Fitting a new bolt head

[Parashooter]

Experienced .303 handloaders have the data to answer the original question, even if they may not know it.



1. Normal .303 case walls don't stretch at all below about 30000 c.u.p. If there's any cartridge end-play ("head clearance"), uncrimped primers are left protruding since the case head doesn't move back to the bolt face.
2. Somewhere between approximately 30000 and 40000 c.u.p. (depending on case wall thickness and hardness) cases stretch just ahead of the web, placing the head in solid contact with the bolt face.
3. Above about 40000 c.u.p. the bolt is fully in contact with the case head. Additional pressure causes a bit of bolt compression and action stretch, giving a hair more case stretch.

Because most case stretch occurs well below peak pressure, it makes no difference to the action if original end-play was present or not. Above ~40000 c.u.p. either condition has become the same - head in full contact with bolt face.

[ssj]

If you are reloading it may help with case life if the CHS is on the minimal side, or so they say. If I could figure out a way I'd like to test that theory as lots of ppl tell me this. Here in NZ a number of no4 Enfield shooters run them very tight, but also pretty hot, and some dont so blah. So far my Privy, 1943 DI and S&B brass has stretched to suit my size 1 heads and seems stable in length in my wilson gauge (if wee a bit long) but I am running 38gr of ADI2208 so pretty light loads. For headspace I can almost close on a no-go gauge on all three no4 mk2s so Im happy. One thing for sure 43grains and over of 2208 will bugger brass in 1 or 2 firings. How do I know? well my electronic weight gauge lost the plot, and under read. Now I use an electronic gauge to get close and double check on beam gauge each time, slower but I like my face.

[Bindi2]

I have had case head seperation on the 2nd firing. Purely a poor quality brass in fact i dont think that batch of cases could be called brass, also made to minimum specs in a generous chamber BUGGAR.
Find some HXP ammo or cases shoot them till the cows come home then shoot them some more, Privi is pretty good. I have a small # of IMI cases that are very old with many many firings still going strong and have never been annealed in my hands.

[Bruce_in_Oz]

I would suggest that the problem that is causing early head separation on "new" brass is not headspace, per se., but chamber dimensions AND brass dimensions. Not to mention undersized / thin-walled brass.

If your rifle has a chamber that was actually cut with a "fresh" reamer, it MAY be a bit on the generous side. Subsequent sharpenings of said reamer would steadily reduce chamber size so that eventually, the chambers cut by that reamer would fail diameter and shoulder gauging and thus that reamer would be discarded / "repurposed".

There isn't much excuse for brass that is undersized or thin-walled or made from "underspec" material / incorrectly heat-treated etc.

Interestingly, SAAMI spec for .303 chambers is not radically, or even significantly different from PROPER Brit MOD spec as per the original drawings.

One problem that has reared it's ugly head from time to time is the appearance of chambers that have been "freshened up" by some "creative" individuals, both private and commercial.

Finally, it has been a while since ANY major military indulged in bulk reloading, though it has happened in small packets in the 20th Century. Logistically, it is a better bet to start each cartridge off with brass that is newly formed from fresh material, rather than fool around inspecting EVERY piece of brass recovered from firing ranges and battlefields, and then de-priming, sizing, trimming, heat-treating if necessary etc. before sending for priming and refilling. If you have to remove the crimp for the previous primer, where do you find the material to crimp in the new one (even "stab" crimps would be a pain).

Having separate "training" and "operational" ammunition grades is a logistical pain in the proverbial.

Besides which, where are WE going to find brass for our "hobby" shooting if it is all "re-processed" until it falls to bits; thus causing a major stoppage in some poor digger's weapon, probably at an extremely inopportune time?

[ssj]

Im buying privy at the moment.

regards

[ssj]

I have had case head seperation on the 2nd firing. Purely a poor quality brass in fact i dont think that batch of cases could be called brass, also made to minimum specs in a generous chamber BUGGAR.
Find some HXP ammo or cases shoot them till the cows come home then shoot them some more, Privi is pretty good. I have a small # of IMI cases that are very old with many many firings still going strong and have never been annealed in my hands.

what load powder? hot loads and some brass....

[Peter Laidler]

Thank god for BinO for bringing us back to earth on this subject. In other words if the rifle is in CHS spec, leave the bloody thing alone.

Here's an example. While I was rebuilding my old ancient Mini Cooper gearbox a month or so ago, one of the end float specs was between .002" and .008". Mine, using the OLD thrust washer I took OUT was sitting at ,006". I COULD machine a new one up to bring it to exactly .002". The question is simply one of very simple mechanics, 45 odd years of mechanical/engineering (and I am by NO means a VM either!!!!!) and what the workshop manual says. Do I fit to .002" or leave at ,006". I just left it alone. It wasn't broke so I didn't bloody fix it. (But I did fix the whiney diff and cure a very slight oil weep)

[Bindi2]

what load powder? hot loads and some brass....

I only use 2208. I have been loading for this rifle since the mid 70s. As a farmer using under ground water brass pumps etc i know by look what is a good quality golden coloured brass, when it is a pale washed out blotchy yellow i know there is a short life and trouble coming very soon.
That batch of brass had all the signs and proved to be correct. That manufacturers brass has not improved enough for me to buy any more.
I also load for a 308 i use in FO and have just trashed 150 cases after their second firing because some primer pockets were loose from new are now stuffed . These cases were supposed to be the BEES KNEES, you guess the colour box, will no longer have a place in my ammo room.

[CINDERS]

It was just a Q and I appreciate the input from those with the experience and knowledge you have answered my Q very well and the T will remain as is

[Peter Laidler]

It wasn't just a Q Cinders, but a very GOOD Q! The subject of CHS is a regular on the forum and among shooters/shooting club members. And whether to tighten it up '...a bit' is another aspect of it. It was one of those Q's that would be bounced around during trade-test times as apprentices and on courses that we regularly used to attend. There was also another very similar Q that would be bounced around too but I won't mention it until it's raised. NO cans of worms but just interest........