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tricrown
01-25-2009, 06:04 PM
Any idea why flipping the unpinned .353” recoil lug on my Kelbly Griz2 cause the headspace to change?

The recoil lug itself mics to within a .0001” on the 2 sides and top. The bottom may be off .0002”+ at the most.

A Shilen and a Krieger barrel hand tighten up pretty much the same, around an 1/8 of a revolution early when the recoil lug is flipped so that the action side is facing the muzzel.

Thanks,
Bill Slattery Jr.

JerrySharrett
01-25-2009, 06:17 PM
Any idea why flipping the unpinned .353” recoil lug on my Kelbly Griz2 cause the headspace to change?

The recoil lug itself mics to within a .0001” on the 2 sides and top. The bottom may be off .0002”+ at the most.

A Shilen and a Krieger barrel hand tighten up pretty much the same, around an 1/8 of a revolution early when the recoil lug is flipped so that the action side is facing the muzzel.

Thanks,
Bill Slattery Jr.
How do the barrels end up when they are torqued to at least 50 ft/lb?

Just curious, is this a big caliber?

Bob Kingsbury
01-25-2009, 06:22 PM
The lug may be chamfered differently on one side

tricrown
01-25-2009, 06:25 PM
Both are 6BRs.
I have no way of measuring torque. Usually use a Davidson rear entry action wrench when I have to. Doubt it would cause the barrels to turn much more, as they tighten up pretty good with a final slight jerk of the hand.

Bob, please explain.

Niccolo, M.
01-25-2009, 06:37 PM
... headspace change do you get?

It could be that the bore of the recoil lug is not perpendicular to the matting surfaces, think parallelogram. In a parallelogram the sides are parallel to each other so are the ends however the ends and sides are either greater or less that 90 degrees or perpendicular to each other depending which one you are looking at.

If the recoil lug is not bored square to the matting surfaces then you will have the same thing. The indexing of point where the surfaces touch will change relative to the direction of rotation of the thread when the angle of diversion is flipped.

The solution is to carefully bore the recoil lug for slightly more clearance to the barrel shank. This will remove the parallelogram from the equation because you have removed the material holding the matting faces of the recoil lug askew.

Tighter is not always better,
Nic.

JerrySharrett
01-25-2009, 06:49 PM
IMO, using a recoil lug on a 6BR would just be asking for trouble. A recoil lug sets up a whole 'nuther set of vibrations.

WSnyder
01-25-2009, 07:47 PM
Not Bob but I think what he was alluding to is the ID of the recoil lug may be chamfered more on one side than the other. Or maybe the ID of the lug varies from one side to the other (slight taper)? At the root of the barrel shoulder there is probably a radius that maybe the recoil lug is touching when facing one direction and not the other. If you leave the OD of the tenon just undersized of the ID of the lug to keep it from moving around and the lug does not have a chamfer on the ID, the shoulder needs a relief cut at the root (or the lug needs needs a chamfer cut) to allow the shoulder of the barrel to mate properly to the lug without the lug binding on the shoulder radius.

For example: On an action and recoil lug I just had (Pierce). The lug did not have a chamfer on the ID and was sharp as ground. The lug ID was 1.066" and the thread major dia 1.058. I left a shoulder with an OD of 1.063 for the lug and the tenon for threading at 1.058. I made a relief cut into the shoulder recessing the shoulder slightly at the root so the lug would not bind on the radius. If I did not relieve the root of the shoulder/tenon junction the sharp ID of the lug would bind on the radius (the tool I use has a .015" radius) at the shoulder/tenon. Many factory Remington's are done just the way I described although a bit rougher and a bit more generous on dimensions.

tricrown
01-25-2009, 08:09 PM
Thank you, thank you all. Knew I’d get it solved here.

Yep there is a chamfer on one side of the lug's center bore. After reading Nic’s reply I tried feeler gauges around the lug and found that there was a gap between the lug & barrel face most of the way around when put on backwards. Figure if it was off by around 1/8 turn, it’d be changing headspace 1/8 of .050” if it’s 20 TPI or more if its 16 or 18TPI. But when flipped the original way, with chamfer towards the barrel, there was no place that the .002” gauge would go in and looked like a tight fit all the way around.

Jerry, are you thinking it is better to glue the action in with no lug even with the 105g & 108g bullets and max loads we use in benchrest groundhog shoots?

Thanks again,
Bill

Bob Kingsbury
01-26-2009, 06:50 PM
Wsnyder is correct. A sharp corner on one side of the lug and a radius/
chamfer on the other could cause what you are finding. That is if the
inside corner of the tenon and shoulder face have a radius.Without
tightening anything, place the lug on the tenon and hold it up in good light,
or use a feeler gauge. Flip it over for comparison. In manufactureing, it is
neccessary to remove all burs from one side before grinding, but not always done on the other side. We are looking for a quality fit here, not quantity
so a small chamfer harms nothing.

Pete Wass
01-26-2009, 07:02 PM
Both are 6BRs.
I have no way of measuring torque. Usually use a Davidson rear entry action wrench when I have to. Doubt it would cause the barrels to turn much more, as they tighten up pretty good with a final slight jerk of the hand.

Bob, please explain.

Is to place a piece of masking tape on the action and one on the barrel with witness marks. Tighten the barrel until you have moved the barrel witness mark past the action witness mark I think some go 3/16. I use a 100 FP torque wrench and I think it would end up pretty close to that. I think setting a standard like i discribed is a good practice.

JerrySharrett
01-26-2009, 07:07 PM
Thank you, thank you all. Knew I’d get it solved here.


Jerry, are you thinking it is better to glue the action in with no lug even with the 105g & 108g bullets and max loads we use in benchrest groundhog shoots?

Thanks again,
Bill
You bet. A properly glued action will out perform a pillar bedded and recoil lug equipt setup every time. If you are using a round action and are concerned with adhesion, glue and pillar bed it, leaving the action screws just slightly snug, say 10-20 in/lb or so.

If using this method, make sure the action screws have clearance in the pillar holes. This eliminates the action screws acting as a recoil lug. Any surface "hanging down" is going to cause additional vibration patterns that are not conducive to good accuracy.

You are getting into the performance area where the "square" action, like the Panda or Viper is superior in structural integrity. These actions have way more surface area for the glued area and also have a nice recoil lug on the back that most round actions don't.

tricrown
01-28-2009, 04:57 PM
Thanks gents. Would gluing an action like this with a recoil lug setup make any sense? Would one glue the recoil lug also?

Pete are you saying I should use the Davidson wrench to turn the barrel in 3/16” past the hand tight witness marks. Or get a torque wrench and tighten to??

JerrySharrett
01-28-2009, 05:10 PM
Thanks gents. Would gluing an action like this with a recoil lug setup make any sense? Would one glue the recoil lug also?

Pete are you saying I should use the Davidson wrench to turn the barrel in 3/16” past the hand tight witness marks. Or get a torque wrench and tighten to??

Like I said, glue it and screw it. As to the recoil lug, get a spacer made with the same outside diameter as the barrel and the same thickness as the present recoil lug. Use this spacer to replace the lug.