case head expansion

mikeystew

mikeystew

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I know excessive headspace in a rimless case will cause head expansion, but today i shot a rimmed 303 brit LeeE and on firing the old imperial rounds that came with it i noticed that the case heads were expanding too much to be safe to reload, and seemed to be expanding more on one side than the other.

i am fairly unexperienced with 303 brit so i need to ask, could this be caused from excessive headspace? and if so where would i be able to find a replacement oversized bolt head if you know?

Secondly could it simply be that the chamber is too large to prevent expansion regardless even if the headspace is correct? And i'll throw it out there that i live nearly 3 hrs away from the nearest smith so that is for now not an option.
opinions please...
 
You are referring to the expansion ring that is about 3/16" up the case? If so, it is common for this to be quite noticeable in Lee Enfield rifles. Chamber dimensions are generous.
There are a couple of reasons for the expansion ring to be more pronounced on one side than on the other. The case wall being thicker on one side that on the other is one reason. Another is that the casehead is off-centre when fired. Unless it is extreme I wouldn't worry about it.
Excess headspace can cause the primer to be backed out of the case, or the case can separate, or begin to separate. Take a fired case or two, and use a hacksaw to section the head. File the edges smooth so you can examine the brass. If there is a groove running around the inside of the case about 5/16" up, there is a problem.
 
tiriaq said:
You are referring to the expansion ring that is about 3/16" up the case? If so, it is common for this to be quite noticeable in Lee Enfield rifles. Chamber dimensions are generous.
Click to expand...

thats exactly what im talking about, can these cases be reloaded in some instances? is there a way to center the brass for fireforming them?
 
I have heard of an thin O-ring being slipped over the case. Centers it, and holds the rim hard against the boltface. I have not tried it, but it should work.
Even if it looks a bit off-center, you can still reload it.
Check for incipient separations, though. That is more important.
 
You might be able to see it with a flashlight. You might be able to feel it with a little L shaped probe.
Something else that affects the appearance of the expansion ring is the diameter of the brass before firing. Some cases are on the small side to begin with. Some cases have rims thinner than others, and this can give an indication of excess headspace.
Separated cases in Lee Enfield rifles do not seem to be a problem other than the front of the case being left in the chamber. Not difficult to remove, but can be a bother. Over the years, I've experienced a number of separations, never noticed any gas leakage.
I once inspected a sandbag full of fresh IVI brass fired in issue Ranger rifles. 20% of the cases had to be culled because of incipient separations.
 
If you're looking for incipient separation, unfold a paperclip, sharpen one end a bit on a stone or grinder (doesn't have to be pretty, but pointy is good), and make a TINY (1/8" or so) "L" bend at the tip. Run the "L" against the inside of the case wall, up and down - it should snag on an incipient separation.

-M
 
A dental pick will also work if you have one.

Incipient case head separation can sometimes, but not always, be seen as a thin bright ring on the outside of the case as well. This is different from the ring left on the case body by full-length resizing.
 
tjhaile said:
A dental pick will also work if you have one.

Incipient case head separation can sometimes, but not always, be seen as a thin bright ring on the outside of the case as well. This is different from the ring left on the case body by full-length resizing.
Click to expand...

The incipient separation ring will be a bit above the expansion ring.
 
now that someone mentioned the ring from sizing, i had noticed that these cases did have a ring 1/8" above the rim before firing them, and i've upon closer inspection discovered that the primers are flattened... something i hadn't checked when i thought they were factory made. im thinking these may have been stout handloads which would also explain the mad expansion... Hmmm
 
That could be a possibility, if they weren't 100% guaranteed to be factory rounds. The flattened primer is a good indicator, for sure.

Pics?

-M
 
Bingo! i just talked to the guy who gave... yes, gave me the rifle and he said they very well could be handloads, he dosen't remember where he got them. i'll try some "from scratch" handloads and see what it does.
 
tiriaq said:
I have heard of an thin O-ring being slipped over the case. Centers it, and holds the rim hard against the boltface. I have not tried it, but it should work.
Even if it looks a bit off-center, you can still reload it.
Check for incipient separations, though. That is more important.
Click to expand...

I use dental floss for fireforming my brass. Makes it center perfectly and no jumping around inside the chamber. Once the brass is fireformed, the firing pin can't shoot the brass up into the chamber, causing it to expand and then shoot back, causing the cracks and separation you guys are discussing.
 
NiceRice858 said:
I use dental floss for fireforming my brass. Makes it center perfectly and no jumping around inside the chamber. Once the brass is fireformed, the firing pin can't shoot the brass up into the chamber, causing it to expand and then shoot back, causing the cracks and separation you guys are discussing.
Click to expand...

Could you explain the process briefly on how you wrap the case with floss?
 
i fired a few more rounds this morning and one of the case heads was split and the primer slightly backed out... slight excessive headspace and weak brass? the rounds are 60 year old dominion.
 
MikeyStew. are you able to give us how many larger is your hadspace? It is possible to fix an headspace on Enfields by changing the bolt head, all depend of how is the rifle condition. If it is looking as an Very Good and more condition you may invest some$, but if your gun is under, reduce yours loads but please if you have a separation ring print on your new brass do'nt take any chance to reload these just for saving $. Security firts.

I have try this fireforming process: choose a round and heavy tip bullet, use 10% less powder than the top load and lets the bulet to toutch the rifling, then fire. It's my way and if you are feeling bad whith it do'nt do it. It a personnal advise only and everyone can contest my process.

Judes
 
i dont know the headspace yet, im awaiting my sizing dies in the mail and i plan to do the spent primer seating with the bolt to find out headspace trick to determine where i sit.
 
mikeystew said:
Could you explain the process briefly on how you wrap the case with floss?
Click to expand...

I tie it around the middle of the brass and then slip it down to the rim. This stops your brass from shooting forward into the chamber when the firing pin strikes it. The reason that headspace causes case head separation is this:

The firing pin shoots the brass into the chamber.

The case expands when the propellant ignites, expanding the case (that was shot forward) to the walls of the chamber.

The bullet starts to accelerate and shoots the case back to bolt face, but it's stuck to the walls of the chamber because it expanded.

The dental floss stops the brass from being shot forward, thus avoiding all this BS. Now that the case has been fireformed to your chamber, if you neck size only, it can't be shot forward by the firing pin and you can take the dental floss off for the remainder of the brass' life, usually 5-6 reloads with a medium charge.
 
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