303B Headspace, Sizing

[I Dont Care About You]

Soooo ......

I just began to look at sizing fired cases for my minty No4 Mk2 and discovered a few interesting things. Just to be clear, I am only going to talk about headspace as it refers to the case shoulder. Don't particularly care about stupid headspace to the rim.

I measured up some fired cases that came out of my rifle. I have a few hundred fired cases I bought from a guy online that have clearly been fired through different rifles. The headspace of fired cartridges varies wildly, like way more than I'd expect from a SAAMI spec'd cartridge.

If we assign the shortest measured headspace for a fired case as 0, then the longest is 0.075", which is a HUGE range. Too make this easy I listed the various headspace measurements below.

Shortest fired case: .000"
Hornady Factory case, unfired: .021"
Full Length sizing die set per instructions: .035"
Fired cases from my No4. .050"
Longest fired case .075"

I adjusted the full length sizing die to produce a headspace of .053" which creates a very slight crush upon closing the bolt. This ought to minimize case stretch and keep the cases pushed against the bolt face nicely to stop the cases stretching and splitting at the web ... or at least minimize this effect.

One thing I can't work out, is how the hell a chamber with .000" headspace can accept any commercial ammo? I'm gonna assume that Hornady loads ammo to a relatively short headspace to ensure it fits into all and any chamber, yet there are clearly chambers that are shorter. How is it even possible to jam a case that is .020" longer than the chamber, into that chamber? I tried to chamber the .075" fired cases into my .050" chamber and there was no way that bolt was gonna close. My .050" chamber wouldn't even accept a .062" case.

FWIW I also have a Lee Collet neck die, which will get used once all the brass has been fire formed to my chamber.

 

[I Dont Care About You]

The other thing I noticed while comparing different fired cases, unfired Hornady ammo and the cases that came out of the sizing die was that the new factory ammo and the cases from the sizing die have a shoulder that resembled that of a 30-06 round, nice and sloped. Most of the fired cases, from my rifle and from other unknown rifles have fire formed shoulders that are a completely different shape, much less distinct, and which resemble the small shoulder found on a 300 Blackout case.

I've been reloading rifle ammo for more than 25 years and this is the first time I have some across ammo that is a completely different shape than the chamber it is meant to be shot in. The 303B really is an odd duck in many respects.

 

[nitro-express]

Odd Duck. Yes, I'll agree with that.

The 303 Br was one of the first cartridges that I reloaded for, and some of my first 303 rifles were well worn(out). Add to this a RCBS FL die that would size about 0.010" smaller in diameter than a new factory shell. That was a few decades ago. It was also a time before the internet, so most of my lessons were learned from my own experience.

I now load for various 303 Br chambered rifles without issues for the most part. The 303 Br is not like most other calibers, and my FL die usually is spaced off the shell holder by 0.025" IIRC. Surprisingly, for most of the rifles I've loaded for this dimension stays pretty much the same. To my way of thinking, the issues would be mitigated for the most part if the dies were made to Min Chamber specs, after all, what's the chance of running into one of those.

I have found that on most bolt action rifles I adjust my dies for about 0.003" shoulder setback. I avoid setting with a bit of bolt resistance. Closing the bolt under any force wipes the grease from the locking lugs and they wear or gall fairly quickly.

My best 303 Br was a single shot Martini. I also owned, or shot a couple that did not see much combat that were nice to load for. But most were worn out battle weary surplus, and few of those had a shoulder that looked like the rounded weatherby style shoulder.

Have fun.

 

[tiriaq]

A case fired in a Ross (not one that had the chamber reamed out) is quite different than one fired in a Lee Enfield. One fired in a SAAMI chamber cut with a current reamer is also unlike a LE.
If I am starting with cases fired in assorted rifles, I set my die to size just enough to get the things to chamber in the LE I'm loading for. I do not set the die to contact the shell holder. Do that and the incipient separations start.
If I am preparing LE fired brass to use in my Mk. II** Ross target rifle, I do FL size, then size the rear body of the cases in a die I made to reduce the diameter a bit more, so that they will fit the minimal chamber. LE brass FL sized will not chamber in the Ross. The rear body diameter must be reduced.

 

[bdft]

I now load for various 303 Br chambered rifles without issues for the most part. The 303 Br is not like most other calibers, and my FL die usually is spaced off the shell holder by 0.025" IIRC. Surprisingly, for most of the rifles I've loaded for this dimension stays pretty much the same. To my way of thinking, the issues would be mitigated for the most part if the dies were made to Min Chamber specs, after all, what's the chance of running into one of those.

I have found that on most bolt action rifles I adjust my dies for about 0.003" shoulder setback. I avoid setting with a bit of bolt resistance. Closing the bolt under any force wipes the grease from the locking lugs and they wear or gall fairly quickly.
Have fun.

How do you "adjust " your dies? My 303 Hornady dies have no adjustment. The case goes in until the shell holder hits the die and that's a full length resize. If I can get the case up past the expanded ring just above the rim. Do they make dies with adjustable length or have I been doing it wrong all these years? The challenge I have pushing the shoulder back into spec is getting the case into the die past the expanded ring above the rim.

 

[Snider shooter]

Don’t screw the sizing die down to the shell holder. I have a gap approximately 1/4” between the shell holder and die. It’s what is called partial sizing. Your pushing your shoulder back too far every time you resize. Your cases probably don’t last long with full power loads.

 

[I Dont Care About You]

How do you "adjust " your dies? My 303 Hornady dies have no adjustment. The case goes in until the shell holder hits the die and that's a full length resize

Turn the die out a half turn or so. Size a case and measure case headspace. Continue to adjust the sized headspace of the case by turning the die in or out by a small amount until you get the sized headspace that matches your rifle chamber.

 

[I Dont Care About You]

I have found that on most bolt action rifles I adjust my dies for about 0.003" shoulder setback. I avoid setting with a bit of bolt resistance. Closing the bolt under any force wipes the grease from the locking lugs and they wear or gall fairly quickly.

This is an interesting comment. I will make sure to lube my bolt lugs and maybe back my sizing die off a smidge to eliminate the squish on bolt closing.

 

[cosmic]

The question begs - where did the .000 case come from? Suggest you compare the Hornady case to some other unfired factory case. That should resolve matters. BTW - How are you measuring shoulder headspace?
You are going to run into another issue at some point. Some rifles will have long and skinny chambers. They display largish shoulder headspace, but wont accept what appears to be a properly sized case.

 

[bigedp51]

Below is a new unfired Remington .303 case in a Wilson case gauge. As you can see the shoulder is back to far for a military chamber.

Below is a fired case from a No 4 (1943) Enfield rifle. The case gauge is made for commercial nonmilitary chambers. During WW1 and WW2 much of the ammunition was poorly made by commercial manufactures and did not fit military chambers properly. Then the military chambers were made larger in diameter and longer to the chambers shoulder.

Below a fired .303 case from a military Enfield, this shows how far off commercial reloading dies are off from military chambers.

Below you set the die up using feeling gauges and away from the die holder. This distance can vary between rifles and the installed bolt head So the feeler gauge thickness used can vary and should give you .002 to .003 head clearance.

If the headspace is set too long the case will stretch.

Below a small and thin rubber o-ring is used to hold the rear of the case against the bold face. This only needs to done on the first firing to push the case shoulder forward.

 

[I Dont Care About You]

The question begs - where did the .000 case come from? Suggest you compare the Hornady case to some other unfired factory case. That should resolve matters. BTW - How are you measuring shoulder headspace?
You are going to run into another issue at some point. Some rifles will have long and skinny chambers. They display largish shoulder headspace, but wont accept what appears to be a properly sized case.

No idea what the .000 case came out of. I bought a mixed bunch of brass off a guy. It contains a variety of case types and headspace lengths.

I don't have any other unfired ammo and at the price of ammo these days I won't be getting any.

Hornady LnL headspace gauge.

Doesn't really matter what length cases I have, all will be FL sized to fit my rifle.

 

[bigedp51]

Below the case diameter can vary, below each case was fired once in the same 1943 made rifle. The Prvi case on the left has a thicker rim and is larger in diameter. The HXP Greek case is smaller in diameter and has a thinner rim. Also remember a military Enfield rifles headspace is good between .064 and .074

Your rifle can be setup with two bolt heads for deferent rim thickness.

I have a bolthead shorter than .064 to make up for thinner rims.

Below left to the right a new unfired case, the middle case was fired once, and the case on the right was fired in the same rifle with excess headspace.

 

[Fox]

No idea what the .000 case came out of. I bought a mixed bunch of brass off a guy. It contains a variety of case types and headspace lengths.

I don't have any other unfired ammo and at the price of ammo these days I won't be getting any.

Hornady LnL headspace gauge.

Doesn't really matter what length cases I have, all will be FL sized to fit my rifle.

You want to partially size them.

I have notes, I backed off my die so that they chamber but not much more, I then checked with feeler gauges and wrote that down. I am essentially neck sizing and a tad of shoulder set back.

Remember though, you are not fixing headspace in this case, you need to use the proper terminology, you are reducing your case stretch, you are treating every rifle like it is an "Improved" and they are all going to be individual wildcats.

The No 1 rifles are cavernous, the No 4 rifles are not nearly as bad, some No 1 cases look like bananas.

 

[I Dont Care About You]

You want to partially size them.

I have notes, I backed off my die so that they chamber but not much more, I then checked with feeler gauges and wrote that down. I am essentially neck sizing and a tad of shoulder set back.

That exactly what I said I was doing in my OP. I have the die set so there is a tiny amount of crush on a sized case.

Remember though, you are not fixing headspace in this case, you need to use the proper terminology, you are reducing your case stretch, you are treating every rifle like it is an "Improved" and they are all going to be individual wildcats.

I also noted this in my OP. Said I wasn't interested in the rim headspace but only the headspace to the shoulder. Yes, I know for a rimmed case that's not technically correct but for every other case we reload it is and thus this discussion is based upon that concept.

 

[I Dont Care About You]

Below the case diameter can vary, below each case was fired once in the same 1943 made rifle. The Prvi case on the left has a thicker rim and is larger in diameter. The HXP Greek case is smaller in diameter and has a thinner rim. Also remember a military Enfield rifles headspace is good between .064 and .074

So in my first post you missed the part where I said I wasn't interested in the headspace to the rim and this discussion was only related to headspace to the shoulder?

Below left to the right a new unfired case, the middle case was fired once, and the case on the right was fired in the same rifle with excess headspace.

Ignoring the last case, cause I don't care about stupid headspace to the rim. Doesn't it interest anyone that the loaded round is not even close to the same shape as the chamber? I have live round and fired cases that have nice sloped shoulder like a 30-06 and I also have fired cases that have a short, curtailed shoulder like a 300 Blackout. THIS interests me that ammo is a different shape from the chamber and that chambers all ostensibly 303B can be so different in size and shape? Anyone else?

 

[Fox]

That exactly what I said I was doing in my OP. I have the die set so there is a tiny amount of crush on a sized case.





I also noted this in my OP. Said I wasn't interested in the rim headspace but only the headspace to the shoulder. Yes, I know for a rimmed case that's not technically correct but for every other case we reload it is and thus this discussion is based upon that concept.

Ya I read that, just weird terminology.

It is interesting, some machine guns with rimmed cases headspaced off the shoulder and some guns headspace from the shoulder to a block of metal on the gun rather than the bolt face, I just watched a video on that.

The main point it, as you understand, the case head separation is due to the huge chamber and not the traditional headspace, not something easily measured or adjusted. I guess one thing someone could do would be to turn the barrel a bit, set it back and then ream with a tight reamer, but then you are ruining your most likely collectible.

 

[Fox]

So in my first post you missed the part where I said I wasn't interested in the headspace to the rim and this discussion was only related to headspace to the shoulder?





Ignoring the last case, cause I don't care about stupid headspace to the rim. Doesn't it interest anyone that the loaded round is not even close to the same shape as the chamber? I have live round and fired cases that have nice sloped shoulder like a 30-06 and I also have fired cases that have a short, curtailed shoulder like a 300 Blackout. THIS interests me that ammo is a different shape from the chamber and that chambers all ostensibly 303B can be so different in size and shape? Anyone else?

You are speaking to British Commonwealth military specifications, just shake your head and move on, ba ha ha.

I have a bunch of military surplus 303 Brit ammo, but the only stuff that does not seem to do weird #### is the Canadian stuff, the stuff they made to feed the sniper rifles.

 

[I Dont Care About You]

Ya I read that, just weird terminology.

It is interesting, some machine guns with rimmed cases headspaced off the shoulder and some guns headspace from the shoulder to a block of metal on the gun rather than the bolt face, I just watched a video on that.

The main point it, as you understand, the case head separation is due to the huge chamber and not the traditional headspace, not something easily measured or adjusted. I guess one thing someone could do would be to turn the barrel a bit, set it back and then ream with a tight reamer, but then you are ruining your most likely collectible.

I understand the terminology issue but for every other rifle case the headspace is to the shoulder and so that shouldn't be a difficult leap for us.

Instead of screwing with my barrel, which isn't out of headspace anyway, I can just set my sizing die to match the chamber? .... this is a rhetorical question.

I can't do anything about the sizing die producing a sloped shoulder when the rifle chamber produces a short-sharp shoulder but I can adjust sizing die to the "headspace" to the shoulder and thus minimize case stretch and the potential to split brass.

 

[Potashminer]

...
Ignoring the last case, cause I don't care about stupid headspace to the rim. Doesn't it interest anyone that the loaded round is not even close to the same shape as the chamber? I have live round and fired cases that have nice sloped shoulder like a 30-06 and I also have fired cases that have a short, curtailed shoulder like a 300 Blackout. THIS interests me that ammo is a different shape from the chamber and that chambers all ostensibly 303B can be so different in size and shape? Anyone else?

It was my impression that WWI and previous military designers did not care one bit about reloading those cases - I think their concern was to chamber and fire - once - some really sub-standard made stuff - they apparently were stuck with bazillions of those rounds, so the solution was to enlarge the rifle chambers enough to allow use of the crap stuff they had to use, without the case bursting or splitting - on its one and only "first firing" - most of the time. It is us, more than 100 years later, that have to figure out the "work around" to reload brass from those chambers - I do not think it was a concern of theirs, at all. I think SAAMI was formed in USA as a "voluntary standard" among cartridge and rifle makers - not sure even today that it has any "clout" in Britain or most of Europe - Britain had been making .303 British at least 30 years before SAAMI existed, so not sure how appeals to SAAMI standards for 303 British can be relevant? It seems to me much more akin to reloading for a "wildcat", then it is to be reloading for a SAAMI compliant chambering?

 

[bigedp51]

"Britain had been making .303 British at least 30 years before SAAMI existed, so not sure how appeals to SAAMI standards for 303 British can be relevant? It seems to me much more akin to reloading for a "wildcat", then it is to be reloading for a SAAMI compliant chambering?"

How many of you have reloading dies made to British military Enfield standards? All my dies are made to U.S. SAAMI standards and over resize cases fired in an Enfield rifle.

If you want your cases to last then they should headspace off the case shoulder. And the cases vary in rim thickness and case diameter.

Below a primer seated by the bolt face and shows the amount of excess head space. Meaning the case will stretch that amount when fired. This is why they make different size bolt heads.

Below the case exceeds maximum military headspace of .074. The primer below was seated by the bolt face and shows the excess headspace. This is why they make longer bolt heads.

Below a rimed 30-30 case with .011 head clearance, and if this was a .303 case it would stretch .011.

Below a once fired .303 case and shows how much the case stretched.