PPU and 7.5x55 Swiss

[Silver87]

G'day all,

So lately I picked up a Swiss K31, had always had an interest in them but what made the cartridge more appealing was finding out they took .308 projectiles which are in abundance. I was lucky to get 180 Prvi partizan rounds, boxer primed with no crimp making them great for reloading once I shot them off. Well it appears they were a little on the hot side and I was blowing/piercing primers straight away.



Now against my better judgment I pushed on for longer then I should have (2 boxes) as I put it down to soft/crap primers and the more I could shoot the more reloadable brass I'd have. I learned a lesson and no damage was done to the rifle but some of the cases now have loose primer pockets. With brass being scarce I decided to pull the rest instead of taking a refund from my local (which was nice of them to give the option) so I can work up a safe load using 2209 and 168gr SMK's which will suit the service matches I shoot.



And here we are, glad that's over

So do we have anymore Swiss rifle shooters among us?

[Westy]

Yes but none that do that!!!!!

[Silver87]

After some more reading my rifle's short throat could have been causing the fat 174gr soft point to jam in the lands, soulution could have simply been seating the projectile deeper. Still I think I've gone the right way by pulling, after a FL resize, trim and work up from minimum charge I think it will be worth it. Lovely rifle and can really admire the workmanship which has gone into it's construction

[chacka]

That's a loooot of blown primers

[Westy]

Yer that just can't be good for anything sure looks like the loads aren't working at all well??????

[Tinked]

At least you had the puller I suppose and didn't end up with 7 boxes of paperweights.

[inventurkey]

Now against my better judgment I pushed on for longer then I should have (2 boxes) as I put it down to soft/crap primers and the more I could shoot the more reloadable brass I'd have.

Even so, is it safe to shoot with primers which are piercing because they're crappy even if it isn't a pressure issue?

[Silver87]

I would now say it isn't a good idea, was wearing protective eyewear but would never continue shooting like that again.

Now some results, after pulling, FL sizing, trimming and loading up from starting load things are looking good now. I set up my target only at 50m as I'm still getting used to iron sights on a rifle I wanted to take a little shooter error out of the equation.



Most groups were good with the one on the right being a grain below max which is around what other blokes are finding is an accurate load. I'll do a little more playing around with this load but I think it will be great for shooting on service targets.

[RealNick]

Is that a 10c or 20c coin there? Can't make it out in the photo.

[1290]

G'day all,

So lately I picked up a Swiss K31, had always had an interest in them but what made the cartridge more appealing was finding out they took .308 projectiles.......

They actually take 306 projectiles (7.78mm)......not 308 (=309spec)

the swiss chambering is 7.5 because that is the bore size 7.51, while the groove diameter is 7.77 and the projectile is sized at 7.78mm!!!

Caution - if its a spec sized barrel, as opposed to the standard 30 cal barrels (308win,30-06Spr. etc) use a 7.62 bore, 7.82 groove (0.300/.03079) barrel. Sure, plenty of guys might be using plentiful standard 308cal projectiles.... would the oversized proj warrant pre-swaging?? I cant answer that, but I would consider it if the slightly smaller bullets couldnt be sourced....

Sure, many chamberings use bullets this or ever more oversized to the groove, but with your rifle you're not meant to....

summary:
7.5x55 - 7.78mm projectile in 7.77mm hole = 0.01mm swaging through barrel
308win - 7.85mm projectile in 7.82mm hole = 0.03mm swaging through barrel

Your reloads:
7.85mm projectile in 7.77mm hole = 0.08mm swaging through barrel

[Bark]

Now some results, after pulling, FL sizing, trimming and loading up from starting load things are looking good now. I set up my target only at 50m as I'm still getting used to iron sights on a rifle I wanted to take a little shooter error out of the equation.

How did the remade bullets group compared to the factory stuff?

Any difference you could tell once the brass had sized and reseated?

Wondering how uniformity of neck and brass compared to the factory build and your resizing.

[Silver87]

I haven't been back to this thread for a while but have been out shooting with some results I'm happy with. After my initial load testing I loaded up and shot a 50 round high power match for a bit of fun and even got an X at 600m off the elbows. This was also the first time working the action fast in rapid details and had the biggest s**t eating grin



Winding down for the Christmas break these are the last targets from when I shot at the 100m off the bench, the left being my best and the right more what the average group sizes were, the black circle are 6.1" and look pretty small at 100m so I'm happy for now.

It is true that the .308 is slightly oversized for the bore with about one thou of swagging taking place but this is a common practice and nothing to worry about. the load I'm using now show's no pressure signs with only a slightly flattened primer with a still rounded edge.

[agentzero]

Good times

[Mich]

Not bad, not bad:)

[Gregg]

Winding down for the Christmas break these are the last targets from when I shot at the 100m off the bench, the left being my best and the right more what the average group sizes were, the black circle are 6.1" and look pretty small at 100m so I'm happy for now.

Nothing wrong with that using the irons.

[KWhorenet]

Old thread i know but

1290 wrote;
"...summary:
7.5x55 - 7.78mm projectile in 7.77mm hole = 0.01mm swaging through barrel
308win - 7.85mm projectile in 7.82mm hole = 0.03mm swaging through barrel

Your reloads:
7.85mm projectile in 7.77mm hole = 0.08mm swaging through barrel"


Silver87 wrote;

"It is true that the .308 is slightly oversized for the bore with about one thou of swagging taking place but this is a common practice and nothing to worry about. the load I'm using now show's no pressure signs with only a slightly flattened primer with a still rounded edge."

So if I read correctly and if 1290's math is correct, wouldn't the 308 pills be getting swaged 0.08mm, almost 1/12th not 1/1000th ? Big difference.

Any clarification on the above?

I'm interested in the 7.5 swiss ammo options as I have a Schmidt-Rubin rifle on the way.

[Silver87]

Since getting the rifle I've put over a thousand reloads through it without a single issue. Every reloading manual will list .308 diameter projectiles and it's what's recommended on the Swiss rifle forum as well as many other places. I've now switched to 155gr Dyer projectiles and despite a higher point of impact they shoot really well. Most projectiles will need to be seated fairly deep due to the short throat, for sizing I use redding dies and bump the shoulder back approximately 3 thou. Some of my brass is on its 9th firing and has only required trimming once since initial case prep.

[KWhorenet]

Good work. Might get in touch when it arrives and I have more time to delve into it further.

[Sender]

I've now switched to 155gr Dyer projectiles and despite a higher point of impact they shoot really well.

Why do you say the higher POI is an issue?

Re-zero?

Or am I missing something?

[Silver87]

I've now switched to 155gr Dyer projectiles and despite a higher point of impact they shoot really well.

Why do you say the higher POI is an issue?

Re-zero?

Or am I missing something?

The factory iron sights are hitting high at there lowest setting requiring a hold-under, the only remedy for this is a taller front sight blade which are currently hard to get hold of.

[KWhorenet]

If anyone in Victoria sees factory 7.5x55 ammo or even brass available, please let me know. Also looking for 8mm Mauser.

Also, if anyone is traveling to Victoria and sees some available, and is OK with buying for me and bringing it down with them...I'd make it worth their while. Allot to ask, but would be appreciated.

[Vati]

Must be really tough finding it down there if you're resorting to calling in favours to get it transported in from interstate

[Silver87]

I've sent you a PM.

[KWhorenet]

Must be really tough finding it down there if you're resorting to calling in favours to get it transported in from interstate

Only just now started looking for it. See recent ads offering PPU 7.5 Swiss 60 rnds for $45. Would grab 180 at that price.

[<<Genesis93>>]

Old thread i know but

1290 wrote;
"...summary:
7.5x55 - 7.78mm projectile in 7.77mm hole = 0.01mm swaging through barrel
308win - 7.85mm projectile in 7.82mm hole = 0.03mm swaging through barrel

Your reloads:
7.85mm projectile in 7.77mm hole = 0.08mm swaging through barrel"


Silver87 wrote;

"It is true that the .308 is slightly oversized for the bore with about one thou of swagging taking place but this is a common practice and nothing to worry about. the load I'm using now show's no pressure signs with only a slightly flattened primer with a still rounded edge."

So if I read correctly and if 1290's math is correct, wouldn't the 308 pills be getting swaged 0.08mm, almost 1/12th not 1/1000th ? Big difference.

Any clarification on the above?

I'm interested in the 7.5 swiss ammo options as I have a Schmidt-Rubin rifle on the way.

Naaah, he probably made it all up...

anyhoo, why would anyone believe the 7.5 swiss would have a 7.5mm bore? Like trying to convince people that the 308win, AKA 7.62NATO has a 7.62mm (0.30cal) bore!!

....and they suggested to use the 308 proj (actually 309!)
Of course they did, because NO ONE PRODUCES 306 bullets

Run the caliper over those pulled bullet......

The oversize-'ness' of the proj will obviously give greater pressure, but the 0.08mm is not out of the ordinary, but mostly pistol and other lower pressure round are this or even more oversized... vast majority of high pressure rounds are slightly oversize / at groove / few are undersized like 303Brit and 6.5x55SE

Note there are other 30cals with smaller proj, like the weatherbys (308) and Rem (307), but these are probably also loaded with 309s....

Your 7.5 might even have a 7.62 barrel, who knows, might be worth measuring.... Note the 7.62x53R was the 7.62x54R with a 30cal barrel, so it would not be unexpected with barrel switcheroonis....

Interesting is the ADI loads, although theres no pressures stated, the bigger case of the 7.5 takes more powder for less velocity compared to the 308win with the same proj, I'd say the more oversize proj to groove plays a part sapping away driving energy....

[Rocker]

Interesting is the ADI loads, although theres no pressures stated

Yer annoying... They state it on half their data and not the other half for some reason