6mm Dasher Bushing Size?

[AR Shooter]

Just received my 6mm Dasher and need to order the FL sizing die and am wondering if the 0.267", 0.268" & 0.269" bushings would be a good range to start with. Using Lapua brass. Thanks.

 

[johara1]

What is chamber neck size? What is your bullet pressure ring size? what is your neck wall thickness? and do you plan to turn necks?….. jim

 

[dkhunt14]

Is it a 271 no turn neck? Matt

 

[ShootDots]

I shoot both 6mmBr's and Dashers... I "turn my brass to clean up the high spots on the necks only" and my "non-bushing" F/L sizing die is honed out to .266 which gives me 1.5K neck tension. If I did not turn my necks and wanted 1-1.5K neck tension I would go to a .267 bushing>>>going over that you MAY not be able to keep your bullets in place in the case..

 

[AR Shooter]

New rifle with a 0.267" neck. Have not done any brass turning as of yet. Thought I would fire-form the brass with something like a 31gr of RE15 pushing an 85gr bullet before doing any neck turning.

 

[ShootDots]

AR, when I do my Dasher forming, I run the 6BR cases into a mandrel to "iron them out".. Then I neck turn them to a hair below the neck / shoulder junction. Then I make a false shoulder, anneal them (yes new brass) and fireform with 29.7grs of Varget and a 105 VLD set 15K into the lands. After all that is done I size them, trim them and chamfer. Now they are ready to go..

 

[johara1]

If you can use Varget or H4895 for fire forming, I would use a 105 or heaver for fire forming. You are running very close on clearance, you had better measure everything because i come up with .267 loaded round ………jim

 

[WyleWD]

Just received my 6mm Dasher and need to order the FL sizing die and am wondering if the 0.267", 0.268" & 0.269" bushings would be a good range to start with. Using Lapua brass. Thanks.

FWIW, I'd get a .263, .264, .265, .266, .267, and a .268 bushings if you are around a .267 on a loaded round. This might allow you to do some testing on neck tension with any given load and or primer combination. Again, FWIW. WD

 

[dkhunt14]

You want to do like shootdots said and turn before forming. That way you can turn past where the Dasher neck will be and get no Doughnut. I like to use 105 plus bullets to form the cases better like johara1 one says. I also like to run .003 total clearance which would be .0105 wall thickness. Matt

 

[savagedasher]

My full length die is honed to.269 I full length size every time with a .0015 bump. Then I change to my bushing die.265 and do less then half of the neck. I haven't annealed the brass in 20 plus reloads. Now I could use a .264 because of the case wear. I never have split a case or loosened a primer pocket. I shoot only H4350 and wolf primers. Larry

 

[AR Shooter]

Thanks for the input and explanations.
Wondering why the 105s for fire-forming? Do they work better than 85s?
Same question on the use of Varget or H4895 rather than RE15. What's the thinking on why either would be better?

 

[bugman]

This must be getting confusing to you.

To answer your question, IMO.....if the chamber neck of this rifle is .267 then do not buy the .267 thru .269 bushings. You will want a .265 OR LESS, loaded round case neck OD. Therefore, start with bushingsin the .263 to .264 range to give you .001 to.002 neck tension.

Since you are single feeding, .001 tension is adequate. You can use the smaller bushing to find out what it likes, or will probably need it if you don't anneal.

With a .267 chamber neck, you will definitely need to turn. I would not fireform these without turning. You do not have enough clearance with that .267 chamber neck.

 

[bugman]

105 trumps 85 because you need to blow out those cases. The 105 means more case pressure and better fireform. The burn rate of 4895 does better for the fireform. Not much difference between varget and re15, so help yourself. In fact lots of people save their re15 for matches.

 

[savagedasher]

I like a flat base 100 gr hunting bullet best for fire forming. And I use my varget or RL 15. I save my H4350 for shooting Larry

 

[dedeadeye]

I recently had my new Dasher chambered with a .267 neck diameter also. You must run all the numbers. Mainly bullet diameters at pressure ring that can vary from .2431 to .2438 from various manufactures and lots. You will probably shoot various bullets, but what I would normally look for is a loaded round clearance of .002. For example a new lot of Berger hybrids measures .2434. So .267 -.002 (clearance) -.2434 (pressure ring diameter) = .0216 divided x 2 = .0108 neck wall thickness. Bear in mind the various bullet diameters. The above example would require a .263 bushing. With slight spring back the neck tension would be .0015. If you are into the rifling you will probably need more tension, off maybe less. So I would also recommend various bushings such as .261-.262-.263-.264 etc. I fireform with 107 Sierra's .025 in with 29.4 grains of 8208. Gotta save that RL 15. Good luck with the .267.

Roger Gower

 

[ShootDots]

If you can use Varget or H4895 for fire forming, I would use a 105 or heaver for fire forming. You are running very close on clearance, you had better measure everything because i come up with .267 loaded round ………jim

Jim is exactly right on with his calculations. You may not get your loaded round chambered. My suggestion (to start) is to turn 2K OFF the necks and use a .264 bushing. I would try that>>>if the bullets seat with some "umph" needed, turn another 1K off. A .267 chamber is quite tight.. AND the 105's set into the lands, even with a false shoulder will give you a better more uniform "blow" on the shoulders.. Annealing them PRIOR to fireforming will save your shoulders from splitting. I lost only 1 in 200 rounds..

 

[AR Shooter]

OK......... am looking at K&M neck turner (have not done any neck turning before) and the set of 24cal mandrel pilots to go with it. Is that a good set-up?

 

[ShootDots]

I have never worked with the K&M but I know they make first rate stuff.. make sure you get a 40degree cutter for that 40 degree shoulder on the dasher..

 

[johara1]

I use both the K&M and a 21st century both work but with starting out i would go with the 21st century kit. Tell him it's for the Dasher and you should get everything you need. You turn the necks and stop cutter at the proper place it will be your false shoulder. The stop is easy to set up and so is the depth of the cut…….jim

 

[AR Shooter]

Thanks, Jim. Have an inquiry in to 21st Century asking what they recommend. Don't want to piece together the wrong parts on my own and have to start over.

Have ordered the Whidden FL sizing die and am wondering if the standard steel bushings are good or does one need to go the extra mile and get the carbide?