After reading this thread https://forums.accuratereloading.com/eve/forums/a/tpc/f/2511043/m/810104443 and ALF’s reply (What blows a rifle? Usually not primary failure of the reciever and bolt. Most blow ups occur because the primer blew or the case seperated.

The violent massive escape of gas blows the non- structural parts of the action and the stock and whatever's attached to it.

So what comes asunder is the stuff that is attached to the reciever and bolt. They are not designed to withstand the forces brought about by this sudden bleed of gas.

It's not the gun, it's the cartridge case that can’t take the overload ! …)

I still believe that the rifle receiver is the week spot. Do not get me wrong, this is nothing against Savage rifle, it’s one of the strongest on the market. However, we have to accept the fact that the brass is the week and WILL fail under high pressure, and majority, if not all receivers, have insufficient relieve ports to get rid of huge amount of gasses in case of brass failure.

The plain fact is that when gases escape into receiver, behind brass case, suddenly we have LARGE diameter pipe under the pressure. I didn’t do calculation but if opening where the locking lugs are located is about .900â€, the outside dia should be at least 1.800†to have the same strength as the barrel in chamber area. And that is without counting thread, corners and other cutouts that are weakening integrity of the receiver. The bottom line is that the pressure in the receiver in case of brass failure, even at nominal in the barrel WILL blow up the receiver. Look at the pictures, the receiver shattered like the cannon shell. At the same time, barrel was basically intact.

Considering what could be done, I was thinking of making larger escape holes, 2-3 of them, 5/16†dia or even 3/8â€, drilled in the raceway where bolt locking lugs are entering receiver. This method would weaken receiver very little since the main metal body in front of the receiver locking lugs wouldn’t be affected, yet it will prevent pressure buildup within receiver.

Would be nice if somebody has an old rifle and safe place to make an experiment…

Let me know what you think. Regards, Onty.

since you asked what we think, I’ll offer my two-cents.

The weakening that would result from boring these sized holes in the receiver would far outweigh any assumed benefit of gas venting.

Just spitballing mind you, but, what about
pop-off valves in bottom of the reciever? I know the pop-off on superchargers and propane tanks are very low psi compared to a rifle but it is worth a look.

quote:

Originally posted by dick broussard:
Just spitballing mind you, but, what about
pop-off valves in bottom of the reciever? I know the pop-off on superchargers and propane tanks are very low psi compared to a rifle but it is worth a look.

Not a bad idea...except that you would then have mutiple projectiles flying around at pretty high velocity if you had a failure that popped them loose.

There are many ways to approach this and I'll limit my discussion to bolt repeaters. The Single Shot breech block is as close to a cannon breech as we have concept wise. If a case head ruptures and allows gas into the receiver. Remington takes alot of beating about their extractors but their intent is to restrict or impede the flow rate of gas into the receiver due to the bolt nose and breech fit. Most all other makers allow unrestricted flow when the case head ruptures and therefore the front ring, extractor, an bolt race blocks have to withstand the pressures when this happens to allow the pressure to bleed off in a safe manner.

The most original concept I saw thus far was a rifle designed by Dick Casul. It incorporated a steel cartridge case head and an internal extractor groove which enables the barrel to fully support the case head all the way back to the extractor so its difficult for the case head to fail without splitting the barrel or shearing the bolt. To top that off the action incorporated buttress threads. The website is no longer but the firearm cartridge combo operated above 70,000 psi safely. But you have to take into account what such pressure does to the bullet and I suspect that along with the 2 piece case to have limited its success.

.

If the two holes are drilled left and right on dual locking lug receiver and plugged with rubber plugs, I don’t se any big problem if they got blown sideways. Even if they hit somebody (very rare possibility) it would be still less harmful than rubber bullets used by police, certainly less than steel bits and pieces from exploding receiver.

As for the strength, don’t have any rifle on hand, but assuming that outside receiver is 1.45â€, inside bore .900â€, two side holes .375â€, and steel strength 140,000 PSI. Our receiver will have theoretical strength about 113,000 lbs. Considering all those little corners, sharp edges, thread, etc., and reduce it for 1/3, that receiver should take at least 75,000 lbs force developed by cartridge.

If we use typical magnum case that has about .45†inside dia, at 100,000 PSI, the trust supported from the back will be about 16,000 lbs only. So, our drilled receiver will be still 4.68 times stronger than required to support the force developed by 100,000 PSI pressure in magnum case.

In other words, our “swiss cheese†style receiver has plenty of strength, and by drilling those holes we are giving little in order to gain a lot safer rifle.

Please, correct me if I omitted something. Regards, Onty.

(Booboo corrected, Onty)

onty,

I will preface this by saying that I am not an engineer.

Having said that...where did you come up with your theoretical PSI reduction of only 20,000 PSI after boring two .375†holes in each side of the front ring?

What formula did you use to arrive at that figure? Not an arguement, just a question.

Another approach is to go with a brass cartridge case with a deliberately thicker head and case wall. I think the .338 Lapua uses this approach, or so I have read anyway.

Both Frank de Haas and Stuart Otteson wrote considerable text in their respective books on bolt actions and their gas handling.

I would not be drilling those holes by the way.

jim

Nothing wrong to ask!

(1.45†x1.45â€x3.14/4 large dia)-(.9x.9*3.14/4 minor dia)-((1.45-.9)x.375 holes)=1.65-.636-.206=.808 sq in

.808x140000=113000 PSI

113000x.667=75.000 LB

My apology, I was in rush to move the car and made booboo, total capacity is 75000 lb.

onty,

Great math formula’s for calculating PSI...but how does that tell you how much the ring has been weakened by boring those holes?

Exact formula is bit complex. What I used is a simple one, but for our calculation the error is negligible.

1.45-.9=.55

.55/2=.275 receiver wall thickness

.275x.375=.103 area of the one hole in longitudinal direction

.103x2=.206 area for both holes, same as (1.45-.9)x.375

If you want exact one, I’ll try to work it out tomorrow, younger generation is blowing at my back, some projects are very urgent. Better be fast than sorry…

Is this formula is for calculating the lengthwise strength of the reciever.
And it seems a correct one for that.
But if a case blows out the stress tearing reciever apart is radial,and it takes less to
push reciever apart that way. So I think the secret is to have cases with thick enough bases so that base can't give out through corners, and
barrel bulges first rather than reciever being
blown apart.I had about 200,000 psi load in a Ruger 77, in my wildcat 458. The brass being thick base held, locked up bolt, bulged chamber,
but action held, and it is rebarreled and still going strong.Had reciver and bolt checked, no cracks.If that case had blown out, the reciever
would have blown out radially I think.Ed.

onty,

Perhaps I am missing your point...and I am not questioning your calculations.

What is puzzling me is how your mathematical formulas can accurately calculate the strength of this hypothetical receiver before, or after, boring two holes into it.

Does it matter where on the front ring the holes are bored? Must they be located exactly across from one another? Do they have to be exactly on the centerline of the receiver? Is the bolt head totally enclosed, or only partially enclosed? Does it matter what type of threading system joins the barrel and receiver? Is the receiver round or flat bottomed?

Or...are you saying that none of these things matter?

quote:

Originally posted by Onty:
Exact formula is bit complex. What I used is a simple one, but for our calculation the error is negligible.

onty,

I would respectfully disagree that the calculations you are using are too complex...in fact, they are not complex enough, IMO, because they do not factor in the conditions inside of a rifle chamber/barrel that are being subjected to huge fluctuations in pressure from expanding gases that have a variable, and inconsistent seal/resistance being provided by the moving bullet.

Have you ever lifted something with a steel cable rated at 2,000 pounds of static strength? What happens to that cable if a 1,000 pound load is allowed to dynamically load the cable by bouncing on it?

Doing a quick FEA on one of my action models. 1.25" OD round receiver .25" gas relief holes with 1.063 OD barrel, 70,000 psi pressure load. You end up with 173,000 psi VM stress concentration near the holes. Around 110,000 psi VM around the reciever ring away from the holes. Mind you its a linear calculation which means it doesn't consider yielding. Alloy steel yields ( depends on Heat Treat method/procedure )
410 stainless HT around 140,000 to 160,000psi
15-5 stainless HT 150-180,000 psi
4140 QTSR 130,000 psi
4340 QTSR 160,000 psi
Properties can vary depending on heat treat and source. Kind of makes you wonder what pressure is induced to cause the action to split doesn't it?

DemoSam,

Using mathematical/theoretical static pressure figures for this discussion is extremely deceiving because the pressures (note that I used the plural form) in a rifle ARE NOT static in anyway shape or form. They rise and fall depending on any number of variable conditions that are next to impossible to factor into a simple (or even complex) math problem.

Yes Ed, the calculation is for lengthwise strength, and I totally agree with your statements. As you mentioned, inside pressure will create radial stress that will blow up almost any receiver, once high pressure gases are inside locking lugs. I doubt that any receiver is designed to take such load. By adding those holes radial strength will be considerably weaken. However, if those holes are large enough, pressure buildup could be dramatically reduced thus preventing catastrophic overstress in radial direction.

Rick, the only complex calculation is for those two relieve holes. I was working on formula today and if you want, I’ll scan the paper and send it to you.

Let’s take, for example, Winchester post 64 action:

Two holes should be located horizontally across each other, in locking lugs raceways, through the centerline, right behind the barrel end. If the receiver’s height and with are identical, flat bottom or square receiver will have more lengthwise strength than round one because of larger cross section. However, radial strength will be basically the same because receiver will split where is the area with minimum thickness of material. Dynamical load, thread, sharp corners, etc. are another animals that should be considered.

As for enclosed bolt like Remington action, that’s different ball game again. This action should prevent, in the most cases, brass separation (“three rings of steelâ€) in case of overload, and should prevent gases from entering the locking lug area. Any pressure should be contained inside the barrel. How it work in real life in case of overload, I have no such information.

In many cases, open raceways do work as relieve ports, at least partially. However, the shooter might receive the blast in the face, depends of the design.

PLEASE, CONSIDER THIS DISCUSSION JUST AS AN IDEA EXCHANGE, AND NOTHING ELSE. Any serious work on this subject should be done by professionals, experienced in this type of design, and truly tested before released as a final product. Things are much more complex than they look and the information Demo provided illustrates this very well. So, if you find that somebody worked year or more on new rifle receiver design, don’t be surprised.

Take care, and if you do any experiment on your own, make sure that everything is safe and properly secured. And don’t forget the prayer. As a kid I did some stupid things and I am very thankful to the Almighty that I reached half the century intact. Lost pride doesn’t count!

The peak pressure will coencide with peak stress assuming mass and inertia effects negligable which I feel is fine in this case. So the static and dynamic model will be close and the dynamic model will tend to show less stress than the static model. I have done a Dynamic model but had to guess a P vs T curve. The question is what is the peak pressure inside the action when the case head has failed. You have the bullet headed down the barrel on one end and gas escaping on the back side from a split case and leaking out around the bolt and lug recesses. I'm not 100% up on my chemistry of powder an explosives but I have read double base powders can detonate. I'm not sure what needs to take place to get that to occur in a rifle. My suspicion would be larger cases overloaded with DBL base powders. Quickload will estimate extremely high pressure rise per additional grain of double base powders in a 300 Ultramag. Typically the higher the temperature and pressure the faster the reaction rate which creates higher temperature and pressures exponentially. So the debate becomes let the case head fail and vent the gas once pressures exceed 90,000 psi etc or do you best to hold it all back and send it out the muzzle away from the shooter. My vote is out the muzzle but could you carry that rifle.

I'm just simulating a case head failing at 70,000 psi peak chamber pressure and used 70,000 psi. Due to a weakened case head caused by stretching. Which is a bit of overestimate as the pressure on the action should be somewhat less. The case head failures I have seen which split the actions ruptured around the extractor cutout in the bolt. The Sako in 257 Roberts that I have seen which split and got me curious on this subject ruptured the casehead where the extractor cutout is in the boltface. The pre64 Winchester '06 case which I saw that failed blew the side of the case out near the rim I expect that to be related to the extractor clearance cut also, I'm not sure as I didn't see the action. That being said the strongest action in my opinion needs its bolt to support the case head as much as possible with minimal cuts for extractors unless we can prevent detonation circumstances by allowing the case head to rupture at a determined point assuming a bore restriction etc. Its interesting to see how actions are designed and what safety factors they incorporate.

onty,

I wouldn’t know how to read or interpret your formulas if you sent them to me!

As for any “experimentsâ€...don’t worry, I have no desire to conduct any in this area.

Here's the rub on experiments. They tell us what we already know. The case is the fuse and when we blow that the systems fails to some degree.

I'd like someone to prove my point that pf actions will contain worse reloading errors than CRF actions but in the end it's still academic. It's a required discipline to reload properly. Failure to do so can be serious regardless of what gun you have.

I frankly can see little value to testing as I don't think anyone will be swayed by the result anyway. I'll use PF for varminging regardless of the outcome and others will use CRF again regardless of the outcome.

quote:

Originally posted by vapodog:
I frankly can see little value to testing as I don't think anyone will be swayed by the result anyway.

You mean like your tests for hardness/heat treating?

quote:

Originally posted by Rick 0311:

quote:

Originally posted by vapodog:
I frankly can see little value to testing as I don't think anyone will be swayed by the result anyway.

You mean like your tests for hardness/heat treating?

We don't want to discuss that again do we?

quote:

Originally posted by vapodog

We don't want to discuss that again do we?

Not on your life!

The three rings of steel won't make a difference
either with big case blowing.It just makes a little smaller slot for the gases to jet through
still blowing reciever open if case fails in the corner.If recievers had outside diameter
like McBros BMG action with regular small bolt,
then they would hold, but gases then would
jet back toward shooter still a dangerous
situation. If action in the area of the lugs has a spot that is say the same thickness
as the barrel over the chamber, even then a third of the the pressure, can split it radially, because of the larger diameter allowowing gases many more square inches
to apply the force pushing it apart.
I know in the one Ruger 77 overload
incident I had, if case had failed in the
corner with all the powder in that case the reciever coming apart would have taken my head off.Ed.

"Varmint Als" website had an interesting analisis of the pressures exerted on a bolt action and alink on it http://www.varmintal.com/abolt.htm

I think that airspace behind the case head is the problem. Gas venting from a ruptured case enters any air space behind it, and continues expanding (powder still burning), and this blows actions apart. If we could get a lock up with no air space (like a falling block), then we would only have to worry about blowing barrels (which takes a hell of a lot more pressure to do). Picture a bolt action feeding a rimmed cartrige into a squared, resessed chamber, by a flat faced bolt that butts up to the barrel. The extraction system would be a TINY cut in the barrel, and a miniture rotating claw.

A single shot action is fine but we want a repeater and positive extraction. Maybe something along the lines of a falling block like on a 870 Rem shotgun action but more substantial.Would you get the accuracy desired with such a design. The biggest question in my mind is what pressure to design the action to for a given case head diameter and capacity. Will we create a condition where we are just making a "bigger bomb" so to speak by restricting all the gasses trying to force everything out the muzzle. I forget which action its on ( Blaser ? )but one maker came up with what I would describe as a collet that expands in the breech to lock it. It would seem contamination prone. Dick casull's action had buttress threads like a cannon breech and appeared not much larger than the bolt body maybe an 1/8" larger diameter.

Any idea where to get copies of these reports less expensively. There seems to be a wealth of info on cannon breech design, vibration tuners. Including barrel coating and wear studies.
http://www.stormingmedia.us/corpauthors/ARMY_ARMAMENT_R...T_NY_BENET_LABS.html

Wow. An interupted buttress thread. That's really progressive thinking now just as it was when used on the 1910 Ross. Or the Newton rifle of around 1912.
Full diameter bolts (Weatherby, Wichita RPA and others) do a fine job of sealing the breech in the event of a cartridge failure. The Savage system with their little baffle isn't bad either. Having seen a whole bunch of rifles which had been fired with severe overloads, I feel the problem is not as serious as some might think. The only real receiver failure I have seen was a 96 Mauser wherin the receiver had been damaged in barrel removal. In this case the ring split when the case let go. Regards, Bill.

I agree with Bill, “blow-ups†in modern bolt action rifles are so rare that they literally fall into the range of insignificance. Now, obviously if you happen to be among that insignificant group the fact that 99.9% of other actions didn’t blow up doesn’t really mean all that much to you!

Much ado about nothing, IMO.

It is true that rifles like the Wby. and Savage (and Rem 700), seal off the chamber area pretty well, but they all have significant "air space" behind the bolt. If a case head lets go (faulty case, void in the brass), and enough still expanding gasses get into this area, the reciever will blow.

I am not saying the sky is falling (I shoot pre-64's excusivly), just that it CAN happen.

quote:

Originally posted by DougH9:
It is true that rifles like the Wby. and Savage (and Rem 700), seal off the chamber area pretty well, but they all have significant "air space" behind the bolt. If a case head lets go (faulty case, void in the brass), and enough still expanding gasses get into this area, the reciever will blow.

I am not saying the sky is falling (I shoot pre-64's excusivly), just that it CAN happen.

A few months ago a poster on this site showed pictures of a massive case failure that blew a portion of the bolt nose off his Remington 700. According to him (and I have no reason to doubt him), all he felt on his face was a slight “puff.†The receiver didn’t explode, and nothing on his rifle was damaged other than the bolt nose.

Love em or hate em...Remington 700’s have one of the strongest and safest breeching systems of any bolt action rifle out there when it comes to containing/diverting gas from a case failure...and they are certainly way ahead of pre and post Winchesters in this area.

If you want to dislike 700’s for other, reasons then that’s your business...but of all their faults, the breeching system and gas handling ain’t among them.