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Had these today......



Cases are PPU, bullets were 174gr SMKs, I loaded five rounds at 44.5gr of Ramshot Big Game and the cases were perfect.I then fired five loaded at 45gr of Big Game and two of the five came out with the dents shown in the photo but extracted perfectly.

A further five rounds at 45.5gr were dent free and gave the smallest group size with no pressure signs etc.From what I can gather these dents can be caused by a low pressure charge and blow back gas pressure causing the dent but it seems odd to me that the lower 44.5gr charge gave no problems......any thoughts on this?.

The only time I ever saw cases with dents like this was years ago at camp with the school cadet force when firing ENERGA grenades from a no 4 Le Enfield with wire binding around the front wood work. The report from the ballistite blanks was deafening and the recoil was such the butt would be pressed into the ground for firing. Nothing low pressure about those blanks, but occaisionally they extracted looking just like the cases in your photo.

It occurs to me that if this were due to blowback pressure coming past the neck there would be more residue around the case body. Also surprising how uniform the deformation is.

Is it possible its not a pressure symptom, but something mechanical..?

were you single loading, or 5 in the magazine..?

Consensus around the web seems to agree on low pressure. Its got to be either pressure from the outside pushing the case in or low pressure sucking it in.

I wonder if there's a resonance effect in that a particular load/firearm causes a pressure wave which produces the dent. The first case certainly seems to have the sharper edge on the dent at the case mouth end as if the brass has been pulled in and forward.

The ring around the neck also doesn't seem well defined in the photo suggesting a lack of obturation.

I've had this with a few of my Mossie M44s milsurp rounds - hundreds of rounds shot either side of the incident without seeing the like before or after. I didn't notice until I'd picked up the (steel) cases at the end of the session. I'd just assumed it was some sort of quality control faux pas at the factory and I hadn't noticed before sending them down range.

Wow, can't say I've ever seen this before! I've fired some low pressure loads in my Yugo Mauser and all it did was project some cool gas back through the action,the cases were sooty on the exterior but the case was not physically mishaped.

My guess low pressure not allowing full case obturation therefore some gas leaking back into the chamber.

knewmans wrote:Consensus around the web seems to agree on low pressure. Its got to be either pressure from the outside pushing the case in or low pressure sucking it in.

I wonder if there's a resonance effect in that a particular load/firearm causes a pressure wave which produces the dent. The first case certainly seems to have the sharper edge on the dent at the case mouth end as if the brass has been pulled in and forward.

The ring around the neck also doesn't seem well defined in the photo suggesting a lack of obturation.

The ring around the neck is actually intentional, there is a ring in the chamber in Russian domestic market barrels on Izhmash civilian 7.62x54r/7.62x39/5.45x39 rifles that marks the case so that Russian law enforcement can ascertain if a case was fired in a civilian or military rifle in those calibres.Although it is only applicable in Russia some domestic market barrels end up on export rifles, I have had a couple of Saiga AKs that ring the case neck in the same way.

Daryll.....loaded 5 in the mag, definitely not mechanical as rifle feeds/ extracts flawlessly and chamber surface is perfect.Out of a good many rounds, both brass and steel cased, these are the only two cases that have ever had this dent.

My point was that the ring doesn't seem well defined as if the case neck hasn't been fully deformed into it.

If that's the case it suggests a low pressure load or a slow rise to peak pressure insufficient to get a good seal with those cases and load.

With the 7.62x54r headspacing on the rim and the marked taper I would have thought this cartridge a good candidate for gas leakage between the case and chamber if there isn't full obturation.

knewmans wrote:My point was that the ring doesn't seem well defined as if the case neck hasn't been fully deformed into it.

If that's the case it suggests a low pressure load or a slow rise to peak pressure insufficient to get a good seal with those cases and load.

With the 7.62x54r headspacing on the rim and the marked taper I would have thought this cartridge a good candidate for gas leakage between the case and chamber if there isn't full obturation.

The ring around the neck is quite subtle on this rifle but they are actually more defined in the flesh (metal?) than they appear in the photo , the ones on these cases are no less defined as they are normally though.

It all points to low pressure but it just seems odd that it happened at 45gr but not at 44.5gr, each batch of 5 rounds of each charge weight were done at the same time starting with the 44.5gr and each charge was weighed not thrown and the seating depth etc was the same.