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Re: Stiller Predator Short Action
Sorry about that,
here is the article in its original form.
Hi All,
At the request of Col48 I have undertaken a dimensional accuracy check of the Stiller Predator action.
This action has a polished finish and the bolt has an Armoloy hard chrome finish in order to reduce possible galling with the mating parts.
Now, as for as I know Armoloy cannot be applied to stainless steel which makes me wonder if the bolt is made out of chrome-moly steel.
Galling is said to be a problem only with stainless on stainless, not stainless on moly-steel, so I cant see the point.
The OD of the action measures 1.3502-1.3505 a difference of .0003 over its length.
The bore comes in at .7062 and the bolt diameter is .7028 which is within the max .004 tolerance specified by Stiller.
The bolt lug ways are .998 diameter with lugs being .986dia. over the highest point. A clearance of .006 a side although this is not a critical dimension.
The receiver threads are the usual Remington spec 1 1/16x16 tpi Unified and measure 1.0009 basic minor diameter, which is within the specs for a class 2A fit.
Now for the important bit, concentricity, squareness and headspace.
The key to good concentricity is that all measurements are taken from one datum.
This would usually be the bolt bore so I made a .706 mandrel, locked the action to the mandrel and supported it between two vee blocks.
Using a finger type dial test indicator of .0001resulution I rotated the action and recorded these dimensions.
The outside diameter of the action is concentric to the bore within .0003,
The threads are concentric to .0005 and the lug ways .0007, thas all well within one thousandth of an inch on concentricity.
The firing pin hole in the bolt is concentric within .0003 to the bolt diameter.
The action face showed no measurable movement on the DTI which translates to being exactly perpendicular to the bore.
The depth from the front face to the bolt lug recess face is 1.1594 at both points, again completely square.
With the bolt inserted the bolt face, from the action face was perpendicular to within to .0002, measured at three points.
Being a Remington clone this action headspaces at .700, the distance from the barrel shoulder/action front face to the bolt face.
Taking measurements at three points around he bolt face the results were .7008, .701 and .7009.
Finally I measured the trigger slot to establish its concentricity to the bore and came out to within .0015.
This test would have been much more complete had I had a top end custom and standard Remmy actions to which to do a comparison.
However, I consider the Stiller Predator action to be a very precisely machined, accurately dimensioned and very well finished. Thanks Colin.
Ian.
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