Thread: 6mm cartridge comparison

Originally Posted by Tentman

Hey @Flyblown - any update or further thoughts on this ??

A cobber mentioned that there are a some new reamers about for some older cartridges with the leade/throat design updated for modern projectiles - be very interesting to know of this has been done for 6mm Rem. Supposedly Trueflite have a couple of the "updated" reamers.

Yes, True Flite do have updated reamers, but they are for the likes of 280/AI, 7mm RM, 30/06, 300 WM and maybe a couple of others. Nothing smaller than 7mm bore as far as I know.

I would have thought the most you ever -might- need to do with a 6 Rem reamer is to lengthen the freebore with a throat reamer. Damn good cartridge as it is.

Originally Posted by winaa

Yes interesting.
I like the 243W as well my go to load is a 95Gr Targex with a mid load of 2209. I would be interested if you added Win760 and RL-16 to the 243 data and see how that compares to the 6mm CM.

Try the 95gr with RL17. Nice combo.

Originally Posted by Flyblown

Fellas

As you know I've always been a .243 kinda bloke. But the move towards higher BC, heavy and long for calibre bullets has got me interested in what else I can do with 6mm.

I ran through some of the options yesterday in Quickload, to see how they compared.

The assumptions I used was (a) the same bullet - 90gr ELD-X - so it would work in all rifles and not just fast twists, so 1:10" .243s are in the mix; (b) either a 100% case fill or maximum specified chamber pressure (Pmax), whichever occurred first. Obviously there's no accuracy component, what your rifle likes isn't quantifiable.

The results are really interesting. It shows that there's a couple of cartridges that are super efficient, with light powder charges for really decent velocity (6mm Dasher and 6 BR Norma), then the midfield is pretty much of a muchness, and as you'd expect the highest velocities belong to the highest charges (243 AI, 6mm Creedmoor and 6mm XC).

But what really stood out for me is the use of slower powders to get high velocity but low pressures. RL26 being the one I chose to look at... you can go on all day looking at dozens of powders. This is potentially a big positive for the throat erosion problem of fast 6mm rifles derived from the .308 parent case or similar.

However, we hear reports that not all rifles like RL26 and velocity and accuracy can be problematic. That said a good mate in the UK who I caught up with a couple of weeks ago (6mm Creedmoor) has nailed it using OBT and some very fine tuning of seating depth and is getting pretty much exactly what the model says he should.... plus one ragged hole. That's in a high end custom rifle however, but he's using it with great success in long range field sports - targets, hares, foxes and so on. He's a bit fussy about his deer shooting so no deer (yet).

Anyway, food for thought. I'll be adding to this spreadsheet and if anyone wants a copy that you can sort easily then flick me a PM.

Attachment 117363

By the way, those the say Quickload doesn't work.... I'd say 9 times out 10, once I get every single assumption 100% correct (particularly case capacity and consistent neck tension), my field outcome is pretty close to the model outcome. Batch-to-batch powder variability is a factor in differences of model vs actual, I've seen that with AR2209 when the only change to the velocity of 100 reloads is the powder batch number. But consistent neck tension is also a biggie (starting pressure).

Running a 90gr pill with 45.5 of 2209 is a full load. Your cases would show that after a short while.