Murom Primers and .223

[Maggot]

Ello flowers

I ( and a few other CSR types) have experienced issues with Murom KVB-223 primers leaking in 223. In my case this has been either pierced primers or small pinholes blowing on the angle between the flat face and the vertical wall. The latter has resulted in a pitted bolt face but not a damaged firing pin from the pierced primers.

It appears the cups are too soft. The correct Murom primers for .223 are KVM-556 by all accounts. Now to quote a chap on the CSR forum....

Now you would think that having 223 in the name might mean they would be suitable for 223, but no

Avoid on higher pressure loads. I was using 24gr of RS52 or Wildboar behind a crimped 77grain SMK. Not an issue with CCIBR4s or the copper coloured Wolf primers.

[Laurie]

Unlike LR primers which have a standardised brass cup thickness (0.028"), SR types vary according to variety. Standard SR (CCI-400, Rem 6 1/2, F205 etc) are 0.020", Federal 205Ms are 0.0225" and all SR Magnums and BRs are 0.025" and also usually employ a slightly harder brass alloy.

The original SR primer was designed for the very small charge and relatively low pressure .22 Hornet in the 1930s and subsequent larger but still low pressure designs like .218 Bee and similar. They are designed for 50,000 psi or less pressures and so are at or approaching their cup strength limits in the .222 Rem. This is still the 'industry standard'.

Higher pressure cartridges loaded to exceed 50,000 psi which includes the 223 should always be primed with a Magnum or BR type. At one time, Remington used to warn that the 6 1/2 shouldn't be used in modern high-pressure cartridge designs, but that seems to have become lost in recent years.

With the advent of the AR-15 / M16 / M4 and similar employing unrestrained floating firing pins and using very high pressure Nato loadings, still harder cup versions were introduced for use in ordnance supplies to reduce the chances of an accidental firing or 'slam-fire' which could happen in the early days of the M193 5.56mm cartridge in the M16A1 rifle back in Vietnam war days.

[WelshShooter]

Unlike LR primers which have a standardised brass cup thickness (0.028"), SR types vary according to variety. Standard SR (CCI-400, Rem 6 1/2, F205 etc) are 0.020", Federal 205Ms are 0.0225" and all SR Magnums and BRs are 0.025" and also usually employ a slightly harder brass alloy.

The original SR primer was designed for the very small charge and relatively low pressure .22 Hornet in the 1930s and subsequent larger but still low pressure designs like .218 Bee and similar. They are designed for 50,000 psi or less pressures and so are at or approaching their cup strength limits in the .222 Rem. This is still the 'industry standard'.

Higher pressure cartridges loaded to exceed 50,000 psi which includes the 223 should always be primed with a Magnum or BR type. At one time, Remington used to warn that the 6 1/2 shouldn't be used in modern high-pressure cartridge designs, but that seems to have become lost in recent years.

With the advent of the AR-15 / M16 / M4 and similar employing unrestrained floating firing pins and using very high pressure Nato loadings, still harder cup versions were introduced for use in ordnance supplies to reduce the chances of an accidental firing or 'slam-fire' which could happen in the early days of the M193 5.56mm cartridge in the M16A1 rifle back in Vietnam war days.

To echo what Laurie has mentioned, I had an issue with pierced small rifle primers in my 6.5x47 Lapua when using regular CCI small rifle primers, which happened on the starting load and had low velocity so I know it wasn't an over pressure issue. I migrated to CCI small rifle magnum primers and no longer had any issues with pierced primers. The cup is thicker on magnum primers compared to standard ones which is why my issue was resolved.

An interesting bit of information Laurie. I didn't realise that regular small rifle primers weren't suitable for .223, but I don't understand why the primer manufacturers haven't caught up yet. At the moment, no-one local to me have a good availability of small rifle magnum primers, I had to drive ~2 hours from home to pick up a supply of 1,500 (then had to pay the Severn Bridge fee to go home!).

[Maggot]

Thanks for that Lauri, excellent.

I hope you dont mind but I have nicked that and stuck it on the CSR Shooter forum as it explains a lot. I never had an issue with CCIBR4s, but they are pricey for blasting away by the hundred.

Mark has found me some that should be fine.

[Pete]

The first lot I bought were copper coloured and much harder than the next lot, although in an identical box marked KVB-223.
I assumed they were the same, despite the different colour, and this assumption led to two blown primers, a stuffed up 223 bolt, and having to pull 48 cartridges..........
We still use them in 6BR and 223. They crater, but hold up OK with modest loads (2850fps).
Good consistent velocities as well, and at £18-90/1000, I'm fine with that.


Pete

[Maggot]

Ditto, the copper coloured ones worked well but were thicker. Anyhow mine have all been passed on for a lower load application.

Mark Bradley has sourced something else that looks like it will do the job and is not too pricey. I dont mind paying but when you shoot 100 a time it adds up.

[WelshShooter]

Maggot, see my post above regarding magnum primers. These are cheaper than benchrest primers, but dearer than standard primers. If you can get them in your area they would be a more affordable alternative compared to benchrest primers.

[Laurie]

Ditto, the copper coloured ones worked well but were thicker. Anyhow mine have all been passed on for a lower load application.

Mark Bradley has sourced something else that looks like it will do the job and is not too pricey. I dont mind paying but when you shoot 100 a time it adds up.

The last I heard, Mark stocks the Brazilian CBC Magtech 7 1/2 primer. This is an excellent performer, very good value, and is reasonably 'hard', although not quite as much as the CCI-450 SRM and CCI-BR4 grades.

FWIW, in my 223 SGC SSR-15 days, the Magtech copy of the US M855 5.56mm round was the best factory ammo that I shot in the rifle - an excellent performer out to 500/600 yards.