chambering thru headstock

[jackie schmidt]

You all know me, I will actually do something in order to see what actually happens, so in keeping with this conversation, I did this.

I took a piece of 8620 at about 58 RC hardness and measured it. About .9905 at 95 degrees. (Big block Chevy wrist pin).

I then warmed it to about 300 degrees using a thermal laser heat detector to Check the expansion. .993.

I then took it to about 600 degrees. .9950

That is a .005 expansion on this wall thickness tubing in a 500 degree swing.

At 250 degrees, it would burn you.

http://benchrest.com/attachment.php?attachmentid=23688&stc=1&d=1592512530

http://benchrest.com/attachment.php?attachmentid=23689&stc=1&d=1592512625

http://benchrest.com/attachment.php?attachmentid=23690&stc=1&d=1592512837

http://benchrest.com/attachment.php?attachmentid=23691&stc=1&d=1592513341

 

[Bob Smeltzer]

You all know me, I will actually do something in order to see what actually happens, so in keeping with this conversation, I did this.

I took a piece of 8620 at about 58 RC hardness and measured it. About .9905 at 95 degrees. (Big block Chevy wrist pin).

I then warmed it to about 300 degrees using a thermal laser heat detector to Check the expansion. .993.

I then took it to about 600 degrees. .9950

That is a .005 expansion on this wall thickness tubing in a 500 degree swing.

At 250 degrees, it would burn you.

http://benchrest.com/attachment.php?attachmentid=23688&stc=1&d=1592512530

http://benchrest.com/attachment.php?attachmentid=23689&stc=1&d=1592512625

http://benchrest.com/attachment.php?attachmentid=23690&stc=1&d=1592512837

http://benchrest.com/attachment.php?attachmentid=23691&stc=1&d=1592513341

I dont think a gun would get that hot!Thanks Jackie!

 

[liljoe]

That looks like a table off an old shaper. Good solid work table for sure.

Joe

 

[Joel]

Joel,

the simple fact is that some folks have set tolerances too tight and had the barrel tenon expand and touch the bolt head.

I commented because you muddied Dan's post up with your initial statements re "everything heated at the same rate" and other irrelevancies, in an attempt to look knowledgable.

Sorry, in the real world this doesn't happen

sorry to get yore pannies in a wad

sorry to have stood for Dan Armstrong in 'your post'........ contrary to your statement that "Jackie's the only smart one left" I consider Dan to be a valuable asset to this board.

alinwa

Without actual data to back your incorrect claims your statement has as much credibility as claiming that rainbow colored unicorns are real.

Since you are having a hard time comprehending the relationship of the barrel heating and transferring the heat to the action and bolt nose/cone clearance we will discount what is actually happening and ONLY use your unrealistic worst case scenario.

In that scenario the only component heated and expanding is the the barrel and the only direction this expansion happens is towards the bolt face.

In Jackie's test he used 8620. Since 8620 is not normally used as barrel steel we will pick 416 stainless steel which is a very commonly used as a barrel steel. The thermal expansion rate for 416 is 5.5 millions per degree per inch. For 8620 the thermal expansion rate is 6.78 millions per degree per inch. Please note thermal expansion is not linear. Closer to absolute zero it is less and at higher temperate it is more.

We will use 5.5 millions per degree per inch for the 416 since that is correct for starting at room temperature. We will totally discount the the receiver ring expanding and moving receiver face expanding away from the bolt nose as the heat transfers to the receiver ring. The only expansion calculated will be the barrel independently expanding towards the bolt nose. The barrel tenon will be 1.000". We discount how the expansion actually happens and use the full tenon length of 1.000. We will set the clearance at .003". Normally .005" is recommended as minimum.

Again with this unrealistic scenario and the only expansion calculated will be towards the bolt nose starting at the receiver face. The barrel and action will start at room temperature with a .003" cone to bolt nose clearance. Again we will also be discounting any heat transference and expansion that actually would be happening. In reality some heat would be transferred to the receiver and the receiver expansion would also be expanding also thus offsetting some of the barrel tenon expansion .

Not even remotely close to what is actually happening since none of the offsetting factors are taken into account and giving you every benefit to eliminate the .003" barrel cone bolt nose clearance the barrel temperature will have to be increased 545.5 degrees while the receiver stays room temperature. Starting at 70 degrees you need the barrel to be 615.5 degrees. Other than extended full auto firing shooting a barrel to those temps makes rainbow colored Unicorns more realistic..

Real world temps, heat transfers, and expansion makes this a non-issue unless your bolt nose clearance is under a .001". Carbon, unburnt powder, brass shavings and any type of debris will be a problem long before expansion is.

Some perspective on touching different temperatures on bare skin.

https://www.reference.com/world-view/temperature-human-skin-burn-82a1af6b1322b289

Human skin burns to varying degrees of severity as the applied temperature rises. Humans begin to feel a burning pain when skin temperature rises to 111 degrees Fahrenheit, with first-degree burns developing at 118 F.

More severe burns occur at higher temperatures. An applied heat of 131 degrees Fahrenheit causes second-degree burns on exposed skin. Pain receptors overload and become numb at a temperature of 140 F. At 162 F, human tissue is destroyed on contact. The entire range of burn temperatures, from the first appearance of pain to instant destruction, falls well below 212 F, the boiling point of water.

As to Dan I've only read the one post in this thread. No slight intended as stated. I just stated what I disagreed with and laid out my case. That was done in a civil manor. That appears to be something you are incapable of.

I used to hang out a lot here back in the day when world class smiths used to freely share their knowledge here. Alan Warner and Chad Dixon come to mind. I know there were others also but I am not sure if it was this forum or others. It appears you maybe the only one left. I haven't back read the older posts so if I am slighting any of the truly knowledgeable posters that is not my intent.

Stopped hanging out here when Alan Warner and Chad Dixon stopped posting. At the time Chad Dixon had built the raining 1,000 World Record holding rifle. Chad used somewhat of a different threading and chambering technique. He shared his method and was savaged for using a different methodology by people that probably never barreled a rifle let alone a world record 1,000 yard grouping rifle.

.

Yup other than less participation NOTHING has changed here. If you want to see a major reason for that I suggest a mirror.

Also if you are going to quote me use the complete quote.

Also the bolt lug and face will be at a lower temp than the chamber throat area of the action/barrel. Due to the differences in temperatures of the different areas calculating the clearance change is in not an easy undertaking.
While the bolt, receiver and barrel are three pieces they will act as a single piece if the temperature increase is the same for all three piece. In that case the clearance will increase not decrease. It will act the same as if it was a slot or a hole in a solid piece.

 

[alinwa]

Couple of items that perhaps haven't been considered

#1, the barrel tenon on the big boomers is much longer than a "normal" inch-long tenon most of us are used to.

#2, take it to any extreme you want in running your number scenarios but the bolt and action ring stay relatively cool during a normal firing cycle. Just reach out and touch the action ring or bolt next time you shoot. Of course there is some transfer over time but not enough to make modeling of "all parts heating equally" relevant IMO.

#3, steel under tension yields more readily under heating, ie "expands more" than a block of steel in a quiescent state. The tenon has tens of thousands of pounds pulling it toward the bolt face.

#4, there is an added component of the expansion of the threaded tenon which may come into play, that of the thread angles "climbing" and driving back toward the boltface both from the expansion due to heat and the momentary expansion from pressure.

Simple fact is that the guys shooting the big boomers have learned to keep a little extra play between the face of the lugs and the end of the barrel.

Regarding my responses;

I took umbrage at you discounting the experience of a man who shoots big guns.....

I took umbrage at your modeling of "all parts heated equally"

I took umbrage at your statement "expansion is hard to understand"


Model all you want, but in the real world setting the clearance betwixt barrel and bolt too short can cause interference.

 

[alinwa]

You are correct that you need the clearance but not for the stated reason. Mostly for unburnt powder and brass shavings. On a cone bolt anything between .005 and .015 will work.

The thermal Expansion for metals varies depending on composition but for normal firearm steels it's going to be somewhere around 0.0000053" to 0.0000099" per inch per degree. With a 100 degree increase that is still less than a .001" expansion per inch. Also the bolt lug and face will be at a lower temp than the chamber throat area of the action/barrel. Due to the differences in temperatures of the different areas calculating the clearance change is in not an easy undertaking. While the bolt, receiver and barrel are three pieces they will act as a single piece if the temperature increase is the same for all three piece. In that case the clearance will increase not decrease. It will act the same as if it was a slot or a hole in a solid piece.

Joel,

regarding my initial response, I'm not exactly sure how you worded it the first time as you went back and edited the post 5 days after posting it.... but you've still got the ".005-.015 will work" in this version.

IMO .005 is not enough for a large, long-tenoned rifle.

 

[alinwa]

Also to Joel,

if you sincerely believe that I'm the reason for attendance falling off, mayhap it'll be best if I leave y'all's alone so things can get back to your version of "better."

Since the way of the world these days is that "better" is to bear to center in all thinking.

Rock On

 

[Joel]

Couple of items that perhaps haven't been considered

#1, the barrel tenon on the big boomers is much longer than a "normal" inch-long tenon most of us are used to.

#2, take it to any extreme you want in running your number scenarios but the bolt and action ring stay relatively cool during a normal firing cycle. Just reach out and touch the action ring or bolt next time you shoot. Of course there is some transfer over time but not enough to make modeling of "all parts heating equally" relevant IMO.

#3, steel under tension yields more readily under heating, ie "expands more" than a block of steel in a quiescent state. The tenon has tens of thousands of pounds pulling it toward the bolt face.

#4, there is an added component of the expansion of the threaded tenon which may come into play, that of the thread angles "climbing" and driving back toward the boltface both from the expansion due to heat and the momentary expansion from pressure.

Simple fact is that the guys shooting the big boomers have learned to keep a little extra play between the face of the lugs and the end of the barrel.

Regarding my responses;

I took umbrage at you discounting the experience of a man who shoots big guns.....

I took umbrage at your modeling of "all parts heated equally"

I took umbrage at your statement "expansion is hard to understand"


Model all you want, but in the real world setting the clearance betwixt barrel and bolt too short can cause interference.

Yes they have been consider and it's even more clear that you really don't understand expansion. Items 1 -4 are an excellent cases in point. Actual expansion happens in all directions and tenon length is not a factor in bolt nose coned breach clearance issue but on the point that on the large calibers the tenons are longer your are correct. After that not so much.

As to the models that is to help people understand this complicated issue and yes it is a difficult issue for even people that work with it in industry of which I have been part of for over 40's years both in hands on and as a trainer. I've yet to find a properly designed thermal expansion model that is not accurate and verifiable.

As to your "umbrage" apparently a very large number of folks take "umbrage" to you based on the number of emails & PM's I have received. I will say my email traffic has had a lot more participation in the last couple of days than the gunsmiths corner has had in a month.

Seems the consensus is that you believe yourself to be the forum god that is all knowing that can not be disagreed with (not my words) but I can't disagree with them based on your first two posts and stuff from the Alan Warner, Chad Dixon and David Tubb actively posting days.

That is the "stuff" that kill's forums. Seems the "umbrage" folks have done a good job here based on the low amount of posts and participation compared to what it used to be. I've been a member since 2003 under this profile and for awhile before that under a different profile when I had a different email address.

If you bring some actual data or verifiable experience I will continue this discussion. Until than not some much.

I've stated my position. Some may agree some may disagree. Not my job to bully someone into submission.

Frankly it makes zero difference to me if someone agrees or disagrees. Freely sharing ideas is a good thing. It up to whoever reads them to agree or disagree and even if they disagree they may still learn something.

I participate in various forums learn or to help others learn not to argue.

 

[Joel]

Also to Joel,

if you sincerely believe that I'm the reason for attendance falling off, mayhap it'll be best if I leave y'all's alone so things can get back to your version of "better."

Since the way of the world these days is that "better" is to bear to center in all thinking.

Rock On

If you want I can post the comments from the emails and PM's on this forum stating as much. I would keep the sources confidential.

"Better" is being able to disagree without the condescending SA peanut gallery comments. Yes your first two posts on this thread set the tone. I also remember folks from the more active days of this forum. Did I mention I really respected Jackie??? Not sure who else is still here of the folks held in high regards and yes I do remember you as also.

 

[Joel]

Joel,

regarding my initial response, I'm not exactly sure how you worded it the first time as you went back and edited the post 5 days after posting it.... but you've still got the ".005-.015 will work" in this version.

IMO .005 is not enough for a large, long-tenoned rifle.

Changed a typo not the content.

When you build them do it however you want. I have no problem with you doing it your way.

I've only barreled two 50 BMG's maybe a 1/2 dozen of the plus sized magnums and a couple hundred standard sized however maybe only 1/4 have been cone breeched. I normally I shot for .008" clearance on coned breech. Most of the coned breech rifles were for NRA across the cross competition so they had to run smoothly for rapids.

 

[Louis.J]

Interesting conversation, interesting information from an interesting question. That is until it turned into a not so friendly who is it who is correct answer session and personal attacks. Can't we all just get along and have a civil conversation unlike the rest of the country these days. I come here to learn and to get away from all of that BS to get a little peace in life.

 

[alinwa]

Well Joel, you've made your case.

You're a powerful and influential man with an inbox full of complaints and a clear understanding that I've ruined Wilbur's Forum.

This issue is now rectified,

Enjoy The Day

 

[Butch Lambert]

Alan Warner is good.

 

[fourspear]

sad to see

Mr. Chet, would you please start over with your results, second thought it probably isnt worth it.

 

[Louis.J]

You are probably correct it didn't take long for this one to go sideways instead of staying on track. Poor ole Chet probably now regrets that he even brought it up to begin with.