Measured Headspace - Now What?

[Parashooter]

I am intrigued. I have been reloading .303 for a while, but I've not heard of this O-ring thing. Please tell me/us more; size, type, source, etc.

If you handload for a .303 with generous headspace, there's often no need to mess with bolt heads - changing the rifle's clearances to yield longer case life. You can control cartridge end-play simply by changing technique.

When you fire a new case for the first time, use an improvised spacer ahead of the rim - anything from a precision metal washer to dental floss can work to hold the the cartridge head firmly against the bolt face and eliminate or reduce stretch even if end-play without the spacer would be significant. Another way of accomplishing the same end is to use a bullet seated out far enough to jam into the lands, "headspacing" on the bullet instead of the case. Such techniques are useful only if the rifle has excess headspace (or cartridges have abnormally thin rims). With normal headspace and cartridges, initial stretch isn't enough to worry much about.


O-rings are a slightly more costly spacer material preferred by some.

After you've fire-formed your new cases they will fill the chamber fully, stopping on the shoulder just like a rimless cartridge. If you neck size, you'll have zero "headspace". If you have to full length size, adjust the die so the cases chamber with just a bit of resistance in the last few degrees of bolt rotation. The result, if combined with reasonable-pressure loads, can be extended case life despite generous headspace.

[Edward Horton]

before this gets out of hand again, a quick word on the rim thickness gauges and 2 boltheads.
When these where in vogue the ammo was ALL factory stuff or as you yanks call it ex milsurp. Each rifle club would submit a forecast as to how many rounds where going to be needed for the years shooting. This was mostly over exaggerated as you would do and then it was railed to the club, picked up at the local rail siding. The club captain would issue the ammo to the shooters as needed and THEN the shooter would check the rim thickness and batch them to as close as possible to his rifle. The 2 boltheads where used if the batch of ammo was of a different size. remember this was all ex WW2 and later mil ammo so all factory spec length but with varying rim thickness due to manufacturing tolerences.As we can research and know that when we use reloaded ammo we fire form the cases to our own rifle after the first firing and if only neck sized then the headspace and overall length of the case is tailor fitted to each individual rifle, negating the need for the rim thickness gauge and batching ammo due to rim thickness.
A common theme today is rimfire competition shooters do the same batching of thier favourite ammo for each rifle, they need to achieve the same thing as the old target rifle shooters using factory ammo.
Hope this helps.
Cheers

Para

Your forgetting the American SAAMI rim thickness standards are .064 to .054 for American commercial ammunition, and I have measured rim thicknesses from .062 to .057.

Then to add insult to injury the American SAAMI chamber standards are NOT the same as British military chamber standards.

On top of this you have .303 ammunition made all over the world to their countries standards or tolerances.



Are you going to tell me the base diameter on the HXP ammunition is the same diameter as the Prvi below or that the Prvi isn’t .010 thicker in the base web area and has a thicker rim.



So before this gets out of hand, don’t tell me I can’t read a gauge.



Don’t tell me all brass cases are made from the same grade brass.



And don’t tell me every manufacture makes the same quality cartridge cases and they are the same thickness in the base web area.





The “Enfield inch” story covers more than the Lithgow factory or how many grains of corn or barley make up an inch in Australia or the U.S. of A.

Or are you going to tell me the Australian Shooting Champion James Sweet didn’t know what he was talking about when he said this in 1946.



Don’t make me send Quigley back to Western Australia

[trooper554877]

Ed,
I was only making observation to the rim gauge. the only constant in the ammo was that they where given it. Of course there where differences in rim thickness, case length etc, thats why the chambers are so generous, to accommodate for any ammo supplied from any factory in the world. Te target shooters like Jim sweet had only one way to control the quality of ammo they feed into their rigs and that was to measure rim thickness. they knew what shot good in their rifles and procured ammo that fitted. they had no control over any of the loading procedures etc that you mention. It was new off the shelve stuff, fired once and discarded.
we now have the luxury of being able to afford and have the components readily available.
My obs where only ever pointed to the measuring of rims, not headspaceing, that was allready done and hence the 2 boltheads, to accommodate to the variance in tolerances of Mil factory ammo.
Keep Quigley over there, he is full of it!!! magnum PI indeed!!!
Cheers and all the best wishes for Xmas, To coin a phrase, Hope your chooks turn into Emu's and kick your dunny door down!!
NED

[Parashooter]

Then to add insult to injury the American SAAMI chamber standards are NOT the same as British military chamber standards.

What do you imagine to be the significant differences between the SAAMI and British chamber standards?


Lower (British) drawing courtesy of Mr. Horton. Upper from SAAMI.

From what I can see, base diameter (.462"), shoulder diameter (.4036", .4045"), neck diameter (.345" at shoulder, .341" at mouth), leade (~.313 > .3102) and length to mouth (2.158"+.064"=2.222") are virtually identical, shoulder position and radii very much the same, and there is no practical difference if one remembers to add the .064" rim clearance to the British length figures (to adjust for the SAAMI lengths being measured from the bolt face instead of the barrel face).

[Edward Horton]

If you handload for a .303 with generous headspace, there's often no need to mess with bolt heads - changing the rifle's clearances to yield longer case life. You can control cartridge end-play simply by changing technique.

When you fire a new case for the first time, use an improvised spacer ahead of the rim - anything from a precision metal washer to dental floss can work to hold the the cartridge head firmly against the bolt face and eliminate or reduce stretch even if end-play without the spacer would be significant. Another way of accomplishing the same end is to use a bullet seated out far enough to jam into the lands, "headspacing" on the bullet instead of the case. Such techniques are useful only if the rifle has excess headspace (or cartridges have abnormally thin rims). With normal headspace and cartridges, initial stretch isn't enough to worry much about.


O-rings are a slightly more costly spacer material preferred by some.

After you've fire-formed your new cases they will fill the chamber fully, stopping on the shoulder just like a rimless cartridge. If you neck size, you'll have zero "headspace". If you have to full length size, adjust the die so the cases chamber with just a bit of resistance in the last few degrees of bolt rotation. The result, if combined with reasonable-pressure loads, can be extended case life despite generous headspace.

Parashooter

Your entire premise for your original “Headspace 101” was oiling and greasing your cartridge cases to keep the cases from stretching and thinning in the web area. When “someone” made your method “controversial” you edited your “Head space 101” to eliminate the words oil and grease.

The problem I have with your comments here is you admitted that you still oil your cases to fire form them, you read about the rubber o-rings like I did at Jouster and yet you are here writing about fishing line and dental floss as if you use it every day or at least after every meal.

Parashooter the o-ring method came from a Canadian at Jouster, the rubber o-ring centers the case in the chamber and fishing line and dental floss will not. I will say it again Parashooter you can’t have it both ways.

Oiling your cases doubles your bolt thrust and shortens the Enfield’s life expectancy by half and your “Headspace 101” told everyone to oil and grease their cases for over seven years.

Mr. Laidler told us during an Enfield FTR/overhaul an oiled proof round was fired and if the bolt was hard to open the action was scraped. This was because the surface hardness in the lug recesses had worn through.

It’s a little late for fishing line and dental floss and changing horses in midstream on a Enfield battered by excessive bolt thrust caused by oiled cases.

[Amatikulu]

Both of my No.4 Mk.1* rifles have failed the no-go and field guages. They both have #1 bolt heads. Am I correct that replacing the bolt heads with higher numbered ones will/might fix the problem? If so, I have a couple of questions: How can I determine which bolt head (#2 or#3) will yield correct headspace? Where am I likely to find them?

Thank you for your help.

Mike

Above is the initial post on this thread. I think the question has been answered

[Badger]

Ok, enough folks ...

Thread is now locked ...

This subject has been beat to death a hundred times on every Enfield gun forum on the Internet in the past 10 years.

It always results in the same arguments, often by the same folks ..

As Amatikulu pointed out, I think it's safe to say that the original poster got his answer by now...

Regards,
Doug (Badger)