Cartridge pressure and primary extraction

[stubbicatt]

Been thinking on it. With respect to classic lever actioned rifles, which typically have a straight rearward pull on cartridges upon extraction, I notice one tends to find lower pressure cartridges. Bolt actioned rifles, and semiautomatic rifles which have a camming action in primary extraction, seem friendlier to higher pressure cartridges.

Is it that, say the Winchester 1894, action is weaker due to its rear locking lugs, or is it more a question of lower primary extraction forces which limits the pressures at which cartridges chambered in such rifles operate?

I wonder, as a rule of thumb (if there be such a thing) at what peak pressure will a given cartridge in a lever rifle no longer readily extract?

I understand that cartridge taper has a part in this. Ferinstance the venerable 303 British cartridge in the Enfield rifles, does not really have a camming action on primary extraction due to the non rotating bolt head, and a rear locking lug, it is loaded to higher pressures, but the system works just fine? Is this due to greater taper than say, a 30-06 which is long in the body and comparatively straight walled.

Another action which seems to be loaded to higher pressures, is the modern, Japanese version, of the Winchester High Wall. Yet it seems to be able to extract such cartridges readily, while seemingly lacking any significant primary extraction. I have seen examples chambered in 30-06.

Or are there other limitations or strengths I am missing here?

 

[Slamfire]

Is it that, say the Winchester 1894, action is weaker due to its rear locking lugs, or is it more a question of lower primary extraction forces which limits the pressures at which cartridges chambered in such rifles operate?

I have never seen a structural analysis of the Win M1894, but I think it is very safe to say that all rear locking actions stretch more than front locking actions. Let's say that steel compresses 0.001" per inch (swag) at load. So a rear locking action is going to stretch (given a cartridge length of 3") 0.003" just due to locking system stretch. There may be more as the bolt will bow.

This will cause case rupture and was a real concern in the Lee Enfield days and in the development of the FAL.

The roller bolts don't use primary extraction, the case is popped out of the chamber.





The absolute last thing a designer wants is case to chamber friction during extraction. Both actions and cases are designed so that the case is clear of the chamber walls. The curve on the right is the bad curve, because the chamber is crushing the fired case.

 

[44 AMP]

I wonder, as a rule of thumb (if there be such a thing) at what peak pressure will a given cartridge in a lever rifle no longer readily extract?

yes there is such a pressure, but I can't give you a number, it will be different for different case designs and actions. One thing it will be is above the max working pressure for the gun and cartridge.

Such a thing CAN happen, even with standard pressure rounds, in conditions of extreme heat.

Look at the classic African Double Rifle rounds of the "premagnum" era, and even the first magnum rounds, the .375 and .300 H&H.

They are all long, very tapered rounds. to aid in extraction in the HOT African environment. Pressures are kept "low" (40-45000psi) and cases are big so desired performance can be had without higher pressures. The designers knew where the rounds were going to be used, not in the cool and damp of Europe, but in the sweltering heat of Africa, and built what would work there, and work in a double rifle that didn't have the turnbolt's primary camming extraction.

Now, about the old classic leverguns, here there is a somewhat different story at work. They are all designed for black powder rounds, or an upgraded version of those actions. The 94 Winchester actually hit the market the year before smokeless ammo was available for it. The pressure of rounds for the 94 is kept to what the 94 will handle. That is deliberate.

Other lever gun designs have other pressure limits. Look at the Savage 99. Also technically a "rear locking" system, the 99 was able to handle .243, .284,.308 & .358 Win pressures (modern 50-55Kpsi levels)

The BLR uses a multiple lug rotating bolt lockup, and will handle any modern high pressure round just fine.

Another point to consider is that the classic Mauser turnbolt rifles, with their powerful camming action were designed in an era when case failures and stuck cases were much, much more common AND that they were built to be military rifles, that would work under the worst possible conditions, without fail. Huge extractor claw, holding close to a third of the rim, and camming extraction were big selling points for reliability.

Those were not as important for sporting arms, which generally don't get quite as abused.

 

[stubbicatt]

My memory is straining a little bit here, but IIRC, wasn't there a 307 Winchester built for a '94 action? It was a 308 with a rim and a flat nose bullet, operating at 308 pressures? Strange to me, as that cartridge has minimal body taper, and presumably it operated ok in the 94 action.

Let's attack it from another angle. Assuming a strong bolt actioned rifle were chambered in 30-30, could one safely load the 30-30 to say, 60,000 psi., be safe, and still get reliable easy extraction? In essence is it the shape or construction of the brass case which makes certain combinations work well at higher pressures? It seems to me there was a 38-55 loaded to some pretty high pressures they called like 375 Winchester or something like that? Again, IIRC, they modified the case in some way... maybe a stronger web or something?

Slamfire, I am studying those curves you provided. I wonder if you can offer up what is x, x1, and y as I would like to understand it better?

 

[44 AMP]

The .307 and IIRC the .356Win were put in a re-enforced model 94 action. And, if memory serves, I believe they were still both loaded to slightly lower pressure than their rimless ancestors (.308 & .358). Higher pressure than other "original" model 94 rounds, but slightly less than the rimless rounds.

The .375 Winchester was dimensionally the same as the .38-55 other than the case being very slightly shorter, overall. Pressure, (and velocity) however was much higher.

The .375 Win was sold in the Model 94 Big Bore rifle, which has a beefed up 94 action. The action of the Big Bore is much thicker at the rear (where the locking lugs are) than the standard model 94. If you can find a picture of both, its easy to see.

Let's attack it from another angle. Assuming a strong bolt actioned rifle were chambered in 30-30, could one safely load the 30-30 to say, 60,000 psi., be safe, and still get reliable easy extraction? In essence is it the shape or construction of the brass case which makes certain combinations work well at higher pressures?

The short answer is, "yes".

It is a matter of many factors working together at the same time. The design of the gun's action, the design of the case, the construction of the case, how these fit together, and of course the pressures. Probably another thing or two I'm leaving out...

Modern brass begins to fail above the 65,000psi mark, even when "fully supported". Can (and does) fail at much lower pressures under the right conditions.

There are many rounds that can be safely loaded up in the right gun. Literally, all of the older rounds can be, IN THE RIGHT GUN.

The most obvious example is the classic .45-70 Govt. Originally a blackpowder round. Straight case. Today, there are three different levels of loads known as Tier (or Group) I, II, & III.

Group I are loads at black powder pressures. Safe for use in the "Trapdoor" Springfield, and similar rifles of the era.

Group II are loads for the 1886 Winchester (and modern Marlin 1895) and are loaded to higher pressures, which are not safe in the weaker Trapdoor rifles.

Group III are loads for bolt action and modern single shots, like the Ruger. These actions are the strongest, and the max loads are dangerously unsafe in weaker rifles.

Another example is the 6.5x55mm Swede. The Swede is a 45k psi round, because that is the pressure limit of the 95 Mauser action it was "born in ".

In a modern bolt action, the Swede can safely be loaded up to the 55k psi range, with an improvement in performance.

Case design (taper, etc) does play a part. RIFLE design plays a LARGER part.

So, yes, in a well built bolt action, you could load that .30-30 case up to the 60k psi point. Shooting one of those rounds in a model 94, however would likely leave you with a stuck case, if not worse.

 

[Jim Watson]

P.O. Ackley overloaded and mistreated a '94 in .30-30 AI, claiming great things for the straighter case.

 

[Gunplummer]

I probably mentioned this before on this forum. The 99 Savage was mentioned. I still have one in .243 and it "Springs" with a hot load. I did not want to bother to reload and bought ammo from the 'Big Three". Federal and Winchester felt hot and the extraction was "Stickey". Remington was OK. These rear locking actions will actually stretch apart (Not permanent) and cause excess pressure on the fired case when you go to extract. I bought some loaded ammo from a Gunshop at a show for my .22 HiPower. Way too hot. I had to force the action open and the head had actually swelled. The rifle went back to normal with reasonable loads. The thing about the 94 Winchester is that by the time it starts to spring, it may be too late because of the lighter design of the early ones.

 

[RC20]

P.O. Ackley overloaded and mistreated a '94 in .30-30 AI, claiming great things for the straighter case.

Yea good old PO did a lot of stuff that modern analysis has proven to be bogus or so little improvement it was a waste.

Or as I have told my brother, if you want a 30-06, 308 or the like to perform better, use R17 and you actually get a discernible improvement (in velocity not necessarily accuracy)

More than the measly 150 PO was claiming as I recall for 30-06.

 

[Slamfire]

P.O. Ackley overloaded and mistreated a '94 in .30-30 AI, claiming great things for the straighter case.

Yea good old PO did a lot of stuff that modern analysis has proven to be bogus or so little improvement it was a waste.

Agree, Old PO was selling rivers of snake oil. None of his data is instrumented so his results are not repeatable. The idea of taking the lugs off a 30-30 AI to show there is case friction, well I could have told the world that. I discovered case friction decades ago when I had to get a cleaning rod to knock out a stuck case. I have repeated this experiment time and again, as loads developed in 70 F weather occasionally cause problems in 90 F weather.

What P.O Ackley did not do was try to fire a 30-06 AI and see if the case would stay. Well it would not, at least the case head. Around 24,000 psia the sidewalls will give way and the case head would pop out, assuming the front of the case stayed in the chamber. A 30-06 AI ought to operate around 60,000 psia. I have never heard Ackley supporters volunteer to fire their AI cartridges without locking lugs or a locking mechanism. I would like to find some Ackley fan boys and photograph them as candidates for the Darwin Awards. It would be funny to see one of them with a cartridge case sticking out of their forehead. Look Ma, no lugs!

P.O Ackley was claiming that his straight case design increased case to chamber friction, therefore it was OK to add lots of powder. His claim was that transferring the load to the case lessens the load on the bolt and therefore, increasing chamber pressures is just wonderful and A OK with AI cases. He never really proved that his case design reduced bolt anymore than any other case, and he totally ignored the problem of where the load goes. In P.O Ackley's world, it just went into the dark universe. It does not, it goes somewhere, and that somewhere is the case and the barrel. He was increasing the stress on the brass case, which is a lot worse than increasing the stress on the bolt, because the bolt is steel. And he ignored barrel loads, though in one of his experiments he bulged the barrel of a Savage M99. He sort of ignored that too.

 

[Gunplummer]

It would kind of make sense if you dealt with normal loads. The problem with most people is they can't seem to deal with normal. There was some horse crap problem on this forum about difficult extraction from a tight chamber a while ago. What nonsense. "Tight chamber" usually means a screwed up reamer, probably the neck or free bore area. Take the extractor off your rifle and fire a round. Pull the bolt, then pick the rifle up so it is up right and GENTLY tap the butt on the table. The case should fall out. Most of the time the case will drop when you pick up the rifle. If not, you have a problem. I tested reamers I made like this for years. If I was using O-1 tool steel for the oddball chamberings, it really gave a ratty finish. I mean, if you looked close, you could see the reamer marks on the brass. Obviously the brass grabbed the chamber wall when it expanded. Who the heck knows what people REALLY do when they describe a condition. I just resized some 7.62x39 mixed brass I bought. Some of the cases had a serious reduction about halfway down the neck. I mean SERIOUS, not like it was .311 shot in a .308 barrel. It had to have been shot in the wrong gun. Even a short chamber would not do that to the brass. Like Paul Harvey used to say: "And now the rest of the story....".

 

[FrankenMauser]

As mentioned in previous posts, the reason for the pressure limitations of common levergun cartridges is due to the design strength of the actions.

Even more modern cartridges like .444 Marlin (1963) and .450 Marlin (1999) are held to fairly low chamber pressures (42k and 43.5k MAP, respectively), since the firearms can't take 'modern' pressures.

The cartridges themselves, in stronger actions, are more than capable of significantly better performance. But the primary platforms (evolutions of the Marlin 336) can't take it.

P.O. Ackley overloaded and mistreated a '94 in .30-30 AI, claiming great things for the straighter case.

So did my grandfather.
He pushed 150 and 170 grain projectiles so hard in that .30-30 AI Marlin 336, that he started having instant case head separations with factory loads.
He took it back to the gunsmith that did the rechamber, and the guy asked him if he had a death wish.
"What the [fleep] were you doing? You bent the locking lugs and stretched the action, you [dimwit]!!"

To this day, that gunsmith (whom I do business with) keeps two of the fired cases from that 336 on his work bench (one from testing after the rechamber; one from my grandfather's string of case head separations/failures). They're a reminder to him that he needs to get a better idea of the customer's expectations before taking on certain jobs.

 

[Llama Bob]

For MOST lever actions, the reduced pressure limits are due to limits of the bolt and action flexing/flowing, and resulting headspace problems.

In lever guns with very strong lockups on the .45-70 or smaller bolt face (as opposed to the .50-110 bolt face) which basically means modern 1886s you can get cartridges that are a bit hard to extract but which will not stretch the action. This happens in the neighborhood of 45-50KPSI. This is the only pressure sign you will get on those guns too, so you best pay attention to it...

 

[stubbicatt]

Thanks fellas. Glad I asked the question. As I read the responses and reflect upon the experienced and knowledgeable responses, I think maybe I have a better understanding of my 1904 High Wall. The reason that action is as strong as it is, given the period steels of which it was made, is that the locking lugs are right there... right behind the case head. The further from the breach face the locking lugs are located, the more likelihood of a stretched action, such as the 1894.

Even so, the relatively thin area where the barrel tenon threads in is a limitation of sorts. I've read of receiver bulging at that point.

--I still wonder how the Lee Enfields accomplished their success. Two design features, non rotating bolt head and single rear locking lug which do not typically add up to success.

 

[6.5swedeforelk]

... the venerable 303 British cartridge in the Enfield rifles, does not really have a camming action on primary extraction due to the non rotating bolt head, and a rear locking lug, it is loaded to higher pressures, but the system works just fine? ...

The Lee Enfield never gained that good reputation among the better battle rifles by not having sufficient primary extraction!

A rotating bolt head is no criteria for extraction.

The left locking lug has front end angle that , on lifting bolt, cams against its' recess.





edit: I just read stubbicatt's last post...

Lee Enfields have single locking lug??????

 

[stubbicatt]

Lee Enfields have single locking lug?????? says 6.5swedeforelk

Don't they? I had a couple over the years, a SMLE and a No4 Mk*. That's how I remember it... One long lug that locked on the right side of the action and butted against the rear of the receiver window...

 

[6.5swedeforelk]

Open the bolt on the Lee Enfield & the left locking lug is now at the bottom of bolt,
opposite to the rear of the right lug.

You may have missed it as it's only .6" long.


Good hunting

 

[James K]

I believe Stubbicat is thinking of the U.S Krag action, which has a single forward locking lug and a long safety lug which does not bear in the normal setup. The Norwegian Krag action, though, is set up so both lugs bear, making it a stronger two lug action even though the lugs are asymmetrical.

Jim