AR Colleagues,

I’m going to install a mercury recoil suppressor in my Ruger 416 Rigby based on advice and input from various posts on this subject in the past.

I have a question regarding the proper angle for the hole to be drilled in the butt stock. I’ve seen instructions that seem contradictory. Though I have not yet purchased the recoil suppressor, I am leaning towards the C&H 5 inch, 7/8†diameter, 16 ounce stock model. I expect that this is described in the instructions that come with the unit, but I’ve seen three options for installation:

1) The hole is drilled perpendicular to the butt stock or

2) The hole is drilled parallel with the bottom line of the stock (which will not then be perpendicular to the butt) or

3) The hole is drilled parallel to the top of the stock (i.e. comb) which may/may not be perpendicular to the butt

I’d appreciate any advice from those gunsmiths who have done this installation or shooters who would know.

Thanks
Paul

the instruction included with mine call for installation parallel with the bottom of the stock

Based on the physics of the principle involved, I always install mine parallel with the bore of the rifle. Works fine for me, including on the .404 Jeff I most recently did. Essentially, the mercury is a viscuous weight sliding in a tube......

What will it weigh with and without scope after you add 16 more oz.? Also, what kind of recoil pad are you using?

I saw a .243 Tuesday with a Vias muzzlebrake!!

quote:

Originally posted by Alberta Canuck:
Based on the physics of the principle involved, I always install mine parallel with the bore of the rifle. Works fine for me, including on the .404 Jeff I most recently did. Essentially, the mercury is a viscuous weight sliding in a tube......

Well by the physics involved, ideally it should be installed as close to directly in line with the bore as possible. To do this it probably needs to be as close to parallel to the bore as possible and as high as possible. Mercury is realy not that viscous though but I suspect that a mercury weight is cheaper to manufacture than a Tungsten mass of the same weight. If the mercury is allowed to "slosh" at all then it will not suppress the initial recoil much at all since the rifle would be free to slip past it for a bit before having to move it's additional mass.

I have recoil reducers on my .416 Rigby but recoil was in no way redused "dramatically". The extra weight and reforming the stock probably did most of the reduction.

quote:

Originally posted by Vibe:

quote:

Originally posted by Alberta Canuck:
Based on the physics of the principle involved, I always install mine parallel with the bore of the rifle. Works fine for me, including on the .404 Jeff I most recently did. Essentially, the mercury is a viscuous weight sliding in a tube......

Well by the physics involved, ideally it should be installed as close to directly in line with the bore as possible. To do this it probably needs to be as close to parallel to the bore as possible and as high as possible. Mercury is realy not that viscous though but I suspect that a mercury weight is cheaper to manufacture than a Tungsten mass of the same weight. If the mercury is allowed to "slosh" at all then it will not suppress the initial recoil much at all since the rifle would be free to slip past it for a bit before having to move it's additional mass.

Yes, it's true the rifle will "slip past" the weight a bit before starting to substantially move it (the mercury). As I understand the principle (which may or may not be a sound one), it is intended to do just that.

If it was just a question of adding weight, then lead would likely work about as well as anything....simply melt it and pour it into a hole in the buttstock or forend, (wherever is the shooter's choice). But, I believe it was originally intended to spread the recoil over a slightly longer time frame...acting something vaguely akin to the effect of the "long recoil" systems of some semi-auto rifles and shotguns. Essentially, the rifle starts to move and then a bit into it's movement, it runs into the "wall" composed of the additional weight of the mercury...which acts to suppossedly reduce the recoil by slowing the already moving rifle a bit.

That is again akin to the effect on recoil of having a gas-operated semi-auto like the Garand, which is commonly felt to have less recoil than a Springfield '03 of the same weight. I.e., first the rifle starts to move, then the op rod/etc. also begins to move, thus spreading the energy applied by the firing over a longer time frame.

Recoil is probably more effectively reduced in the Garand because the op rod and associated weight continues to move after the rifle is already stopping, and some of the energy is stored in the recoil spring to move the op rod. bolt, etc., forward again.

I don't believe mercury recoil reducers are highly effective, but they do seem to help a bit.

According to the manufacturers, installation parallel with the toe line of the stock is the correct method.

quote:

Originally posted by mrlexma:
According to the manufacturers, installation parallel with the toe line of the stock is the correct method.

Well, that may be according to ONE manufacturer, but then I have seen manufacturers of muzzle brakes advertize their products as being "muzzle breaks" too. And for years I noticed that American car manufacturers said their products were the best in the world. Just because a person can manufacture a product which was invented by someone else does not really mean he understands the principle(s) on which it operates.

So, before I bought into that instruction, I'd need to know WHY that manufacturer says that. He could be right, but he'd have to prove it.


(IF he said that testing showed the mercury had a better recoil reduction effect by being forced to flow slightly uphill because of that angle, then I'd buy his statement. But without the testing, that is a surmise, not necessarily a fact.)

I believe it is because (for reasons you note in your post above) the mercury needs to be at the rear of the tube as the shot is fired in order to for the device to be most effective.

Installing the mercury tube parallel with the toe line of the stock assures this.

quote:

Originally posted by mrlexma:
I believe it is because (for reasons you note in your post above) the mercury needs to be at the rear of the tube as the shot is fired in order to for the device to be most effective.

Installing the mercury tube parallel with the toe line of the stock assures this.

That makes sense. So, I'll try that angle on the next one I put in one of my own guns. If it improves its performance, then even one of us old guys can still learn something.

Lead is 11.3437 g/cm 3
Mercury is 13.5336 g/cm 3
Meaning you can get 20% more mass in the same volume using mercury or it would about 20% more volume (bigger hole) to use lead. Room is already tight so the use of the higher density material is beneficial.
Tungsten is probably the "heaviest" that you could fill a stock void with to add the most weight with the least amout of stock removed since it has a density of 19.3 g/cm 3. So using Tungsten as a weight would result in either 40% more mass in the same hole required for mercury, or the same mass in a 30% smaller hole.
But mercury IS cheaper.

inline with the toeline

seems to help more than just the weight, in recoil reduction.

jeffe

ask the manufacturer to supply you with the calculations showing how their mercury tubes reducle felt recoil more than just adding weight. Then post them here-I will get a kick out of seeing it

Be very careful pouring molten lead in a stock. ANy one who has ever poured molten lead in wood even one time knows that you burn a lot of wood, th elead shrinks and will rattle around, and in a stock you can split it pretty easily

if you are just adding weight, use lead, rocks, feathers, whatever. as long as it is a solid, 16 ounces is 16 ounces

I always assumed the recomendation to bore the hole for the mercury tube parallel to the toe line was to prevent drilling through the outside.

I have installed mercury tubes in the existing through bolt hole of Ruger No. 1's by machining nylon spacers and sleeves. They did offer some degree of "spreading the recoil", thus feeling a little softer.

You have my curiosity up now and I think I will call the manufacturer for their opinion.

Beware that there are two types that often get confused. One has mercury loose in a cylinder (also in a vacumn) and one has a sliding weight held to the rear by a spring. The spring type should be parallel to the bore and is often installed in a stock bolt hole. It comes with a piece of hydraulic hose that you can trim to length to secure the device in the hole without rattling. The spring keeps the weight to the rear until firing.

The mercury type is ususally installed on the toe line to help ensure that the mercury is in the rear of the tube when the gunis fired so the the most mass slams into the front of the tube on recoil. Canuck's time delay explanantion is right.

I called the owner of C&H Research who manufactures the mercury tubes I use and posed the same questions that were discussed on this thread about angle of installation.

He said having the tube parallel to the toe line is good in theory but in practical use and testing they could not determine any differance in performance between that and having the tube parallel to the bore.

He explained that the suggestion of boring the hole parallel to the toe line was to prevent drilling through the stock.

He also pointed out that they make mercury tubes designed to be used in shotgun magazine tubes and chambers which of course are parallel to the bore.

This reflects the same experiences I've had over the last several years of intalling this brand of mercury tube for customers.

How the reducers work is a subject that has come up before.

The mercury moves.

Its inertia (assuming it is at rest in the rear of the tube) is first overcome, and then it is propelled forward in a direction opposite that of the recoiling rifle.

The lead does not move.

I do not see how the adduced formula for an inelastic collision accounts for this difference.

AR Colleagues,

Apologies for not keeping up with this thread and to keep it dragging on, but have been away on business and I wanted to respond to a few of the posts:

First thanks to all who gave feedback-very useful

Oldcoyote: The rifle is a standard configuration Ruger Model 77 RSM. I haven’t actually weighted it but Ruger lists the weight at 9.5 pounds. I am going to add a red Pachmayr Decelerator English style recoil pad and my reason for the original query was that I wanted to install the recoil suppressor before adding the pad. The scope is a Leupold VariX III 1.5x5x20 in standard Ruger mounts. I’d guess the overall weight with scope and recoil suppressor to be right around 11.0 pounds

Craftsman: Thanks for your post and calling C&H their recommendations. I was going to do the same and you saved me a phone call.

Not sure if I’m any clearer though on my original question: So it looks like most prefer the suppressor installed parallel to the toe line (my poorly worded option #2) but it in fact may not matter according to C&H which is the brand that I will probably use. I had not considered just using lead because I assumed that the mercury does have another secondary recoil reducing effect. However if I read correctly from Nitroman’s calculations they have same effect in overall recoil reduction? So in effect I’m back to square one and will therefore ask:


For those shooters who have had suppressors installed and can compare before and after-did you notice a difference and if so how is the suppressor installed?

Thanks

Paul

quote:

The mercury moves.

Its inertia (assuming it is at rest in the rear of the tube) is first overcome, and then it is propelled forward in a direction opposite that of the recoiling rifle.

The mercury, being a liquid, sits where it is. When the rifle begins moving reaward, the blob of mercury continues to remain where it is, until the rifle runs into it.
Think if you had a transparent riflestock and a high-speed video camera. You would watch the rifle begin to move towards the rear, while the blob of merc just sat there...being a blob of merc. But the tube it is contained in is only so long, so within a very short period of time (or about three inches/7cm), we have a collision with the heavy blob of mercury and the end of the tube it is in.
The mercury reducers slow the recoil, rather than being more effective than just weight. You have the additional weight of the reducer tube, and when you have that collission, your body tells you it feels less. But it is your brain lying to you.

So to answer Mr. Paul's question:
1. Yes I have had several of the expensive little buggers installed, yes I "felt a difference" and was happy with the result.

2. The installation of the reducer is simple and straightforward: install the reducer at an upward angle so the blob of mercury will be sitting at the rear of the tube when the rifle is parallel to the ground. I had one in my ZKK-602 in .375 Weatherby, and two in my .500 A-Square. Some do not like the feel of the mercury when it moves inside the rifle when you hold it. I thought it was a really unique feeling, and all who I pointed it out to also thought it was "neat", or some other description. I removed the reducers and added lead after I had enough physics at university to tell me they were no more "reducing" than a simple lead weight. But the brain is surely fooled by the perception of reduced recoil. I would say try it and see how you like it.

Thanks for the explanation. I have always reacted better to English than equations!

The rifle moves - not the mercury - and the rifle collides with the mercury. It seems obvious to me now, with the benefit of your explanation, but I clearly was not conceptualizing the motion or the collision correctly.

So, are you saying that the adduced formula proves that the collision between the rifle and the mercury does not slow down the rifle's recoil velocity and reduce its recoil energy to any appreciable extent?

I think maybe the relevant points here are:

1. That the total recoil energy remains about the same as in a rifle of equal weight (achieved by whatever means) but

2. The speed of it's application to the shoulder varies as the mass of the mercury is encountered by the recoiling rifle.

That causes the brain to

3. "Assume" the recoil is less, even if it really isn't.

Doesn't matter to me. As long as the brain likes it better, so do I.

MrLexma and Alberta Canuck,

Bingo! Exactly correct. The rifles velocity slows after it runs into the mercury, and that slowing is what is perceived as softer recoil.

When I had the two reducers in my Hannibal stock, and all the metal out, I could whip it back and forth and clearly feel the mercury moving around. It made for good conversation with a couple engineer friends of mine.

Draw a graph..............The foot pounds of recoil being the vertical line, the time being the horizontal line.

The recoil with the lead weight (same weight as the mercury tube) should make a graph line that is rather pointed at the apex.

Recoil with the mercury tube should make a line that is the same height but much more rounded at the top because the same recoil energy was spread out over a longer time frame.

The Remington 1100 shotgun is endeared by many hunters because it has a "soft" recoil. That is because Remington purposely designed a sloppy fit of eleven differant parts in the action. It creates the same effect of spreading the recoil accross a greater span of time. It still has the same recoil as any shotgun of the same weight but is delivered to your shoulder over a greater time span, thus feeling softer.

If you think about it the shock absorbers on your car work the same way by displacing a liquid from one location to another thereby spreading the impact of a bump over a greater time frame. Would you rather have Monroe shocks on your car's suspension or lead weights?