6mm Rem and 243 WSSM: Virturally identical ballistics?

[Brians356]

I have been wanting to try CFE 223 powder in my 6mm Rem, but Hodgdon does not publish the load data. Since they do publish CFE 223 for both 243 Win and 243 WSSM, I started looking closely at those data, to see if I could extrapolate anything. (I also e-mailed Hodgdon asking for any unpublished 6mm Rem load data they might share, but so far I have not received so much as an automatic form response ala "Thank you, ... we will respond shortly.")

I was soon startled to discover how similar 6mm Rem and 243 WSSM data are. I defy anyone to find any two cartridges which are as close WRT their interior ballistics. (Yet 243 Win and 243 WSSM are not nearly as similar, somewhat surprisingly since they have nearly identical case capacities.)

Specifically, consider 70-grain bullet data for these two cartridges: the "Max Charge" values listed are identical for both cartridges for the following five powders:

Superformance
H414 (and W760)
IMR 4007 SSC
H380

The max charges for two other powders - IMR 4320 and Varget - are within 1% and 2%, respectively.

Similarly, listed max velocities are all within 2% between the two cartridges for every powder common to both 6mm Rem and 243 WSSM in Hodgdon's data! (< 2% in velocity is well within the measurement noise.)

Given the foregoing, and given that CFE 223 falls between H380 and Varget in Hodgdon's burn rate chart, it seems not unreasonable to simply refer to the CFE 223 data for 243 WSSM when working up loads for 6mm Rem.

Oh, and for a 70-grain bullet, CFE delivers velocity second only to Superformance in 243 WSSM, so if it is at all accurate in my 6mm I will be quite pleased.

Brian

 

[mikecr]

They may be basing their predictions purely from capacity, as you might with QuickLoad.
You'll find the WSSM more efficient with actual testing, because it confines more powder burn in the chamber instead of down range.
This also means less recoil.

 

[Brians356]

They may be basing their predictions purely from capacity, as you might with QuickLoad.
You'll find the WSSM more efficient with actual testing, because it confines more powder burn in the chamber instead of down range.
This also means less recoil.

Are you saying Hodgdon may not actually chronograph all the loads they publish? I would bet they do clock them all, but I wouldn't risk more than a day's pay. (They probably don't clock both loads from identical but rebranded powders such as H414 / W760.)

One upshot of my finding is that 243 WSSM is somewhat more efficient than the 243 Win, in that from the same case capacity it produces 6mm Rem velocities.

Brian

 

[3Ackleys]

I use cfe 223 in my 243 AI with hbn coated 70 gr Bal tips. I worked up from 243 win data. They shoot .2 @ 100 yds. no side by side tests with standard loads but they seem to not foul the bore as much.

 

[Brians356]

I use cfe 223 in my 243 AI with hbn coated 70 gr Bal tips. I worked up from 243 win data. They shoot .2 @ 100 yds. no side by side tests with standard loads but they seem to not foul the bore as much.

That's very encouraging.

According to one article I read, starting with a clean copper-free bore, CFE will prevent copper residue. Do you find any copper indications (e.g. blue color on patches) when cleaning it?

Brian

 

[3Ackleys]

so far after 2 shooting then cleaning sessions the patches were black

 

[Brians356]

so far after 2 shooting then cleaning sessions the patches were black

I want to use CFE 223 in 6mm Rem behind 70/75-gr bullets, but also a 107-grain bullet. But Hodgdon does not publish any CFE 223 data for 6mm Rem, so I need to extrapolate from 234 Win, 243 WSSM, or something like 243 AI.

Did you just start with 243 Win data when working up CFE loads for 243 AI? What was your though process?

Brian

 

[3Ackleys]

Yes I used max 243 win data from the Hodgdon web site and worked up from there