7mm saum in 7mm rem mag

1899 said:
OK, I am not asking this to preach to anybody, just asking. If you look at back thrust, say of a .300 Win Mag at 61,000 PSI you get - .156 sq.in (inside case area) x 61,000 PSI = 9516 lbs. Increase the pressure to 75,000 PSI and you get 11,700 lbs of back thrust. How much surface area of the bolt lugs are in contact with the receiver? What is the Rockwell Hardness on the action and bolt? And given that, what is the yield strength? And forget even about yield strength, what about the pressure required for lug set-back?

Maybe one of you can explain the findings from this write-up:
http://www.varmintal.net/abolt.htm
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1899.............Looked at the link and found immediately a couple of things to think about. a) the whole formula and subsequent potential damage is based on a head separation scenario. This changes the failure dynamics of the lugs drastically, and we all know that case separation has nothing to do with pressure alone or necessarily at all. b) all the calculations are based on the failure of 4140 steel and it is my understanding that Rem, Win, and Sako, probably more, use 4340 for their bolts for sure and actions as well. I'm sure you know 4340 is much, much tougher steel than 4140, which is what is used for barrels.
 
C-FMBI - yes, I understand the issue with respect to head separation, but that is at only 50,000PSI, which is quite low. But even at that low pressure "the maximum effective stress level of 97,390 psi is located at the surface of the bolt lugs where they contact the receiver."

Let's assume that the bolt face on a magnum chambering has an area of 0.225" - in that instance, using the Panda action as noted above, the pressure on the bolt face in the first scenario (61,000 PSI) should be around 42,293 PSI. In the second scenario, 75,000 PSI, the pressure would be 52,000 PSI. Assuming the maximum effective stress level remains constant, the 61,000 PSI load would have a maximum effective stress level of 82,394 PSI and the 75,000 PSI load would be at 101,286 PSI.

In case of a head separation, which can happen, the 61,000 PSI load would have maximum effective stress of 118,816 PSI and the 75,000 PSI load would be at 146,085 PSI.

So these higher numbers seem problematic, no? Especially if the maximum effective pressures are higher on, say a M700 or M70. Am I missing something here?
 
rimfire458 said:
More berries but W/out length it seems I'm buggered. Now 257 weath seems to be a long range stinger too
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If all you are looking to hunt is deer out to 500 yards the 257wby is great (I am a 257 wby fan), but you already have a 7mm rem mag ( Im also a 7MM rem mag fan) which will shoot almost as flat at 500 yards with the right load zeroed at 300 yards. Try using some 140 grain accubonds at about 3250 fps. Beyond 500 yards the 7mm has the ballistic advantage.
 
1899 said:
C-FMBI - yes, I understand the issue with respect to head separation, but that is at only 50,000PSI, which is quite low. But even at that low pressure "the maximum effective stress level of 97,390 psi is located at the surface of the bolt lugs where they contact the receiver."

Let's assume that the bolt face on a magnum chambering has an area of 0.225" - in that instance, using the Panda action as noted above, the pressure on the bolt face in the first scenario (61,000 PSI) should be around 42,293 PSI. In the second scenario, 75,000 PSI, the pressure would be 52,000 PSI. Assuming the maximum effective stress level remains constant, the 61,000 PSI load would have a maximum effective stress level of 82,394 PSI and the 75,000 PSI load would be at 101,286 PSI.

In case of a head separation, which can happen, the 61,000 PSI load would have maximum effective stress of 118,816 PSI and the 75,000 PSI load would be at 146,085 PSI.

So these higher numbers seem problematic, no? Especially if the maximum effective pressures are higher on, say a M700 or M70. Am I missing something here?
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I have to run some math here I'll get back this eve I'm on the "heavy duty honey do list" right now
 
quarterman said:
If all you are looking to hunt is deer out to 500 yards the 257wby is great (I am a 257 wby fan), but you already have a 7mm rem mag ( Im also a 7MM rem mag fan) which will shoot almost as flat at 500 yards with the right load zeroed at 300 yards. Try using some 140 grain accubonds at about 3250 fps. Beyond 500 yards the 7mm has the ballistic advantage.
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With the advent of ballistic reticles and externally adjustably turrets and high BC bullets, the advantages of a flat shooting rifle are pretty well irrelevant....within reason of course. Why not select a scope that allows you to be zeroed for every range you shoot at if your desire is to shoot long range?
 
stubblejumper said:
If someone feels that it is a smart idea to load their firearm to 100,000psi, more power to them, as long as they aren't doing it near me. I have an engineering background, where I studied applied mechanics , statics,dynamics, fluid mechanics, as well as metallurgy courses, and I also hold two trades tickets. In my studies , and on the job, I have seen first hand what happens when something lets go due to METAL FATIGUE, and I will not tempt fate by repeatedly exposing a firearm to chamber pressures well in excess of what it is designed to be used at, when I am holding it next to my face.
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Stubble, I am not and engineer but I do a lot of work with them designing and building process equipment as well as take part in investigations were there is a failure. I Have had things blow up in my face or seen the aftermath. One really gets involved in, and learns a thing or two when doing an investigation were someone was killed. Corrosion, erosion, thermal cycling, high frequency vibration, carbon content, hardness, external stress,.....yada yada... the two that concern reloaders...Over Pressure and Cumulative Metal Fatigue.

People need to know that backyard engineering, farmer logic, or tinkering will NOT give us ALL the answers. There are things like Cumulative Metal Fatigue that will take your head off. The average Joe will not see it coming or be able to predict it and I can tell you the failure will most likely be spectacular with absolutely no warning.


For those interested in why one should not be loading to 75,000-80,000psi on a regular basis Cumulative Metal Fatigue is what you need to be researching. Guns DO blow up from this!!! It may take 10 shots or 10,000 or it may never happen at all (while you own the gun) It is not something to mess with.



I am glad there are guys with some technical knowledge like StubbleJumper on this board to help us out!!! I would hate to be lured into something dangerous by some of the posters here!!!
 
Lazzoroni has a 7 mm. Forget the name right now. But if speed is the prize Lazzoroni is the place if you can afford the price



I'm not at all sure how it compares to the 7x300wm or stw. I'm sure someone can post the numbers
 
a 7mm with 90,100,110, or 120 grains, loaded with the same weight leads as the .257, in every case, the 7mm reminton will absolutely smoke a .257 wetherby....much faster. and its cheaper to reload belive it or not.
 
a 7mm with 90,100,110, or 120 grains, loaded with the same weight leads as the .257, in every case, the 7mm reminton will absolutely smoke a .257 wetherby....much faster. and its cheaper to reload belive it or not.
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The 7mmremmag will start those light bullets out a bit faster, but the B.C. of the same weight .257" bullet is higher, so the .257" bullet gains back the advantage at longer ranges.
 
maybe, but i bet it loses them again once your past 500... but both darn nice flat shooting rounds....wouldnt talk s#it about the .257, but i wouldnt want to pay for the bullets either lol
 
maybe, but i bet it loses them again once your past 500... but both darn nice flat shooting rounds....wouldnt talk s#it about the .257, but i wouldnt want to pay for the bullets either lol
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The .257" bullet with the higher B.C. gains more and more as the distance increases. And buying the same make and model of bullets, the .257" bullets are generally cheaper to buy than .284" bullets.
 
I guess I was wrong:D. Wether by bullets are extremely expensive.. Check it out... I guess if u had the casings bought they might bcheaper to reload!
 
bulletbox...........Just to help you out here, I'm going to correct some of your words, not to be a jerk but to assist you in being understood..............The term Weatherby is a man's name and is correctly spelled as I have............The term bullet applies only to the part that leaves the barrel when a cartridge is fired...........the whole thing when loaded is called ammunition or loaded cartridge. The empty piece which you remove from the rifle after firing the loaded round is called a fired case or brass. This is not meant to ridicule, just thought you might like to learn the correct terms, which you cannot know if someone doesn't take the time to teach them to you.
Using the correct terms helps a lot in being understood and reduces confusion.
 
6.5mm/300WM... 140 grainers.... or 6mm/300WM.... wait! 17/300WM!!! even better!!


Or just stick with the 7mm RM and enjoy having a barrel last more than 1,000 rds
 
c-fbmi said:
bulletbox...........Just to help you out here, I'm going to correct some of your words, not to be a jerk but to assist you in being understood..............The term Weatherby is a man's name and is correctly spelled as I have............The term bullet applies only to the part that leaves the barrel when a cartridge is fired...........the whole thing when loaded is called ammunition or loaded cartridge. The empty piece which you remove from the rifle after firing the loaded round is called a fired case or brass. This is not meant to ridicule, just thought you might like to learn the correct terms, which you cannot know if someone doesn't take the time to teach them to you.
Using the correct terms helps a lot in being understood and reduces confusion.
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