Gunsmithing 1 Piece Scope Base Not Flat

[ebnash]

New rifle, HMR Pro and I have a one piece scope base from Area 419 and when checking the base for flatness my straight edge wobbles and shows light. This is with base off the action. If I bolt it up, same issue.

With rear of base bolted, front has a gap.

Should I just bed the whole base and work out problems by lapping rings??? I’ve left a message with Area 419, but waiting a response.

I would just return the base, but I bought it with a package including brake and forward rail.

Would you guys proceed with this mount, or go elsewhere?

 

[whatsupdoc]

Are you are checking the top of the base with a straight edge or the bottom?
My bergara came with a shim just for that reason.

 

[ebnash]

Using a precision straight edge across the top of the base and it wobbles like there is a high point in the center. When I test fit the base to the receiver, the surfaces appear to mate up decently. However, if I only install rear screws, there is a audible tap on the front of the rail. Unfortunately, that means if I install and tighten all screws, the receiver pulls the base even further out of flat.

Not sure what Bergara you have, but I have a Premier Action, which should be a Remington 700 Clone. I did not receive a shim, but didn't expect one. My main concern at the moment is that the base is not flat, but it is not slotted all the way from front to rear. There is a scalloped area in the middle. It is possible this area interferes with the use of a straight edge.

It's also possible I'm overthinking this whole thing and should just bed the base and lap the rings. I was hoping to forego the ring lapping since I spent the money to purchase precision match rings from Vortex. I will not have the rings until the scope comes in. 6 week wait on my order and I'm a couple weeks out.

I'm tempted to go buy a different base for comparison, but thought I would check in with cooler heads...

 

[colchester]

You could bed he base

 

[ebnash]

You could bed he base

I could bed the base, but that doesn’t address the fact that it doesn’t measure flat to begin with

 

[jetmd]

I would give 419 a call directly. Before I would do anything.

 

[ebnash]

I would give 419 a call directly. Before I would do anything.

Sage advise. I have called and left a voicemail with them. Hopefully they will call back or I will try again tomorrow. Thanks

 

[EXTREMEPREJUDICE]

Even though it could be out of spec Jon does great work so..............................perhaps the problem is with the action and not the base?! I always bed the base, just takes a few minutes and eliminates the stress when matching the base to the action. Even though an action might be off a footprint they are not always excact (or between two actions of the same manufacture.) As far as the top rail, unless it's not square laterally (twisted) it won't have any effect.

 

[ebnash]

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So I’m confused why anyone measures top flatness while unstressed? I thought this was to confirm it would not stress the scope.

I always bed the bases, as well, but only after confirming they are flat to start with.

 

[ebnash]

Well, after a couple email exchanges, they believe there is an issue with the mount I received. They have overnighted a replacement. Hopefully tomorrow I will be bedding the new one

 

[EXTREMEPREJUDICE]

Frankly, I've never heard about anyone measuring the "flatness" of a base....................straight/true sure. Glad you got it sorted out!

 

[ebnash]

I’m not saying that you tube and internet are the authority, but almost every video and tutorial includes holding a straight edge across the base to make sure it’s not bowed, before you mount to the action.

If the replacement comes in and it looks the same, I’ll just bed it and lap the rings to make sure there is no irregular forces on the scope tube.

I just removed a scope from my Savage 93r17 that was stringing shots from new. I had originaly mounted the scope with no checks or lapping. When I took it off, it had creases in the tube body. I’m assuming that is because the mounting system was not flat and straight.

Maybe I’m just over complicating things but I don’t want to damage a $2000 scope.

 

[308pirate]

that doesn’t address the fact that it doesn’t measure flat to begin with

There's a flatness tolerance of .005" for the top of a Picatinny rail according to MIL-STD-1913. Don't know who told you that no deviation from perfectly flat is permitted.

How far off was yours?

Perfect example of internet engineers and experts.

If you had returned it to me I would have sent it right back if it fell within the .005" flatness tolerance.

 

[SporterII]

419 did not ask for dimensional evaluation. They acted to help him.
Sometimes its the most helpful thing to do.
If I am not mistaken, owner of 419 opened his shop after time at another very reputable shop.
I would have specialty work done there.

 

[ebnash]

There's a flatness tolerance of .005" for the top of a Picatinny rail according to MIL-STD-1913. Don't know who told you that no deviation from perfectly flat is permitted.

How far off was yours?

Perfect example of internet engineers and experts.

If you had returned it to me I would have sent it right back if it fell within the .005" flatness tolerance.

That's good information to know. This is why I post here because all the information I read just said, look for light passing. Any way, with a Mitutoyo straight edge of a claimed edge to .001" tolerance, I was able to fit a .010" feeler underneath. I was pretty honest about where I got my info and it is why I posted here with the question.

Area419 just said if your straight edge wobbles, then that's not right and we'll send you another with a return shipping label for the suspected bad one.

I guess if I had ordered from you, I would have got a different response...

 

[ebnash]

Replacement from Area419 is perfectly flat. Will be working on bedding the base today.

Thanks for suggestions and information

 

[LRI]

Granite tiles found in home improvement stores are pretty darn flat. Never a bad idea to pick one up and use it as a surface plate to verify flatness of a part.

It's not all that uncommon for a base to develop a bit of an arch to it. When the lug features are cut on a pic rail it's basically stress relieving the material a bit. As you do this, the side with all the "meat" pushes against that and it yields. Machining these from extruded round stock helps a lot as the grain structure of the material runs axial to the part. Just means they move around less.

Cast bar stock is probably the most unforgiving. Forged barstock is better, but it tends to cost close to 2 or 3 times as much.

Merry Christmas all,

C.

 

[ebnash]

Luckily, I have precision flat granite tables at work, but the granite tiles suggestion seems like a pretty great home solution.

 

[ken4570tc in WY]

The granite tiles turned over with a little oil and ultra fine abrasive also serve to precision hone straight flat edges for many projects.

 

[Terry Cross]

Replacement from Area419 is perfectly flat. Will be working on bedding the base today.

Thanks for suggestions and information

Glad you were able to resolve your issue. Rest assured that Jon Addis at Area419 is extremely reputable. He is a rare combination of very talented machinist, designer and damned good rifle shooter. In spite of the part you received that had an issue, I would encourage anyone to buy with confidence from 419.

./

 

[ebnash]

Absolutey! Have nothing but good to say about my dealings with Area419.

 

[308pirate]

I guess if I had ordered from you, I would have got a different response...

If a customer complains of a defective part that we've shipped we take it back no questions asked, we send a replacement, and we refund the amount invoiced.

The part in question, however, gets looked at for 100% conformance to drawings and specifications by our engineers.

If the complaint is validated we take a hit both in our bottom line and in our customer's quality rating.

If the part we made is found to be in conformance, we put it back in inventory, the customer is contacted, and our credit reversed.

We don't give shit away just because someone complains. This ain't Walmart

 

[ebnash]

Just to be clear, I made no demands of Area419. I contacted them with a concern. They asked me if the observation of it not being flat was while it was mounted or unmounted.

I answered honestly and they sent me a tracking number 1st, followed by a response that they had sent a replacement piece because that was not acceptable.

I didn’t ask for a replacement, only advise on whether or not I should proceed to bed and mount the base.

 

[Jowens]

Can't ask for better than that. Jon is a good dude. Shit happens even with the best people and equipment. It's how they handle the isssue that counts.

If you think the best of the best haven't made mistakes or made products that were defective, you're wrong. They are the best because they learned from those mistakes and took care of them and their customers.