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Stugotz
01-04-2008, 09:55 PM
Can anyone shed some light on what M.L. McPherson means by "pinning" a Picatinny rail to an action in his article about the Savage M-12 in this month's P.S.? Is he using an additional means of attachment???

RPrecision
01-05-2008, 06:41 AM
However i pinned a 1913 rail on my savage. I mounted up the reciver in the mill and reamed a .001 under 1/8 hole through the base and through the rear portion of the reciver. Pressed in a 1/8" dowl pin and presto.

dont know if thats what you talking about :)

Jkob
01-05-2008, 10:13 AM
IMHO, and probably mine only, I think that the reason the Ruger #1's are so inacccurate in some of their rifles is due to the dowel pins in the Rib. I suspect when the barrel gets warm there is a bit of torque applied to the barrel by the rib and causes a shift in POI.

Anybody?

wnroscoe
01-05-2008, 11:48 AM
However i pinned a 1913 rail on my savage. I mounted up the reciver in the mill and reamed a .001 under 1/8 hole through the base and through the rear portion of the reciver. Pressed in a 1/8" dowl pin and presto.

dont know if thats what you talking about :)

Bingo, that is a pinned base.

Dave Short
01-05-2008, 12:10 PM
IMHO, and probably mine only, I think that the reason the Ruger #1's are so inacccurate in some of their rifles is due to the dowel pins in the Rib. I suspect when the barrel gets warm there is a bit of torque applied to the barrel by the rib and causes a shift in POI.

Anybody?

I believe it has more to do with the forend attachment. Why don't you test your theory be removing the pins (or the rail)?

-Dave-:)

Crow99
01-05-2008, 12:58 PM
Re: The Ruger No. 1.... I KNOW that one cause of inaccuracy is the dowel pins in the base. Some years ago I relieved the rear dowel pin in a couple of these and accuracy did improve. I seem to remember as the barrel heats, there being 3" or so between the pins, that you can get up to .003" linear expansion, depending on the actual temperature change. If the pins are in full contact, you definitely tend to get warpage. Relieved the front and rear of the rear dowel pin hole with a round file and there was definite improvement. I seem to remember that I also glass bedded the rib to the barrel (with release agent) so there was better fit / contact and this also helped. The rib is definitely an accuracy weak spot..

Another factor of course is the forend bedding.... but not in this discussion..

themachinest
01-05-2008, 01:40 PM
Stugotz,
In the ps article McPherson is trying to add rigidity to the action. He is concerned with the lack of bedding area for the rear of the Savage action and the subsequent misalignment or stress induced when torquing the rear action screw.
Pinning is indeed installing dowel pins of some sort through the scope base and in to the action. This practice has long been done to prevent sheering off the base screws in high recoil dangerous game rifles.
Scott

Stugotz
01-05-2008, 02:01 PM
I don't know how the Savage action is threaded for scope mounting, but If we can use a Rem 700 as an example; If a person were to attach a rail to the action with (4) 8X40 screws, is there some additional rigidity to be gained by adding pins? Or is the purpose of the pins to prevent the mounting screws from being sheared during recoil?

themachinest
01-05-2008, 06:18 PM
Stugotz,
Most mounts are held on with socket head cap screws. Socket head cap screws have a flat surface that is perpendicular to the axis of the screw that mates with a flat surface that is perpendicular to the drilled axis of the hole and the only force that holds anything is the friction created by torquing the screws to the action and sandwiching the base in between. If you are trying to increase rigidity, this method is the least capable.
When I was up helping Barney, I noticed that he takes the next step by not using socket head cap screws. He bevels the inside of the holes in the mount and uses Weaver screws that are beveled to attach the mount. This still does not address the clearance between the screw and the receiver though.
I take things one step further still. If I use Barney's mount or make my own, I use Weaver type screws or if I use any other style mount that requires the use of socket head cap screws, I countersink the holes in the action and in the bottom of the mount and bed the mount to the action and screws with a high quality epoxy with release agent on screws and action.
The next step to gaining action rigidity through a one piece base is to install dowel pins front and rear.
Now the ultimate is this. I was at the championship shoot in Missoula, MT in 2006. A guy and a women came and shot a light gun made from a Remington 700 action at this shoot. On top of this 700 action was a one piece base that was welded on. This is not the first time that I've heard of this but it is the first time that I saw it.
I hope this helps and inspires some thought.
Scott

Stugotz
01-06-2008, 04:12 AM
Thanks for the insight Scott, definitely gives me some things to ponder.

RPrecision
01-06-2008, 04:25 AM
Pinned the front but i just didnt feel comfortable punching another hole in the front bridge. The way I saw it the rear of the action sees litle stress compared to the front where the upper locking lug bears a great deal of stress. While I didnt think this would cause a problem on a .308 I didnr want another hole between the lug and the threads? I just didnt think it was worth the risk comprimising the action ?

On a side note I pinned a Warne mount. While doing some load devolopment I noticed a POI shift. It always effected the entire group and it never settled down. After pining the base that problem disapeared. I assumed the culprit was the base moving as it hassnt been a problems since.

I like the idea of pinning front and rear, has this been done sucussfully, what calibers, ETC.

One last thing to keep in mind. I had a guy ask me ho to re-pin a action. He picked out a base set it up drilled it reamed it and pined it. Thing was the base turned out to not work for his eye relief and scope. I was able to pin his new base to match the reciver but it was a real pain in the @#$%. So make sure you set everything up dry once before you commit ! It can be fixed but its alot of time in setup to re-pin right !

:)