Headspace...

[Ovidio]

Funny enough, some other guy at the range Saturday, while I was shooting with my SMLE, addressed the matter of headspace, asking me which measure of bolt-head I was using.
Seems to be somewhat an argument to sound as experts.......
Good luck on your deployment Amadeus!

[englishman_ca]

You will find a lot of experts at the range, there is a lot of good and bad information on the internet. I enjoy chatting with them, but some come out with some remarkable comments.

I have heard some interesting tidbits and some gems over the years.

[Ovidio]

This is really interesting, thank you.

[browningautorifle]

I have heard some interesting tidbits and some gems over the years.

Interesting way to put it...

[CINDERS]

Well at least I learned a few things from this thread but for those of you in the world of firearms and weapons think you are hounded by those that cannot think well this from my world of operating cranes for nearly 18 years I learned allot.
Some things that have entered my world from the universe of DADS (Dumb As Dog Sh*t)
If I had a $1 for every time I have been asked by a noob "Have ya tipped one over yet mate." I would be fliking rich and no I haven't but have had a few scares with ground liquification and unknown soak wells put there 30+ years ago!.
"But it is a 160 tonne crane why can't it lift it" "Well its 160 tonne at 3 meters with basic boom and 50 tonne of counterweights" not 30 bl**dy meters away."
"Look here you can drive up my concrete driveway it will be ok its 75mm thick." "Sir, the crane weighs 60 tonnes without counterweights best you get some sand for the trenches my tyres are going to leave in your front lawn." usually 900mm wide by anything up to and beyond 300mm deep.
"There is plenty of room you will fit through the gate its 3.5m wide." " Well Sir I do not think so I am 3.9 meters wide with the mirrors folded in and 16 meters long!"
Then you have the classic a 60 tonne vehicle doing 60kph and a car pulls out 20 meters in front of you its an automatic crane there is another car beside you in the camera (Left hand drive crane) you only have the telmar and the brakes if thats not bad enough a young child gets up and looks up over the rear sill.

Once I pulled out of an irrigation drain a van which had aquaplaned off the road and the young child (4 years old) was missing the police stopped me and commandeered me and the crane I slung the vehicle as no one there had a clue and winched that van upside down out of the full drain I half expected the little tyke to fall out of it, but he didn't his body was found 2 klm's down the channel.

We all in our lives or trade have horror stories good and bad, but one thing I did when training people on cranes because a crane can kill and maim just as well as an artillery round or a bullet with my students I had under my wing in my mantra there was "Never a dumb question just a dumb answer..........."

Next time you see a large crane say with 60 meters of boom out roughly 180-185 feet then if your within a 60m radius of that crane then your in the death zone if it goes pear shaped and falls your way, also if he has his headache ball with 20 meters of rope out under the boom tip then if it tips sideways then that can be flung further out like a lead ball on a string............
That is @1 millionth of the stuff I learned or had to contend with whilst operating a variety of hire crane across this state Western Australia look it up and you will get the drift how vast our state is, at least at 80kph top speed you got to see the scenery.
Last one, we were issued with salt to throw out the windows to keep the snails back whilst going up hills they caused you to lose traction........Cheers.

[Brian Dick]

The new Criterion barrels are chambered to SAAMI specification and come with short chambers and long shoulders so they can be turned for proper "crush" and headspaced to a "0" bolthead using a finish reamer.

[Bruce_in_Oz]

Well done, Criterion.

They took the "risk" AND put in a LOT of thought and research.

[Son]

Have a close look at the operation of the extractor on a Lee-Enfield: It actually holds the case fairly close to the bolt-face whilst in operation..

The extractor claw is disengaged from the rim when the bolt closes. With the aspect of the claw to its pivot, as it comes away to the side it would also be opening the gap back to the bolt face.
I did some pics with a dial indicator on my skeleton action a while back.... I'll see if they show how much.

[Bruce_in_Oz]

"The extractor claw is disengaged from the rim when the bolt closes."

Good point. You can see the extractor start to pivot outwards as the bolt-handle is locked down. But, as near as I can make out, it never deflects far enough to be completely clear of the outer diameter of the rim. Again, this ties in with the whole beauty of the helical locking system on these rifles.

As the bolt handle is raised, because the bolt-head thread is a coarse right-hand thread, the bolt head only moves back a little, initially, until the "little" lug on the bolt body picks up the 1: 1inch unlocking cam surface and starts the primary extraction process properly.

Clever things, these old rifles.

[CINDERS]

I think it shows pure genius of the designers of the rifle between the 2 rifles the MkIII and the No.4 did they alter the lock up at all on the system or left well enough alone and designed the receiver for the No.4 around that principle