Neither did I, nor did I ever mention that. Get your reading comprehension fixed.
The point went over your head too, I see.
Re. your headspace question- the headspace that matters is the difference between your chamber and the ammo. The headspace measured by gauges is only a comparison to a standard; presumably the ammo was also made to that standard, but sometimes it’s not.
I agree with most of what you said, but shear is the wrong term. Shear is a wiping separation, like if the bolt lugs were wiped off leaving a mostly round bolt head intact. Shear failure generally implies a softer material, and leads to the wrong conclusion if used for something like this. The word “shear” gets way overused but it is not just a general term for failure. Fracture is more accurate for a failure like this.
I’m not arguing with either one of you, but the OP has fired cases that tell him what the chamber dimensions were. He can compare those to unfired cases to determine actual headspace, and to the gauge to compare headspace to spec. He’s already done some of that (although I suggest checking a bunch more of those loaded rounds). He doesn’t need a new bolt or even the intact original bolt to know as much as can be known at this point. What is unknown is headspace of that particular round.
I am not going to call any makers of swappable bolt heads on their tolerances, but one would have to think ,001" is huge today, esp on a custom action.
No, the failure was not shear. What your diagram shows isn’t shear either. Shear involves slip planes sliding against each other instead of pulling apart; shear failure is perpendicular to tension failure. Tension and shear happen at right angles to each other, and a clean break without the failure surfaces sliding against each other is generally not a shear failure.
I thought all his fired cases were in pieces. If not, you're right. A damned close approximation can be made because of brass springback.
Ahhh jeez, maybe try reading the thread before responding.
The new bolt would be exactly identical to the old bolt, there are never any variations between bolts. They are always exactly the same and perfect. Matter of fact, every single gun part that is currently being made by everyone has the exact same measurements. Fuck man, if we are going this route the OP might as well super glue the bolt back together and pull out the old dollar store yard stick to get an exact measurement.
Sarcasm bud, I thought I laid it on pretty thick. You cannot get a trustworthy measurement with a different bolt that was not in the failure.
Alright man, this is pretty good logic. More often than not I won't bump shoulders until the brass has been fired twice as it hasn't even grown to fit the chamber on the first firing, especially fireforming to a new cartridge. At this point I don't think any measurements are worth while.
Ok that changes things a bit, since it’s pretty unlikely you ended up with a bad bolt and a bad receiver all in one package. That looks more like you’ve had some pretty high pressure loads running through it (for example when guys try to meet ball powder velocity with Varget), and collapsing the bolt lugs led to loading the receiver through the bolt handle.
Speaking for myself only - I was suggesting that headspace may have been the reason for the “pressure signs” on the case in the picture (in response to people jumping straight to claiming high pressure), not saying that it broke the bolt. The thought being that we don’t know that high pressure was involved based on those signs because they could also mean excess headspace instead, and the bolt may have failed as a result of metallurgy issues instead. Sorry if I contributed to any confusion there.
I probably should’ve included this pic from the onset, but I honestly was in shock. I believe the scrapes show continued contact from round 1. I believe the gouges came from the incident. Again, I’m not a metallurgist, physicist, engineer, or machinist. That could be another possibility.
I am an uneducated idiot myself, but i would say those marks occurred trying to free the bolt after the come apart. Separated parts created a gap between the bolt head and separated lugs. Now, working the bolt to free it scratched things up.
sooooo ... "excess headspace does contribute to the impact forces of the case against the bolt face". I'm going to pose a scenario in order to ask a question. Suppose: the bolt is intact with proper headspace. OP inserts a round with insufficient headspace, say .020 too short. I chose that number because if it was more than 30 thou too short, would the firing pin energize the primer? If it was 10 thou short, the case head would not get much "running start". So 20 thou. Firing pin drops, case slides forward against the extractor, primer fires, pressure builds in the case (because they are closer, side walls first) then the case expands along the case axis shoving the case base to impact the bolt face and starting to push the bullet into the barrel.
Okay, not 150%, 121 percent. However, that is avoiding the question. I was trying to understand the mechanics of how excess headspace causes bolt lugs to shear off. For the purpose of discussion, I assert that a cartridge that is too short (when measured from base to datum) will not generate pressure sufficient to cause this specific bolt head failure. I make this assertion so that smart guys like you can show me the error of my ways. I'm trying to learn something.
