This is just a theoretical question, so please don't all jump on my inquisitive back!

If you build a rifle on an action desiged to take more pressure than a certain cartidge can create, can you safely load to higher pressures at the cost of ruining brass?

Example: .308 built around a .300RUM action, or a .223 on a .308 action, with a sturdy barrel and chamber.

would the action still stick?

Well, I will be brief, but I think you have your wires crossed.

There is absolutely NO reason a 308 Winchester cannot develop as much pressure as a 300 RUM or that a 223 cannot creat as much pressure as a 308!

An improperly loaded cartridge of most any kind can destroy most actions!!!!

I understand your premise, that a big strong action should be safer; BUT, any cartridge can be loaded to unsafe pressures!

Especially in the case of the 223 vs 308 cartridges, they are generally built on the very same actions.

And even if you took an action that was designed for a 300 RUM and did all the work to make it a mere 308 Winchester (Gee would that be a project)
you still would be in deep shit when the case gave up the ghost.

Good question, but I would not like to think of the results. Brass is cheap, but why tempt fate?

R F

My view, yes with a suitable action you can overload a case and expect shorter brass life and barrel life. In any loading the more intense the combustion temp and pressure, the brass and barrel won't last as long as with a milder load. HTH

All of these rounds produce very close to the same max pressure according to saami specs (~62000psi). The actions are all designed to stand up to the same pressure range and switching from one chambering to a larger in a given action won`t make any difference in how much more pressure it can handle.

There may be a difference in actions built by various manufactures but they all are built to handle the same pressure range of ammo reguardless.

A more important question is how well does one action handle gas at high pressure then another. If you excede the brasses limit it can/will fail allowing gas to flow in the action. Whether the action fails or not you could be in a world of hurt.

Pressure limitations are always given by thy ignition system:
The primer will give way to the expanding gases and the blow back may ruin the gun.

I know because I have such a piece at home.

Maybe I'm the dumb one. Isn't 50,000cup in a 300WM the same as 50,000cup in a .223??? Or is the question, if we had the massive locking lugs of a magnum action, etc, with a .223 sized opening in the bolt face, and a .224 hole down the fat barrel, could we go far beyond the pressure limits associated with a .223?

I agree with Ray and think he hit the nail on the head. The weakest link in most any modern firearm is not the gun, but the brass case. You could build a gun that could take 100,000 psi or more, but the case is going to be destroyed in one shot, and may even come apart, what good is it? To get above the pressures we currently use, IMO there is going to have to be a new delivery system developed, such as electrical ignition and caseless ammunition. That way a completely closed breech system could be developed, but all that begs the question, why? Current loads and ammunition can already reach out farther than most can shoot accurately, so I don't really see any real driving force behind such development outside of military uses.

Beemanbeme-The only way to take a rifle like you
describe and say double the pressures is to use
a different case and ignition system.Regular 223
brass and primers wouldn't hold no matter what brand or who made them.You could use a
steel case and electronic ignition,and get to
a 100,000 psi, but it would cost as much per shot as a 600 NE.Ed.

If I understand your question correctly , I believe the answer would be yes , the action would handle it. My reasoning is that , for the sake of conversation , if you have a block of steel that will withstand a force of 50,000cup detonated in a 1 inch hole , then reduce that hole in same said block to 1/2 inch , yet still apply the same amount of force , the said block will withstand the pressure better because you have increased the stress level the block will handle by adding extra mass ( decreasing the size of the hole) but kept the force the same , pressure being measured by force applied over a given area .As for the brass it wont take the increased pressure so well as it does not get extra reinforcement , only extra stress . My question to you is what are you thinking this will give you. I would think that for the little extra range you would achieve that the trouble you would have to go through would not be worth it .JMHO.

65,000 psi is the highest SAAMI lists.
.308 is 62,000 psi
Loading a .308 to 65,000 psi is probably done every day while those reloaders and their brass don't know it. 3000 psi isn't extremely dangerous here but it ain't safe either. Read between the lines.

There is no action that can't be blown up from its own cartridge, ever here of Bullseye? But if you want to load a .223 (55,000 psi) to 65,000 psi then buy a .22-250 I wouldn't rely on thick brass to save my ass, it probably would though if under 65,000 psi.

You CAN'T safely load to any pressure that ruins brass. If gas escapes out the back it usually goes out in a hurry and little pieces of debris go with it. This fact makes it unsafe.

Two cents worth

Everyone seems to agree on this one. The ultimate limit of the brass is, I believe, somewhere in the 70K range. Almost any gun can withstand this. That's why you hear of cases letting go, which often shatters stocks, blows off floorplates etc. It is actually pretty rare for a rifle to actually blow from an overload. When it happens, it is generally actions which are heat treated to too high a hardness such as the Enfields. Most action failures are due to obstructions or gross loading errors(wrong powder or detonation of underloads.)

Maybe I'm wrong, but I think most new reloaders confuse pressure with bolt thrust.

As stated before 65,000 PSI in a 22-250 would be the same as 65,000 PSI in a 300 RUM, but the bolt thrust would increase do to the heavier bullet at high velocity.

This is at least my understanding. Please correct me if I'm wrong.

Jim

Bolt thrust is a function of pressure and cartridge head size, primarily. It is offset by case grip on the chamber wall. That is why cases with minimum taper yield lower bolt thrust and put less load on the locking lug. However, this benefit goes away with an oily case or chamber. That's why calcs are conservatively done based soley on the head size.

One of the books I have on building single shot rifles has the entire first chapter devoted to the design calcs for the rifle. It's very informative for the nontechnical. I'll look up the name and author for anyone interested. I am not sure if it was one of de Haas's books or another one.

Art -- you are mostly right about bolt thrust. It is a function of the area of the case head (internal, not external) multiplied by the internal pressure of the case. However, actual bolt thrust is pretty much the same regardless of case design or chamber condition. What changes (with a tapered case or an oily chamber) is the manner in which the case stretches and can then bind the bolt on opening, ie., tapered cases and oily chambers exhibit stickier bolt opening. This sticky bolt opening is often assumed to be a result of higher bolt thrust, but if this were the situation the stickiness would be permanent from set back or galled locking lugs rather than temporary from a binding brass case.

Sorry, but I don't agree with that analysis. My comments didn't concern sticky cases, it was pointed toward stress on the locking lugs. The reason that bolt thrust is affected by case design and oily chambers is that brass is elastic (unless you exceed its elastic limit, even then somewhat just not 100%). When the cartridge fires, the brass expands outward and actually grips the chamber wall with a very significant force. It releases as the pressure diminishes and the the brass "restores" itself. This gives clearance for the brass to be withdrawn. Steel is also elastic, although it moves much less than brass. This is what leads to sticky cases in even a smooth chamber(chamber problems are a separate issue). With a very high pressure load, the bolt head and locking lugs are compressed more than normal. You can view this as temporary setback, if you will. This is normal and happens everytime you fire the gun. In another thread, I calculated the barrel expansion due to pressure. It turns out that a large bore barrel expands about 0.001" in diameter when fired. As pressures go up, the steel is temporarily compressed more. During this compression, the brass expands to fill this new larger "chamber". When the steel relaxes, the case and locking lugs are then under compression. At some point, this residual force is enough to cause a sticky extraction.

This wall grip is normal and well documented. The fact is that it supplies almost all the locking force for blowback automatics. Calculate the spring pressure alone that would be required for a 22 automatic rifle. You wouldn't even be able to open the bolt manually. (Case ID .222, therefore area = .03905 sq inches;pressure=15,000(?)psi, therefore backthrust vector=586pounds; I may be low on the pressure). Obviously, in a blowback automatic, such as a Ruger autoloader pistol, the recoil spring is nowhere nearly strong enough to provide this resistance. While critical to a blowback design, the same effect contributes to the operation of any cartridge firearm.

The contribution of the wall effect to recoil resistance is a function of wall geometry (case taper) and coefficient of friction. That's where the oil comes in. If the case or chamber is oily then the coefficient of friction is drastically reduced and the case wall effect is minimized. In that case, all the rearward thrust of the cartridge is born by the locking lugs. That is the reason that oily cases can cause a sticky extraction. If you are using a load that is already borderline and then have an oily case, the temporary bolt setback can increase enough to cause an extraction problem. If you carefully measured the headspace of the two fired cases, you would find the oily case to be just slightly longer. It is this length that causes the problem.

This is all well documented and the methods for calculating the effect are included in any technical book related to gun design.

I got a copy of Walter B Mueller's "Building a Single-Shot falling-Block Action Rifle Action" 1998 The Home Shop Machinist.

It was fun to read his calculations after I done a similar calculation on my NEF 45-70 handi rifle. I am not a mechanical engineer, and I got help from an ME professor and a military gun designer. The section modulus calculations of a complicated shape in bending that require a calculation for many cross sections are the worst. That process took more time than to simply earn the money, buy a gun and destructive test it. Then calculations could be concentrated on the part that failed.

I have bought allot of guns just to take them apart, look and the parts, put them back together and overload them [there is another gun show Saturday].

I am sure there is a load that will blow up any gun available, but I have found three kinds of guns in incremental overload work ups:

1) Those guns not stronger than the brass, and are not tough. When I work up an overload incrementally, the gun explodes, sending pieces at lethal velocities.
I have reached this point with; CZ52 7.62x25mm, RG 38 Special

2) Those guns not stronger than the brass, but are tough. When I work up an overload incrementally, the gun shows damage.
I have reached this point with; Iver Johnson break top revolvers in 32 S&W and 38 S&W, Colt Agent Aluminum framed 38 special.

3) Those guns that are stronger than the brass. When I work up an overload incrementally, the brass gives up; the bolt sticks, the cases stick, the primer pierces, the primer falls out, the case bulges down the feed ramp, etc.
I have reached this point hundreds of times with dozens of gun design / cartridge combinations

I have done enough tests to convince myself for my own safety that 1903 and 1938 Turkish Mausers and VZ24 Mausers, with .470" case head cartridges, are in the third category. I would probably extend that to allot of other '98 Mauser actions.

[ 03-13-2003, 23:30: Message edited by: Clark ]

Clark

That's the book I was trying to remember. The design section should be required reading for any amateur interested in this subject.

As to your destructive testing, I have always found that interesting. Unfortunately, there's not a lot of data available, particularly in weak guns such as you have tested. Ackley did quite a study of military bolts that is still widely quoted. It is in one of his two volumes, don't remember which. The thing in that study that caused me pause was the performance of the Enfields, even the high numbered ones. They tended to let go catastrophically at relatively small overloads, due to the nature of their heat treating. That's not a good thing considering the number of large bore customs based on them. The best marks, as you mentioned, went to the "tough actions such as mausers. These tended to yield instead of fail. Some of them, practically, couldn't be destroyed.

ughhhh

If I use my Quickload program to estimate the pressures that destroyed the Enfields in Ackley's book:

P.O. Ackley 'Handbook for Shooters and Reloaders Vol. 2', 1966, page 2, actions to be tested:

6. Eddystone-Enfield Number 952302
62 gr 3031 140 gr .270 Ackley magnum
102,000 psi

7. Remington-Enfield Number 673777
68 gr 3031, 180 gr .270 Ackley magnum
197,000 psi

13. British Lee Enfield, Mark III caliber .303, Number 41469
50 gr 2400, 150 gr .30-40 Improved [.303 Epps]
159,000 psi

Ackley thought that the P14 was a strong action in Volume 1, but when he tests it in volume 2 he finds differently. This is obscured by the use of the term "Enfield" on page 10 that can only be identified from inference from the test ordering corresponding to the paragraph description order.

1962, Volume 1 , page 447:
"Any rifle chambered for the 303 British can be rechambered for the Epps version but the SMLE type rifle will not accept the heavy charges as the P14 Enfield rifle"

1966 Volume 2, page 10:
The Enfield action [Remington and Eddystone] proved somewhat of a disappointment in these tests. It was expected that it would be the strongest one, and further tests will be run with this particular action to see if the two used were representative. However, the two which have been tested so far are widely different in physical characteristics. That is, the heat treatment given the two actions varied a great deal. One action [Eddystone] was extremely hard and blew up rather easily. When the blowup occurred, the action was nearly disintegrated and is one of the few blowups which would have perhaps proven fatal to the shooter. The other Enfield action [Remington] was extremely soft. It was practically impossible to break the action but after the loads reached a high pressure level, excessive setback was indicated on each successive shot, resulting in a dangerous headspace condition."

1966 Volume 2, page 13:
The British Enfield gave us an example of the rear locking lug system. The strength of this action seemed to be good; probably a little better than the Krag. [page 15: "The Krag actions tested showed surprising strength."] However the locking lugs are over four inches back from the face of the bolt. When this action gave way, the receiver itself went down at the rear, allowing the front end of the bolt to come up out of the receiver ring, thus allowing the bolt to be bent and to be broken.
The locking lugs themselves did not give way. The whole action appeared to have plenty of strength except for this one characteristic, which allows too much spring in the bolt and receiver. This action is not of prime consideration, however, because it des not have the appearance or another feature which make it desirable for sporting use. It also must be noted that regular .30 caliber bullets were used in this rifle instead of the oversized .303 British bullets. This, doubtless, gave slightly lower pressure than the standard bullet would have given."

Ackley II 1966 page 13:
"The locking lugs themselves did not give way. The whole action appeared to have plenty of strength except for this one characteristic, which allows too much spring in the bolt and receiver."

[ 03-14-2003, 02:18: Message edited by: Clark ]

Found one other interesting reference on the oiled cartridge issue. If you read the gunsmithing section of Kuhnhausen's Mauser book, you will find a picture of the test rig he uses to function and safety test barreled actions he works on. He gives a detailed description of the use. Basically, he clamps the BA in the rig, then cleans and drys the chamber and barrel. He then takes factory loads and lubes the cases. After firing five of these, he measures locking lug setback and headspace.