Bolt Lug/Recess Wear and Headspace Question

R

RC20

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A nuance here on that specific aspect (and yes I know this will touch off a firestorm so if we can keep it to that specific aspect)

If a bolt lug is worn and or the recess for the bolt lugs in the receiver are worn, is that headspace or is that separate?

Clearly a new rifle with a good bolt lugs and lug recess n the receiver (staying with a standard rifle) would have X headspace.

Worn lugs/recess would have X+ and obvious a changing situation until the lugs sheared.

I lean somewhat strongly its first a severe safety issue and a worn part issue that only incidental by definition is it headspace.
 
If wear to bolt lugs or recesses increases the headspace measurement, the result would be excess headspace.
 
Wear on bolt lugs and bolt lug recesses increases headspace.

Modern rifle bolt lugs and lug recesses wear very slowly. The barrel wears out before the headspace increases enough to make any difference.
 
I would offer (opinions invited) that lug interface wear rarely causes headspace dimension growth.
Rather, I give you action stretch as a result of repeated pressure impact.
 
That why you don't reload with zero headspace , also must have wear on the back end of the bolt camming area . Keep grease on the back of the lugs .
 
"...is that head space..." No. Headspace is a rifle manufacturing tolerance(only) that is the distance between the bolt face and, for a rimless case, a spot in the chamber, usually on the shoulder, that permits any manufacturer's ammo to be used in any firearm of the same chambering. Different case types like rimmed or belted test that distance in different places in the chamber. None of 'em involve the lugs.
Worn lugs do not affect the distance between the bolt face and that spot in the chamber. The lugs lock the chamber closed and nothing else. They have nothing to do with headspace.
 
Bolt Lug/Recess Wear and Headspace Question
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I have bolts very few have ever seen and or ever heard of. I purchased a mill from a resource person on anything military like the 03, 03A3, M1 Garand, carbine etc., etc., etc.. He was building a period correct Rock Island 03 with a straight handle bolt. Problem, his chamber was go-gage length + .0025" long from the datum/shoulder to the bolt face. He wanted the chamber to be -go-gage length. Between us we have 140 03 and 03A3 bolts. I offered to check each bolt for its effect on the length of the chamber.

All I had to do was find a bolt that reduced the length of the chamber.0025". I knew I did not have a bolt that would reduce the length of the chamber .001" and I doubted he had one but I offered to check his.

Now, as to what you guys are talking about; I do not have a clue because to decrease the length of the chamber the back of the lug must be thicker and to increase the length of the chamber the lug must be thinner.

For years and years I have said placing the third lug on the 03 was a stroke of genius by Springfield. For years and years determining the length of the chamber in an 03 has never required anything but a feeler gage and a round in the chamber. But from the beginning that little technique has escaped the notice of all (as they say when describing the pearls of Melville's whaling shop) SAVE ONE.

F. Guffey
 
Worn lugs do not affect the distance between the bolt face and that spot in the chamber. The lugs lock the chamber closed and nothing else. They have nothing to do with headspace.
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Ummm, yeah. The locking lugs are what holds the bolt face at that point in space since they are the bearing surface for the bolt. Wearing the locking lugs or the locking lugs recess will ABSOLUTELY affect headspace. Lap bolt lugs? Check headspace. Replace a bolt? Check headspace. True an action? Check headspace. Anything that modifies the bolt lugs or the locking recess will change headspace.
 
I'd be more worried about throat erosion than over the lugs. A new barrel can always be fitted (or the existing one set back).
 
I would offer (opinions invited) that lug interface wear rarely causes headspace dimension growth.
Rather, I give you action stretch as a result of repeated pressure impact.
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The explicit question is true head-space or is it a varying entity (true being OEM with the bolt/recess right and varying due to all other possible causes)

I find action stretch implausible. It was suggest you could compress steel by someone a short time ago. That would be no different regardless. Many receivers shot out more than one barrel, it may be possible with excess pressures but not normal.

Its almost academic. Trying to wrap my mind around it.

Yes a bolt issue creates excess headspace but its not a head space issue, its a bolt lug/lug recess issue. Its the same symptom.

Underlying remedy with head space being large would be to let the brass fire form and neck size and or minimum shoulder bump back. that would apply to both an excess ream (to a finite point) or a barrel set too far out (more applies to a modern replaceable barrel like a Savage as a fixed barrel would normally be finished reamed.

Its also to me almost a circular logic thing, possibly best defined as subsets of head space being too much (or beyond what the gauges would allow). How hard the extractor holds vs no shoulder to let the firing pin strike correctly.
 
While front-lugged bolts minimize action stretch potential, rear-lugged bolts see rail/frame stretch on a far greater scale.

Handloaders can accommodate for it when sizing (and keeping track for specific rifles)
Commercial ammunition use is "OK" until chamber headspace exceed Field gauge dimensions.
 
That (is) why you don't reload with zero headspace
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Who is 'you'; again I have one rifle that I have fired with .016" clearance. I have two rifles I have fired with .127" clearance, I have never asked, "What happened?" after firing.

The same three rifles: I have fired all three rifles with zero clearance because my presses and dies have threads and I am a case former. I off set the length of the chamber with the case length from the shoulder of the case to the case head.

F. Guffey
 
Its almost academic. Trying to wrap my mind around it.
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If you do not know pull that thing called academic, and then once you realize you were wrong pull that thing called semantics.

F. Guffey
 
While front-lugged bolts minimize action stretch potential, rear-lugged bolts see rail/frame stretch on a far greater scale.
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A metal under stress is either elastic (springs back) or plastic, permanently stretched.

If you manages to fire an overloaded round or max pressure in a weak action, you could push it to plastic (I would guess other issues erupt first)

If its gone plastic the gun is shot. Each round after that will stretch it again.
 
How does one explain a gradual increase in headspace then?
It's either incremental action stretch or lug wear.
Not much else in-between . . . .
 
Guff
I'm sure you heard of galling or gauling . Zero is not .016 clearance , so I guess ( you ) isn't Guffey . Now back to the post , I think wear on locking lugs wouldn't change the chamber measurement , the hole lug would have to be worn . Could you be thinking of the barrel being washed out , changing your OAL.
 
Either lug wear of the recess wear would cause it to increase. One is going to affect and allow the other.

So yes you would have more effective head space, but is that head space or worn part that turns head space into a symptom and not the underlying cause?
 
How does one explain a gradual increase in headspace then?
It's either incremental action stretch or lug wear.
Not much else in-between . .
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Normally there is no increase in head space.

If there is, its possible the receiver went plastic. But that will never stop and could be dangerous by itself (usually its a cap screw that does that the cap screw) - most of the time you can see it on a fastener.

Other most likely is as noted the lugs or recess wear or pound out of both.
 
Can lug wear affect headspace is the question I believe and the answer to that question is yes if you are using the same ammo from the same manufacturer all the time. This problem is something that commonly occurs in military weapons that have seen heavy use. There are 3 head space gauges. Go, No-Go and Field. The military uses the Field gauge to determine when a rifle is no longer serviceable. The military does not reload ammunition.

In the civilian world we can reload ammo and correct for lug wear during the sizing process using fire formed brass.

In civilian rifles, the number one cause of head space change due to lug wear is people lapping them after the barrel has been final reamed. People don't understand that lug lapping needs to be done prior to final reaming and that it doesn't accomplish much if the action is not blue printed. In fact, if the action is not blue printed, it's better to just let the lugs wear in naturally.
 
The question is, would bolt lug or recess wear be true headspace issue or would headspace issue be a symptom of that?

And no, those gauges would be for a new barrel not any wear and tear in the filed. New barrel and reaming then requires the checks to ensure its deep enough.

Headspace will only change once set if the bolt lugs and recess are worn.

Filed gauges for anything else would be the Throat Erosion (which is the main factor) as well as MW (which I am doubtful would occur before TE took it off line)
 
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