Goldilocks 6mm between 6CM and 6UM?

[solarshooter]

I'm not so sure the goal of 3k fps from a 6 creed in an 18" barrel is unachievable. I just got my new Tikka up and running with an 18" Bartlein in 6 creed. First trip to the range I did a pressure test with Berger 108 EH, H4350, CCI 200, and Gunwerks brass, got noticeable pressure signs at 44.0gr and 3038fps avg over 3 shots. I stepped down to 43.0gr, and am using that as my baseline load, 2930fps. I'd expect some speed up since this barrel only has 30rds, but I might have to back the load accordingly to avoid pressure.

If you used a slightly slower powder, like H4831SC, you might be able to squeeze more out of it since there's room for roughly 46.0gr in the case (crunchy). This is also with the 108 EH seated right to 2.800" COAL (0.040" jump with SAAMI throat, boattail just above neck-shoulder junction) so I could use all my SA Tikka mags. If you went medium or long action and had it throated a bit longer you could seat further out and squeeze some more capacity out of it.

 

[wind gypsy]

I'm not so sure the goal of 3k fps from a 6 creed in an 18" barrel is unachievable. I just got my new Tikka up and running with an 18" Bartlein in 6 creed. First trip to the range I did a pressure test with Berger 108 EH, H4350, CCI 200, and Gunwerks brass, got noticeable pressure signs at 44.0gr and 3038fps avg over 3 shots. I stepped down to 43.0gr, and am using that as my baseline load, 2930fps. I'd expect some speed up since this barrel only has 30rds, but I might have to back the load accordingly to avoid pressure.

If you used a slightly slower powder, like H4831SC, you might be able to squeeze more out of it since there's room for roughly 46.0gr in the case (crunchy). This is also with the 108 EH seated right to 2.800" COAL (0.040" jump with SAAMI throat, boattail just above neck-shoulder junction) so I could use all my SA Tikka mags. If you went medium or long action and had it throated a bit longer you could seat further out and squeeze some more capacity out of it.

I can't see going medium or LA for a 6 creed. 2.950" is awful long for one and to get there a 108 EH wont hardly have any bearing surface left in the neck. RL26 or N555 will get velocity if that's what one seeks.

 

[Ryan Avery]

I can't see going medium or LA for a 6 creed. 2.950" is awful long for one. RL26 or N555 will get velocity if that's what one seeks.

N555 is an undervalued powder.

 

[solarshooter]

I can't see going medium or LA for a 6 creed. 2.950" is awful long for one and to get there a 108 EH wont hardly have any bearing surface left in the neck. RL26 or N555 will get velocity if that's what one seeks.

I think medium might work, it's roughly a 0.25" neck, so scooting out to 2.950" would leave 0.1" bearing surface in the neck, for this particular bullet. Agreed LA wouldn't be worth it. And I don't think a custom/non-saami throat would be worth it in general because it might negatively impact your results with box ammo. So yeah, 2900-3000 with an 18" barrel and a saami chamber/SA, and call it good. There would be no material difference between 2900 and 3k anyway.

 

[wind gypsy]

I think medium might work, it's roughly a 0.25" neck, so scooting out to 2.950" would leave 0.1" bearing surface in the neck, for this particular bullet. Agreed LA wouldn't be worth it. And I don't think a custom/non-saami throat would be worth it in general because it might negatively impact your results with box ammo. So yeah, 2900-3000 with an 18" barrel and a saami chamber/SA, and call it good. There would be no material difference between 2900 and 3k anyway.

Medium could work but I cant think of a single benefit to choosing it on purpose for a 6 creed.

 

[B23]

I think Shawn's 243 Terminator would probably get you there. He gets around 3300 from a 26 so 3000 from a 18 would probably be attainable or damn close to it. Shawn has dies and Lapua formed brass you can buy also which makes things nice and easy.

243 Terminator

You have entered the home of data for the Terminator family of cartridges. Like all loading data this is just a guideline to help you and not absolute information. This is simply what worked for us in just one or two rifles with our lot of powder, bullets primers etc. It is still your...

defensiveedge.net

 

[Lawnboi]

I’d have a really really hard time not just adding a couple inches of barrel and reaping the benefits of an easy button cartridge

 

[Shootinsurveyor]

243 hits 2925 with a "light" load of 39GR H4350 and 22" barrel. Lotta guys say they run as high as 43. That being said anything CM will be the easy button with factory ammo., but the 243 will get there if you don't have a super slow barrel. Brass life is another rabbit hole.

 

[WKR]

I can't see going medium or LA for a 6 creed. 2.950" is awful long for one and to get there a 108 EH wont hardly have any bearing surface left in the neck. RL26 or N555 will get velocity if that's what one seeks.

N555 actually produced the slowest mv's in my 25 creed bartlein barrel. Its accurate and has good ES/SD but wasn't faster than good old H4350. Takes up more case volume as well.

 

[bpctcb]

I highly suggest you look at a Savage 110 Magpul Hunter in 6.5 Creedmoor. It comes with an 18” threaded barrel, 20 moa rail and takes AICS mags.
I shoot 147 gr ELD-M ammo (0.697 bc) through it and it’s ridiculously accurate for a $700 rifle.
705 yard target below.

BP

 

[eLightfoot]

I’m doing a 6mm ackley improved for my next build. For my niche requirements it’s is the perfect size

 

[willfrye027]

N555 actually produced the slowest mv's in my 25 creed bartlein barrel. Its accurate and has good ES/SD but wasn't faster than good old H4350. Takes up more case volume as well.

Hmm. It’s beat out h4350 for velocity in my two 25 creedmoors and two 22 creedmoors.

Did you work up to pressure?

Wish I had more n555 stockpiled one of my favorite powders..

 

[Bert01]

I would think 243ai throated for the 108’s would get you reeeeaally close, although I’m making that assumption from a bunch of research and no real world experience.

 

[6mm Remington]

I’m doing a 6mm ackley improved for my next build. For my niche requirements it’s is the perfect size

I bet it's a screamer. I love the 6mm Remington and it would only be just a wee bit better!

 

[eric1115]

OP here, I ended up with a 19" .243AI Tikka doing 3020 with 108 ELDM and 3050 with 106 TAP and H1000. I ran out of case capacity before I hit pressure, and so far accuracy looks very promising.

Probably could see higher MV with H4350 or similar, but happy with the H1000 for the supposedly lower flame temps and therefore long barrel life (plus I have a few lbs of it from my magnum days and won't put it to use elsewhere).

Edit to add, after barrel speed up I'm at 3150 at 49.5 and mild pressure signs, hoping to back off another half grain and be somewhere around 3100+

 

[Jimbee]

OP here, I ended up with a 19" .243AI Tikka doing 3020 with 108 ELDM and 3050 with 106 TAP and H1000. I ran out of case capacity before I hit pressure, and so far accuracy looks very promising.

Probably could see higher MV with H4350 or similar, but happy with the H1000 for the supposedly lower flame temps and therefore long barrel life (plus I have a few lbs of it from my magnum days and won't put it to use elsewhere).

Did you rechamber a tikka barrel?

 

[eric1115]

Did you rechamber a tikka barrel?

Yes, had it rechambered when it was getting cut and threaded.

 

[Jimbee]

Yes, had it rechambered when it was getting cut and threaded.

How are those 106 tap shooting? I have a tikka factory 243 barrel that's getting chopped and threaded.

 

[eric1115]

Good! I've got a thread on that project here...

Tikka .243 AI

Who has rechambered their 8 twist Tikka .243? Do you run LA mags and bolt stop? I mocked up a .243 case with 108 ELDM and got 2.94ish with boat tail junction at neck/shoulder junction. Seems like this is potentially the peak of the convenience/velocity curve? Considered a 6x55 or 6-284 or...

rokslide.com

 

[762 ULTRAMAGA]

Funny I just saw this thread, I'm in the process of designing just such a 6mm..