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.

anyone reloading 6 dasher alpha brass? what size neck bushing are you using ?

look guys may seem a dumb question but I dont reload in fact have not paid for ammo in ohhh well since 1975- so 6mm 243 comparing 6mm whats wrong with the the 25-06 and even the 270 compared with many of these new calibers ( the new 6mm calibres ) interested in your awnsers thanks to those who reply to a dumb old hunter ( well reloading wise )

Both 25/06 and 270 are great cartridges BUT they are long..so need longer action,more powder and have both been traditionally hamstrung by less than ideal twist rates and projectiles options.the 277 family got a boost but still playing catch up to the imposter 7mm wantabe 284s.

Originally Posted by Barry the hunter

look guys may seem a dumb question but I dont reload in fact have not paid for ammo in ohhh well since 1975- so 6mm 243 comparing 6mm whats wrong with the the 25-06 and even the 270 compared with many of these new calibers ( the new 6mm calibres ) interested in your awnsers thanks to those who reply to a dumb old hunter ( well reloading wise )

Pretty much all of the new 6mm cartridges are 100% aimed at competition shooting, while they work just fine for hunting that's not the intended purpose.
Many of the new cartridges aren't even new, being based of 6BR means they've been around in benchrest shooting for many years.

The two cartridges that aren't just aimed at competition are the 6 Creedmoor and 6 ARC.
6 ARC is simple in that it's the latest attempt at gettign maximum performance from an AR15, it gives up a lot of performance to other cartridges but good, cheap factory ammo is going to be readily available and in a micro action like a Howa Mini it makes a lot of sense.

6 Creedmoor is a little more complicated but not really.
Basically it's just an improved version of the 243, just like the 6.5 Creedmoor is an improved 260/6.5x55, and 22 Creedmoor is an improved 22-250/22-250AI.
While the Hornady cartridges don't do anything new, they are actually better than the old cartridges they copy/replace, less taper, longer necks, and sharper shoulder angles mean they give better performance for the same powder charge and stretch less so get longer brass life, they are also optimized for a short action (3" COAL) which is pretty much the standard now, at least in the USA.

What Hornady has done has made small but important improvements to their cartridges, produced ammo that is accurate and takes advantages of newer bullet designs, and made sure manufacturers producer rifles with barrel twists that are suitable for the heavier, higher BC bullets. Many of the older cartridges (25-06, 270, 243, 260, 22-250) were initially designed around lighter, faster bullets and slower barrel twists (1:10, 1:12, 1:14) but the newer versions are designed around heavier bullets and faster twist barrels, with 1:8 basically being the standard twist for every cartridge now.

The clearest example of old vs new is all old rifles in 22-250 used to come in a 1:12 or 1:14 twist, designed around 50-60gr varmint bullets. 22 Creedmoor barrels will be 1:8 twist and will use 80-95gr bullets.
Will the 22-250 with 60gr SPs will kill a deer just fine, a 22 Creedmoor and 80gr ELD-X will carry more energy and buck the wind better making it a 600meter deer rifle rather than a 300meter one.

It's worth mentioning all of this is being driven by the US market and US hunting.
The average NZ hunter who barely takes a shot past 200meters isn't really going to notice a difference, but if given the choice you may as well take the better performance/cartridge design.
If nothing else because that's what factory ammo and reloading components are easy to get these days.

The Chart isn’t very good, In so far as the pressures should be about the same, the 6 mm Remington a 65 psi case limit, is at 49 and 51 psi limit. The dasher and XC are 63, 62 psi cases at 63 and 62 psi pressures.
Larger case will generally have more speed.
We have a lot of new development in new cartridge and better twist rates, able to run heavy for calibre high BC bullets, not that long ago a heavy for cal, meant a round nose,
Haven’t seen any mention of the 6x45 or 6PPC, both should be in a 6mm discussion, both for accuracy and efficiency.
No flies on the 6mm Remington,

Originally Posted by Beetroot

Pretty much all of the new 6mm cartridges are 100% aimed at competition shooting, while they work just fine for hunting that's not the intended purpose.
Many of the new cartridges aren't even new, being based of 6BR means they've been around in benchrest shooting for many years.

The two cartridges that aren't just aimed at competition are the 6 Creedmoor and 6 ARC.
6 ARC is simple in that it's the latest attempt at gettign maximum performance from an AR15, it gives up a lot of performance to other cartridges but good, cheap factory ammo is going to be readily available and in a micro action like a Howa Mini it makes a lot of sense.

6 Creedmoor is a little more complicated but not really.
Basically it's just an improved version of the 243, just like the 6.5 Creedmoor is an improved 260/6.5x55, and 22 Creedmoor is an improved 22-250/22-250AI.
While the Hornady cartridges don't do anything new, they are actually better than the old cartridges they copy/replace, less taper, longer necks, and sharper shoulder angles mean they give better performance for the same powder charge and stretch less so get longer brass life, they are also optimized for a short action (3" COAL) which is pretty much the standard now, at least in the USA.

What Hornady has done has made small but important improvements to their cartridges, produced ammo that is accurate and takes advantages of newer bullet designs, and made sure manufacturers producer rifles with barrel twists that are suitable for the heavier, higher BC bullets. Many of the older cartridges (25-06, 270, 243, 260, 22-250) were initially designed around lighter, faster bullets and slower barrel twists (1:10, 1:12, 1:14) but the newer versions are designed around heavier bullets and faster twist barrels, with 1:8 basically being the standard twist for every cartridge now.

The clearest example of old vs new is all old rifles in 22-250 used to come in a 1:12 or 1:14 twist, designed around 50-60gr varmint bullets. 22 Creedmoor barrels will be 1:8 twist and will use 80-95gr bullets.
Will the 22-250 with 60gr SPs will kill a deer just fine, a 22 Creedmoor and 80gr ELD-X will carry more energy and buck the wind better making it a 600meter deer rifle rather than a 300meter one.

It's worth mentioning all of this is being driven by the US market and US hunting.
The average NZ hunter who barely takes a shot past 200meters isn't really going to notice a difference, but if given the choice you may as well take the better performance/cartridge design.
If nothing else because that's what factory ammo and reloading components are easy to get these days.

thanks for the reply Beetroot - there are some good buggers on this forum - ( not me just ancient and more crotchety every day ) I was not thinking of the twist rates being a factor - clears it up - I must admit some things dont change if I had a budget it would still be a Shultz and Larsen Victory in .270 ( if one could even still get one ) but I picked up one of the new Weatherby series 5 the other day in our local and thought that would be nice to carry for a day - damn light in .308 - always liked the look of those fierce they look the business - but then a mint Forester lol the feel of walnut dreams are free-- of to Waverly for a fallow might be one croaking to - and out the safe a vintage 788 in .308 still does it