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Bolt head sizes?

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Goosic View Drop Down
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Post Options Post Options   Thanks (1) Thanks(1)   Quote Goosic Quote  Post ReplyReply Direct Link To This Post Posted: June 08 2022 at 8:53am
Typically between .0042" - .0050" is acceptable...
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Post Options Post Options   Thanks (0) Thanks(0)   Quote scottz63 Quote  Post ReplyReply Direct Link To This Post Posted: June 08 2022 at 8:54am
Originally posted by Goosic Goosic wrote:

Typically between .0042" - .0050" is acceptable...

Got it. Thanks!
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britrifles View Drop Down
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Post Options Post Options   Thanks (1) Thanks(1)   Quote britrifles Quote  Post ReplyReply Direct Link To This Post Posted: June 08 2022 at 11:54am
0.04 to 0.05 inches for striker protrusion from bolt head face. 

One of my No. 4 rifles has only 0.03 inches of striker protrusion, not had any issues with primers not igniting.  I suspect that is in part due to a fairly tight headspace, in that the cartridge can’t move very far away from the bolt head face before the rim hits the back of the chamber face.  This was a rifle that headspace exceeded 0.070 (don’t know by how much) and I replaced the #1 bolt head with a #3 bolt head which brought headspace to between 0.064 and 0.070, which I suspect reduced the headspace by .005 to 0.010. 


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Post Options Post Options   Thanks (1) Thanks(1)   Quote Shamu Quote  Post ReplyReply Direct Link To This Post Posted: June 08 2022 at 12:37pm
People go on about "headspace" but I see little to nothing about "Free Headspace"!
Whats the difference?
Rim thickness!
If your rifle has a loose, but within limits headspace & the rim is thin then, the rim doesn't fill the space available. The gap is the Free Headspace.
There's always a little, there has to be, but when it gets excessive it can cause issues like primers backing out & cases stretching excessively.
Don't shoot till you see the whites of their thighs. (Unofficial motto of the Royal Air Force)
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Post Options Post Options   Thanks (1) Thanks(1)   Quote Goosic Quote  Post ReplyReply Direct Link To This Post Posted: June 08 2022 at 1:07pm
The, "Free Space" can be made near non-existent if you consistently use cartridge cases with the same rim thickness in combination with the longest bolthead available that will almost fail a .070" NoGo gauge. 

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Post Options Post Options   Thanks (1) Thanks(1)   Quote britrifles Quote  Post ReplyReply Direct Link To This Post Posted: June 08 2022 at 1:10pm
I agree Shamu.

  I could see a condition where striker protrusion is on the low side, headspace on the high side and rim thickness on the low side combining to result in erratic primer ignition (as one problem that can occur with these combined issues).  The cartridge will first get pushed forward by the striker until the rim contacts the back of the chamber.  

A cartridge case that has been fire formed and then neck sized will then “headspace” on the shoulder and take up the “free headspace” that you described. 

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Post Options Post Options   Thanks (1) Thanks(1)   Quote britrifles Quote  Post ReplyReply Direct Link To This Post Posted: June 08 2022 at 1:47pm
It’s mostly an issue with commercial cases made to SAAMI specs, which specifies a rim thickness of 0.054 to 0.064 inches.  I’ve measured some cases with rims very close to this minimum (0.054 inches).

Combine that with headspace at or near Field (0.074) then we get a awful lot of “free headspace”. Potentially as much as 0.020 inches.  

One of the things I like about PPU brass is that it has rim thicknesses in the 0.060 to 0.062 inches.  The Canadian military brass I have has rims in the 0.062 to 0.064 range.  







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Post Options Post Options   Thanks (1) Thanks(1)   Quote Shamu Quote  Post ReplyReply Direct Link To This Post Posted: June 08 2022 at 3:22pm
We're all experienced L-E owners so we're familiar with these things.
But we do have several members on here concerned with head-spacing & new to the rimmed .303 rounds peculiarities.
I just figured I'd run it up the flagpole & see if anyone saluted.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote scottz63 Quote  Post ReplyReply Direct Link To This Post Posted: June 08 2022 at 6:05pm
Thanks everyone for all the info. .303 is a new cartridge for me. I have 30 plus years of Military surplus experience, but .303 has eluded me until now, somehow. Lol 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote scottz63 Quote  Post ReplyReply Direct Link To This Post Posted: June 08 2022 at 7:17pm
Just checked a couple of S&B .303 rounds for rim thickness. .061
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Post Options Post Options   Thanks (1) Thanks(1)   Quote Goosic Quote  Post ReplyReply Direct Link To This Post Posted: June 08 2022 at 10:35pm
All of my Herters brass has a rim thickness of 0.060"
Using a Forster .070" gauge, the bolt almost closes. I made a set of custom brass feeler gauges that I can slip between the cartridge case rim and the bolt, face with the bolt closed. My "free space" is only 0.008" 
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Post Options Post Options   Thanks (1) Thanks(1)   Quote britrifles Quote  Post ReplyReply Direct Link To This Post Posted: June 09 2022 at 4:20am
Just for grins, I check several R-P cases I have. Rim thickness measured 0.056 to 0.058.  A bit on the thin side.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote scottz63 Quote  Post ReplyReply Direct Link To This Post Posted: June 09 2022 at 6:01am
I have a couple of WW2 303 rounds. Going to go check what they are.

Edit:  "U" marked .054   "CAC" marked .057



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Post Options Post Options   Thanks (0) Thanks(0)   Quote scottz63 Quote  Post ReplyReply Direct Link To This Post Posted: June 13 2022 at 3:14pm
Originally posted by Shamu Shamu wrote:

An Arkansas stone will do just fine.

What Arkansas stone should I get? There is hard, medium, and soft. Also different hardness scale ones.

Thanks, Scott
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Post Options Post Options   Thanks (1) Thanks(1)   Quote Shamu Quote  Post ReplyReply Direct Link To This Post Posted: June 13 2022 at 5:42pm
Hard
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Post Options Post Options   Thanks (0) Thanks(0)   Quote scottz63 Quote  Post ReplyReply Direct Link To This Post Posted: June 13 2022 at 7:40pm
Originally posted by Shamu Shamu wrote:

Hard

Got it. Thanks!
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