Why are factory recoil lugs not parallel?

Watching copious amounts of YouTube and reading all I could in advance of my very first Savage barrel swap, I came across several folks who were swapping out their factory recoil lugs for aftermarket machined lugs. One video even showed a guy mic' his factory lug to show it was not parallel.

When I pulled my factory lug off, I did the same and sure enough I got the same result. The top of the lug was slightly thinner than the bottom. Not having a machined aftermarket lug to replace it with, the new barrel went on with the factory lug and it shoots just fine (sub MOA at 100-300 yards).

What I'm wondering is why the factory lugs would not be parallel? Does that actually serve a purpose, or is it just a product of quick and inexpensive production (stamped vs machined most likely)?

The factory lugs are stamped out of a sheet of steel. So if the sheet of steel they are stamped out of is not perfect, neither will the lug. Also stamping it can cause a little warpage.
Most of the aftermarket lugs are either surface ground or machined to be perfectly true.

I would think that a company that has a reputation for making accurate rifles would address this - IF it actually affects accuracy. Having said that, they have a reputation for accuracy despite this relatively small and inexpensive part, so maybe it doesn't make that much difference?

Does anyone have any before/after data from a rifle that shows a difference in using a machined aftermarket lug vs. a stamped factory lug? IOW - is it worth worrying about?

Just bed the front lug if you are worried...$1 worth of JB Weld to make a perfect fit.

The lugs are stamped with a progressive die that does 3 separate operations. The hole is punched first, then it progresses to the next station where the key is formed, then to the final hit of punching out the outside profile. On the last hit, the metal stretches around the top of the hole because it lacks the support of the material that was solid before the hole was punched.
This creates a taper between the nut and receiver face and draws the barrel slightly upward. After the barrels are head spaced to the receiver, the are checked on a vee block and indicator for run-out. To correct the run-out, they are put in an arbor press and bent into the right direction to correct the run-out to .020" or less.
Ground lugs insures that the barrel is square with the receiver,(this is if the receiver is actually square, but at least the lug is square with the nut). It's not so much about accuracy, but more about keeping things straight in line with the scope and it's adjustment range.

These are parts for a Remington but you get the point.


https://www.youtube.com/watch?v=Qn3jnVmhPWs

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Originally Posted by celltech

Just bed the front lug if you are worried...$1 worth of JB Weld to make a perfect fit.

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I don't know whether to be "worried" or not. Which is why I ask.

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Originally Posted by sharpshooter

The lugs are stamped with a progressive die that does 3 separate operations. The hole is punched first, then it progresses to the next station where the key is formed, then to the final hit of punching out the outside profile. On the last hit, the metal stretches around the top of the hole because it lacks the support of the material that was solid before the hole was punched.
This creates a taper between the nut and receiver face and draws the barrel slightly upward. After the barrels are head spaced to the receiver, the are checked on a vee block and indicator for run-out. To correct the run-out, they are put in an arbor press and bent into the right direction to correct the run-out to .020" or less.
Ground lugs insures that the barrel is square with the receiver,(this is if the receiver is actually square, but at least the lug is square with the nut). It's not so much about accuracy, but more about keeping things straight in line with the scope and it's adjustment range.

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I appreciate your reply. I had wondered if they weren't okay with this as it may address some barrel droop and keep things in line with the action. Just a guess though.

Mass production, and cost-cutting.
Precision hardened and ground recoil lugs, and barrel nuts that have been trued with the face perpendicular to the threads, cost a few more bucks...
Sub-minute can and does happen with non-precison parts. But, when you're shooting for 1/2 minute and less, best to do everything possible from these items (for the few extra bucks involved), stress-free bedding job, etc. for the most accurate system you can assemble

I've thought about buying machined recoil lugs considering they are not all that expensive, but my action and nut aren't trued/squared so I figure it's a fools errand to do so.

I fine hone and a friend with access to a Blanchard goes a long way.

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Originally Posted by celltech

Just bed the front lug if you are worried...$1 worth of JB Weld to make a perfect fit.

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While you may use the bedding compound to compensate for an imperfect bearing surface of the lug on the stock that isn't all that is at play with a warped lug. You need a perfectly flat ground lug or you get side loading of the threads on the barrel/action. While not critical at all on a hunting rig, if small shot groups at long range is what you're after, putting a custom lug on might be worthwhile, but only if you also have a squared up action face, threads and the end of the nut squared off too. Just a perfect lug alone without also having perfectly square surfaces on the action and barrel nut won't make much difference.

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Originally Posted by PaddyD

While you may use the bedding compound to compensate for an imperfect bearing surface of the lug on the stock that isn't all that is at play with a warped lug. You need a perfectly flat ground lug or you get side loading of the threads on the barrel/action. While not critical at all on a hunting rig, if small shot groups at long range is what you're after, putting a custom lug on might be worthwhile, but only if you also have a squared up action face, threads and the end of the nut squared off too. Just a perfect lug alone without also having perfectly square surfaces on the action and barrel nut won't make much difference.

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This is my understanding also. Not sure how much the ground lugs help but it will make you feel better.