Load Development 6.5X55 S.E.

[Brick]

Once more out to the range!

This time the rifle is a CZ 550 American in 6.5X55 S.E. This is named such to avoid confusion with the 6.5X55 Swedish Mauser of military surplus fame although it is the same cartridge loaded to higher pressures. The loads listed below are intended for use in STRONG COMMERCIAL ACTIONS only.

This time out I chose Norma MRP and IMR 4064 because they are currently available on the market. Oddly enough last year when I was working on .308 Win. my limiting factor was powder, this year it is bullets. The 140 gr. Sierra Gameking SBT has become unavailable.

Comparing the results to the loading data I used for source material I find the Norma MRP gave higher velocities than published loads and IMR 4064 gave lower velocities though by only 20 to 50 fps.

Most disheartening though was compared to other outings with this rifle (which hitherto had never shot greater than a 1" group) accuracy sucked! Even though there would 3 or 4 shots in each group of 10 that would clover-leaf the 10 shot groups were in the range of 2" to 4". Granted some of that might be due to "operator headspace and timing".

C.O.A.L. used was 3.050" nominal

[Delkal]

10 shot groups!!! No reloader does that

Its rare when max loads are the most accurate...

Impressive velocities but what does SE stand for?

[Brick]

I have no idea! Sometimes it is shown as S.E. as on the barrel of my rifle and sometimes as SKAN. But, European loadings and data for that cartridge run considerably higher pressure than standard Swede loads. The S.E. runs at 58,000 psi compared to 51,000 psi for standard Swede loads. At least that what Speer # 14 says.

Lapua has lots to say on the subject.

[Guns N'at]

Yeah, I can definitely see how MRP would/will crush IMR 4064 with regards to safe pressures at max velocities... Like comparing coal to gasoline. I load for my AG42, and because of this use propellants with a very moderate pressure curve (IMR 4895 or so) because of the gas system, and velocities are rather low. I always wanted to stoke it up with the 140 FMJ's I use, say with 4350/4831/H414... But it would IMO, be hell on the action. This rifle practically destroys 6.5x55 brass as it is!

Nice results you got, and I liked reading them. I simply love the long range efficiency of a snappy 6.5x55 load!

[Guns N'at]

I kinda figured "Swedish Express"...

[Guns N'at]

Yep, SE/se without periods does mean Sweden, i.e. as seen in at the end of Swedish internet addresses... The periods in the S.E. lead me to think something else.

[Brick]

C'mon guys spare yourself the pain! I don't know what the S.E. means and I'm not even sure of the SKAN sometimes used. Maybe we should ask the folks at Norma or VihtaVuori.

All I know for sure is Speer says their loads approach 58,000 psi and VV say they're pushing 380 MPa (mega pascals?) which converts to something in excess of 55,000 psi. Now fer cryin' out loud do not use the top end of these loads in you Carl Gustav Cavalry Carbine!

[cephas]

Interesting cartridge, thanks for the discussion. From some short reading, one on Wikipedia, here SAAMI sets the standards for ammunition and designates it as the 6.5x55 Swedish. In europe they have the international commission for proof of small arms, CIP, that dubs it the 6.5x55 S.A.
One of the better articles I found if you're interested: http://www.ballisticstudies.com/Know...se/6.5x55.html
Brick's right though watch what your loading for. Kinda like our 45-70 that has three load levels.

[chutestrate]

Check the twist in your rifle. I have a Zastava 6.5 which is I believe is the same or similar to your CZ. The twist is lower than military swedes. Shorter bodied bullets may work better for you. I'm working on my own development as well.