6mm dasher AR15 build question

[jefo65]

Giving the dasher some serious thought lately,..question I have is what bolt assy would I require? Unless I'm looking at it wrong both the 6.5 grendel and 6.8spc bolt faces are still too small. Any suggestions on magazine choice and feeding issues that may or may not exist would be greatly appreciated.
Thanks!

 

[flatlander]

I think you're asking for a lot of headaches by trying to get any cartridge with a .473" casehead dia to work in an AR15. People still keep trying this sort of thing, but for the life of me, I can't understand why. No, a 6 RAT or 6mmAR Turbo don't have quite as much HP as a 6 Dasher, but they'll work in an AR15 - as long as you don't run loads hot enough to break bolt lugs - and I've seen & heard of several guys with that problem.

It's too bad LMT stopped making enhanced bolts for the 6.5 Grendel (parent case of both the 6mm wildcats mentioned above), since I've yet to hear of anyone who's managed to break lug/lugs on one of those bolts.

ASC also makes good, reliable 6.5 Grendel magazines - do you have a supplier for reliable AR15 mags to fit the BR case?

 

[AKShooter]

flatlander has good advise! I was in a similar boat, really wanted the 6mm ar, looked at the 6rat, 6mmar and the 6x45. These are all good choices with pros and cons in the 6

Ended up with the .264 LBC, or Grendel. Just way easier to find components, cheaper, and met the intent of my build.

 

[Rtheurer]

I believe you would be better served going the AR 10 route IF you wanted to experiment with a Dasher in an AR platform. I can tell you this. Doing this on your won wtih out a tremendous amount of Knowledge about pressure curves, gas port Sizes, and a whole host of other issues you might just forgo this idea. It would most likley cost you a $hit ton of money to get it working correctly and fustration beyond belief.
This is not a plug and play type of modification.

The Fine folks over at BR Armament have been working on this type of Modification for what seems like 10 years now.( http://bratrifles.com/ ) Click Link.

The Cartridges based off the Grendle or the 6.8 seem to be pretty dern close the max for the AR 15 type of chassis. Just my opinion.

RussT
Have you seen the FAT RAT or Turbo40?

 

[Rtheurer]

It's too bad LMT stopped making enhanced bolts for the 6.5 Grendel (parent case of both the 6mm wildcats mentioned above), since I've yet to hear of anyone who's managed to break lug/lugs on one of those bolts.

Had Broken lug on a Rat. Not an LMT bolt.

RT

 

[rminut]

there was a guy that posted here that was building bolts and extensions for 6br/dasher and 6.8spc mags but I don't know if he is still making them. I've seen rifles built using them and they shot well but not really any different than a Grendel or Hagar based cartridge. The Hagar based round does give a little insurance in lug strength, and I think most guys take advantage of that, but it probably kills the brass fast when you do. There is always a compromise.

Scott Medesha, Derrick Martin, Gary Eliseo all used to make 6br AR uppers using 7.62x39 bolts and rebated rims. They shoot well but are a bit more work because of the brass, but it's a one time deal and working the lathe should never be shied away from.

none of this matters if you can't shoot 190+ on your feet though!

 

[80x80]

My son and I are very pleased with the 6mmAR Turbo 40 degree upper we purchased from Robert Whitley.

We went with all the upgrades plus dies, brass, magazines and bore guide. Our planned use is varmints and Wyoming antelope.

The Berger 95 grain classic hunter backed with N540 produced 2888 fps and filled two Pronghorn tags with two shots.

Bill

 

[jerdebson]

Harrison Beene (H) of ARP (ar15performance.com)(if I remember right) makes what he calls his super bolt for 5.56, 6.8, 6mmAR, 6br, 6brx, and several others. I have ones for 6.8SPC and 6mmAR and have had no problem with them. Check them out. YMMV

 

[jscandale]

One thing that enyone who plans on building an AR15 in somthing larger than a 6.8 case almost always overlooks is chamber wall thickness. Keep in mind that the minor diameter on the .812"-16 threaded tenon is about .705". A .308 sized case has a head diameter of .473". At the back of the chamber (largest end of the chamber taper, the wall thickness is only .116" ((.705-.473)/2).

There are manufactuers of .473" bolts for the AR15 and I am quite sure that they are very strong, but the chamber wall is the weakest link in the chain, not the bolt. Just think about that as you are lighting off a high pressure rifle cartridge right next to your face with a gun that was originally designed to have a minimum of .166" of chamber wall thickness with a lighter charge that the .223 utilizes.

At the Shot Show in January, I talked with the guys at Olympic Arms who manufacture an AR15 chambered in a 30 cal cartridge with a magnum bolt face (.535"). I asked them what the chamber wall thickness was (its .085"!!). They didn't seem to want to talk about it very much but said that they tested it to failure with pistol powder, but claimed it still held together. That didn't make sense to me at all, so I said thanks for the info and went on about my business thinking; I'd hate to be their insurance carrier.

I built a 6br in an AR15 several years ago after shooting Derrick Martin's at a team train up in Iowa. It shot great, so moved forward and rebated the rims on a few hundred pieces of brass before bailing on the project and selling the parts to someone much more enthusiastic than I was after realizing the inherent dangers of the project.

The moral of the story is BE CAREFUL! I don't enjoy reading about gn related injuries.

JS

 

[rcw3]

Another issue of the AR-15 platform is just how large of a cartridge can you put in it and still retain accuracy. Frankly IMO, the cartridges that are around 38 gr. and under of water capacity are about the max size you can chamber in an AR-15 platform and still push a 105-108 gr 6mm bullet accurately. I tried 6BR, BRX, Dasher in the AR-15 platform and never could get any real consistent accurate performance, especially trying to push the 105-108 gr bullets much over 2800 fps. Just because you put a bigger engine in a car doesn't mean the car can handle the power plant and perform well with it.

 

[johnu]

Might think about 6x6.8 - the 6.8 spc necked down to 6mm. Was messing around with mine yesterday trying out various hunting bullets with different powders. Several combinations were under .5 inch, with the best .249, all three-shot groups at 100 yds. And I'm not even that great a shot! Get one of Harrison's super bolts (when he has any) and you're good to go.

John