6mm GT ?

[horsemen61]

Howdy everyone!

so I found out that this cartridge is not named what I thought I was! I am still looking to learn more about it @taliv mentioned wanting to build a rifle in this cartridge so I was hoping he/anybody else can shed some light on this for me

such as
Parent case
Powder capacity
Why was it designed
Velocity
Why it over say a 6mm dasher ???

thank you for your info

 

[Varminterror]

All of your questions above are answered here:

 

[Walkalong]

All we need right now are more reamers out there, and some Alpha or Lapua brass would be nice. When I wear out a 6 Creed barrel I will likely try one, unless Alpha starts making 6 Dasher brass by then, or I may even still. Like my Dasher though.

 

[Varminterror]

An absolute gaggle of folks in PRS/NRL started shooting 6mm BR cartridges the last two seasons, largely motivated by ease of tuning (any Varget, 4895, or 8208 load will likely shoot well), better barrel life, and lower powder consumption.

The downsides with the 6BR/BRX/BRA/Dasher:
• Fireforming required for most
• Limited velocity potential
• Short COAL’s which can struggle in mag-fed rifles

Equally, a lot of us have been focused on 6 Creed for a handful of years for its massive speed and feeding reliability.

Disadvantages of the 6 Creed:
• So much barrel hate
• Relatively finicky load development (relatively)

So George Gardner and Tom Jacobs - hence GT - determine a necessary COAL to feed properly combined with a capacity sized to suit the massive node powders which make the BR cartridges so simple - and the result is a RIDICULOUSLY FAST smaller-than-creedmoor cartridge which is proving to be a sleeper for load development, with considerably better barrel life (somewhat inexplicably) than 6 creed.

Which, naturally prompts a lot of Dasher fans to talk about their Primal Rights kits which “feed flawlessly” and a bunch of Creedmoor shooters who talk about how easy their load development was...

The 6GT won’t be the only cartridge at the 2020 or 2021 PRS and NRL Finales, but it’ll certainly be there en mass.

I’m exceptionally tempted, after talking data this year with other shooters running GT’s, to get a GT barrel cut, running nothing but Sta-Ball and 110 A-Tips and 109 Hybrids... Impact action, Bartlein barrel, Area419 Maverick, MPA Matrix chassis... full on Rabid Fanboi rifle...

 

[Varminterror]

unless Alpha starts making 6 Dasher brass by then

I’m told my Alpha Dasher brass order is supposed to deliver end of Jan.

 

[horsemen61]

Loving this thread thanks all

 

[taliv]

Sta ball and 110 a tips is my plan too
But I’m not really holding out tremendous hope for sta ball.

 

[Varminterror]

Sta ball and 110 a tips is my plan too
But I’m not really holding out tremendous hope for sta ball.

Me either - certainly not dropped. But a man can’t live on Varget and H4350 alone...

 

[Nature Boy]

I'm kinda intrigued by the new Berger 109's

 

[Walkalong]

Short COAL’s which can struggle in mag-fed rifles

He made a big issue of this in the video, and I am sure it has some merit, but there are so many people shooting BR variants that it can't be that bad.

I do know that with a standard AI .308 single stack mag with a spacer kit the Dasher runs 100% in the Impact I have no matter how I run it, slow, fast, really fast, so zero issues with it for me.

I am not trying to knock the 6 GT, it sounds like a great idea. I wonder if folks end up using shorter spacer kits with it in AI mags. If the rifle I ordered from MPA had the GT as an option, I would have gone that route.

I’m told my Alpha Dasher brass order is supposed to deliver end of Jan.

Nice, I probably should have ordered 500 instead of 100.

Which, naturally prompts a lot of Dasher fans to talk about their Primal Rights kits which “feed flawlessly”

. full on Rabid Fanboi rifle...

Go for it.

smaller-than-creedmoor cartridge which is proving to be a sleeper for load development, with considerably better barrel life (somewhat inexplicably) than 6 creed.

The shorter fatter case is simply more efficient, and less powder burned is better for barrel life. They also seem to be easier to get low SD numbers with, and I have an idea why, but don't know quite how to put it into words.

110 A-Tips and 109 Hybrids.

I'm not going to spring for the A Tips, but would certainly be willing to try the 109 Hybrids in GT.

 

[taliv]

Would you change your mind if 4 of top 5 in Prs finale were shooting a tips?

 

[Walkalong]

Since it would be unlikely that I will be in danger of winning matches anytime soon, doubtful.

I get it though, I really do. I did spring for an Impact after all. Which has been fantastic.

 

[Varminterror]

The shorter fatter case is simply more efficient, [...]. They also seem to be easier to get low SD numbers with, and I have an idea why, but don't know quite how to put it into words.

Agreed - to a point. WSM’s, WSSM’s, and RSAUM’s have not been particularly friendly for me. Not terrible, but definitely not as easy as stuff like BR or Dasher. Not even as easy as 6 Creedmoor for me, with a much proportionately taller powder column.

So eh, “the fun is in the futzing.” Trying our different things to explain what we can and identify what we cannot explain is the fun part.

there are so many people shooting BR variants that it can't be that bad.

Being one of them, even without spacer kits, the ONLY struggle I have had in feeding Dashers has been those random “oh crap, where’s the right target, and I hesitate halfway closed, giving the round just enough time to deflect instead of pushing fast forward into the chamber.

We’re not talking about black and white magnitude changes with any of these. Like I said before - we’re going to see a lot of GT’s out there this season and the next (and we already saw a lot this past season), but it won’t be a night and day, black and white, complete tide change. Just a little better in a few ways which all matter for competitors.

What REALLY surprises me about George’s comments in the video is his relative complete dismissal of the 6x47. So many folks have found it easier to tune than the Creedmoor, his comments of the x47 living in “no man’s land” really hit me off key.

 

[Varminterror]

A Tips are 20¢/ea more expensive for me over Hybrids - not an insurmountable increase to my ammo cost per match, and I’m quite certain if someone offered me 5 extra points for $30, my wallet would catch fire because I’d be ripping it out so quickly, so if A-tips COULD deliver those 5 extra impacts, it’d be a no brainer...

BUT... on a 1400 round barrel, that’s another entry fee for a 2 day match, or my fees for about half of the 1 day matches I’d go to in a year... so it’s a thought, for sure...

 

[Walkalong]

Agreed - to a point.

To a diameter to caliber and case length ratio perhaps. Get too far overbore and the advantage wanes.

 

[Walkalong]

I’m quite certain if someone offered me 5 extra points for $30, my wallet would catch fire because I’d be ripping it out so quickly, so if A-tips COULD deliver those 5 extra impacts, it’d be a no brainer...

Yea, not bad for 5 more points where we may be behind by three. I lost an aggregate by .0012 once.

They would have to shoot better on paper for me, and then we have to ask ourselves how often the small advantage is going to make a difference between a hot or a miss. Somewhere I am not at yet.

 

[Varminterror]

To a diameter to caliber and case length ratio perhaps. Get too far overbore and the advantage wanes.

I agree - I’m not sure if it’s an overbore thing, or maybe a micro influence of powder dynamics, but I really think there’s something critical happening in those proportions. If you look at a 17 or 221 Fireball, they’re relatively similar in proportion, but they’re not quite as easily tuned either. But I tend to think there’s something to George’s “attitude” (my collective inference in watching the video and briefly chatting with him about the GT at our Midwest Finale) about the ability to use the Varget type powders and burn rates efficiently. In Dasher, finding a 0.6-0.8grn wide node is simple, big, wide, distinct nodes. H4350 and RL16 give distinct nodes, but I feel like I tend to beg for a 0.4grn window.

Maybe it’s a simple sampling error bias from a relatively small sample set, but I feel like I’ve played with enough cartridges that there has to be SOMETHING there...

... steps off soap box and takes off tin foil hat...

 

[Walkalong]

I ordered some N150 & N160 and will play with it in 6 Dasher as well as 6 Creed and 6 GT one day I hope. I still have the 6.5 StaBALL to play with as well. I need to fire form some more brass and then play with powders.

 

[horsemen61]

I ordered some N150 & N160 and will play with it in 6 Dasher as well as 6 Creed and 6 GT one day I hope. I still have the 6.5 StaBALL to play with as well. I need to fire form some more brass and then play with powders.

What do you think of the New 6.5 powder?

 

[Varminterror]

What I would be interested to know more about - George comments a GT cleans up a Dasher chamber, and considering I have a spare Dasher barrel waiting in the wings, I was tempted to have the spare reamed out to GT, instead of buying a new one. My smith, however, said he didn’t think it would clean up the throat all of the way, so he wouldn’t go that route.

Not a major hurdle, but something else for me to ponder about the GT.

 

[Nature Boy]

What I would be interested to know more about - George comments a GT cleans up a Dasher chamber, and considering I have a spare Dasher barrel waiting in the wings, I was tempted to have the spare reamed out to GT, instead of buying a new one. My smith, however, said he didn’t think it would clean up the throat all of the way, so he wouldn’t go that route.

Not a major hurdle, but something else for me to ponder about the GT.

what would you have to loose if you gave it a try? $150-ish? I think it would be worth it

(yes, I freely admit I’m trying to be an enabler here )

 

[Varminterror]

what would you have to loose if you gave it a try? $150-ish? I think it would be worth it

(yes, I freely admit I’m trying to be an enabler here )

No worries, I’m going to try a GT soon. Bartlein hooks up our state club with a big dump of barrels at a discount each summer, and I usually buy 5 barrels each time. I’ll pick up another barrel for my 6 Creed, another for my Dasher, and at least one for a GT. Assuming I can hold out that long and don’t end up buying a Proof before then.

 

[MarshallDodge]

No worries, I’m going to try a GT soon. Bartlein hooks up our state club with a big dump of barrels at a discount each summer, and I usually buy 5 barrels each time. I’ll pick up another barrel for my 6 Creed, another for my Dasher, and at least one for a GT. Assuming I can hold out that long and don’t end up buying a Proof before then.

What would be the reason for having so many different calibers?

 

[horsemen61]

What would be the reason for having so many different calibers?

Variety is the spice of life!

 

[MarshallDodge]

Variety is the spice of life!

Variety is a good reason. My curiosity wants to know if this gives a competitive edge on different courses, he likes one over the other, etc

I'm a big fan of 6mm calibers and wish the military would adopt one. Maybe we can talk them into the 6GT