6XC load info from Norma

[aubrey]

12365.1

I asked my contact at Norma R&D about Norma 203B powder vs Reloader 15 powder, the answer:

"Both powders are made at the same factory and the specs are very very close so you can use the Re 15 and fiddle with the charge up or down a little. We are now finished with the testing of the XC. Since one of the int matches is 60 shots prone at 300m we have been shooting some 60 shots groups. The best we have got so far is 2.165”,all of them hit the 50 mm X ring). The load is 37 gn of 203B and 105 Berger LTB seated .020 off the lands and a soft RWS primer. Velocity out of a 26” barrel is 920 m/s or 3018 fps) The XC seem to group very tight and that is what the shooters told us."

Regards

Aubrey

 

[chrisj]

2.165" @ 300 meters? That's nothing to get excited over...and that was their best group. Doesn't sound too promising after extensive testing.

Chris

 

[rcw3]

A 2.165" 60 shot group shot prone at 300M - that's great! Prone = sling with pulse & body movement included in group.

Most good prone shooters have at least .5 to .75 MOA of body movement wobble built into their group.

Robert Whitley

 

[jb1000br]

me thinks their testing was NOT shot prone...not really a good way to test anything except the shooter...

There is also a 60-shot 6mmBR group around somewhere...300M...also NOT shot prone.

JB

 

[chrisj]

I would highly doubt that their testing was done prone Robert. I give you a lot of credit for doing your testing prone. I never heard of a bullet, powder or rifle manufacturer testing loads in the prone position. Machine rest is the standard. I'm sure they want to get the best accuracy results from their testing.

Chris

 

[Asa_Yam]

A 60 shot group of just over 2" @ 300 meters is nothing to sneeze at, for a number of reasons.

* With a sample size this large, you are almost 100% assured that all ammunition from this batch will shoot groups of this size or less.

* Groups of fewer shots will likely be much smaller. Somewhere online, there's a discussion of estimating final group size based on the results of firing a smaller # of rounds. Somehow, I seem to recall a 20 shot group can be expected to be about 1.5x larger than a 5 shot one. I'm not sure how the results from a 5 shot group relate to a 60 shot one - but the 60 shot group WILL be significantly larger.,2x Or more extreme spread than the 5 shot group?)

* Another thing to remember about this thread is we're discussing mass produced ammo, not handloads. Sure, most of us can produce ammo that outshoots it. But how many of us can maintain this level of quality for 10,000 rounds or more, all loaded in one session?

 

[rcw3]

Interesting additional tidbit. Apparently Norma has been using Bartlein cut rifled barrels with their 6XC's, but set up in a bit different of a configuration to try to get more barrel life out of the 6XC barrels,i.e. 1:8" twist with .236" x .2441" bores, with 50/50 land/groove ratio). The 50/50 land/groove ratio certainly should make for big wide lands and with the .236" x .2441 bore, the lands are also tall as well.

When I did the Precision Shooting article that featured the Lilja 3 groove barrels, there seemed to be a consensus by some Lilja three groove barrel owners that the big wide lands that characterized the 3 groove barrels acted as a better heat sink and resisted blistering and wear better.

Something to consider if you want to try to maximize barrel life.

Robert Whitley
www.6mmAR.com

 

[chrisj]

I misread the original post stating that the test group was 60 shots. If the group was fired without resting the barrel between shots...then that group was very respectable.

Chris