An interesting theme in regard to bolt thrust of the new short magnums:

http://www.eabco.com/WSM01.htm

Yep! It turns out it doesn't matter how long the action is. These cases still stick. I've built 3 6.5 WSM rifles. All exhibited early case sticking. Sure it does what a 264 Win mag does (maybe a little better) if you can get it up to the same pressure without sticking the cases. This case starts sticking around 58000psi and by the time you get to 65000psi you almost need a hammer to open the bolt. These were tested with peak strain gauges. The least symptomatic rifle(had pretty good results) was built on a Win M70 action. Here the barrel tenon was only .7". One was built on the Rem 700 long action and one on a Savage M11 as a sporter. The barrel tenon with a competition lug was about 1-1.1". I believe the difference between these two types of "systems" is the amount of chamber covered by the wide part of the barrel. The 1.24" diameter barrel better resists strain by this oversized case and allows less brass expansion against the chamber wall which means less sticking when the chamber returns to its normal conformation. I can identify this difference in that the absolute value of microstrain is about 880=65000psi for the WSM and about 700=65000psi for a typical belted magnum. Clearly the chamber is expanding much more at the same pressures in the WSM cartridge.
The impact this phenomenon has on performance is best illustrated by the following example. In the rifle built on the M70 action, I was able to obtain 3350fps=65000psi with a 120gr Nosler ballistic tip. There was some sticking but not bad. In the one built on the Savage M11, I had to settle for 3180fps before significant sticking occurred. The barrels were only one inch different.
Its interesting that a cartridge designed by winchester works better in their actions!!

My local gun plumber recently showed me a box of factory Winchester .300 WSM 180 grain Failsafe fired cases. Of the twenty fired cases, two showed extreme pressure. In one the primer had fallen out, both had ejector marks on the head, and both cases had to be extracted with the aid of a mallet. He said that happened to him often with factory ammo in the WSM cartridges.

A lot of people sure do get their excercise by "jumping to conclusions" and "jumping on and off band wagons".

One of the problems with the WSM and the SRUM is the fact the case head is rebated adding to the effect of bolt thrust. Take a look on the Lilja barrel web-site for a good article.

With respect to the case "gripping" the sides of the chamber...I wonder what the surface area in contact with the cahmber is for both the .300WM and the .300WSM....one is longer but the other is "fatter" can someone do the math for surface area?

Poor P.O. Ackley...he either gets credit for everything or blamed for everything. Reading the web-site I can't tell which they are doing.

I think there are probably two reasons for the problems some shooters are having...(1) I think we've all read about poor quality control with respect to canted bolt faces and (2) inconsistent ammunition. I think in the rush to beat Remington that Winchester went a little to fast.

Finally the Lazzeroni cartridges are even shorter and fatter than the Winchester....anyone heard of any problems with them...no...several reasons. First they have a bolt face designed for a 0.580" case head (non-rebated) and second, high quality brass.

There isn't any free lunch...if you want to play where the air is rare you had better be prepared.

Does a rebated rim contribute to bolt thrust? In any case the WSM's rim is .018" smaller than the body.

"The primary cause of mechanical failure is improper assembly".

Why aren't Mark V Wbys sticking with the 378 based calibers, especially given the Mark V action only has about half the primary extraction of a Model 70?

I also have difficulty with this idea of the case sticking to the chamber wall and reducing bolt thrust, at least to a degree than means anything. Ever notice how easy a case fireforms to remove head space.

Mike

Mike, I agree, once you go over 45,000 PSI or so, all the brass does is seal.

The issue of sticking is different from bolt thrust, however. The Lilja article raises that excellent point.

From personal experience with a falling block design (one that is very sensitive to bolt thrust), I dare say that bolt thrust is NOT LINEAR with bolt area.

I do find it intrigueing that the 284, with it's fatter case and smaller bolt face, is not known for any of these problems???????

Personally, I think that MOST of the problems with the WSM cases are related to the case. I suspect (speculate, guess, whatever you want to call it) that the case itself is softer than standard in order to accomplish the substantial necking operations needed to manufacture it. Which DOES recall the manufacturing problems with the 284 case when it first came out. FWIW, Dutch.

Dutch,

With rear lockers like the 303 SMLE (Chambered for 303/25) we always got sticky extraction with any sort of a half way decent load. The actions stretchs a bit an of course the case fireforms and when the pressure drops the action attempts to return and of course forces the fire formed case in and hence hard extraction.

Is this problem being reported with 300 WSMs also occuring with 300 Rem Ultras?

It would be quite funny if after all of these years and all the Wby bullshit if it turned out old Roy's Mark V was the strongest

Mike

[ 09-30-2002, 17:45: Message edited by: Mike375 ]

My guess is that at least in factory model 70s the case sticking and pressure signs are caused by poor quality control on the part of U.S. Repeating Arms. I had an early 300 WSM, and Winchester had cut the chamber severly out of round. Needless to say, I experienced major case sticking, ejector marks and other pressure signs. This was my second model 70 in a row to have serious problems. My assumption would be the problem could be attributed to out of square bolt faces or locking lugs, bad chambers or bad barrels. I would recommend sending factory loads that are showing signs of pressure back to Olin for pressure testing. Mine checked out alright and Olin sent me a voucher for two boxes of ammunition.

Take this for what it is worth, an opinion. I do think there are too many people having no problems what so ever with the WSM for it to be an inherent design problem with the case when chambered in a modern bolt action rifle.

This is purely anecdotal, but my M70 FWT in .300 WSM has roughly 500 rounds through it. Not one problem with sticky extraction. I load it up to published max loads with mostly 180 and some 150 grain bullets. Primers are normal, no unusual pressure signs. I know that's only my limited experience but I've been shooting and reloading for over 25 years and load for over 15 different rifle calibers.
FWIW, my model 71 .348 Winchester factory ammo shows more signs of high pressure than my WSM.

I've got a new MDL 70 in 300WSM. Same thing, sticky bolt sometimes, and extractor marks. The pressure signs were pretty distinct with the 180gr failsafe loads, less so with the 150gr BTs.

Jack Belk believes it to be an out of square bolt face, and I assume he's correct, because all three boxes of ammo I've tried had some sort of extractor mark.

The chamber where the shoulder rests must be incredibly rough, as well. The shoulders of the case all come out with circular, fairly deep scratches.

The gun is incredibly accurate, though.

Mr. MD
What did you end up doing with your rifle?

There is one inaccuracy in the article from that website- about chambering WSM's in long actions. The magazine for the mdl 70 has plenty of room...You could probably seat the bullets out far enough that they wouldn't stay in the case.

I suspect that in most cases the sticky extraction is due to chamber finish and, in some cases, to misshapen chambers. As well, the crooked bolt face is almost a given with many of the new Winchesters and the 700s.
I suspect the WSM would be less of a problem if it had a little more body taper. This would perhaps make it easier to achieve a good finish on the chamber from the factory. Regards, Bill.

Gatehouse,
I had a gunsmith look at the fired cases, and he said the chamber was too far out of round to turn the barrel back a thread or two and rechamber. I sent the gun to a Winchester service center, and I believe they turned the barrel back and rechambered. I got the gun back and the problem was still there, but not as bad. By this time I had spent two or three months dealing with Winchester's horrible customer service, and I wrote a long letter to them asking for my money back. They had me send the gun back and then sent me a refund.

I love the design of the model 70s, and inspite of the quality problems, I would buy another if the customer service was better. Right now, I wouldn't buy one unless I was planning on building a custom gun from the action (squaring locking lugs, new barrel, etc.). I guess for now I will stick with pre-64s and FNs. I may try a Dakota 97.

Bill
How would you fix the rough chamber, like what I described on the shoulder area?

Could it be polished without altering the headspace? I guess the questionis really academic, because to fix the bolt face, it's going to alter head space anyway, but I'm just wondering...

Mr MD
When I called them about my problem, the very polite fellow on the phone said that they haven't had any problems like mine...I just think he was telling stories.

I'm really pretty disappointed with Winchester, too. I like the design as well, but the more I look at this rifle, the more I think it is a rough platform to be built on...

I suppose I could say I was warned!

Speaking of chambers. The reamer used to cut my 300 WSM evidently had a fairly large nick in it. The imperfection would show up on the shoulder of fired cases.

DB Bill

My father owns a Lazzeroni 6.17mm spitfire built by lazzeroni arms. The same phenomenon occurs as with the WSM cartridge(sticks long before typical maximum working pressures). It has something to do with short, fat, nearly overbore cartridges. Long fat cartridges work great for example the 300 RUM. I work mine at about 65kpsi and never had a hint of bolt lift.

grkldoc

Do you mean he is getting excess pressure signs before he is reaching the velocities shown by Lazzeroni? Is his rifle a factory rifle built by Lazzeroni or did someone else do it? Does the same thing happen with factory ammo or just his handloads?

As an aside, I had some problems with my Lazzeroni Hellcat initially but found out it was a bad batch of RL15....once I changed lot numbers the pressure signs went away and I go another 100+ fps of velocity.

The sticky bolt lift in the 300 WSM might be a combination of high chamber psi & the SLICK nickle cases that don't grab the chamber walls upon expansion like brass does.

DB Bill
The spitfire case sticks at low pressures and are unable to obtain reported velocities its only slightly better than a 6mm rem. These are with the loads worked up by Lazzeroni. Once again, it was built by Lazzeroni arms.
Physics determines what can be done. These short fat nearly overbore cartridges are at the limits. Some function better by changes we can make in a rifle's construction. However, with current production action design these cases will be prone to exhibit the previously mentioned problems.

grkldoc

Bear Claw
Can you elaborate a bit about the nickel cases? I'm afraid I have little experience with them except for the recent 300WSM episodes...

I generally handload, but haven't got set up for this cartridge yet. I don't plan on loading plated brass.

grkldoc.....sorry I should have seen it was a factory rifle.

My other question was "are we talking about factory loads or your father's handloads"?

DBBill

They were handloads using the loads reccomended by lazzeroni. If I recall correctly, he was unable to get as high as the reccomended loads before his cases stuck and therefore did not achieve the reported velocities.

Gatehouse,
The most effective way to fix your problem would be to set the barrel back and rechamber. However, if the headspace is currently at minimum it might be possible to simply ream an extra .002 or so and still be within specs. It would take very little to clean up the angle of the shoulder. As well, since there are no sights on the rifle (are there?), one could set it back just .006" which would amount to about 1/10 of a turn and rechamber by this amount. It would be necessary to slightly widen the xtractor cut but this wouldn't be any problem either. This may be the one advantage of the push feeds, no extractor cut! As you mentioned, it is all academic if you have to have the bolt face fixed anyway. Usually, by the time you have trued the face and achieved something approaching full lug contact you will have increased the headspace measurement by around .010 anyway. This means a setback is necessary and the chamber can be fixed up at the same time. Regards, Bill.

grkldoc....when I first got my 9.53 HellCat from Lazzeroni I had a problem similar to what you describe....John told me he had gotten 2600+ fps with a 300gr Nosler and I was getting pressure signs at 2450 fps...big time pressure signs. Had John send my some ammo and presto I got 2600+ fps. I measured them...took them apart...weighed the charges etc.....I was dead on with everything John had done except I had seated the bullet just a tad deeper into the case. In desperation I tried a different production lot of RL15 and Bingo I went to 2600+ fps. Every since then I have been very cautious when dealing with any Aliant Powder...by the way, I bought 8 lbs of that lot.

I just don't think that the SLICK nickle cases grab the chamber walls upon expansion like brass does.

I was hesitant to join in this thread since the concept of "bolt thrust" has been beaten like a dead horse over and over again. But fools rush in . . .

First, imagine that there is no bolt face backing up that WSM case head, only a firing pin. Now imagine what happens when the firing pin strikes the primer: I see pressures inside the case quickly rising to the point that the case head separates from the case walls -- don't you? In other words, the tensile strength of the case walls is not enough to keep the case head from blowing off. Agree? If you do, then you'll also have to agree that no matter how much or how little friction there is between the case walls and the walls of the chamber, that the bolt thrust will not be effected. The bolt thrust will equal the chamber pressure times the interior area of the case web perpendicular to the bolt face. If that area is, say, .2 square inch, and the peak chamber pressure is 50,000 psi, then the peak bolt thrust is 10,000 lb. No amount of flimsly stretch-resistance of the thin brass case walls is going to significantly change this thrust.

With a rebated case, the total pressure acts on a smaller area of the bolt face, but that total "bolt thrust" is still the same and is proportional to that interior case area, rather than to the size of the face of the case. Yes, a WSM will have more bolt thrust than a standard belted magnum, because the interior area perpendicular to the bolt face is greater (its a "fatter" cartridge). This has nothing to do with the rebated rim. The bolt thrust would be the same even if the WSM rim were the same diameter as the case.

Likewise, an '06 size case (.473") will have less bolt thrust than a magnum (.525"), and a .222 family case with it's .372 head will have less still (at the same peak chamber pressures).

All of this means that all things being equal, which they never are (brass spring back, peak pressure, etc, etc), a WSM will show a sticky bolt at a lower pressure than a belted magnum or an '06 case. This is simply one of the trade-offs necessary to get more powder capacity in a shorter case.

"Agree? If you do, then you'll also have to agree that no matter how much or how little friction there is between the case walls and the walls of the chamber, that the bolt thrust will not be effected".

Untrue. It's a well known fact that case shape, as in degree of taper and/or length of chamber engagement can increase bolt thrust at a given pressure. I can give you other mechanical examples of this principle if you wish.

First, tell me whether you agree that the case head would come flying off, then we'll discuss what this means to bolt thrust.

There seems to be confusion between "bolt thrust" and "sticky bolt lift". Resistance to bolt lift is caused by the tension of the fired case against the bolt. That tension may or may not have much to do with peak pressure, but rather may be caused by lack of brass springback and/or by the shape of a case which tends to impede brass springback. The .22 Jet, with it's extreme taper, in the S & W Revolver is a prime example of the latter. Another example would be with a straight-walled revolver cartridge in an oily chamber. Rather than gripping the walls of the chamber upon firing, the entire case would slip to the rear until the head bears against the revolver frame. In this case, rather than the case head springing back, there has been no case stretching, therefore nothing to spring back, and the cylinder may be frozen due to the case head bearing against the frame.

Straight-walled cases in dry chambers do tend to have less slippage and better springback and therefore are less likely to result in sticky bolt lift. This doesn't mean that they give less bolt thrust. Again, the shape and condition of the chamber is irrelavent to bolt thrust, but may have a significant effect on bolt lift.

so do i need to really let this bother me if i am thinking about buying a new coyote 270 wsm and shoot factory ammo at whitetails? i really wish it was a remington 700 though!

Gases expand in all directions. A larger diameter case will have more pressure pushing out on it due to more area for the gas to work on. The shape is insignificant as it pertains to an increase in pressure. The pressure will be dictated by how much is in the case. As is illustrated by this thread, those who are using the .300WSM are running at absolute max pressure then whine when their rifle doesn't work right? What's the problem here? Operator malfunction.
pV=nRT and A=(Pi)r^2

Stonecreek, I agree with you! There may be some small thrust force generated by the moving case, but that would be insignificant compared to the thrust force generated by the internal pressure of the case. The case expands to fill the chamber volume. The expansion will be quicker radially than axially.

Roger, you too are correct; however, I believe all these cartridges are loaded to achieve similar operating pressures. Basically, what you have shown provides proof of the fact that a larger case requires more powder to achieve the same pressure. This is due to the fact that the volume increase of the case requires a proportional gas volume increase to achieve the same pressure. To achieve a gas volume increase you have to use more powder.

Axel

Case shape is NOT insignificant. That's the point of my posts. The standard bolt thrust calculation is NOT the whole story. Let's read them thoroughly and if you still can't grasp it, I'll explain it in mechanical terms.

[ 10-03-2002, 21:08: Message edited by: Nickudu ]

Nickudu, the pressure of the gases reacts pependicularly to the internal surfaces of the case. So the largest single component of bolt thrust will be the force generated by the internal case pressure acting upon the case's internal diameter at the case head.

The case taper will allow some additional thrust to occur because of the radial force vectors acting upon the walls of the case. To determine the magnitudes of these vectors in the direction of the bolt thrust is a simple thing.

First you must calculate the radial force acting upon the case wall. The thrust force component due to the taper angle of the case is then equal to:

Radial force on case wall * sin(body taper angle).

Example:
Operating pressure: 55000 psi
Case internal base area: 0.125
Case base OD: .54"
Case base ID: .39:
Case wall thickness midlength: 0.035"
Case diameter midlegnth: .52"
Case body taper angle:0.6 degrees
Axial bolt thrust: 55000*.125 = 6875 lbs
Radial force on case wall: 8800*sin(0.6 deg)= 92.2 lbs

Total thrust force is = 6875 + 92.2 = 6967.2 lbs

The radial force is: pressure time the cross sectional area of the case.
Radial force = 55000 * 0.16 = 8800 pounds

So Nickudu, as I said the body taper's contribution to trust force is insignificant. Additionally, we have assumed that there is not friction acting between the chamber wall and the case. If we were to apply a static coefficient of friction of 0.3, which is unrealistically high the thrust force due to body taper would be equal to 92.2 * 0.3 = 27.7 pounds. Even less significant!

Axel

[ 10-03-2002, 21:28: Message edited by: Axel ]

Axel,
You are disregarding the relationship of headsize to case length and design entirely and applying the standard math for bolt thrust. Assuming you have read the informational links I have posted, I can only say that I agree with them and you do not. There is an inherent limitation in short magnum design and I think these people have properly identified it.

Nickudu, I have read all of the link you provided. I read enough to see that they are clouding the issue.

My calculations have included the case head diameter and the case length. As case head diameter increases so does the thrust for for a given pressure. The shorter case will require a larger body taper to allow for positive extraction. So there will be a larger component of thrust due to the body taper as well. This is all there is to the case head diameter vs. length issue.

I say the link clouds the isssue, because they are overstating the effect of the body taper on the thrust force. This really is very simple mechanics and vector analysis. I have provided you with the appropriate equations to perform the calculations yourself. I do not know how to explain it any better.

Axel

Where's Harald when you need him?...

He said something a while back that I disagree with. He said that bolt thrust is purely a function of bore area and peak chamber pressure, and has nothing to do with the shape/configuration of the case. I was one of the idiots that knew nothing about calculating bolt thrust because I was using base diameter (not bore diameter) and pressure.

On one hand, I can see his point. Every force has to have an equal and opposite reactive force. If you put 40KPSI against a 308 caliber bullet, the bolt must react that force through the bolt, to the firearm/shooter. It didn't matter if the case looked like a 30 carbine or 30-378WBY, if the peak chamber pressure/bore diameter was the same, the bolt thrust was the same. On the other hand, I think the chamber acts as a pressure vessel, where the force on the bolt would be equal to the peak pressure times the area that the pressure is applied to.

To take this to an extreme using Harald's bolt thrust equation, let's assume a closed bore with 40kpsi peak chamber pressure. Harald's bolt thrust would be zero - 40KPSI times NO bore would be zero bolt thrust. Obviously, this cannot be.

Now back to this discussion, my opinions only on this matter. The brass does not have enough strength to contain, or affect to any degree, the chamber pressure - I think that it is there only to seal the bolt-to-chamber gap like a gasket. The sticky bolt is due to the residual compressive forces of the action/chamber acting on the brass. Both stretched, but the action sprang back more than the brass did, hence the action/chamber is putting the stretched brass in compression, creating a sticky bolt lift.

I do not think tapered cases cause more bolt thrust than straight tapers. Tapered cases extract easier because of the geometry of the case, they "fall away" from the chamber walls more readily. Given the same case body area, the bolt thrust would be the same, because thrust is simply area times pressure.

Just my opinions, sorry for the dissertation, but as you can tell, I've been giving this (too much) thought, Bill

(Edited to add) Back to the original post, I think EABCO is just trying to sell more long action WSMs....

[ 10-03-2002, 23:12: Message edited by: Bill M ]

I think you've got it about right, Bill M. The only force creating "bolt thrust" is the same force creating "chamber thrust" and "bullet thrust", ie. the gas pressure in the chamber. That pressure pushes relatively equally in all directions (with the caveat that it is not static pressure but dynamic pressure and therefore may act differently than just taking an air hose and pumping up the chamber to 50,000 psi).

You are certainly correct that it is the expanded case binding against the bolt, after all pressure and thrust have been relieved, that causes sticky bolt lift.

I'm not sure that I agree, as Axel contends, that there is an effect on bolt thrust, however small, due to radial forces from the shape of the chamber. As an example, if a chamber were shaped (impossibly) with a reverse taper, the bolt thrust would still be only equal to the pressure acting on the area of the case supported by the bolt face. I think this would be true no matter the shape of the case, but then again, the behavior of dynamic pressure vs. static pressure is a wildcard that I have no way of calculating.

[ 10-04-2002, 00:04: Message edited by: Stonecreek ]