In the latest issue of Rifle magazine, Ross Seyfriend points out that Boddington's theory that the 500 NE recoils less than the 470 NE is bunk, and then advises his reader to 'consider the source' (i.e., Boddington).

hee hee hee

Why is it bunk? Are not the .500's built somewhat heavier? Perhaps Boddington is correct?

As near as I can tell, almost all of the "gunwriting" that comes out of the pages of any Primedia publication is nothing more than disguised ad copy. In Boddington's recent article on Springfields he says he had his Springfield rebarreled with a 26" six groove military surplus barrel. I could be wrong, but I don't think there ever was such a barrel. If the byline is Boddington, I definately consider the source.

Ross is right about one thing, one should cosider, and the sourse, and the MOTIVATION , when believeing anything, especially when reading anything form one writer, about his compition!

Like Nickudu says, "IT COULD HAPPEN!"

i'll say it COULD be that felt recoil is greater in craig's pet 470. See, if you read his book, safari rifles (got is as an xmas present) he is more than a little stoked about his "no-name army-navy 470." Of course he wants it to be the baddest thing on the planet... after all, who wants to be a known african white hunter, who is also overly modest (and proud of it).

On the other hand, i'll bet my last dollar that his 470 loaded with modern loads recoils lots more than a 500 BPE, loaded to the safe side.

but, I've not seen, nor have I seen em all, a 470 built as heavy as a 500 NE, either one.

jeffe

Was he talking about a .500 nitro or a .500 BPE? If it is a B.P. gun it would not be near as severe a recoil as a modern .470 load.

I don't know which one recoils less, but a good ballistics software program ought to resolve the issue quickly enough, I should think.

I do know this: FELT recoil might be another matter altogether, and that's the brand of recoil that concerns me. Some .470s & .500s are simply better-stocked and either lighter or heavier than other rifles in the same calibers. So even if the raw numbers indicated that one produces more recoil energy than the other, it might not feel that way to the guy behind the rifle, depending one WHICH particular rifle he happens to be firing.

For a more down-home example that works at proving my point, there are certain .375s that I'd rather shoot from the bench than some light .30-06s with crooked stocks that I've fired.

AD

I don't have the magazine here or I would quote exactly. But Boddington said something like the 500 Nitro Express kicks less than the 470 Nitro Express because the 500 has a straight walled case and the 470 has a tapered case, and because the 500 operates at lower pressures than the 470.

Seyfried took Boddington to task on these issues. Seyfreid said there was little if any scientific evidence that using a tapered case will produce more recoil. He also published pressure figures showing that in a standard factory loading the 500 NE operates at higher pressure then the 470.

Felt recoil is a different story. Maybe Boddington 'feels' a 470 kicks less than a 500. Maybe he also 'feels' that a 30-40 Krag shoots flatter than a 270.

Well if the argument is premised on the idea that recoil is reduced by a less tapered case, I can put that notion to rest directly. Its not true. This goes back to the very widely believed (but no less mistaken) idea that the rearward thrust on the bolt or breechblock is lessened by the taper on the case. Recoil is the ultimate expression of the bolt thrust acting through the almost rigid frame and stock of the rifle.

The thrust on the breechblock or bolt is a function of the force acting on the bullet as it moves down the bore, so it is a matter of bore pressure (which is slightly less than breech or chamber pressure) multiplied by the bore area (not the chamber area), and has nothing to do with the shape of the chamber except in the subtleties of second order gas dynamics (which would be less pronounced than the differences between different grades of propellant). Loaded to the same pressure and with the same pressure-time histories, the maximum thrust will be delivered by a perfectly straight case in which the chamber and bore have the same area. We usually note that big bores kick harderand here is the main reason.

There is a popular misconception that bolt thrust will be less with a straighter case because the gas pressure won't be pushing back on as large a surface area as for a tapered case. This is due to a really goofed up understanding of fluid mechanics. The pressure acting in the chamber is acting equally in all directions. So its pushing outward on the tapered case walls with exactly the same effort that it is pushing down the bore and on the base of the case. Whether the case is tapered or not the same presented area (not surface area!) is being acted on. Now, overbore cases may develop very different pressure-time histories with a given barrel length as compared with straight cases, but that is comparing apples and oranges.

The proper rule of thumb is that bolt thrust is best gaged by recoil, which is the real reason why bigger cases need to be loaded to lower pressures in order to stay within design limits for an action strength. Bigger cases imply larger bore areas and the potential for much heavier bullets. Loaded to the same pressure you get a big increase in both thrust on the locking surfaces and in recoil. It doesn't have anything to do with the diameter of the case head and the breech pressure. A .257 Wby at 65,000 psi doesn't produce the same bolt thrust as a .458 Win Mag loaded to the same pressure.

If you go to www.accuratereloading.com/recoil.html you will see a nice table of calculated recoil for various calibers. In this table, with similar weight rifle (12#) and the 470 shooting a 500 gr. bullet and the 500NE shooting a 600 gr. bullet, the 500 generates over 50% MORE recoil! This table also agrees with what I have often thought of as a popular misconception in that (again, same weight rifle) the 416 Rigby with a 400 gr. bullet has more recoil than a 458WM shooting a 500 gr. My experience with both calibers agrees with this but most writers think the Rigby has a lesser recoil than the 458. My shoulder always put the 458 right between the 375 and the Rigby.

Someone want to tell me what is on the cover of this issue of Rifle magazine?I have a subscription,but don't recall reading this article.Maybe I just haven't gotten my copy yet?

Harald,

I agree with you, but those generalities will always bite you in the ass. I am not so sure that the bolt thrust of a 458 Win Mag is any greater than the 257 Weatherby. I think you may find that peak bolt thrust is greater with the Weatherby than with the Winchester. There is a VERY large difference in efficiencies between those two cases so you pressure vs time plot will be greatly different.

The internal case dimensions of the bases of the 470 NE and 500 NE are almost identical. The expansion ratios are not very much different between the two either. I would expect the the 500 to generate substantially more thrust and recoil than the 470 simply because the 500 is loaded to higher pressures. Put into Harald's terms. The pressure time histories between these two cartridges will be almost identical. Since the cylinder dimensions are the same, but the bore is larger for the 500 the 500 will thrust harder than the 470 if loaded to the same pressure.

Todd E

I have not reloaded for either of these cartridges, but generally, the 500 would take more powder than the 470 to produce similar velocities with similar weight bullets. (The "hole" behind the bullet is bigger and requires more gas in it to make it go the same speed.) Remember that the weight of the powder is also figured in the recoil equation. Although a gas, its mass also goes out the barrel. Ku-dude

Who knows what Boddington was trying, so poorly, to Say? Spreading himself too thin and had a brain fart? Fart proudly, Craig!

Ross Seyfried is always right.

I can't tell much difference in a 470 and a 500 when it comes to recoil...The are both pretty grim in my book and about the same to me in felt recoil...For that reason I would choose the 500 NE. Also for that reason I shoot a 450-400 Jefferys.

DaggaRon and Atkinson - well said! I like Ross Seyfried. He's the real deal. I don't know Boddington so I can't comment one way or another. But, if you read the "Handloader" article about "Little Skeeters" recently by Ross, the mention of West Point in the opening was very pleasing to me for obvious personal reasons.

Despite that, like I said, I like Ross. He's the real deal.

I'll be disconnected for a bit while relocating but encourage you to keep in touch at twielinski@wm.com

Best regards,

redleg

redleg,
How about a report on the 460 G&A? I have recently changed positions back to an employee situation and understand the problems with range time very well! Hope you are settling in well, and good luck to me too! I am working all weekend, on call starting today. I just don't get enough shooting time. You know, the "quality time" of life.
Stay in touch.

I don't want to get into it with the number crunchers here, because that is a loosing battle!

The recoil is dirrectly porportionate to the pressure pushing both on the bullet, and the rifle while seperateing them, one from the other. While both cartridges we are speaking of here are real kickers, the weight, of the bullets of each, combined with the pressure, plus the weight of the rifle, and finally the shape of the stock will all effect the FELT RECOIL dirrectly. Now, I like Seyfried, and read everything he has to offer, but he is not the final word by any means, there is the afore mentioned Boddington, and Graeme Wright, amoung others who's opinions, are just as valid as Ross'!

Let me throw a rock in the pond, and raise a tidal wave! First off most 470 NE double rifles are built lighter than most 500 NE rifles, secondly the shape of the case has one thing to do, not with recoil, but with the thrust pressure on the standing braech of a double rifle. The more taper, the less the case grips the sides of the chamber, the streighter the case the more likely it is to grip more of the chamber wall. The expanded streight case must move farther to loose it's grip on the chamber walls, while the heavily tapered case has only to move a very small amount to be free of the walls. This is the reason revolvers don't work well with bottle necked cartridges, the cases are too ealily moved back in the chamber, locking up the cylinder, while the streight cases work fine!

None of this has anything to do with recoil, however, this is simply as described above the pressure on two ogjects trying to seperate them.

Jeffe, Boddington's 470 is not an ARMY&NAVY, but a C.W. Andrews!

[ 06-14-2002, 20:36: Message edited by: MacD37 ]

Mac,

Harald's post addresses the physics (fluid dynamics) of why a tapered case makes no difference in thrust and recoil.

Boddington's point was that 500 NE's kick less than 470 NE's because (i) the 470 NE has a tapered case, and (ii) the 500 NE operates at lower pressure.

Seyfried showed that Boddington is wrong about the 500 NE operating at lower pressure than the 470 NE. In fact the 500 operates at higher pressure than the 470 NE.

And Harald showed that Boddington was wrong about the tapered case theory.

So, it seems to me that Boddington made a boo boo.

Harald,

I believe Ackley did some work where he held cases in chamber while firing with little more than finger pressure. It's been a long time since I read that material so I don't remember specifics of how he accomplished that experiment.

The thought is that the reduced taper cases are better able to bind against the chamber wall thus reducing bolt thrust compared to tapered cases that aren't as adept at binding the chamber wall. I think he went further to say that cases should not be lubricated on the outside to allow for this binding and it's corresponding reduction of bolt thrust.

Would you agree that if bolt thrust were not variable between cases it would be a great way to measure pressure? Obviously the pressure measurement devices, at least that I'm aware of anyway, measure pressure on the chamber walls. It may not be as great as some believe but I think it exists as a variable nonetheless.

I don't necessarily want to get into a discussion that Ackley's work is outdated, etc., just wanted to mention that he had some pretty graphical evidence to the contrary.

Thoughts?

Reed

Reed that study is in P.O, Ackley's book HANDBOOK FOR SHOOTERS & RELOADERSVolume 1, on pages 137, to 147.

I agree, however, that the shape of the case makes absolutely no difference in the forming of recoil! But there are many things that DO effect recoil that Todd E and Harald did not mention! like the weight of the two rifles, and the stock fit to the shooter.

In regard to case thrust, though, there are two ways to measure chamber pressure, with the American method of copper crusher to show pressure in the sides of the chamber. The Europien way of a copper crusher tube behind the cartridge to measure thrust of the case. One little clue here is, the method which measures thrust, the case is lubricated to avoid the case binding on the walls of the chamber! Wonder why they lubricate the case, would it be to let the case move back?

Ackley's studies were made with a 30-30 AI in a mod 94 Win rifle with the locking lugs removed, only the weight of the rifle resting on the lever keeping the chamber closed. The cases were loaded progressively hotter till the sides blew out of the chamber, and never opened the rifle. This was because of the streight sides of the 30-30 AI, compared to the slopeing sides of the factory 30-30 round. Anyone who has handloaded the 30-30 for a Mod 94 win knows the cases move back enough that the case heads bend out of line with the rest of the case, ruining the brass quite quickly. This isn't a problem with the AI version in the same rifle.

All this is another thing though, and has nothing to do with recoil, but does have to do with case thrust!

I think, however, Boddington is talking about one thing,(felt recoil) and Ross is talking about another(actual recoil numbers). The way I see this is, Ross, and Boddington, are two different types of personalities, with Ross being a numbers man,and is only swayed by numbers,when it suits his purpose,more about that later, and the Bodd, being a SEAT OF THE PANTS man behind a rifle,who is directed by what he feels in his shoulder. Both are right, in different ways. If you will notice Ross Seyfried disagrees with every other person who writes about anything haveing to do with guns. That is simply the personality of a numbers man, and he is intitaled to that personality, as is Boddington his! Graeme Wright is a results man, and abides by his testing, backed up by the proofing houses of England. Ross disagrees with him as well. In this case numbers do not matter to Ross, only his opinion! Ross uses numbers to disagree with Boddington, and opinion to disagree with Wright. Soooo, now, do we consider the source when there are numbers to back a study, or not? You can't have it both ways!Nor can Ross Seyfried! There is no doubt Ross is far more schooled in the complex math used in such matters, than Boddington, but the preveous sentence tends to say he uses what ever method that agrees with his opinion, at the time! I'm not saying he's wrong in this case, just that he is not God!


I do believe the statement of " " I CONSIDER THE SOURCE " to be in poor taste, when uttered by someone who is supposed to be a professional writter, when speaking of another writer. A simple, "I disagree" would have been far better, IMO!

[ 06-15-2002, 02:04: Message edited by: MacD37 ]

MacD37, thanks for the info. I agree that the case shape shouldn't make a significant difference in recoil if the parameters are held steady (bullet weight, powder charge, case volume, barrel, etc.,). I think some of the gas effects may make very slight differences but they are extremely small and probably impossible to quantify. I was not aware of the euro's testing pressure in that manner so my thanks for the info. The fact they lubricate the case seems to lend credence to Ackley's original premise.

Much of what I read about ballistics is open to interpretation in some way shape or form. Much of what we discuss could be (dis)proven with proper testing. The problem is that the testing would be costly and the benefit is not of value to those with that sort of funding...no real application to profit from the information...just arguments settled perhaps.

Thanks again for the info.

Reed

500 I GOT YA, I heard you the first time! All I'm saying is nobody is beyond makeing a mistake, even ME I did make a mistake back in 1942, or there abouts!

DaggaRon,

I wish I had something to say about the 460 G&A...I'm still waiting for it to arrive. I keep getting promises, but I'm not into rushing 'smiths.

I'll be shutting off for a bit after tonight. I'll be posting about the rifle somehow when it arrives.

Please keep in touch. If you send a message to me at work (twielinski@wm.com), I'd be glad to get back with you when the rifle arrives.

Best regards,

redleg

[ 06-15-2002, 03:32: Message edited by: redleg155 ]

Reed, I have not seen Ackley's study in which he uses his finger as a breech block, so I don't know what to say about that except that I think that could only be meaningful with very mild loads. Any charge that could propel a 500 to 600 gr bullet at better than 2000 fps would presumably also propel the case (and one's finger!) backward through one's body. I know that blasting caps have killed people this way. Maybe somebody could provide some details... (Mac?)

Lubricating the pressure cylinder in a crusher device is necessary to reduce friction because the soft copper will deform (by design) and otherwise one will get a lot of variability in results.

Given that cases slip into chambers with gravity initially and that the peak pressures of firing for rifles are 30 to 65 ksi, I find it very hard to believe that any significant difference can be seen in rearward movement between tapered and straight cases. The fully improved straight case with positive head spacing may well reduce stretching vis-a-vis an overly re-sized (full length resized to factory specs) tapered case, but that is a separate matter from the force applied to the bolt.

Put another way, if there were no case invovled at all, just powder and a bullet, would the recoil be less or more or about the same? I submit that with identical burning behavior by the powder you would not see (or feel) any difference in the recoil and hence the bolt thrust would be the same. Case to chamber wall friction may eat up a tiny fraction of energy, but in a fired case and a tight chamber the case really doesn't move anyway. The whole thing expands infinitessimally.

As fond as I am of Seyfried and as guilty as I can be of contentiousness and as much as I lament the current obsession with politeness to the extent of suppressing plain speaking, I confess that I am sorry to see such a personal observation published. Boddington is given to making generalizations (like this one) that can be rather sweeping, but I like him just the same and I think I can filter out the views that I may take issue with and yet respect him. I don't respect everyone who pontificates on the subject of guns, but I think he is far from a fool, if not as careful with his technical details as Seyfried. But here is one of the reasons why I now read Rifle and Handloader and only rarely buy a RifleShooter, Guns`n Ammo, Guns, GunWorld, Shooting Times, etc. I am more interested in real facts than in what some gun writer feels about some subject. I want measurements, tests, and first hand knowledge, not a mis-quoted, recycled, third-hand corruption of a pithy remark made by somebody 75 years ago that was wrong in the first place. Other than the Wolfe publications, the shooting literature is way too touchy-feely and vague.

Harald,

Only three points, then I'm gone!

#1
I did explain the concept in a general way, but you did not read it in a general way, that is evident! The charge and bullet weight make absolutely no difference,where rearward thrust of the case against the bolt face, as long as the fireing developes the chamber pressure you want to test with regard to the rearward thust of the case. A charge that developes 70,000 PSI chamber pressure, pushing a 600 gr bullet, is exactly the same as a charge pushing a 150 gr bullet that developes 70,000 PSI chamber pressure, as far as rearward thrust of the case is involved. The difference in the shape of the case has nothing to do with recoil,that is the effect of the weight of the rifle in dirrect opposition to the pressure against the bullet, seperateing the rifle, and the bullet, at a given velocity, but it does have to do with the rearward thrust of the case against the bolt face, or standing breach. This was the whole idea of the Ackley improved cases, contrary to the common belief that it was to gain velocity. They did gain velocity with less pressure, but that was a byporduct.

Your contention that this must have been done with very mild pressures, is not unexpected, but the pressures were enough to blow the chamber walls to bits,a peak pressure that is estimated to be in the 100,000 PSI range. But did not move the case rearward enough to open the breach,which was only held closed by the weight of the little rifle resting on the lever. The locking lugs were completely removed for this test. Dispelling your contention that the shape of the case has no effect on the rearward thrust of the case. What he was trying to fix was the mod 94 30-30's propencity to stretch cases, by springing open under very mild pressure, with the tapered case. The shape does not, however have any effect on recoil, so we are saying the same thing about recoil, but differ on the effect on rearward case thrust!

#2
The copper crusher tube that measures rearward thrust,in Europe, is not lubracated, the case, and chamber walls are, so it will not bind on the chamber walls! If the case cannot move back no reading of chamber pressure will be given with this method. Big difference! This is the pressure that damages double rifles, not necessarily chamber pressure. Most rifles that fail from too much chamber pressure, fail in the chamber walls, not to the rear!

#3
This misunderstanding is my fault, because I injected the effect of the case shape on rearward thrust in the chamber, when the string had only to do with the case shape effecting recoil. Two intirely different test, for two different things! Sorry about that!

BYE NOW!