I no longer own one, but if memory serves, I don't think they're meant to be adjustable. Just a screw on cap, with detents to hold it in place, isn't it?

 

It is not as if the torque wrench will work.
One time the cap screws on comfortably and when taking it off it seems to be a job for vice grips. It would be interesting to see if there are adverse results when you hear the first click of the detent and count up accordingly. There is no rule set by Cooper and it difficult to say there is a "Too Tight" point. Next opportunity to shoot is Sunday and if there are few attendees then I will see if I can find a suitable starting point. For you I will take both rifles . . .

The JSR has 6-7 detent clicks from the first to stop. It will fire on the first detent. It will fire when backed off one revolution from the first detent.

The Montana Varminter has 9-10 clicks.

I may be worthwhile to start at the last detent and go back one or two to start and then 3, 4, 5, and six if conditions are favorable and five shot groups will be telltale hopefully.

 

The Montana Varminter was tested first and the groups were shot LL, UL, UR AND LR.
The first five shots were with detent -2 from tight. and measured 0.63, then at -4 for five shot, then -6 for five shots, and at -8 there was no resistance but there were two distinct groups so that aspect was abandoned as I was also getting FTF.
At this point I reversed to -6 for five shots in the same target (UR) to the same point of aim for 1.20" group. Then to the UL for another five shots and the 10-shot group measured 0.96". Back to the LL and holding on the 7 and the four shots in the 10 ring measured 0.65. Why four shots? Someone was talking to me and I held on the X and that shot is part of the first five.

Whether a little bit less pressure is good or not remains to be seen but I will play with that though over the next few shoots. I went two detents at a time as there were too many shooters at the range so this would speed up the process. A little mark on the cap is a good thing.

 

The JSR was tested using the same sequence LL, UL, and UR. The detent was moved -1, -3 and -5 (very close to lose) and that group opened up with a 7 at 7:00. The four five-shot groups worthy of consideration measured 0.96 to 1.37"

There was sufficient information garnered from that I went back and shot four groups at about -2. The groups measured 0.94", 0.89, 1.28 and 1.22"

How tight the cap is attached depends on whether you can crank it to "Farmer Tight" where no one would ever get it off or finger tight. As stated earlier, a small mark on the cap at the detent will always serve as a reminder and from there one can adjust accordingly. Final conclusions will undoubtedly take some time.

There was virtually no wind and the temp was about 6 degrees C.. The ammo was Remington Eley Match at 1062 published velocity. All shooting was from a Harris bipod with a rear sand bag.

As to the shooter I was trying to help at the time . . . first he had to turn his scope 90 degrees. The scope is something never heard of before, he was using HERTER'S ammunition (cheap) but he was grouping at 25, 50 and 100 yards.

 

57m bolt

I received a reply from Cooper Firearms Service Coordinator ,
"57m Bolt is not adjustable , Notches are for Cosmetics"

I did find that the cap backed out enough would
decrease firing pin tension to the point of FTF .

.... skwerl

 

The first Cooper I got had the cap turned on to Farmer Tight. A leather glove and a pair of pliers to get it to break free. As I loosened off the cap yesterday I did get some FTF.

Cosmetics . . . looks better with it on than off? There was an article going around some time ago about Hollywood actresses . . . they all looked better with their bondo on. Prime Minister Trudeau's picture was followed by the southend of a northbound horse.

 

Thought I'd chime in here- from my archives- from Dan Cooper himself, 2006.
I spent a lot of time tuning my 17 HMR LVT. All for fun. The "click it 4 times" refers to from the bottomed (all the way in) cap position.
Sadly, I don't think the gun has been out of the safe in 10 years....
HTH.

RE: M57 firing pin retainer cap setting

Rob Behr <rbehr@cooperfirearms.com>
To:
xxxxxx

Thu, Jun 15, 2006 at 4:32 PM

The best way to tune our knob is to click it 4 times and shoot a group. Then back it out once and shoot another. By monitoring the position you will find a setting that shoots better for that particular load. Take care, Dan Cooper.