Bolt Face Vs Locking Lugs...which is the strongest?

If you could mount some sort of ram against the bolt face and then start pressing, would the lugs and locking recesses give way or would the bolt face shear out of the bolt?

Mike

Mike,

Call around to some of the auto and heavy truck repair shops and find the outfit with the heaviest press. Take one of your loose actions in and toss $20 to the shop boss and ask him to put it in his press. See how much pressure is exerted before it breaks.

Remind me NOT to try any of your handloads

When you say "bolt face shear out of......) I guess you mean that a cylindrical section would be forced rearward? I dunno.
I do know that I've disassembled some Remgington Rifles that had very high pressure loads fired in them. Loads that were over 100,000 per the NECO Quik Load program. The first place to show the signs of high pressure are the lug abutments in the receiver and the chamber in the body area. The "three rings of steel" did their job and contained the pressure within the chamber.

Jay,

Would the press ram push the bolt face clear or would the lugs go. Perhaps it would all happen together. We know if the bolt was "supported" and the press and ram were strong enough, the bolt face would be pushed out. So the question is, do the locking lugs provide enough support to satnd the force required to push out the bolt face.

Did you measure bolt face setback on those Remington actions.

How would the shear area of the bolt face compare to the lugs.

Has anyone ever seen a photo of a "blown action" where the lugs have let go.

Mike

Mike---

I've got a couple around here and I'm still looking for them.

The lugs fail first by breaking at the lug- bolt junction. The lugs pivot outward which helps the gas pressure to blow the reciever ring apart on "sealed" actions.

I've seen bolt faces dished by ..010 or so but never sheared from the bolt.

The lug/bolt junction acts as a stress riser. I'll take pictures as soon as I find the Ruger M-77 bolt that's stuck *somewhere* in the shop.

Jack,

A question for you. If you machined .003" from the back of one of the locking lugs, would you expect the action to set back and the lug that had been machined back to bear?

Mike

Mike---

No- It won't set back, it'll just spring. The groups will be vertically strung and the bolt will have harder than normal lift once the pressure is high enough to reach yeild strength of the brass.

You don't have to take material from a lug to see that. Just put a high place in the inletting between the screws. It does exactly the same thing.

Bedding of the action determines the contact of the lugs....thats why bedding is important.

Jack,

What I am trying to get at here, is that many members feel that calibers such as the 505 Gibbs if loaded to normal max pressure (that is, per 243, 270 etc), will cause the actions such as CZs to set back (permanent set back, as in increased headspace) due to increase in case head area and therefore additional back thrust. But I just can't see it.

What say ye.

Mike

I don't know about the CZ actions, as to material and heat treat. I have a Mauser action that was removed from a ~'60s built heavy bench rifle that was in 6.5-300 Weatherby Mag. The loading ramp had been ground away to allow long cartridges to feed. There was so little remaining of the bottom lug that it became a "one lug" magnum rifle. The upper lug had setback quite a bit, maybe .010. I sectioned the action to show folks at gunshows as an example of "bad gunsmithing" practices. I think that a lot of early Mausers were made from a steel that was case hardened. They were like "Twinkies", hard on the outside and soft in the middle. Most modern receivers are through hardened 416 S.S. or 4140 or similar CrMo.

Jay,

On your quick load program can you work the pressure for 110 grains of Varget in the 378 Wby with 270 grain bullets.

I have fired such a load. The powder measure had been set for 108 grains of IMR 4350 and you know the rest of the story

Did not notice a thing until I went to open the bolt and of cause it was frozen right up. previously fired cases that had not been sized and had been fired just before seem to indicate maybe about .001" of set back.

Chamber all seemed fine since we could load neck sized ammo as normal after the overload.

Mike

Mike---

To answer the question about the bolt face.

PSI is exactly what it says. Pounds per square inch of the *interior* of the case. Remember, if the diameter is doubled the pressure rises by four times!

The "thrust" against the bolt face is PSI times the area of the inside of the case in axial alignment with the bolt face.

Remember the thick web on a small cases? Want to compare that with the bottom of a 505 with it's squared off web and large flat floor? Yikes!!!

That means a 505 Gibbs (which is a 37000psi cartridge) loaded to pressures like a 243 is straining the action with every shot....and for NOTHING, since the bullets aren't designed to work at those velocities.

I'll repeat---- 95% of ALL rifle problems are a direct result of the quest for velocity....and velocity ain't worth it!!

[ 10-06-2002, 09:38: Message edited by: JBelk ]

Mr. Belk, thank you for sharing you considerable experience with us. You speak wise words, in my opinion.

Mike375, if you want a high velocity big bore just get a 50 BMG. You could load it up with the 570 Woodleigh soft pont, push it to 3400 fps and have the ULTIMATE varmit rifle! Of course the Woodleigh's may not stay together at those velocities, even in the air! I would leave the 505 Gibbs as Mr. Gibbs intended it.

Axel

[ 10-06-2002, 17:46: Message edited by: Axel ]

JBelk,

I just wanted to clarify one thing. For a given constant force, the larger the diameter of the cartridge, the less stress will be produced. This is because stress is equal to force over an area. However, the opposite is true for a "thrust" force as the a larger diameter would produce a larger resultant force with a given PSI. This is may be the reason why most European big bore cartridges designed to operate at a milder pressure. Other than that, I have a lot to learn from your expertise. Thanks.

Jack,

A 505 is .640 and the Rem Ultra is .550 so that makes the 505 Gibbs about 35% bigger in head area. I reckon for the margin that Remington, Winchester and any other factory that chambers the 300 Ultra uses, there would be enough to spare for the 505.

The Lazzeronis are .585 so the 505 is on 20% bigger then those cartridges. I don't know ow big the lugs are on the McMillan actio for the Lazzeronis. I think the Prairie Gun Works action for the 408 Chey Tac is a .75" diameter bolt so I guess the lugs would be a bit larger on that action than CZs and Rem 700s.

Then of course there is the 378 based calibers in the Mark V Wby. Would you expect a Mark V chambered in the 378 based calibers to have all 9 lugs bearing after one has fired several shots?

Mike

Mike,

To answer your question from a theoretical point of view, there is no “set back” at all at the bolt face, as the locking lugs would take all the reaction forces for whatever pressure you apply to the bolt face. May be someone here can do a quick static analysis to prove me wrong. The bolt face would see a little bit of stress but the most von mises stresses are concentrated on the back side of the locking lug areas. I can do a complete finite element analysis in this scenario to show exactly what would happen in the bolt assembly, as the cartridge is fire. However, I can only do this at work and it will cost somebody some money to do it. Have fun.

Ming,

But the bolt face (or at least the point where the bolt face joins the bolt body) is the point where the force is transferred. Let's say the bolt face was made from tin foil, then the locking lugs would hold up if they were made from lead as the cartridge head would just blow off and punch the bolt face out of the bolt.

Mike

Mike--

On a nine lug Weatherby action the lugs that touch before firing will flex on firing which then allows the others to contact.

The heat treat on alloy actions is to about 35 Rc on most actions. This equates to about 200K yield strength. That means at pressures below that figure the metal flexes and returns to the original dimension. Above that figure will deform the metal enough it can't spring back.

I think it's pretty dumb to try to push big cases over the pressure line. Any advantage you get from velocity is lost in bullet performance and extraction problems.....Ross proved that with the first Nyati. He pushed a 750 solid to 2650 only to find out the bullet became too unstable to act like a solid and hard bolt lift made a second shot slow.

Load to bullet performance.....not a drop table.

Your "lugs or face fail first" is a moot point, anyway. When there's enough pressure to make either of them fail the case head will certainly fail first. That means the action is wrecked from gas cutting long before enough pressure acts on the lugs enough to make them fail.

This M-77 Ruger 338 Win was fired ONE more time after being recovered from a house fire and rebuilt by the owner.
The bolt and receiver are dead soft. The left lug deformed. The right lug sheared.

Jack,

I don't have a 505 and it is highly unlikely I will ever have one and if I did have one then recoil would limit me to air rifle pressures

But I am intrigued to know if loading a 505 (or the 378 case on the Rem 700) to normal 243 or 270 pressures will result in locking lug setback on actions like the CZ as is often suggested.

I think Lilja says Rem 700 lugs are too small for the 30/378 and set back could occur. To me, if all this stuff is true, then the easiest way to get the lugs on a 378 based Mark V to bear is just to shoot it a few times

Lilja and I think others also say the barrel thread is too small for the 378 Wby case. However the Wby Mark V is the same as the Rem 700. I have owned 1 338/378, 2 378s, 1 416 Wby and 2 460s on Mark Vs and never had any problems. All of those, especially the 338/378 and 378s were used with top loads. For example, 378 factory ammo usually chronographs around 3060 to 3080 with 270 grains and my loads were always from 3100 to 3150 with 270 grains.

With the Bolt face Vs lugs I was not thinking in terms of blown cases heads but rather if the 505 loaded to full pressure might set back the bolt face before the lugs. What would be the shear area between the bolt face and bolt as compared to the lugs.

Might be easier to buy a Remington 710 in 30/06, use PMC ammo and take up model areoplanes

Mike

[ 10-06-2002, 22:37: Message edited by: Mike375 ]

Mike375, the picture posted by Mr. Belk is a text book example of shear stress failure! The von Mises stresses, which is combined stress, of any Mauser or Weatherby style action will be concentrated at the stress concentrations associated with the junction of the bolt lug to bolt body at the rear side of the bolt, and the rear side of the lug race corner radius in the action ring directly adjacent to the bolt's lug. There is no point arguing this. Mr. Belk has done an EXCELLENT job explaining precisely what happens during firing as well, from the transmission of the thrust force to the deflections of the locking members. I can tell you that Mr. Belk very obviously KNOWS A LOT MORE ABOUT GUNS THAN YOU! You are obviously trolling for a fight, IMHO.
Mike, are you German? Your desire to be right all the time while everyone who disagrees with you is wrong, is incredibly German! I have countrymen who will work against all that is right and holy, and the laws of physics too, just to prove someone is wrong. They do this because 1.) they cannot accept that their opinion on things are only opinions, or 2.) they cannot admit making a mistake. What is your excuse?

So everyone understands. I stated that a M700's lugs and bolt body were approximately the same size as a CZ550, M70, or M77. Therefore, if the 378 Weatherby magnum could be chambered in these actions it should be acceptable for the M700 as well. Robgunbuilder and Mike375 disagreed and attacked me, immediately. This attack is still going on. You all may continue trying to explain this to Mike375, but I fear it will all be in vain until someone tells him that what he is saying is correct. He is obviously very ignorant of how a gun's locking feature works. If he cannot figure it out after reading everything thus far, provided on this post, he is very dense as well. My 8 year old son can explain to me why that M77 Ruger pictured above broke after I read Mr. Belks and Mings posts! Mike are you not sharper than an 8 year old child?

I believe the biggest problem Mike, with a M700 in 378 Weatherby magnum would be the extractor. This is simply fixed. I have shot two different M700 in 338 Lapua. Same case as a 378 Weatherby. In my opinion, the M700 is too light of an action for the thrust forces generated by these cartridges since they are loaded to 63000+ psi. By this I mean that the action flexes too much and is therefore, not stiff enough to provide optimum accuracy potential. This does not mean that the bolt is going to be blown out of the gun Mike! For your information the flat bottom receivers are MUCH STIFFER than the round bodied M700! No degree of bedding is going to stiffen up a M700 to be an optimum platform for the thrust forces of a full house loaded 338 Lapua, 378 Weatherby, or other Rigby based cartridge, IMHO. There are much better actions for these cartridges and no they are NOT M70, M77, or CZ550, Dakato Africa, etc.

Have fun Mike375,
Axel

[ 10-06-2002, 23:50: Message edited by: Axel ]

The Lugs will shear first or set back in the action. The Bolt face will not move.

To the Axel handle,

Much of the content of that post suuggests another personality has appeared via the Axel handle and forgot to compare notes. If you are going to launch these attacks you should at least have the correct details from other threads.

Just check with the other users of the Axel handle. Then there might be confusion because of the Todd E handle.

My suggestion is to keep written notes on what your different handles are posting and reading and also make sure that each of the pesonalities are up to date with each other.

Also you should contact Mike Boyd who played and plays so so many different parts through different handles. He will be of tremendous help to someone like you who is just starting out on the multi personality and multi handle career.

>>There is no point arguing this. Mr. Belk has done an EXCELLENT job explaining precisely what happens during firing as well, from the transmission of the thrust force to the deflections of the locking members. I can tell you that Mr. Belk very obviously KNOWS A LOT MORE ABOUT GUNS THAN YOU! You are obviously trolling for a fight, IMHO.<<

HAHA!! Axel acussing others of picking fights!!

Mike375 - I think that you are asking if there is enough material behind the bolt face to support pressures that deform lugs and lug recesses, or will the face "dish" before lugs/abutments deform.

The answer should be "yes". In a properly designed action, the first point of failure will not be the bolt face.

Take a look at this web site:

http://www.varmintal.com/aengr.htm

Just a little ways down, there is a finite element analysis of a Stolle Panda action, showing that the highest points of stress are at the lug/bolt body junction and lug recesses in the action. The bolt face shows lower stresses.

As for the Wby Mark V, Jack Belk did address this, but I'll go ahead and re-state. You will not get all 9 lugs to bear (assuming that not all 9 are bearing originally) just by shooting a few proof level loads in it. The steel has enough yield strength to spring back to its original dimensions. Keep shooting loads with more and more pressure, and you'll fail a case before you get all 9 lugs to bear.

Regards,
Scott

Scott,

Given your comments on the Wby Mark V, would you expect a CZ chambered in 505 Gibbs loaded to full pressure (as measured by brass limitations) to show inceased headspace.

Obviously if we exceed the elastic limit of the metal, we will have increased headspace.

Do you think it could be a case of the bolt thrust with everything from 223 through to 505 Gibbs is within the locking lugs/metal capability.

To me, lack of lugs bearing in Mark V Wbys in 378 based calibers, suggests that locking lugs in 2 lug actions, are way stronger than required.

With Jack's comments earlier about higher velocities are not needed, I am suspecting there is some Political Correctness going on.

Let's make it simple. If we have 4 CZ 550s chambered in 30/06, 300 Wby, 30/378 and 505 Gibbs all firing rounds loaded to pressures that are considered reasonable maximum pressure for the 270 Win, will we see after 2000 rounds a difference between each of the 4 CZ actions.

Mike

Mike,
There is no question that the CZ lugs and seats will deform at some point. Just exactly what that point may be I can't honestly say. Ican say that it will be the lugs and seats that will deform first rather than the face. I'm also quite certain that loads in the 505 case at 270 levels will cause deformation of the lugs over time.
I have seen a BRNO 602 with the lugs very definitely set back. This from a steady diet of too hot loads in 300 Weatherby. So if the 300 will do it the 505 definitely will. Also, if the Rem 700 lugs are inadequate (according to Lilga) then the CZs are as well. So are the M70s.
Thread diameter (within reason)is a lot less important than some would have us believe. Regards, Bill.

Bill,

Back in 60s 219 Zipper Improveds on 310 Matinis were quite common out here. I (and some others) expanded the chamber on them. Although this was with loads that were stiffer than normal. Real flat primers etc. They seemed OK when loaded to what you would expect from a 225 Winchester so I suspect you are correct on barrel thread diamter.

How would you compare the Wby Mark V to the actions such as CZ, Rem 700 etc. within the context of this back thrust/setback question, both in terms of one or two shots with an overload and also a steady diet of normal maximum loads and using 378 based calibers

Mike

[ 10-07-2002, 22:21: Message edited by: Mike375 ]

Mike,
It is difficult for me to comment on this simply because the numbers of weatherbys I see are not as great as the two lug action numbers. Also, it seems like the guys who really stressed the rifles all owned two lug actions. The exceptions were a couple that came in based on Browning A-bolts. Judging by the way these setback I would have to say that they would not handle a steady diet of too hot loads as well as the 700. I don't think the A-bolt has the lug area of the Mk V though. I've never bothered to figure it out.
Another rifle of the multiple lug type that showed an inability to handle a steady diet of heavy loads was a Browning BLR long action. I had barreled this one in 358 Norma. The owner was a bit of a fool when it came to reloading and he brought the rifle back in about a year later because he was experiencing misfires. I checked the headspace and it was way long. I pulled the barrel and the seats were badly deformed. The lugs on the bolt head seemed fine but the receiver was toast. These problems with the Brownings would not have been problems with normal loads. I suspect the setback was more due to metallurgy than design. And of course stupid loading practices! Regards, Bill.

Bill,

I don't have that book by Stuart Otteson anymore, but as I remember he said the Mark V had far more bearing area (if lugs contacted) than the two lug actions but similar shear area.

I am imagining that much of the length of the locking lug on two lug actions is wasted.

If Roy Weatherby was still alive and we could have a chat with him, I am sure that he would have some interesting stories on overloads and different actions

Mike

JBelk/ Bill Leeper- What is your opinion of the conversion of a M700 to a 460WBY? Besides the issue of this resulting in a single shot, do you feel this is a safe thing to do? Would you do it for a customer?
This issue comes up repeatedly as M700's are so cheap and some people are so desperate to find a cheap way to build a 30-378 wby for example. Dan Lilja as well as many others reccomend against it based on the exact bolt thrust concerns you have described. and I for one totally agree with them. Personally, I'd be very concerned with the receiver locking lugs setting back under heavy loads. As you know, most of the people who build these things load them till they see smoke coming from the blown primer holes. I would appreciate your opinion.-Rob

Per Otteson's book: Wby MkV lug bearing area =.108 sq. in., lug shear area .342. Remington 700 lug bearing = .107 sq. in., lug shear area .428. Both have 1 1/16" X 16 TPI. The numbers for the 1917 Enfield were .411 and .089 and the Texas Magnum numbers were .489/.505 shear and .068/.066 lug bearing. More would be better, I think.

Robgunbuilder, I thought you had performed all the stress calculations on these actions and knew for a fact which were safe and which were not. Frankly, I am shocked by your question to Mr. Belk and Mr. Leeper. After all, you attacked me vehemently about suggesting that the actual strength of the locking mechanism on the M700 is on par with the M70, M77, and CZ550. I find it difficult to understand how you felt justified slandering me and now you ask the experts if you were in fact right. You sir, are a fraud and you know it!

Based upon the figures provided by Jay, I would think that the M700 is very comparable in the strength department to the other 378 Weatherby magnum proof actions. Namely MkV, M1917, etc.

I reread my earlier posts for your benefit Robgunbuilder. I admit that some of these posts did possess some poor grammar. I apologize for this poor use of english. I still see no evidence of an accent. The only person I know of that posts with an "accent" is BBBabbler. He has, shall we say, issues.

Axel

Axel- I was simply asking the opinion of some professional gunsmiths whose opinions I respect on this issue. I have not changed my view and continue to believe that the potential conversion of a M700 to a 460WBY is a stupid and potentially dangerous idea. I believe even you have begrudgingly admitted that . As I and others have told you multiple times before, I was only attempting to help you. Your use of English ( which we note has dramatically improved in the last few days) may in fact be the cause of why you felt you were unjustly attacked. However, your response back to me was insulting and immature and as a result you have been given a sound thrashing! You can deceide to end this now or I can continue forever! I'm really starting to feel sorry for you as you have been getting the worst beating imaginable from BBBBabbler, Jeffeosso,and many more. It's hysterical, but even I am starting to feel sorry for you! I really suggest you run up the white flag! Frankly, Continuing to argue with you over this issue is wasting my precious time and I'd prefer to discuss the building of big bore rifles and more interesting issues with people who know what they are doing and have a track record of doing so.-Rob

[ 10-09-2002, 09:22: Message edited by: Robgunbuilder ]