Thread: Case head separation imminent

Was only made worse by using magnum primers standard primers good as magnums were causing them to split

Thanks VC, good writeup that is easily understood.

Originally Posted by veitnamcam

This creates a space between the case head and the bolt head called "Headspace"

This bit isn't quite correct, what you are referring to is excessive headspace. Headspace is the area from the boltface to the shoulder (rimless cartridges, e.g. 308), the front of the rim (rimmed cartridges e.g. 30-30) or the front of the belt (belted magnums, e.g. 7mm rem mag).

Originally Posted by Cigar

This bit isn't quite correct, what you are referring to is excessive headspace. Headspace is the area from the boltface to the shoulder (rimless cartridges, e.g. 308), the front of the rim (rimmed cartridges e.g. 30-30) or the front of the belt (belted magnums, e.g. 7mm rem mag).
Attachment 209386

That is how it is measured yes, but the headspace is the amount of clearance between the cartridge and chamber dimensions.

Originally Posted by Padox

Was only made worse by using magnum primers standard primers good as magnums were causing them to split

Greetings @Padox,
Magnum primers have negligible effect on the cause of head separations. In a chamber that is too long for the cartridge (or a cartridge that is too short for the chamber) the case starts to stretch at a pressure of less than 40,000 PSI. The front half of the case is gripping the chamber walls and the solid head of the case is forced back against the bolt face. This results in a groove as shown in the OP. Most cartridges operate at a maximum pressure of between 55,000 and 65,000 PSI so the small amount of additional pressure from a magnum primer has no effect on head separation. 40,000 PSI is around or below start loads for most high pressure cartridges.
Regards Grandpamac.

This is in a 270 running 52gr of win 760 so 1.5gr below max book load and it only seems to happen in the 1s I used magnum primers in the rest are fine so far I've had 2 sleeve in the chamber and prob 10 actually split the casing around that Grove line I was contemplating weather it was my load or my rifle I have been using the same load for prob the best part of 10yrs and the 1st time iv ever had an issue with it and the only dif was I had to use cci mag primers cos I couldn't get any Winchester large rifle

Very early in my .303 "career" I had a quantity of milsurp 174gn ball IIRCmk7rounds
.Anyhow a few of these rounds did this -bloody disconcerting when you opened the bolt only to eject the case head .A quick but radical solution was a rat tailed rasp inserted -it removed crapped out cases no probs .Later when I was in the process of handing kit in on leaving the TF was given a.303 case extractor of military type !Idid a fairly thorough check of the remaining -approx6cases had a very bright ring around the web-Instant discards .Idid some enquiring about causes most reckoned it was brittle brass getting worse as it aged.after this it was wqinchester brass whichIIRC has had 1xreloading.

Originally Posted by Padox

This is in a 270 running 52gr of win 760 so 1.5gr below max book load and it only seems to happen in the 1s I used magnum primers in the rest are fine so far I've had 2 sleeve in the chamber and prob 10 actually split the casing around that Grove line I was contemplating weather it was my load or my rifle I have been using the same load for prob the best part of 10yrs and the 1st time iv ever had an issue with it and the only dif was I had to use cci mag primers cos I couldn't get any Winchester large rifle

The cases must be getting sized too much, and maybe the batch that got the mag primers were previously fired more than the std primer batch or just got sized more ?. I have a Rem 270 and a BSA CF2 270 no probs with these but a BSA Hunter ( been rebarreled to 270 from 7x57)I have wont fire factory ammo because the chamber is too long and the cases are pushed too far away from and by the firing pin. Maybe the chamber on that rifle is slightly longer than standard ? I have had separation with a 2506 AI when I first got it, caused by a die set that shortened the cases too much on a full length size.

Good post, when I first started reloading I learned this pretty quickly, only having a few fired cases I was working with, and had setup the sizing die as per the included RCBS instructions (ie over bumping the shoulder). Saw the shiny lines appear on the brass, and felt down inside with a bent paper clip to confirm, then sectioned as you did on one to double confirm.

Then researched how to set up the die properly to prevent it again.

I have had a case head separation when firing a 223 before many years ago (caused by the same issue) nothing out of the ordinary happened, apart from the front part of the case having to be fished out of the chamber.

It's something best avoided however.

Firing a load that is loaded way over max pressure and piecing or blowing a primer in my experience was more of a fuss, and best avoided too. (don't always trust Quickload when dealing with wildcat cartridges, always cross-reference with other forms of load data, my starting load that i thought was low, wasnt.

Originally Posted by Padox

This is in a 270 running 52gr of win 760 so 1.5gr below max book load and it only seems to happen in the 1s I used magnum primers in the rest are fine so far I've had 2 sleeve in the chamber and prob 10 actually split the casing around that Grove line I was contemplating weather it was my load or my rifle I have been using the same load for prob the best part of 10yrs and the 1st time iv ever had an issue with it and the only dif was I had to use cci mag primers cos I couldn't get any Winchester large rifle

Greetings again,
From your description I assume that you are using 130 grain cup and core projectiles. Looking at the data your pressure is around 48,000 CUP. This is well above the 40,000 CUP or PSI (the two are very similar at this level) by which the case stretching and head separation occurs. Ball powders like 760 are harder to light than the extruded stick powders and the WLR primer is formulated for it. Consequently the WLR primer is often considered to be hotter than other non magnum primers. My old Speer No 9 manual from the 1970's lists the CCI 250 Magnum for use with their 130 grain projectile and 760 in the .270. I don't doubt the experience you have had but find it hard to blame the primer for case separations. That said if you can get the Winchester WLR primers they are likely to be the best match for 760 in your loads.
Regards Grandpamac.

Originally Posted by Moa Hunter

The cases must be getting sized too much, and maybe the batch that got the mag primers were previously fired more than the std primer batch or just got sized more ?. I have a Rem 270 and a BSA CF2 270 no probs with these but a BSA Hunter ( been rebarreled to 270 from 7x57)I have wont fire factory ammo because the chamber is too long and the cases are pushed too far away from and by the firing pin. Maybe the chamber on that rifle is slightly longer than standard ? I have had separation with a 2506 AI when I first got it, caused by a die set that shortened the cases too much on a full length size.

All casings are 3rd firing fired 1ce as factory ammo reloaded 1ce reloaded again and separating all been batch loaded 100 half had win primers other half had cci mag rifle is a Rem 700

Originally Posted by Padox

This is in a 270 running 52gr of win 760 so 1.5gr below max book load and it only seems to happen in the 1s I used magnum primers in the rest are fine so far I've had 2 sleeve in the chamber and prob 10 actually split the casing around that Grove line I was contemplating weather it was my load or my rifle I have been using the same load for prob the best part of 10yrs and the 1st time iv ever had an issue with it and the only dif was I had to use cci mag primers cos I couldn't get any Winchester large rifle

Go back and read post no 1 and 2 again.
Primers are not going to cause case head separation.....even overloads are unlikely to.
What causes it is explained in post 1 and how to avoid it in post 2

Originally Posted by veitnamcam

Go back and read post no 1 and 2 again.
Primers are not going to cause case head separation.....even overloads are unlikely to.
What causes it is explained in post 1 and how to avoid it in post 2

I understand what causes it vc I just can't understand y 1 lot would do it and the other half of the batch hasn'tso 1s on the left have separated 1s on right were pulled but same batch

Originally Posted by Padox

I understand what causes it vc I just can't understand y 1 lot would do it and the other half of the batch hasn'tAttachment 209399so 1s on the left have separated 1s on right were pulled but same batch

Measure those fired cases vs the ones you pulled as per Cigars picture above to a mid point on the shoulder.
If you don't have a ogive measuring set or something you could use a short bit of tube or a 44mag case or whatever will go over the neck and meat the middle of shoulder.
The actual measurement is not important as long as it's fairly repeatable and you can compare the two.

and section one of them cases...bizzare as heck after 3 loadings,bizzare but not unheard of.
hornady have done some weird shit in last few years,different headstamps= different case capacities,weird undersized primers too...that was really weird one a chap in states struck,slightly smaller primer pocket than normal large rifle.... only slightly but enough to make reuse problimatic till opened out.
the 150grn superpreformance in .308 win my mate had put me right off they were that hot of load it wasnt funny and inconsistant,some primer popping hot others seems fine...same rifle same day completely different results.