus is that the Cooper action should not be used for high end loads with some rounds (PPC and I assume the BR cases). I have a Sako 579 in 6BR I was thinking about rebarreling to a switch barrel 17BR and 20BR. I am a lot like Todd K. as I load them pretty hot. Do you guys feel this action is sturdier than the Cooper or should I opt for something stronger?
Thanks for the help
Brooks
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  #2  
Old 06-28-2007, 12:33 AM
Daryl Daryl is offline
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The Sako action will suffice just fine.
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  #3  
Old 06-28-2007, 01:41 AM
Bryce Bryce is offline
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Brooks,

The issue (probably more correctly - "perceived" issue) was only in relation to the Model 21 in a PPC chambering and only has to do with the bolt opening becoming tight with hot loads. Nobody is suggesting that it is a fundamental safety issue whereby the action is essentially unsuitable for the chambeing and is likely to fail as a result.

The issue seems to stem from the fact that the action was designed for a 223 case head chamberings that due to the smaller diameter of the case (than a PPC) generate less load on the bolt. The skinner cases also leave more steel around the chamber in the barrel tenon area which must help lessen the amount of expansion that happens on firing.

Cooper chambered the 22 and 6mm BR rounds in the Model 22 action which is much bigger than the Model 21 and now the BR's are chambered in the Model 16 action which was designed around the WSSM cases, it is plenty strong !!

I note that Cooper now also chamber the PPC's in the much heftier Model 16 action and not the 21, I have no doubt that they did that for a good reason.

I don't believe that there is any strength issue with any Cooper action/chambering combination and hope that nobody took the comments that way. The little idiosyncracy is only with the PPC in the Model 21 and really only stems from the fact that the Lapua 220 Russian brass is exceptionally strong and that there is data out there for PPC's built on extremely strong custom actions. It isn't so much a case of the action not being suitable for the calibre but a case of the calibre potentially being loaded with data not really suited to the PPC factory actions. The same would apply if one was to try and load an AI Sako 6PPC to extremely high pressure in Lapua 220 Russian brass. Keep the loads to the original SAAMI 22 and 6mm PPC-USA factory (Sako) load pressure levels and all will be well in the factory actions, both Sako and Cooper.

As a point of interest Sako changed the PPC's from the small action to the madium action with the Model 75's.

My Cooper 6PPC is loaded routinely at what are essentially maximum loads for a factory action with no issue at all. Bolt lift only got hesitant to open when loads exceeded that pressure and velocity level by a good margin. My comments about the suitability of the Cooper 21 for a 20PPC really only stemmed from the fact that the 20PPC is highly likely going to be loaded well over 50,000PSI factory load type levels since most data available for the 20PPC chambering was developed in strong custom actions generating far higher pressures !!

So far as your Sako 579, it is a much bigger action (than a PPC Sako or Cooper 21) and is designed for the 308 case head rounds so is perfectly suited to a 6BR loaded to sensibly high pressure. The only issue that may arise is that some 20BR data would have come out of custom actions with small firing pin holes, your Sako probably has a fat pin and a slightly loose fit which could well lead to primer cratering or premature piercing.

Bryce
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  #4  
Old 06-28-2007, 03:24 AM
Brooks Brooks is offline
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Default Bryce my man

thanks so much for the info. The only question I have now is given a choice would you choose a Cooper over the Sako to build a switch barrel in BR? And why? I love the Coopers but have a Sako needing something done with it and it feeds the BR round flawlessly.
Thanks again,
Brooks
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  #5  
Old 06-28-2007, 04:12 AM
Bryce Bryce is offline
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Brooks,

My only issue with the Sako would be the lack of a good trigger. The Cooper isn't a bench rest trigger but it is rather more adjustable than the Sako unit.

If you were buying a Cooper to use as the basis for a rifle and would use the factory stock etc a 6BR chambered Model 16 seems like a hell of a good place to start !! Use the factory 6mm barrel and get that 17 and 20BR as well.

If you have the Sako already and are happy with the trigger pull then that is the obvious one to use, maybe with a firing pin bushing. I loved Sako's and used to have nothing else, these days I am a bit more open minded and will use what works best.

I am not sure I should type the second half ........

Personally, if going to the bother of a custom rifle and wanting a real accuracy, with the cost of the smith work, the stock, the trigger, barrel etc I'd start with a custom single shot action like a Bat or whatever takes your fancy. I have a Kelbly due here soon and have had little experience with custom actions but have realised the limitations of even good factory stuff after 25 years of "making do" !! Slow learner !!

It just seems to me that if you can afford the difference for a good action the rest of the components and the smiths time costs the same so why not build the real deal !

Bryce
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  #6  
Old 06-28-2007, 01:31 PM
Daryl Daryl is offline
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I have a Timney trigger on my L579. It's set at 1-1/2 pounds (25 ounces) and does a great job, crisp and clean.
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  #7  
Old 06-28-2007, 07:12 PM
Bryce Bryce is offline
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Good point Daryl, forgot about the Timney, I had one myself !

While it isn't a "competition" or "match" trigger it is in the same sort of pull quality standings as the Cooper factory trigger.
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  #8  
Old 06-28-2007, 11:19 PM
Rick in Oregon Rick in Oregon is offline
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Default Trigger for Sako

FWIW, I've got a number of Sako's, one has a Timney, another has a Canjar single set trigger. Both are L461 Vixen's used on varmints, one, a Mach IV is used off the bench with the Canjar, and it is set at 8 ozs. The other is a sporter weight in 223 with the Timney.

Both rifles with these triggers were vast improvements over the factory units. The Canjar unit lets off with the same feel as my Jewel triggers when fired in the 'set' mode. The Timney is as good as any of my other aftermarket triggers that cost twice as much.

To me, it appears you don't have to pay over $200 for a very good trigger for a Sako.
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  #9  
Old 06-29-2007, 07:20 PM
Brooks Brooks is offline
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Default Thanks guys,

a lot of great input. I do have someone's after market trigger which is set at 1.5 pounds and crisp as a Cooper. Probably will opt to keep the Sako as it is a repeater and not intended for benchrest only for the occasional crow and yote.
Thanks agian,
Brooks
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  #10  
Old 08-04-2007, 11:47 PM
Mudgegonga Mudgegonga is offline
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Default Sako L461 PPC

Can a L461 223 bolt head be easily changed to PPC diameter? Will the PPC case feed from a L461 magazine?
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