Follow my 7 dumbo project aka 7 dasher!!

[Cz455guru]

Hey guys, I got a wild hair brained idea about 6 months ago to neck the dasher up to 7mm, to be called the 7 Dumbo lol. Going into it with few expectations and viewing it as a experiment, hoping its a success.
I worked together with manson reamers to get a reamer built and sent it off the #620riflewerks to get the chambering done. (By the way he is a jam up gunsmith if somebody is looking for a guy to do your work with good turnaround time.) I opted to use a 8 twist crb comp barrel, finished at 28 inches.
I want to get it to shoot 2400+ with the 180+ bullets, preferably the 190 atip or 190 bergers. If it all works out I will certainly be shooting it in a few matches to see how it handles that vs the 22 dasher and 6 dasher that I normally use.
Follow this thread for updates!!!!

 

[diggler1833]

I applaud your willingness to experiment man. Obviously, you're going into this understanding that you aren't going to break any performance records... but if you get good accuracy (and have fun), then I'm down to read your results. If you can put up side-by-side wind results at distance between this and your 6 Dasher, that would be awesome to see too.

I did similar with the 7-300 PRC over last winter. It probably is a touch behind the 28 Nosler, and definitely the 28 Sherman Mag... but it is something that I wanted to mess with, and I'm very content with my results.

Best of luck!

 

[XP1K]

I mean, there is a 30BR, why not a 7 ? I'd have probably shot for the 160 class of bullet but hey, sounds fun. Do keep us posted.

Is a 180/190 7mm longer than a dasher case ?

 

[4O6shootist]

Is a 180/190 7mm longer than a dasher case ?

A 190 Berger is about 0.040-0.050 longer than the dasher case length depending on the trim.

 

[Cz455guru]

Here's a picture of some dummy rounds from when I was designing the reamer. Left to right, 190 atip, 190 berger, 180 eldm. I may end up shooting the 180 eldm yet.
I have been working on finding max charges with multiple powders with atips while fireforming brass. Powders I have tried, 8208, cfe223, RL15, RL15.5, varget.
The 8208 velocity was lower then I wanted, cfe223 yields the highest velocity at 2510. I think h4895 might be the perfect powder for this but I dont have any at the moment.

 

[Cz455guru]

Rl 15 numbers, slight ejector mark if I use my imagination.

 

[Cz455guru]

Shots 4-6 with 197 smk with Rl 15.5 group was about .7.

 

[Cz455guru]

Cfe223 190 Atips at pressure.

 

[Cz455guru]

Sorry im not organized, I should have clarified the build earlier, so here it is.

Impact 737r
Foundation Samson
Crb comp 8 twist
Botnia maxi
Nf atacr 7-35
Bix'n and tacsport pro x, gator shoe
Warne precision mount
Sg pulse level

 

[fdkay]

Maybe staball 6.5? Slower than the powders you're using, but it's a ball powder, so you might be able to get enough powder in there to make a difference.
Staball does like heavy bullets and high pressure

 

[Cz455guru]

Maybe staball 6.5? Slower than the powders you're using, but it's a ball powder, so you might be able to get enough powder in there to make a difference.
Staball does like heavy bullets and high pressure

Good idea!! Ill have to see if i can find some. Found a place locally with some h4895 I'll be able to try that also.

 

[XP1K]

Cfe223 190 Atips at pressure.

Im actually pretty impressed by this. I didn't think it would push it that fast.

 

[Mike Casselton]

BL-C2 might also be a contender in your powder search.
Like Staball, it likes full pressure for velocity and clean burn

 

[Sea Green Thrilling Turtle]

I have been looking at the 183 smk for my 7SWC, curious how they would do here. Watching for updates

 

[6.5SH]

Given the burn rate of the powders OP's tried, StaBALL Match will likely be a good fit.

 

[Simia Dei]

Try MR2000, I had a 7SAW hitting over 2900fps with Berger 175s out of a 26” barrel

 

[iceng]

7mm is best mm.. Unless its pistol, then its 10mm.

In believe the 7mm is underrated for lots of styles of shooting, and I built a 7 superLR a few years ago which was amazing. I'm a huge 7mm fan.

Well done on having a go.

 

[45-90]

I like the 6 dasher,... but a 7 Dasher with almost twice the bullet weight?

Its Your project, but...Looks to me like ya need more case capacity then the Dasher has to offer.

My 22" 9 twist 308 will do a bit over 2500 with 230s, being tested here.

 

[Kickin45]

@Cz455guru what’s your charge weights?

 

[Sea Green Thrilling Turtle]

My 22" 9 twist 308 will do a bit over 2500 with 230s, being tested here.

What is the COAL though? I suspect one of the goals here was to stay under 2.96”. Regarding larger case capacity, it seems like the 7SWC is about as big as you can good for 0.284 with 190s, unless you go to tiny necks like the 7 Moses. However, I suspect the OP was looking for maximum efficiency to push heavy 0.284 bullets and not highest velocity.

 

[45-90]

What is the COAL though? I suspect one of the goals here was to stay under 2.96”. Regarding larger case capacity, it seems like the 7SWC is about as big as you can good for 0.284 with 190s, unless you go to tiny necks like the 7 Moses. However, I suspect the OP was looking for maximum efficiency to push heavy 0.284 bullets and not highest velocity.

The COAL really doesn't matter in a bolt gun. There are intermediate actions and long actions...and custom machined actions.
That's always an excuse for those who's short actions calibers do not measure up in velocity, then they themselves run the COAL over length to cram in more powder to get a bit more velocity.

The 308 Winchester is not a speed deamon and is beaten by every cartridge in these pages, as the slow dog.
But when you can not beat the speed of a 308 with your new 7 mm dasher ya probably need more case capacity or even longer action.
My 6 dasher runs .6 g1 BC bullets 110 SMK to 3085 fps in a 28" barrel.
So 2400 fps to a maybe 2500 fps appears too slow to be of any advantage at 1000 yds over the orginial...a hopped up 6 dasher, and the accuracy isn't there with the 7.

Preliminary test tell me ya need more case capacity.
Why build a less performance cartridge when you want a better performing cartridge with super high BC bullets?
Ya still need "enough" velocity to accomplish that.

It should be better than a 308 Win regardless of the COAL ...everything beats a 308.

 

[fdkay]

The COAL really doesn't matter in a bolt gun. There are intermediate actions and long actions...and custom machined actions.
That's always an excuse for those who's short actions calibers do not measure up in velocity, then they themselves run the COAL over length to cram in more powder to get a bit more velocity.

The 308 Winchester is not a speed deamon and is beaten by every cartridge in these pages, as the slow dog.
But when you can not beat the speed of a 308 with your new 7 mm dasher ya probably need more case capacity or even longer action.
My 6 dasher runs .6 g1 BC bullets 110 SMK to 3085 fps in a 28" barrel.
So 2400 fps to a maybe 2500 fps appears too slow to be of any advantage at 1000 yds over the orginial...a hopped up 6 dasher, and the accuracy isn't there with the 7.

Preliminary test tell me ya need more case capacity.
Why build a less performance cartridge when you want a better performing cartridge with super high BC bullets?
Ya still need "enough" velocity to accomplish that.

It should be better than a 308 Win regardless of the COAL ...everything beats a 308.

Are you the arbiter of what is worthwhile?
Some folks with the expendable income like to play with stuff and try new things.
With the Atip at 2500, he's got 9.6 mils of drop at 1000 and is still supersonic at 1500 (Per JBM).