Thread: headspace in a break open rifle

So.... GPM asking questions re 6.5x55mm got my brain chewing things over..that and 60 cases waiting for powder n projectiles to be put into them.
my mind was wondering how/where a fella will see fatigue on a case that is repeatedly fired in a break open rifle.
in a normal bolt/lever/pump rifle we see thinning at the web area..its not supported in any of these actions,so the case has a tiny area where it can expand outwards..but in a break open the case walls are completely enclosed so it can only increase in length... making sence so far???
some time back @akaroa1 was testing a lovely 30/30 in same action and fired same case 10 of so times...it was still good...so MAYBE this is the reason???? the case isnt getting the same fatigue????
yes in theory a rimmed case like 30/30 or 303 doesnt have headspace as such..its rim thickness..but we have learnt over the years that resizing these as little as possible so the body/shoulder such as there is ,dont grow much on sizing.
now Im talking 222remington but its same deal really....
also what will pressure signs be??? flattened primer for sure....no swipe mark,no ejector hole to flow into...
thoughts???

also according to manuals it looks like win748 is hands down the best powder for my 16" barrel....even dropping 50fps per inch it looks to be as good as any ADI powder in longer barrel

Interesting will be following this thread as I use a break open .308

The reason the case fails at the web is that it is the point where the head taper meets the 'straight' section of the case wall - a weak point for stress. Any pull forward (case stretching forces) in this area creates a short section of thinning which results in the failure groove that appears at the web. Assisting this is a minimum size case/maximum size chamber situation which blows the weaker section of the case wall out and sometimes you can actually feel a little 'step' in the case head to wall junction area. That's gotta be good for case life...

The other common non-catastrophic failure modes are neck splits, primer pocket loosening and shoulder splits. I've seen a case head failure in a break action rifle, but I never found out what the causes were and I suspect it was not factory ammo. Reloading and oversizing the case (pushing the shoulder back) is the biggest thing that we do that contributes to case failures like this, and the long winded rambling speech here is really just to say that the action type really doesn't have that much bearing on case life so much as how we treat the brass and how good our reloading practices are.

I've had case head separations in my break barrel, not using hot loads either..

In my break actions ive always gone by the theory that i increase powder charge until the action feels slightly tighter to open or the press the open lever, and considered that max. Usually the break gun loads end up being a bit lighter than bolt gun loads.

Havent had any brass failures yet in break guns as i usually lose the brass before they fail.
I usually just FL size them all the way for the break guns unlike bolt guns where im a bit more precise about it all

I repeatedly fired a single case in the 30-30 Baikal I had built because there was still a slight imperfection in the chamber from the original 30-06 shoulder.
The barrel was a 16" 30-06 Bush Pig take off and to get the 30-30 chamber into it I lost about 40mm
That put me within MMs of being under minimum legal length over all.
So I stopped with 2mm to spare ( depending on how you measure LOA ) and there was still a slight feature in the chamber.

I was naturally concerned that this would dramatically shorten brass life.
So I fired and sized and reloaded a single case without annealing it 10 times, with no obvious problems.
I got sick of the game and gave up before the brass gave up.

Admittedly this was merely a 30-30.
But it was a conversion in a 12 Gauge Baikal and the chamber was cut with a reamer I had made myself.

One day when I am bored ( hardly likely ) I might do a full destruction test on one of my Converted Baikals.

I have 9 break action center fire rifles and 8 of them are in high pressure rounds and brass stretch is not an issue with any of them.
Inside neck thickness is important with my 222R and 6.5x65R.
But this is due to Bertram 222R brass being overly thick. Inside neck reaming has solved this.
And the K95 6.5x65R creates doughnuts in the inside neck base which expands the neck when a bullet is seated. Easy fix also with inside neck reaming.
All these calibers are RIMMED CASES except for a Contender 6.8 SPC so that might be an important consideration.

Spacing off the rim means the case isn't forced forward by the firing pin, to ignite and grip the chamber and stretch back to the breech face

@Micky Duck you go do some citizen science and take your loading press to the range and keep shooting until it fails or shows sign of potential failure.

Originally Posted by Micky Duck

So.... GPM asking questions re 6.5x55mm got my brain chewing things over..that and 60 cases waiting for powder n projectiles to be put into them.
my mind was wondering how/where a fella will see fatigue on a case that is repeatedly fired in a break open rifle.
in a normal bolt/lever/pump rifle we see thinning at the web area..its not supported in any of these actions,so the case has a tiny area where it can expand outwards..but in a break open the case walls are completely enclosed so it can only increase in length... making sence so far???
some time back @akaroa1 was testing a lovely 30/30 in same action and fired same case 10 of so times...it was still good...so MAYBE this is the reason???? the case isnt getting the same fatigue????
yes in theory a rimmed case like 30/30 or 303 doesnt have headspace as such..its rim thickness..but we have learnt over the years that resizing these as little as possible so the body/shoulder such as there is ,dont grow much on sizing.
now Im talking 222remington but its same deal really....
also what will pressure signs be??? flattened primer for sure....no swipe mark,no ejector hole to flow into...
thoughts???

also according to manuals it looks like win748 is hands down the best powder for my 16" barrel....even dropping 50fps per inch it looks to be as good as any ADI powder in longer barrel

Greetings @Micky Duck and all,
The normal sequence of events when a cartridge is fired in any rifle is for the case to be driven as far forward in the chamber as it will go by the firing pin strike and primer ignition backing out the primer. As pressure builds the case body expands and grips the chamber walls. If the pressure is high enough the case head is forced back to touch the bolt or breech face stretching the case just in front of the solid head. In a break open action the case head being forced back can spring the action slightly perhaps making it a little hard to open and the case hard to rechamber. This can happen with bolt actions to but at higher pressure. Most modern bolt actions support the case body right up to the head so essentially there is no difference in case support.
For my little .308 Bergara rifle I full length size using the Redding Competition shell holders so that the cases chamber freely but no more. I also keep the loads down currently loading 41 grains of AR2206H behind the Norma 150 grain projectile for around 2,500 fps in a 20" barrel.
As far as working up a load all of the usual pressure signs are pretty much worthless at the pressure levels you would want to stick to in a break open action. The .30-30 and the .222 load data is reasonably low pressure and for the .308 keeping well away from max loads is wise. Using one of the Hornady headspace comparator sets to keep track of case stretching could be useful and checking the inside of the case just in front of the head with a bent paper clip for a developing groove should be mandatory.
At the end of the day a break open rifle is unlikely to be used firing a 60 shot target match or bomb ups on deer or goats at long range so extended case life is not an issue. Culling the stretched cases before they let go in the rifle is.
More later.
Regards Grandpamac.

The key phrase by akaroa the is "All these calibers are RIMMED CASES except for a Contender 6.8 SPC so that might be an important consideration.

Spacing off the rim means the case isn't forced forward by the firing pin, to ignite and grip the chamber and stretch back to the breech face"
With extensive use break action guns can get sloppy in the lockup, how many 12 gauge old shotties have you seen that wobble?. Often they were fixed with a paper or brass shim.
I suggest you get a tally counter Micky and neck size only put me down for 32 reloads before you either give up, loose the case or it fails

You still need to have the rim dimension correct for the rim depth dimension in the chamber.

I have a BRNO Hornet which jacks out the primers when fired.
I measured both the brass rims thickness and the chamber rim depth and there is a discrepancy of several thou.
The bolt does not close on a no go gauge so headspace is not an issue.

Chased ths issue down for ages - selected the brand of brass with the thickest rims, in my case Winchester.
On advise form Robbie Tiffen, I fired a bunch of rounds with the projectile jammed into the rifling to try and form a shoulder, as much as you can with a Hornet, so I would hopefully headspace on the shoulder. The rounds when fired did not jack out the primers. Great I thought, I've sussed it. Next time I loaded my normal seating depth (not jammed) the primers jacked out!

So I sorta gave up on the problem and just fired with primers jacking out. Looks horrible. There have been no issues with seperation.

I added a Walther Hornet to my fleet and low and behold it did the same thing.

I think it's a European chamber versus USA brass issue.

Greetings all,
The thickness of rims on .303 cases can be all over the map and this combined with generous headspace tolerances in the rifles. This results with the primers backing out some when fired. While it looks terrible as @zimmer stated I have found it to be a useful sign that you are not stretching the brass with each firing. Sure performance is less than factory rounds but, in my case, the rifles are not used for actual hunting. A few years ago I tired of using the slightly below factory level handloads in my .308 that had a plastic butt plate. The 43 grain load of 4895 behind a 150 grain projectile was reduced to 40 and later 38 grains. With these loads the primers backed out showing that the pressure was low enough not to stretch the case. I did note that a tight case fired with a light load chambered freely thereafter indicating that the shoulder may have been moved back some on firing so have kept those cases separate just in case.
Regards Grandpamac.

there is a trick with tiny rubber oring put just infront of the rim....hold case in place upon fireing and hopefully a sort of shoulder is formed...neck size or partial length resize thereafter SHOULD reduce case wear.
guess this is why folks decided to make a K hornet.....the 1 grn in case capacity is nice but being able to headspace off shoulder..sort of...gives it more merit.

Originally Posted by Micky Duck

there is a trick with tiny rubber oring put just infront of the rim....hold case in place upon fireing and hopefully a sort of shoulder is formed...neck size or partial length resize thereafter SHOULD reduce case wear.
guess this is why folks decided to make a K hornet.....the 1 grn in case capacity is nice but being able to headspace off shoulder..sort of...gives it more merit.

Tried that with the Hornet. Unsuccessful. Maybe works for other cases.

well I just poked together 60 rounds for the trebly...24.5grns of win748 behind the last of my 52grn hp speers and the rest are 55grn sierra med vel blitz which was a bit of a head scratch...the 50grn sierras are harder than the heavier blitz so figured...well why not???
Bing sure wasnt kidding about the capacity of the older lapua cases he gave me.....I went 24.5 because 25grns wont fit lol,they filled to 3/4 of way up neck..4 cases filled to top of neck...just to see I chucked same charge in another random case from in my container...and powder came up to part way up shoulder!!!!!
the smaller capacity should be offset by lighter charge weight..both are at least 1.5grns below seirra manual max..both seated according to that spec.

Zimmer...so are you just neck sizing/partial length resizing now for hornet or gone back to FLR????