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PROPER CHAMBER DEPTH ?

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Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/04/2007 at 01:22
hot30 View Drop Down
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You know how we all look at things a certain way, Im looking at 3 burned out barrels.  Laying on the bench with the chambers facing me, each chamber depth is

noticeably different in depth. Just put 3 resized .308 cases in each chamber and behold  "WHAT IS THIS". !!!!!!!!!!!  What ever happened to SAAMI specs.  Question.??  Do any of the doctors in the house know what the standard or SAAMI depths should be >??    One case is protruding .200 from the chamber, the others not as much but are different.  Now, I know this one at .200 has some major case showing when its locked in the chamber.  The bolt takes care of the rim when chambered, the chamber has most of the case and I guess the gap in between is going to do what ever it wants.??

 

      Any takers

Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/04/2007 at 07:25
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Hot,

Iím going to take a stab at this. Iím probably going to get told Iím way wrong but we will see.

All guns are different and will take a different length shell. This is true with guns made back to back. Now at first when all gun were new the shell your using might have fit closer to the same than your seeing now.1) the metal that the gun was made with might have been a little softer in the gun that the shell goes deepest in, Iím not positive but it might be an option to look at.2) is the shell your using the shell thatís been resized for that one gun all will fit different gun different. Might be another option.3) when you resized did you full length or neck size? The reason Iím asking is in one of my guns I have way to much head space. My shells stretch a good bit to fit my chamber so I neck sizes them and when I put that shell in another gun it sticks out a good bit to where the bolt would need stainding on to close.

 

Maybe this will help. This is something I would need on my bench to look at and tell you what going on with it. It might not be somethingís wrong. Itís just different guns.

 

 

Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/04/2007 at 13:19
hot30 View Drop Down
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Doctor Daddy, This is true. You have me thinking.  Lets answer this question. Does SAAMI have a standard dimension for the distance between the rim of the bolt head and the end of the barrel.  If this "gap" gets too wide you should see you brass case "bulging" after firing. Bulging more than what is acceptable.  I believe that a gap is always present between these two parts, so is there a standard dimension for this gap.???

 



Edited by hot30
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/04/2007 at 13:27
hot30 View Drop Down
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Once  this gap is at an acceptable range, then "head-space" will be adjusted.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/04/2007 at 13:28
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Hot,

  Does SAAMI have a standard dimension for the distance between the blot face and the case face? This would be an industry standard "gap YES. I'm leaving going out of town for a few days on a hunt but when I get back  I will get my go to books and let you know more about the SAMMI standard and what the tolerances are and what is going on with your toyís. I might be able to help you but it might take some time it figures it out. But I will get you an answer of it kills me.

 

 

Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/04/2007 at 13:54
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GO: 1.630"
NOGO: 1.634"
FIELD REJECT: 1.638"

 

this is some numbers i have ran across on the net.i need my book to tell you a real answer

Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/04/2007 at 17:38
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.308 Winchester

 

 

This is a diagram for the .308.  The only thing that should be exposed when you insert a cartridge into a barrel, without the bolt, should be that part that is engaged by the bolt face and locking lugs.  Here we see that by SAAMI specs, that should be about 0.1516 inches.  Hence, this is compatible with big daddy's headspacing gauges, which accounts for some room for the bolt face.  0.2 inches seems excessive.  Several reasons could account for this.  Your re-sizing dies may not be accurate.  Try a factory cartridge.  Maybe the bolt face does account for that much room.  While I build custom rifles, I usually use barreled bolt actions and the times I have screwed on barrels, I have never tried to insert a cartridge into the receiver end of the barrel, but just to check headspace after attaching the barrel.  Me, I would forget about it.



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Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/07/2007 at 18:32
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hot30, what actions were the barrels screwed into?  Could it be that the difference you see could be due to one barrel being mated to an action with recessed bolt face such as Rem 700 and another to an action with flat bolt face w/ controlled round feed such as Mauser / Win 70 classic / Ruger 77 style action?  On the recessed bolt face action, the barrel tenon aft of the chamber is counterbored approx. 0.150" deep (close to the 0.200" you mention) to accept the nose of the bolt, so the case will seat deeper into the barrel shank with this action than one with a barrel mounted to a rifle where the bolt doesn't protrude into the barrel shank.  Headspace length remains the same, as the relationship between the actual bolt face and the shoulder is approx the same.  It has to be, otherwise, you'd have a dangerous case head separation problem with excessive headspace.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/07/2007 at 19:22
Dolphin View Drop Down
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Originally posted by RifleDude RifleDude wrote:

hot30, what actions were the barrels screwed into?  Could it be that the difference you see could be due to one barrel being mated to an action with recessed bolt face such as Rem 700 and another to an action with flat bolt face w/ controlled round feed such as Mauser / Win 70 classic / Ruger 77 style action?  On the recessed bolt face action, the barrel tenon aft of the chamber is counterbored approx. 0.150" deep (close to the 0.200" you mention) to accept the nose of the bolt, so the case will seat deeper into the barrel shank with this action than one with a barrel mounted to a rifle where the bolt doesn't protrude into the barrel shank.  Headspace length remains the same, as the relationship between the actual bolt face and the shoulder is approx the same.  It has to be, otherwise, you'd have a dangerous case head separation problem with excessive headspace.

Rifledude makes some good points and probably account for some of the differences.  I did not consider this, as you said you had 3 resized cartridges and they were all a little different, but all close to 0.200 inches.

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