Does the Armalite one piece base and ring need to be lapped for proper scope mounting?

No, the rings have been machined in-line. That's one of the primary advantages to a one piece mount.
On the contrary, if you were to clamp the mount incorrectly or clamp it to say a rail that is badly warped it "could" tweak the aramlite one piece rings out of alignment. But, this is highly unlikely.
--RR

Ok that question answered, so how would it be possible to attach the mount incorrectly?

Recieved my second gen Springfield scope sat at noon, three months backordered, 1:30 at the range first shot only two inches off, two three shot groups at 100 yard to fine tune. Then got ready to move to the two hundred yard to finish, at 2:30, the scope was blurry and something rattled in the scope.

So off the rifle and back to Springfield armory on Monday after only eight shots.

Since the mount was off the rifle, wondered if I needed to plan on lapping the mount while I wait?

Seems simple to mount but it could get tweaked if both rail and mount aren't wiped free of debris before interfacing. Also tighten the clamping screws evenly on both rail and rings.

That sucks! Sorry to hear of your bad luck.
I can tell you, I've had absolutely no problems with my Nightforce if you're considering a replacement.

Again, it shouldn't need it as it's "in-line" bored at the factory. Over lapping can actually cause a "bell mouth" or "out-of-round" condition. --RR

FWIW, the mounts may be machined in line, but just out of habit I lap all rings that I use.

I did expect the armalite 1-piece mounts to be aligned a little better aligned that multi-piece mount/ring systems, but that just wasn't the case.

The lapping process clearly showed that the rings of all three armalite 1-piece mounts I have were misaligned...in each case the rings were tilted toward the front of the mount a small amount (i.e. the back of each ring lapped in first, then the full-contact surfaces "moved" forward as the lapping process continued).

YMMV

I'm getting an Armalite one-piece mount. What's the procedure for lapping it? I assume you need a 30mm tube with an abrasive paste? Where would you get such a tube?

Lapping requires a properly sized lapping tool...basically, a properly sized rod with a handle attached to it...and fine lapping compound (a fine, non-embedding grinding compound).

Basic process is that you attach the mount (or base and rings)to the weapon, put a little dab of lapping compound in the bottom of the rings, lay the tool into the rings and while pressing down lightly just slide the tool back-and-forth through the rings while moving the handle in a figure-8 motion to spread the lapping compound/action over more of the tool.

You will feel the lapping process stop "cutting" in a few minutes which is a signal to lift the tool and see what progress has been made. You will see a pretty clear indication of what material has been removed. If it is less than about 3/4 of the surface in the bottom-half of BOTH rings, apply a little more compound to each ring and keep going until you have lapped-in 3/4 or more of the bottom of both rings. You don't need to lap the tops of the rings...but I do drag the tops of my Armalite mounts over the lapping bar a few times to wear-down the high spots.

In talking with "those that know", once rings are installed and lapped, if they are ever removed, you will need to lap them again, even if they are returned to the same mounts on the same weapon (I wouldn't think that would apply to the one-piece mounts, but it certainly does to multi-piece mount/ring systems).

While there are several companies offering lapping kits (specialized tools and compound), you won't go wrong with Sinclair International (www.sinclairintl.com)

My two cents:  Don't do it, if you are worried about accuracy.  Do it if you are worried about scratching the surface of your scope, but not worried about accuracy.  The rings are designed to Xx.xxxx thick, and by lapping the rings, you are going to take off metal, making the rings bigger than they should be, making for some accuracy issues.....
I think the only people recommending ring-lapping, are the ones selling the ring-lapping kits !!!!

Forget about lapping the mount.
Take the money you saved on tools/compound and apply it towards a better (Leupold/Burris) scope. [;D]

Not meaning this as a flame, but it's obvious by your statement that you have no experience in machining.  It is one piece, but the holes are machined from opposite ends, mirroring any defects, instead of creating 2 inline holes.

Actually, two piece bases are preferred by serious shooters because a one piece base can put stress on a reciever, kind of like what you were explaining.  A two piece base with properly lapped rings can actually strengthen the reciever by acting like a reinforcement.


AC_Doc, this isn't quite right.  I'll explain why:

By mounting the rings, lapping, then mounting the scope, you are guaranteeing that the scope has a perfectly straight and aligned set of holes to be mounted in.  If you don't lap the rings, the scope will be torqued and bent to a certain extent.  This is true of any reciever, base, ring, and scope combo.  This torqueing can cause accuracy issues, as you are essetially bending the scope.

The part about the holes being too big if you lap them could be true if you lapped them WAAAAAAAYYYYY too much, but with proper lapping this is not an issue.  The rings are not actually designed to "Xx.xxxx thick."  The tolerences are no where near that close.  It's more like xx.xx+-x.

Don't take my word for it.  Call and talk to any serious precision rifle maker in the country (not Joe-Bob's gunshop down the street.)  It's a process to properly mount a scope, not a conspiracy by lapping equipment companies.

That being said, I'd lap the rings on an AR mostly to keep from scratching the scope.  On a gun that shoots in the MOA range that's only good out to 300 yards it wouldn't make that much of a difference in accuracy.  However, on an 800+ yard gun that shoots sub-.5MOA, it is critical that the scope is lapped.

Sinclair has the lapping tool for $18.25. That's not really too bad. I wish I'd done that on my Arms #22 2-piece mount. You could see from the marks on the scope that they weren't perfectly aligned.

Seems like you'd want to do it on the upper part of the rings too, go ahead and clamp them down snuggly on the base and run it through a bit.

I have no experience in machining? LOL.. ok dude, whatever you say. That statement in itself demonstrates your lack of judgment or reason...
--RR

Greybeard, it is as simple as this...

To believe that lapping scope rings DOESN'T benefit accuracy, you have to believe that one of the least expensive mechanical components of your rifle that directly affects accuracy is also the most finely machined part of the whole system...that there is NO possiblity of misalignment, regardless of materials, machining tolerances, tool wear, production processes, handling/shipping/installation influences, etc...

AND...that a mount system produced at a separate time, most likely on a separate machine, probably at a separate location, with it's own set of blueprints and manufacturing tolerances, will attach to your particular rifle to within 1/10,000" of being mechanically "perfect" (1/10,000" being the internal tolerances of a quality scope, with much more misalignment potentially causing interference within the mechanicals of the scope itself).

Yeah, that is a great argument against spending $20 and 15 minutes to remove that possible source of frustrating inconsitency.

Oh yeah...since lapping scope rings is such hokum and negatively affects accuracy to such a horrendous degree, one has to wonder why the benchrest crowd does it, huh?  ...and why the vast majority of "serious" rifle builders do it, too.

Trying to machine tolerances of .0001" on riflescope rings is complete overkill and a good way to drive yourself insane. There is absolutely no reason the static mounting of a scope tube to rings requires that kind of alignment. I would venture to say a misalignment as much as .002" would go unnoticed in the function of the scope and in fact would be absorbed by flexing of the components with no significant stress being induced. And if I need to present an FEA graph here to prove my point I will. Tolerances of .0001" apply to machining operations being performed in temperature controlled environments and apply primarily to Grinding, Jig Boring, Jig Grinding, Honing and Lapping operations. Once parts machined to these tolerances are brought out of a temperature controlled environment these tolerances are out the window. Keep in mind the CTE (coefficient of thermal expansion) for 7075-T6 (upper receiver) is 14 µin/in-°F; the CTE for medium Carbon Steel is 6.5 µin/in-°F, which is less than half the expansion/contraction rate of aluminum. What this means is when you take your AR out of your 68° gun safe and expose it to winter outdoor temperatures of say 38°? The receiver shrinks .0035" in overall length. Not only does the receiver shrink but it also twists curls, etc. Why? Because it's not a solid rectangular piece of material. It has cavities machined into it that create higher and lower areas of mass, so it doesn't expand/contract uniformly throughout its structure. Throw components into the "scope, mount, receiver assembly" that are dissimilar metals i.e. steel versus aluminum? Now you a real mix of CTEs within your components and more stresses induced when your rifle is exposed to varying temps. Does this microflexing effect the performance of your rifle or scope? I doubt it.
My point is a scope/rifle sees more stress when being moved from indoors to outdoors than it would by mounting a scope in rings that a couple thousands out of alignment. Lapping is a very fine polishing process designed to remove no more than .001" from an established diameter. Removing more than that starts to create bell mouthed and out of round holes. Nah, I agree with an earlier post that said lapping is overkill and not necessary on a Combat Rifle such as the AR15. If you have scope rings out of alignment more than .002/.003”? You have a greater problem than a lapping operation can fix.
--RR

hey guys. just buy a U.S.Optics one piece mount and forget about the issue. I put mine on a CMM the day it arrived and it was within one tenth across the mounting surfaces.  (.0001")

I'm now a big fan of lapping scope rings. I got the tool, and took the scope off my AR. Started working on the lower halves of my Arms #22 rings. They were horrible. They had raised areas on the foreward and aft edges of the rings, and you could see the pressure points where they had marked the scope.

I worked on them for a long time before I finally got a nice even surface. I didn't take it completely down 100%. The original surface was just too uneven, and the instructions say to just get it to about 75% contact area.

Then, I started working on the upper halves, not really expecting to have to do much. They were even worse than the lowers. The left and right edges on each of them, where they attach to the lower halves, would barely even fit over the lapping tool. Only a small part of the upper mating surface was even touching the tool. When looking end on to the tool and where it mated with the ring, there were large uneven gaps. It took a lot of rubbing to finally get a decent surface. I wouldn't say I even got it up to 75% contact area, but it looked adequate.

Then I laid the tool into the lower ring halves and installed the upper rings. I lapped it in a little with the rings held snuggly in place as a full assembly, just to make sure everything was aligned. Then I took it all apart, cleaned it up and laid the scope in place.

Man, what a huge difference! It was a really nice smooth fit, and went back together like it ought to. No more pressure points on the scope which could easily deform the tube and optics, both locally and over the length of the scope. Hopefully my one-piece Armalite mount won't be this bad when I get it (and my AR-10) but I think it's worth doing if you've got a nice setup.

OK, now that I got the scvope back and mounted, don't think that the lapping is necessary. No, repeat no marks at all on the scope tube ( the scope was repaired). Now I will be shooting and getting used to the scope and trying to deer hunt with my beast.
Jury is stillout on the 2nd gen springfield scope for my uses. Later, after the season will be trying more diffrent bullets and the 168gr. Fed GMM load for a benchmark to compare the accuracy to, such as Hornady SST, Remington, and the Georgia Arms Loads,the Estate 150 gr. is about 1.5 inch groups, good enough for my kind of hunting.
Thanks all for the replies
any suggestions for later accuracy test?

I lapped my Armalite mount, and was pleased I did.

Use Sinclair lapping kit - very good.

Worst rings I've found are Ruger and Burris. Always scrape up a scope. Now lapping solves that problem.

1/10th is not .0001"

1/10th is .1"

I am about to get an armalite one piece mount with my SEGR and yes it will get lapped.

I think he was using the shop term for "one ten thousandth".

Well, I have to admit that I am a convert.

I always thought that if I bought high-quality rings/mounts, there was little need for lapping. After reading MF's post, I ordered a 30mm lapping kit from Sinclair. (WTF is Brownell's kit so much more expensive?)

This weekend I sat down with a pair of ARMS #22 high rings on a #38 S-EX rail that I bought for my SEBR, and a set of #35 medium rings on an ARMS #36 EX rail for my Bushy Varminter.

I did the #35 rings first. The bottoms are made of aluminum and, although the rings were FAR from perfect, things went fairly quickly. After less than ten minutes I had the bottoms looking good - about 80% contact - so I installed the tops and went to work. The tops are steel, so it went a little slower. In about ten minutes I had probably 50% contact on the tops and I now had 100% on the bottom halves, so I called it quits.

The #22s were next, after a well deserved adult beverage [beer]. They are all steel, so I knew that it was going to take a while. These things were HORRIBLE. There was probably less than 15% contact after the first five minutes. So I added some more compound and went back to work. Ten minutes later I probably had 40%. Time for another [beer], my arms are getting tired. After another ten minute session, I had about 60%, and progress had slowed to a snails pace. I dropped the tops on and lapped away for ten minutes, then took a peek. WOW the tops were even worse, I only had a small area on each side of both rings were there was contact. I put everything back together and went at it for about fifteen minutes. Now the tops were looking pretty good and I had about 75% on the bottoms. And my fucking arms were trashed!

I really expected much better quality from ARMS. My next build is going to use a set of Badger Ordnance rings. I HOPE that they are better than ARMS.

Glad it worked out, Slash.  I didn't realize the Arms #22s were all steel. No wonder it took so damn long to clean 'em up (duh). It's definitely a job for some coldbeers! [:P]