That's a big one over on the M14 forum.
I do have one question... and this is specifically aimed towards the M1/M1a type of action and bolt... do you ever see/have you ever seen sheared bolt lugs with lubed cartridges? Looking at your photos of the M700 bolt, it's only got 2 lugs as well (as does my Savage,) and no one really worries about sheared lugs in a bolt gun. The theory in the M1a is increased bolt thrust because of the lubed cartridge walls.
Not arguing, and this isn't a tricksy trap question... but I'm curious. You have more experience on the line than I do.
I have seen one new Geneso Springfield Armory bolt crack a lug off with GI ammunition. Either wrong batch of material or bad heat treat.
Bolt lugs will crack given enough firing cycles.
Neat picture of an AR bolt with six lugs missing
http://bulletin.accurateshooter.com...-you-figure-out-what-happened/comment-page-1/
The locking lugs (of proper metallurgy) of a bolt rifle can and have failed due to "fatigue" (work hardening). Rifle bolts are not built with an infinite number of firing cycles in mind. Machine guns are expected to fire more rounds than a personnel side arm, and in longer bursts. Machine guns are therefore made heavier. Heavier locking mechanism lasts longer, heavier gun takes longer to over heat.
You look at M1, M14 and M16 rifle specifications, the weapons had to complete a 6000 round endurance test. The thinking was, after 6000 rounds, the weapon went to depot where anything, or everything was tossed in a rebuild. It is my opinion that the WW2 Germans abandoned the concept of rebuilding during the war. Explicitly take a gander at the Power Egg concept for aircraft engines:
https://en.wikipedia.org/wiki/Power-egg The Focke Wulf FW190 aircraft engine was built to run for several hundred hours, and then, to be pulled and tossed aside. From a recent article I read, the FW190 engine was not made to be rebuilt, or fixed if a component went wrong. The article mentioned this because of how long it took the refurbisher to access a magneto: it took days. The restorer was doing this because he had one vintage FW190 engine and was trying to make the thing work. The Germans assumed there would be a train load of engines, and if the engine in the aircraft had a problem, it was pulled, and a new one installed. They came to the conclusion that repair facilities, depot maintance, took too much manpower and resources away. It was just better to make lots of engines fast. Germany invaded Poland in 1939, and the Russians took Berlin April 1945. There were a whole bunch of aircraft models developed, and junked before the war ended. The Germans ran out of pilots before they ran out of aircraft.
It is obvious to me that the German G3 or HK91 was designed and built to be made fast. And not to be sent back to some intermediate level and be repaired if a part broke. In a major war, it makes sense to build as many rifles as quickly as possible and not waste time trying to repair some mangled or worn rifle. Just been reading a book about the 101 Airborne. About half of E company 506 parachute was dead or disassembled after the Normandy drop. The guys had been with each other for 16 months, but that was their first combat drop. One has to ask the question, why built weapons to last 90 years when the soldiers don’t last a week in combat? It was rare that any soldier lasted 9 months in combat. I read a book by an American Infantry Officer who landed D day plus a couple days, and he made it into Germany before he got his. He was 9 months on the line, and in the hospital where he landed, the medical staff had never run across any dog faces who had been in the line that long.
The German experience was probably worse. Take a look of how many died in Russia. And, how many Russians died.
The guys shooting a lot of rounds are the AR15 guys. I think it is best practice to replace the bolt when replacing an AR15 barrel.
Who has broken a bolt with a mid-length gas system?
https://www.m4carbine.net/showthrea...gas-system&s=53ee3ca309e3e6c3f20c00bccc0d39fc
Sheared lugs on Colt bolts
https://www.ar15.com/forums/ar-15/-/118-590251/?page=1
I broke the unbreakable Sharps Reliabolt - TWO BROKEN NOW! Update Pg. 5 (Page 1 of 8)
https://www.ar15.com/forums/ar-15/-/118-658805/
My Mini 14 Bolt Broke....Now What?***UPDATE***
https://www.perfectunion.com/threads/my-mini-14-bolt-broke-now-what.80123/
Auto Mag Buyer’s Guide (pictures gone, text indicates cracked lugs)
http://www.amtguns.net/articles/yoshi-ishiguro/auto-mag-buyers-guide/
Sheared bolt lugs
https://www.65grendel.com/forum/sho...-bolt-lugs&s=d1a9210dda22f90d0495239c5732f1dc
Socom II broken bolt
https://www.ar15.com/forums/armory/-/6-300423/?page=1
Broken flat carbine bolt
http://forums.thecmp.org/showthread.php?t=28644
Weekend Inland Mishap
http://www.milsurps.com/showthread.php?t=6826&highlight=Bolt+Break
On bud, he had his AR15 rebarreled to 6.5 Grendel. It came with two bolts. Given that the Grendel uses the AR15 bolt, but the Grendel has a larger diameter case head, which increases the load on the bolt face, you would expect AR15 bolts to crack sooner than later. The maker sent two bolts so when the first one lost a lug, the owner could install a new bolt and shoot the barrel out. When the barrel was shot out, the owner would get a new barrel and two new bolts on the rebarreling?
This article from the American Rifleman is worth reading:
Are your Guns Tired and Stressed?
https://www.americanrifleman.org/articles/2015/3/4/are-your-guns-tired-and-stressed/
I am going to offer a suggestion, never actually performed in the history of the world, for someone concerned about bolt thrust: cut your loads.
All those worry warts, and yet none of them understand that putting less powder in the case is the easiest, most positive, way to reduce bolt load. And, the best way to reduce load. Load is pressure times surface area. Cut the pressures, reduce the loads. And since pressures follow an exponential curve, reducing a load from 65,000 psia to 50,000 or 45,000 reduces structural loads considerably.
All I had on this was 264 Win Magnum bolt. Obviously it is a FN Deluxe bolt, and the lugs cracked. I can tell you, the sort of person who owns a 264 Win Magnum is looking for the fastest, flattest shooting load possible, and they do that by jacking the pressures to obscene levels. Well, something has to give.
It is possible the Army is going to an 80,000 psia round, pressures that high are beyond my experience and I predict, only trouble! With something with an exponential slope to the curve, that 80,000 psia will become 150 K psia in no time.
