Dented case.

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Factory load, so hopefully in correct section

This was fired in a modern Tikka.

FNM target 6.5x55.

Would I be correct in thinking this is due to a light load? Had two, one after the other from same box. Will pull the remaining rounds.

[Laurie]

Good Lord! That has to be an old round as FNM stopped manufacturing and trading many years ago (2001 according to Wikipedia). It's the former Portuguese government arsenal which made a range of 10 or so military 'target' cartridges packed in blue and white cartons loaded with FMJ bullets primarily for civilian historic arms shooters + 223/308 for sale in the 80s and 90s for those who've not come across the name before. I still have some fired FNM brass around, but haven't seen any cartridges for a long time. (PPU took over FNM's range after its demise, but changed it to its own name and almost certainly changed many components too.)

What you have there is a 'gas dent' caused by insufficiently quick case obturation in the chamber allowing gas to slip back into the gap between the case and chamber walls before the case expanded fully to give a tight fit. The 6.5X55 is particularly prone to this problem because of lowish pressure loads, slack chambers in former military rifles, and probably the long case with noticeable body taper.

 FNM's 6.5X55 'target' ammo seemed to have more problems than just this though which I'd surmise came from the use of an over-fast burning ball powder whose charges left a lot of airspace in the case. Gas dents were common with this model, but also over high pressures too. (Which is strange as usually gas dents are associated with too low charges and pressures.) I'd say looking at your pic of the case-head that this applied here, as you have a clearly visible extractor extrusion mark over the numeral '6', the classic indicator of too-high pressures for the brass strength. For those who come across other FNM products - 308, .303, 7.5mm MAS and Swiss, 8X57 etc - they seemed to be problem free. They worked fine for me, and the many people I know who used these cartridges at one time.

In your shoes, I'd not fire any remaining cartridges you have, but pull the bullets and dump both bullets (which are cr*p) and powder before reloading the brass with decent bullets and Viht , RS or other extruded powders better suited to the cartridge. This was budget ammo mainly intended for use in surplus military rifles, not high quality match fodder despite the 'target' moniker. The cases are Boxer primed and reloadable, but more likely military arsenal rather than Lapua/Norma quality. 

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Thanks for the reply Laurie, much appreciated.

Interesting stuff. I had some of these in 7.5x55 a long time ago and had a few without powder in the case!

The 6.5x55 case is almost identical in weight to my Lapua ones actually. I might give them a reload and see how they fair.

On another note, I have odd things happen sometimes with my home loads in this caliber. 

139gr scenar over Vhit N160 in Lapua brass. Working up, get an accuracy node at 42.5gr and hit pressure signs at 44 to 44.5gr.

Problem is sooty cases above 42.5gr, fine from my start point of 40gr up to 42.5gr. Seems the opposite of what to expect.

[Laurie]

I had trouble with sooted cases with N160 many years ago in a superb Carl Gustaf M1896 service-match rifle. (44.0gn was my max N160 load too with the 140gn Sierra MatchKing.) I still shoot the cartridge, now in F-Class in a custom rifle, and don't get this problem with N165 - but the match chamber is likely a lot tighter than the old CG's. I'd still recommend N165 though with 140s in the cartridge - it seems to suit it very well.

What I did do and eventually solved the N160 problem was to try different primers until I found one that suited the cartridge / powder / bullet combination. Not a lot of help I know given the current primer price / supply situation!

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I'll have to experiment a little bit I think.

I have a fair bit of N160, hence my initial choice. Also have N150 and N560.

Primer wise I have Remington, CCI, and Magtech. Currently using Fed 210s. Forgot to mention that.

Component supply IS a problem unfortunately, so I'll try what I have.

Rifle is a Tikka M695.

Someone advised magnum primers, the manuals don't mention them so not sure about that.

I'll give some different primers a try.

Thanks again for the info and advice.

[KABOOM]

On 7/1/2024 at 10:14 AM, Laurie said:

Good Lord! That has to be an old round as FNM stopped manufacturing and trading many years ago (2001 according to Wikipedia). It's the former Portuguese government arsenal which made a range of 10 or so military 'target' cartridges packed in blue and white cartons loaded with FMJ bullets primarily for civilian historic arms shooters + 223/308 for sale in the 80s and 90s for those who've not come across the name before. I still have some fired FNM brass around, but haven't seen any cartridges for a long time. (PPU took over FNM's range after its demise, but changed it to its own name and almost certainly changed many components too.)

What you have there is a 'gas dent' caused by insufficiently quick case obturation in the chamber allowing gas to slip back into the gap between the case and chamber walls before the case expanded fully to give a tight fit. The 6.5X55 is particularly prone to this problem because of lowish pressure loads, slack chambers in former military rifles, and probably the long case with noticeable body taper.

 FNM's 6.5X55 'target' ammo seemed to have more problems than just this though which I'd surmise came from the use of an over-fast burning ball powder whose charges left a lot of airspace in the case. Gas dents were common with this model, but also over high pressures too. (Which is strange as usually gas dents are associated with too low charges and pressures.) I'd say looking at your pic of the case-head that this applied here, as you have a clearly visible extractor extrusion mark over the numeral '6', the classic indicator of too-high pressures for the brass strength. For those who come across other FNM products - 308, .303, 7.5mm MAS and Swiss, 8X57 etc - they seemed to be problem free. They worked fine for me, and the many people I know who used these cartridges at one time.

In your shoes, I'd not fire any remaining cartridges you have, but pull the bullets and dump both bullets (which are cr*p) and powder before reloading the brass with decent bullets and Viht , RS or other extruded powders better suited to the cartridge. This was budget ammo mainly intended for use in surplus military rifles, not high quality match fodder despite the 'target' moniker. The cases are Boxer primed and reloadable, but more likely military arsenal rather than Lapua/Norma quality. 

Thank you, I learned a bit today never seen the gas dent before I would have bet good money that dent was from being smashed in some way other than being fired.

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We're always learning 👍🙂.

Great forum, lots of experience on here.