Another thread in which the efficiency of a mercury tube recoil arrestor is doubted by some and supported by others prompts me to post this poll.

Statement 1: We all know that “the heavier the rifle the lower is the felt recoil”. Period and let's not wast time arguing about it at all.

Situation 1(b): A mercury tube recoil arrestor adds weight to the rifle, and therefore reduces felt recoil. We are also not going to aguge about this.

The argument to be decided by majority vote , is about the claimed "additional" reduction in felt recoil by the design and proper installation of such a tube.



In good hunting.

Andrew McLaren.

Question:
Question: In your personal experience with mercury tube recoil arrestors, do they reduce the felt recoil by more than would be expected from the additional weight alone?

Choices:
My personal experience indicates that there is a significant additional reduction in the felt recoil.
My personal experience indicates a slight additional reduction in felt recoil.
My personal experience is such that I cannot really say if there is any additional reduction.
In my personal experience there is definately no additional reduction in felt recoil that cannot be explained by the addiotional weight alone.
I have no personal experience but will argue the case vehemenently one way or another based only on my armchair expertise.

 

Many years ago, I used to add these mercury recoil reducers to both the buttstock and forearm of the Big Kickers I built. My son and I did an experiment once where we fired a .470 Mbogo with Mercury recoil reducers and then replaced them with an equivalent amount of lead shot. The results were a PERCEPTION that the mercury recoil reducers gave a slightly softer recoil pulse than lead alone. in reality probably not enough benefit over adding just shot and epoxy to justify the cost.-Rob

By the look of the poll results so far those with personal experience will still be out voted by those of us with no personal experience of the mercury tube recoil reducers.



Von Gruff.

I tend toward Rob's take, only more like I can't tell any difference.
I have a couple of mercury recoil reducers I tried in a 12gaFH 3.85" NEF.
Two in series in the laminated wood buttstock hole, joined end to end by a small length of allthread/bolt with head cut off.
I ended up going with an equal weight of iron rod and lead. No difference I can perceive in recoil,
with 1400-grain slugs at up to 1400 fps ... soon added the muzzle brake for 1800 fps with those near 4-bore weight slugs in the NEF-er.

I filled the hollow plastic butt of another 12ga 3.5" thumbhole stock with epoxy and lead shot. At 17.5 pounds scoped, IIRC, that Mossberg 835 was comfortable with 1400-grain "Darwin Award Winning Natural Selector" slugs at 1400 fps.

The sloshing mercury is supposed to spread the recoil out over more time, right?
Where are the scientifically measured recoil force vs. time graphs, comparing equal dead weight to mercury?

I picked number 3 in poll.
I am still looking for the perfect application for my twin mecury tubes.

I tried casting buttstocks from ferrocement but had the same latent endothermic issues as Hoover Dam so I now machine them from Wolfram billet.



On a serious note, I'd like to see some time/impulse data too. A well placed tungsten rod would probably be a better solution or maybe some tungsten ball bearings roaming free in a cylinder ... need some rubber stops to cut the clanking sound though.

I voted for slight additional effect. And, if nothing else, they are a compact, easy to use, no fuss item.

Chuck Hawks:

V. Mercury and Mechanical Recoil Reducers

These cylindrical devices are usually implanted in the butt stock of a shotgun, inserted into the empty chamber of a double, or screwed onto the end of the magazine tube of a repeater. Theoretically, they use mercury or a moveable mechanical weight that is supposed to attenuate felt recoil by spreading it out over a longer period of time. The claim is that the mercury (or mechanical weight) moves forward in the tube as the gun moves backward in recoil, thus "borrowing" some of the recoil energy and lowering the maximum amplitude of the kick. The weight returns to its start position, redepositing the borrowed energy, after the stock stops moving backward.

According to my shoulder, these devices seem to reduce recoil no more than adding weight in any other manner. (Adding weight, of course, does reduce recoil.) Dead Mules don't kick, perhaps, but they can nibble at your wallet. The mercury recoil reducers do add a humorous gurgling sound not available in stock factory shotguns. If mounted in the buttstock they also move the gun's point of balance back. This may be fine if the gun started out muzzle heavy, as many pumps and autos do, but is not so hot if the stock gun balanced properly.

From Load From a Disk:

What is Recoil and How is it Calculated?

The same forces that govern the performance of rockets in space also cause a firearm to recoil when it is discharged. In the 17th century, Sir Isaac Newton introduced the concept that for every action there is an equal and opposite reaction. This concept is now known as Newton’s third law of motion, and is the basis for the rearward push of a gun when it is fired or the thrust to send a rocket streaking into the heavens. When a gun is fired the gas from the burning powder forces the bullet out of the case and down the barrel and exerts an equal and opposite force on the breech and stock. If the gun weighed the same as the bullet it would recoil back just as fast as the bullet goes forward. However, the gun weighs much more than the bullet and powder charge so the bullet is moved much faster and farther than the gun.

Three elements enter in producing recoil. The first is the reaction to the acceleration of the bullet as it moves down the barrel until it leaves the barrel at it’s maximum velocity, commonly referred to as muzzle velocity. The second element is the reaction to the acceleration of the expanding gas generated by the burning powder. The third element is the reaction of muzzle blast when the bullet leaves the barrel and the escaping gas gives a reactive push to the muzzle. As a general rule of thumb, the escaping gas velocity is about one and a half times the bullet velocity. For example, the escaping gas velocity would be about 4,000 f.p.s. for a projectile with a muzzle velocity of 2,700 f.p.s. A value of 4,000 is sufficiently accurate for practical purposes with small arms having muzzle velocities between 1,000 and 4,200 f.p.s.

The factors that enter the recoil can be written in terms of momentum where momentum is the product of mass and velocity:
Mg*Vg = Mb*Vb + Mc*Vc


Where:
Mg,Vg = mass and velocity of the gun
Mb,Vb = mass and velocity of the bullet
Mc,Vc = mass and velocity of the powder charge

Based on the information above and correcting for the proper units we can write the following:
(1) I = (Wb*Vb + Wc*Vc)/225400


Where:
I = recoil impulse, lb.-sec.
Wb = bullet weight, grains
Vb = muzzle velocity of bullet, f.p.s.
Wc = weight of powder charge, grains
Vc = velocity of powder gases, f.p.s. (4,000 in these calcs.)
225400 = unit correction factor (7000 gr./lb.*32.2 f.p.s.2)

Note: To calculate the recoil of shotguns it is necessary to add the weight of the wads to the weight of the shot to obtain a value for Wb.

The free recoil velocity of the gun is easily found from the recoil impulse and weight of the gun:
I = Wg/32.2*Vg or rearranging terms:

(2) Vg = 32.2*I/Wg


Where:
Vg = free-recoil velocity of the gun, f.p.s.
32.2 = acceleration of gravity, f.p.s.2
I = recoil impulse, lb.-sec.
Wg = weight of gun, lb.

The recoil energy of the gun can then be calculated from the kinetic energy equation:
E = ½*Mg*(Vg)2 or simplifying:

(3) E = Wg*(Vg)2/64.4


Where:
E = free-recoil energy, ft.-lbs.
Mg = mass of the gun (Wg/32.2)
Wg = weight of gun, lb.
64.4 = acceleration of gravity*2, f.p.s.2
Vg = free-recoil velocity of the gun, f.p.s

Recoil energy is found in three simple steps. First find the recoil impulse (I) from equation 1, then using the recoil impulse calculated, calculate the free-recoil velocity from equation 2. Finally plug the calculated free-recoil velocity into equation 3 and solve for the recoil energy (E).

To illustrate these calculations, consider the .308 NATO cartridge in a rifle weighing 8 lbs., firing a 150gr. bullet at 2800 f.p.s. with 46 gr. of powder.

I = (150*2800 + 46*4000)/225400 (equation 1)
I = 2.68 lb.-sec.

Vg = 32.2*2.68/8 (equation 2)
Vg = 10.8 f.p.s.

E = 8*10.8*10.8/64.4 (equation 3)
E = 14.5 ft.-lbs.

To recap, the items that affect recoil are gun weight, bullet weight, powder charge weight and muzzle velocity. Using a heavier gun, shooting a lighter weight bullet, cutting the powder charge or reducing the muzzle velocity or a combination of these items can reduce recoil.

A table of recoil values for some typical firearms is given in the following Table:

RECOIL TABLE
Cartridge
(HG =
handgun) Bullet
Weight
(gr.) Charge
Weight
(gr.) Muzzle
Velocity
(f.p.s.) Gun
Weight
(lb.) Recoil
Impulse
(lb.-sec.) Recoil
Velocity
(f.p.s.) Recoil
Energy
(ft.-lb.)
.22 Hornet 45 11.5 2690 7 .74 3.4 1.3
.223 Rem. 55 27 3240 7 1.27 5.8 3.7
.243 Win. 80 48 3350 8 2.04 8.2 8.4
.30-30 Win. 170 32 2200 7 2.23 10.2 11.4
.30-06 180 56 2700 8 3.15 12.7 20
.300 Wby. M 180 85 3245 9 4.10 14.7 30.1
.375 H&H M 300 76 2530 9 4.72 16.9 39.8
.45-70 405 30 1330 8 2.92 11.8 17.2
.458 Win. M 500 66 2040 9 5.70 20.4 58.1
.460 Wby. M 500 130 2700 10 8.3 26.7 110.8
.22 L.R. HG 40 1.1 800 .5 .16 10.3 0.8
.357 Mag. HG 158 16 1235 2.1 1.15 17.6 10.1
.44 Mag. HG 240 22.5 1180 3 1.66 17.8 14.7

In our ballistics program, Load From A Disk, we have rated recoil energy into categories that give an indication of felt recoil or "kick." In the table above the recoil of the .22 Hornet would be rated as "mild" while the .460 Wby. Mag. would be rated "severe- OUCH!"


Sincerely,
The Ballistician

quote:

Originally posted by Mike Scott:
I voted for slight additional effect. And, if nothing else, they are a compact, easy to use, no fuss item.

That must be right. They are neat and tidy sloshing weights, but some of us are not sensitive enough in the shoulder to perceive benefit versus dead weight.
However, as the voting is shaping up, some of us think they can tell the difference.
The power of suggestion!
Akin to the placebo effect!

The time involved is a fraction of a second.
How many more milliseconds is the force spread over?
Recoil impulse = force x time = "X" lb.-sec.
Increase the time, decrease the force, "X" impulse is constant.
The graphs must be so unimpressive that they are "closely guarded."

Just eyeballing the situation, the fraction of gun weight represented by the dead weight (iron, lead, or tungsten) or the "live weight" of mercury plus the dead weight of a steel tube,
is of much greater effect than any sloshing of mercury inside that tube.
Miniscule time spread.
Mostly psychological.
Just like recoil tolerance itself, some require more help than others.

I had this explained to me in an old thread on this subject by AR member Nitroman, who knows the mechanics involved.

The mercury colliding with the front of the tube does slow the recoil velocity of the rifle.

Yet the physical formula (as I understand it, the applicable formula is the one for an inelastic collision) indicates that the slowing effect of the mercury should not be significant, as compared with an equal weight rifle without the moving mercury.

Yet we perceive it as a reduction in recoil.

How much of a reduction, I couldn't say.

But I have found that the slowing effect is definitely perceptible, so I voted for a slight reduction.

I have no personal experience with these in rifles but, I have one in a Glock 17 which isn't a hard kicker. I've put ~100K rounds through that pistol and yes, it does reduce perceived recoil in that platform.

Heres' my BS on the topic...I don't think the primary intention of these devices was for big bore rifles but repetitive shooting sports like shotgunning. The theory is/was that over the course of many rounds in a day the slight additional reduction delays the onset of fatigue by some useful amount. Same as the theory of the palm swell; it distrubutes a small portion of recoil into the palm away from the shoulder and extends the number of rounds a gunner can shoot before fatigue begins to affect the quality of the practice. So if you're a competitor or hobbyist that is looking for the last little edge to improve your shooting, they are one of those tools that could help.

Since they are called "recoil reducers", I think the general public and the folks who like to sell them have represented them as more than they are designed to be.

Anyway, that's my story and I'm stickin to it!

Tigger,

May I assume you will be removing the tube from your 550Magnum and replacing with the equivalent weight leadshot and bringing it to the next Hoot & Shoot with the same nasty 800gr loads so those of us allowed the pleasure of punishment may try to percieve the difference?

How about a "switch-tube" model? All I need is a volunteer to fire 5 rounds each way (one set of five from each shoulder to be fair) and publish the results.

I've been head-scratching off and on about why mine is much more unpleasant than similar 550s I've shot. RNS' rifle comes to mind. I know mine's light but I couldn't figure why since it was built from a group buy of ten identical components.

The other day I found the packing slip from Brockman's and there's a note from Jim that the bore was off center and he had to re-profile the barrel to true things up. I wonder how many ounces he took off?

Honestly my 600 Overkill is more pleasant to shoot and that is saying a lot!

I don't know if it's the mercury or just the weight, but I have two reducers in my CZ 550 500 Jeffery and I'm happy they are there! At 12 lbs with scope and sling I wouldn't want it any lighter.

My 600 weighs 10.75lbs unloaded. PWS says there is a couple pounds of shot in the stock. Tubes have been suggested I just had other projects going all at once.

What happens when your shooting position/angle of shot changes? If you have to shoot "up" or "down", lead shot would have the same effect. Would a merc tube still act the same as it does when the rifle is fired level?

Nobody seems to doubt that just the added weight of the mercury tubes help reduce recoil and that the movement forward(or more like delayed movement rearward under recoil)does probably take some shock of the recoil out, but my question is: how is it assured that the mercury is at the rear of the tube to start with before firing the gun?
It appears that to be effect in the second instance above, the gun has to be elevated slightly before taking the shot? I have never seen one of these mercury filled recoil reducer tubes so don't know how they are constructed. Anyone?

A mercury tube recoil reducer is supposed to be installed in the stock parallel with the toe line.

This positions the rear of the tube lower than the front, from most shooting positions

Gravity keeps the mercury to the rear until the weapon is fired.

quote:

Originally posted by drewhenrytnt:
What happens when your shooting position/angle of shot changes? If you have to shoot "up" or "down", lead shot would have the same effect. Would a merc tube still act the same as it does when the rifle is fired level?

I think a lot of mercury tubes are installed wrongly in rifles (parallel with the bore instead of the toe line) in which case you get nothing other than the extra weight. That may explain some of the differences of opinion about them. The Dead Mule reducers use a sliding weight and spring so they aren't as position-sensitive as mercury. Again, since mercury tubes were primarily for shotgunning, putting one parallel with the bore is fine because with most shotgunning the muzzle is elevated.

As far as lead shot, I think mercury is more dense so more effective. Also, a fluid doesn't have the friction of small shot in contact with each other to overcome when setting the mass in motion. That friction soaks up a lot of the energy that would otherwise be used to overcome the inertia of the mass at rest.

I think its safe to say that 90% Plus of the value of Mercury recoil reducers is just added weight!-Rob

In shotguns we have tried with the mercury recoil reducers and with just weight. I think the mercury works a little better at recoil reduction. may be psycological but who cares as long as you shoot better.

BigB

I have had some experience with mercury recoil reducers and from my own experience I could tell a big difference in felt recoil when comparing rifle with them as opposed to rifles without them. The most notable example existed between two Merkel 140 500 Nitro sxs rifles I owned. The first was one of the first 500 nitro 140's Markel made, which was serial number 5. This rifle had a mercury recoil reducer and no recoil pad. The second 140, also in 500 nitro, I owned until recently had no mercury recoil reducer but did have a recoil pad. I didn't weigh either rifle but they seemed to weigh about the same. The rifle with the mercury recoil reducer seemd to kick quite a bit less and the kick was not nearly as sharp as compared to the one without the mercury recoil reducer. Even with the recoil pad the second rifle was unpleasant to shoot and I would usually get a good headache if I shot more than about 10 round through the rifle. I also have a .505 Empire with a mercury recoil reducer. Loaded to 2125 fps with a 600 grain bullet this rifle is not at all unpleasant to shoot. The only downside I can see to adding these devices to a rifle is what it does to their balance.

quote:

efficiency

I think you mean efficacy (?)

There was a comment about Mercury being more dense than lead. Thats crap. These mercury reducers are very light for the volume. Half air space. I got one factory installed in my 505 Gibbs and its a few measly ounces. Good for nothing. Now, I wont argue that for a similar few ounces of lead might be even more useless. No idea. That little tube was a total waste of time and money. I added a ~1 pound lead weight cast into a 1 inch diameter rod. That was effective. A pound to counter balance the heavy barrel and later was able to remove the scope.

These reducers strike me as a waste of money and a waste of the limited volume in the stock cavity.

quote:

Originally posted by fourbore:
There was a comment about Mercury being more dense than lead. Thats crap. These mercury reducers are very light for the volume. Half air space. I got one factory installed in my 505 Gibbs and its a few measly ounces. Good for nothing. Now, I wont argue that for a similar few ounces of lead might be even more useless. No idea. That little tube was a total waste of time and money. I added a ~1 pound lead weight cast into a 1 inch diameter rod. That was effective. A pound to counter balance the heavy barrel and later was able to remove the scope.

These reducers strike me as a waste of money and a waste of the limited volume in the stock cavity.

I thought that was the basis for the original question:

For the same weight, are mercury recoil reducers more effective in reducing perceived recoil compared to static weight (lead as an example)?

quote:

For the same weight, are mercury recoil reducers more effective in reducing perceived recoil compared to static weight (lead as an example)?

True I went OT. I guess the concensus is yes, to a very small degree. FWIW. No science has been produced. No study no data. What left to talk about? Initially, I had nothing to say. I have not voted the poll.

Was stated the original design intent maybe for very long strings of shots in shotgun matches - that was interesting to me. Rings true.

Along the thread there were other wanderings and statements as well. I was addressing some of that peripheral commentary with my 2c.

So FWIW, to make a real difference (for my case) I found more weight was needed. And, on a per volume basis mercury RR tubes seem a bad idea.

I wasted my money. That opinion might interest some?

FWIW, I agree with you - weight is weight and I'd go with the most dense, most simple and most affordable material.

The "sloshing" effect as others have said is probably but a small contributor to overall reduction in percieved recoil.

I'm an evidence-based guy by nature so would like to see data before plunking down my money.

I think it's so subjective you'll never find real useable data on the difference between a mercury tube and an equal amount of weight. Buying one is an act of faith. I won't buy another for a rifle; lead will do me just fine. But I plan on putting one in my Superposed.

I guess I was expecting more from the tubes I put in my 470 K-Gun. They did help as I perceived the hard slap became more of a push. Guess I was looking for more.

To beat the mercury-sloshing-tube unit, just use lead weighing a couple of ounces more than the unit,
but divide the lead into smaller subunits to balance the "piece" properly.
The lead volume will be less than the tube volume, easier to hide, and more effective at recoil reduction.
What bad is a couple of ounces heavier, if you are looking for recoil reduction?

I'm jist gonna weld a MonroeMatic onto the trigger guard of my next rifle and tie an old Keds sneaker on the end ...

I think they work.

When I first began shooting a 375 improved in 1981 I could not shoot it prone. Off hand or sitting with sling only. I added a 12 ounce recoil reducer in stock which helped balance the rifle, and could now shoot it prone. Was the difference familiarity with rifle, weight, balance, or the increased dwell time of the recoil reducer? Dont know, but I could shoot it prone now which was important for me. Weight of pre 64 with bull barrel and 4 X luepold with sling and ammo, 10 pounds for a rifle shooting a 300 grain at 2800 fps, 275 at 2975 fps, and 250 at 3100 fps.

I still have that rifle and stock with recoil reducer in place. I dont think practice made me learn how to take recoil prone as I had previously been shooting moster loads in a 375 h and h in ruger #1 with bullets seated out to 3.75 inches which had almost as much velocity as the improved.

Andy

I missed this one until now but as one of the guys involved in the previous debate, the science of it is quite simple.

Newton's laws of motion prove that they have to work. The larger the mass of mercury, the more it has to work (whether running uphill or horizontally) in conjunction with the energy being produced from the shot equals the amount of energy/recoil absorbed by the arrestor.

I published a shitload of links in the other thread here and they also prove the point.

With all due respect, it's a simple matter of provable physics rather than unprovable opinion.

For example, if someone has one fitted in a rifle and they find it isn't very effective, there can only be a very few answers to that.

Fitted incorrectly.

The recoil arrestor is too small and unable to absorb much energy. ((Assuming correct fitting a larger amount of mercury will be more effective than a smaller amount. )

The rifle doesn't generate sufficient energy for the arrestor to work or be needed to work. (for example if you fitted one into a .22, you'd be hard pushed to notice any significant difference)

Steve, none of the links you have provided, nor any of the equations in those links, proves that adding a mercury recoil reducer to a rifle is more effective than merely adding an equal amount of static weight.

You have no doubt seen that the makers of mercury recoil devices do not claim or cite any proof relative to how much their devices actually reduce recoil?

There's a very good reason for that. They can't prove that their devices produce any significant reduction!

As I understand it, the equation one needs to solve in order to understand how a mercury recoil reducer works (or doesn't) is the one for an inelastic collision between two bodies.

AR member Nitroman furnished it to me in connection with an old thread on this subject, but I can't find it anymore.

IIRC, what the equation proves is that there will be a greater reduction in recoil using a mercury reducer as compared to just adding an equal amount of weight to the rifle, but that the magnitude of the greater reduction is so tiny as to be insignificant.

Yet our bodies perceive a greater reduction in "felt recoil" than the equation proves in absolute terms, because no matter how slight it is, our bodies can feel the reduction in the rifle's recoil velocity.

Perhaps someone who better remembers his mechanics can provide us with the relevant equation.

quote:

Originally posted by shakari:
With all due respect, it's a simple matter of provable physics rather than unprovable opinion.

The above quote, on its own, shows the problem with this thread. I of course voted "NO EXPERIENCE BUT INDOMINITABLE SPIRIT" to the question. However, I do have extensive experience in AR threads and I can safely advance that facts just muddy the waters here.

Wink, that's a hell of an answer from a bona fide techno-dude!

I thought you were some kind of engineer or something?

I have heard they do work pretty well, but I would never want one on any of my guns.

quote:

Originally posted by Michael Robinson:
Wink, that's a hell of an answer from a bona fide techno-dude!

I thought you were some kind of engineer or something?

I'm just trolling today, let someone else do the math. By the way, do shock absorbers (like on cars) reduce felt shocks? Why the hell would someone want a Harley hard-tail?

I've no experience of these things at all. But as "a Brit" I have handled and shot some double rifles up to .470" NE.

What I can say is that the VERY LAST THING a DG rifle needs is to be made butt heavy so that the handling is all mucked about!

You've spent how many tens of thousands of dollars to get the gunmaking expertise of Holland's or someone else...and then you go and stick a weighted tube up its arse?

These things, like a fine shot gun, should have half the weight of the gun between the hands and the balance point there or thereabouts also.

What it needs "like a hole in the head" is a bl**dy great tube filled with mercury in the buttstock. The gun will be butt heavy and feel like a weaver's beam.

I would also, from having handled butt heavy guns (where wood has had to be removed) that its pointability will be very badly affected.

On a DG rifle to do that where a snap shot may be required is just sheer folly!

If you can't handle the recoil - and on a double .470" Nitro Express it really is quite acceptable anyway - then just what exactly are you trying to kill that needs a cartridge that recoils so much more than that?

Or get a .375" H & H and ask your PH to stand behind you with his "back-up" gun!