This is why I check and bed all scope mounting components

[Ledd Slinger]

Putting together a budget 20 PPC varmint rifle for fun on a Howa Mini action. Below is a picture showing why I will never torque down a scope base without checking and bedding first. Nothing against Howa as I've seen this same issue on all types of actions.

I lightly tighten the front two base screws (no rear screws installed at all), place a light behind the rail and inspect for gaps and alignment of rear screw holes. This one has a good gap in the rear, but the screw holes align perfectly. Not a problem if properly bedded before installation and torquing. If you torque a rail down on a bare action and it's off like the one in the photo, you've just bent your rail and will most likely have bad scope ring alignment issues that require excessive lapping and bedding to correct them. If you check and correct issues like this to start with, it's much easier to obtain excellent scope ring alignment.

I always lap and bed my rings regardless, but it's more work to get it right if you have a bent rail. And dont be blinded thinking these issues can't happen on high end full custom actions with custom rails because it surely can. Always check everything

 

[olddav]

Agreed

 

[JFrank]

I’ll be stopping by “your” shop next time buddy.
J

 

[JEFFPPC]

Putting together a budget 20 PPC varmint rifle for fun on a Howa Mini action. Below is a picture showing why I will never torque down a scope base without checking and bedding first. Nothing against Howa as I've seen this same issue on all types of actions.

I lightly tighten the front two base screws (no rear screws installed at all), place a light behind the rail and inspect for gaps and alignment of rear screw holes. This one has a good gap in the rear, but the screw holes align perfectly. Not a problem if properly bedded before installation and torquing. If you torque a rail down on a bare action and it's off like the one in the photo, you've just bent your rail and will most likely have bad scope ring alignment issues that require excessive lapping and bedding to correct them. If you check and correct issues like this to start with, it's much easier to obtain excellent scope ring alignment.

I always lap and bed my rings regardless, but it's more work to get it right if you have a bent rail. And dont be blinded thinking these issues can't happen on high end full custom actions with custom rails because it surely can. Always check everything


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Good catch, but I have a question. How did you determine the problem was the action, not the rail? Could the rail be either bent or improperly machined?

 

[dmoran]

Looks like a perfect gap for a scope shim, and gain some MOA how your at it .... lol

 

[Ledd Slinger]

Good catch, but I have a question. How did you determine the problem was the action, not the rail? Could the rail be either bent or improperly machined?

I never specified which part had the fault. The top of the rail is always checked with a high quality machined straight edge for straightness. The receiver is acceptably straight too. My guess is the machining of the rail mating surface is off. But it could be the machining of the top/rear of the receiver as well. Hard to tell which one is at fault since the receiver is not a full round style. My bet would be the rail machining is at fault.

Doesn't matter either way. The receiver raceway is straight and the top of the base rail is straight, so I just need to bed to make sure I keep the rail straight for proper ring alignment.

 

[Ledd Slinger]

Looks like a perfect gap for a scope shim, and gain some MOA how your at it .... lol

I calculate and compensate for that adjustment in the rings when I bed them

 

[1shot]

Good catch. Thanks for the intel.

Lloyd

 

[JEFFPPC]

I never specified which part had the fault. The top of the rail is always checked with a high quality machined straight edge for straightness. The receiver is acceptably straight too. My guess is the machining of the rail mating surface is off. But it could be the machining of the top/rear of the receiver as well. Hard to tell which one is at fault since the receiver is not a full round style. My bet would be the rail machining is at fault.

Doesn't matter either way. The receiver raceway is straight and the top of the base rail is straight, so I just need to bed to make sure I keep the rail straight for proper ring alignment.

Thanks for the reply.

 

[searcher]

To help with this problem, I have epoxied the gap between the rail and rifle action with Dura Steel or other good minimal-shrinking epoxy. lightly screw rail on, tightly mask the action up to the rail, remove rail, apply 2 light coats release agent to action AND rail screws (not rail) , allowing to dry between and after coating, apply minimal amount of epoxy in a continuous bead on the bottom center of the rail, running lengthwise end-to-end and away from screw holes a bit, install rail, wipe off squeeze-out if any with clean cloth and acetone. On my "frankengun" A/R's - I permanently epoxy the rail onto the upper. As there is no "going back" on that one, I always use a 20 MOA rail.

 

[Ledd Slinger]

To help with this problem, I have epoxied the gap between the rail and rifle action with Dura Steel or other good minimal-shrinking epoxy. lightly screw rail on, tightly mask the action up to the rail, remove rail, apply 2 light coats release agent to action AND rail screws (not rail) , allowing to dry between and after coating, apply minimal amount of epoxy in a continuous bead on the bottom center of the rail, running lengthwise end-to-end and away from screw holes a bit, install rail, wipe off squeeze-out if any with clean cloth and acetone. On my "frankengun" A/R's - I permanently epoxy the rail onto the upper. As there is no "going back" on that one, I always use a 20 MOA rail.

Yep. Good practice.

I use Marine Tex and bed the rail at the same time I'm bedding the barreled action in the stock.
2 birds with one stone.

Later I lap and bed the scope rings with JB weld when installing the scope.

 

[searcher]

Yeah - that JB Weld is great on the rings.

 

[Evan]

No need to use a release agent on the action. It's a heat gun away from popping apart if needed.

 

[Ledd Slinger]

Yeah - that JB Weld is great on the rings.

If you really want a crazy grip on the scope tube:

Test how grippy the JB weld is in your rings by rubbing your thumb firmly across it. Then put your scope in the rings with no tops and twist/slide the tube around. Much better grip than bare rings, but it can be moved easy enough.

Then color the JB weld bedding in the rings with a black Sharpie permanent marker and wipe of the excess marker with a rag so it doesn"t transfer to your scope tube.

Rub the rings with your thumb again and see the difference. Now put your scope back in the rings and try to move it with no tops on the rings. WAY more grip!

 

[Ledd Slinger]

No need to use a release agent on the action. It's a heat gun away from popping apart if needed.

Completely disagree. Always use release agent on the receiver. Kiwi neautral shoe polish is cheap, easy to apply, and easy to take off. No viable reason not to use a release agent.

 

[nmkid]

So, you lightly tighten the 2 front screws and check for gap? Do you expect the gap to remain the same even if you torque down the front screws to specs'. In the end, do you tighten to specs'. after applying the epoxy? Good post along with the pictures.

 

[Evan]

Completely disagree. Always use release agent on the receiver. Kiwi neautral shoe polish is cheap, easy to apply, and easy to take off. No viable reason not to use a release agent.

Just like gluing your benchrest action into your stock to keep everything unified and stable, gluing the base to the receiver helps assure that there will be no movement between them. I have not needed to remove my bases with any sort of regularity - only twice in my life. Those two reasons are entirely viable, and are why I do not use release agent when seating a base on a receiver.

I wasn't trying to diminish or demean your process, which is perfectly fine. I was only offering that someone could forgo the release agent without fear of never being able to separate their base from their receiver. They come apart without difficulty with a heat gun, a clothes iron, or a carefully applied propane torch.

 

[Ledd Slinger]

Just like gluing your benchrest action into your stock to keep everything unified and stable, gluing the base to the receiver helps assure that there will be no movement between them. I have not needed to remove my bases with any sort of regularity - only twice in my life. Those two reasons are entirely viable, and are why I do not use release agent when seating a base on a receiver.

I wasn't trying to diminish or demean your process, which is perfectly fine. I was only offering that someone could forgo the release agent without fear of never being able to separate their base from their receiver. They come apart without difficulty with a heat gun, a clothes iron, or a carefully applied propane torch.

I understand, and yes that does work very well. But it is not necessary in most cases and not a practice I preach to the masses.

I have used a scope tester with a frozen Leupold on a bedded rail (released after bedding) many times. With proper troquing of the rail using a mild thread locker, I have never had an issue with any movement on my bedded rails or rings that have been released and re-installed.

 

[Cecil S.]

Great info right here. Thanks

 

[p-man]

Because of the possibility of gaps in radius between the receiver and the base, I always bed both ends - the high one first with just enough torque to get it re-set solid and simultaneously insert the low end screws just enough to ensure alignment hasn't changed. When the high end is cured, I then bed the low end using mfr-recommended torque on the high end screws and very little tension on the low end - again mostly to ensure alignment. Maybe a little overkill but I always opt for being 'safe rather than sorry'.