Recoil lug thickness studies

[tobnpr]

I'm also in the camp that thickness above factory is irrelevant- PROVIDED the lug is properly bedded.
If the lug is bedded, and perfectly square to the receiver face there's no way it can flex at the receiver juncture.

Factory stamped lugs will never be perfectly flat. Absent a surface grinder, spend the $30-$40 for a precision ground lug when rebarreling. It's not about the added thickness- it's all about being perfectly flat and thus square to the receiver face. This results in recoil forces being "straight back", and not trying to twist the receiver up, down, or to the side as could happen with a stamped lug that's not making full contact. For most factory rifles, just bedding the lug will usually improve consistency.

JMO. YMMV.

 

[Lenny Foffa]

Im Not sure about the need for thicker Lugs, unless perhaps it is some big Magnum caliber. In the old days at the gun shop I saw more damaged bedding, but never a bent recoil lugs. But In truth , we never closely examined the Lug. I have seen some Custom Remington Pattern Actions with Thicker Lugs as options. My Humbel suggestion is to have one machined in a harder material and shoot it a bunch and carefully measure after each shooting session. Or ,. have one machined out of a harder material, a few thousands Thicker, adjust your bedding slightly and feel more comfortable. Just a thought.

 

[Bob Wright]

Accurizing Bolt-Action Rifles | RifleMagazine

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www.riflemagazine.com

In this article mentions some interesting tests/discoveries. Without reading this book, I cannot make a judgement either way but it is interesting:

"However, oversize recoil lugs may actually be counterproductive, according to research detailed in the late Harold Vaughan's remarkable 1998 book, Rifle Accuracy Facts. Vaughan was a prominent rocket and artillery scientist who also happened to be a rifle loony and bench shooter, and his research contradicts many long-time assumptions. (Original printed copies of Rifle Accuracy Facts, like the one I purchased new for about $30, now sell for about $150 or more. Luckily, scanned computer versions are readily available for free.)

Vaughan conducted his experiments on bolt-action rifles using technology often unavailable to even advanced gunsmiths, and he discovered considerable barrel vibration during firing was caused by the recoil lug momentarily bending the front of the action. This is partly why some twenty-first-century factory rifles feature smaller recoil lugs, or no traditional lug at all. Instead, manufacturers are using "bedding blocks" in the stock that fit into notches in the action. Some people still "skim-bed" the block surfaces with a very thin layer of epoxy, but there's no need to bed the entire action area."

 

[dfanonymous]

I went with a thicker lug on most of my long action magnums. I don't think I had any of those lugs bend, even being in some type of aluminum block or chassis. My theory behind it was was two fold:

One, I double pinned it to the action. The thicker lug was more surface for said pins.

The next was to absorb harmonic vibration. This was less to do with the thickness and more the material, titanium, but thickness was a part of it. Obviously this is a hair splitting decision, I wouldn't expect many to appreciate the details, but it's worked out well enough.

 

[Mike Matteson]

Following, and Interestng. Done some reading about it.

 

[bamban]

Years ago I built a switch barrel hunting rifle. I asked a tool and die maker to make me a ground flat washer with the same thickness as the factory 700 lug. Bedded with just an electrical tape around the washer. Changing barrels is no big deal not having to worry about lug orientation, the washer can move ever so slightly. Of course pinning the recoil lug is the answer to the conventional system

The round flat washer was a proof of concept.

On my hunter benchrest to make the washer lug looks better, had a portion machined off to match the action. Still changing barrels does not require a pin to ensure orientation.

I still have these lugs. The surface area of round lug is close to that of the square bottom lug.

 

[FEENIX]

Like it or not, .240"/.250" recoil lugs have become a standard to many tinkerers and gunsmiths. I have transitioned to the thicker recoil lugs and bed them. I still have an old Savage LA in .300 WM with a factory recoil lug; it is bent and needs to be replaced when I get around it, but it will likely be re-barreled.

All my custom rifle actions have integrated recoil lugs (IIRC, it is in the .24-.25" range), which is a plus.

 

[nksmfamjp]

Working on many REM 700's with cheap flimsy stocks…and I'm not the only one to find .185-.187" recoil lugs to bend.
A properly sized recoil lug should be used on all builds starting with .250" and going up to .300" thick and beyond depending on cartridge size. It is good insurance on keeping everything square and true to the centre of the bore.

Cheers.

Thanks for the answer. How are you measuring the lug bending? Do you have some kind of fixture to measure the before and after condition?

 

[Hugnot]

I knew this rifle smith who made many match grade rifles, and he claimed factory recoil lugs were perfectly adequate providing everything was properly fitted & bedded. His rifles won many competitions. How flat is flat? & how much recoil force? - "For example, the modulus of elasticity of steel is about 200 GPa (29,000,000 psi)" - compression or tension force applied - like deformation. Or momentary flexing & recovery, little rigidity, caused by loose fit bedding.

 

[MLN1963]

Just to play Devils Advocate. How would an action in a stock or chassis that is properly secured bend a recoil lug when the human behind the butt plate is going to play shock absorber long before a chunk of steel?

Mount it in a solid and secure firing fixture that doesn't move and all bets are off.

 

[ntsqd]

The answer to that is impulse. The impulse created by a round being shot will try to bend the recoil lug before the rifle as a whole can start to move into the shooter's shoulder.

We've designed the recoil lug to become bent. We've designed it to fail and the only thing that keeps it from failing is that the forces aren't normally high enough to make it fail.

I like bamban's washers above. I would suggest that the stock contact area is really only an important consideration when it is a wood or composite stock that doesn't have a bedding block. If you cut the bottom half off that traditionally shaped lug in his pic I strongly doubt that it would matter to a chassis or a bedding block, and in doing so you would reduce the leverage to bend it by about 1/2. That would be huge.
A simple Shear-Moment diagram would provide the answers. If I'm bored at work today I might just try that and see what it yields.

 

[MagnumManiac]

Thanks for the answer. How are you measuring the lug bending? Do you have some kind of fixture to measure the before and after condition?

No fixture is necessary, the lugs rock.

Those not believing this have no idea how easy it is to bend a standard Rem 700 lug.
If recoil can break a stock through the wrist completely into 2 parts, then it can bend a stamped steel piece of junk if there is movement within that flimsy stock.

Cheers.

 

[sedancowboy]

Like it or not, .240"/.250" recoil lugs have become a standard to many tinkerers and gunsmiths. I have transitioned to the thicker recoil lugs and bed them. I still have an old Savage LA in .300 WM with a factory recoil lug; it is bent and needs to be replaced when I get around it, but it will likely be re-barreled.

All my custom rifle actions have integrated recoil lugs (IIRC, it is in the .24-.25" range), which is a plus.

I have a drawer full of bent and distorted Savage and Remington factory recoil lugs. Often when I measure them they vary .003 or more side to side. Most Savage factory recoil lugs will be bent after shooting a bit.
For those that argue that it is impossible to bend a factory recoil lug haven't taken many apart.
If I am going to take the time and expense to properly bed a rifle then I will want a properly ground and hardened recoil lug.

 

[khmplus]

I have a drawer full of bent and distorted Savage and Remington factory recoil lugs. Often when I measure them they vary .003 or more side to side. Most Savage factory recoil lugs will be bent after shooting a bit.
For those that argue that it is impossible to bend a factory recoil lug haven't taken many apart.
If I am going to take the time and expense to properly bed a rifle then I will want a properly ground and hardened recoil lug.

I have never seen a drawer full of bent recoil lugs. Please send a pic.