6mm ARC mini action chassis rifle

[Jay]

I’ve mentioned it in a few threads. It’s finally complete. So, here’s the story.

I’ve had the thought of building a 6mm ARC since the cartridge came out a few years ago. But was looking at building it in an AR platform. Never really found an off the shelf barrel I liked, and components and factory ammo have been scarce. So I always pushed it back.

Fast forward through a few years.. I helped a buddy of mine build an AR in 6ARC. I like the way it shoots. Then, some jackass came along and did some enabling… I became aware that Brownells was selling Howa barreled actions. They had the mini action in 6ARC, although it was backorder. I was also pointed in the direction of MDT chassis. Before I knew it, I had ordered a Howa mini action in 6ARC and a MDT Oryx chassis. The barreled action got here about 2 weeks after I ordered it. The chassis just got here today.

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[Jay]

Details;

Howa mini action, 20” heavy contour
3.5 pound 2 stage factory trigger. Will probably put a Timney trigger in at some point
Silencerco ASR muzzle brake
Vortex Diamondback Tactical, 4-16x44, FFP, MOA reticle

New brass can still be hard to get. It comes up every now and then. I was able to snag 100 pieces last week. Also have 80 rounds of factory Hornady 108gr ELD-M ammo. That’ll get me started. I bought a set of RCBS Matchmaster dies for it. Bushing sizing die and competition seater. Started brass prep this week. I’ll get some test loads together and take it out with those and some factory ammo and start seeing what it can do.

[sakodude]

Wow, never really been a fan of the chassis stock but that is one fine looking rifle!

[CPJ 2.0]

Man.
I just don’t know about someone who could convince you to spend money like that. Must be a total wanker.

[Jay]

Man.
I just don’t know about someone who could convince you to spend money like that. Must be a total wanker.

I agree. One of those guys who enables you into something, then wants to play with it…

[Jay]

Wow, never really been a fan of the chassis stock but that is one fine looking rifle!

Thanks. I’m happy with how it came out.

[CPJ 2.0]

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Man.
I just don’t know about someone who could convince you to spend money like that. Must be a total wanker.

I agree. One of those guys who enables you into something, then wants to play with it…

[mitdr774]

I'm debating a Howa mini with a rebarrel.to 6ARC. Already have the action wrench. I would have to get another mini action first though as I can't bring myself to pull apart the current one in 6.5 Grendel. It just shoots too good.

I will be looking forward to a range report when it happens.

[Jay]

You don’t need to rebarrel the mini action for 6ARC unless you want a different barrel. They sell the barreled action at Brownells in 20” heavy and 22” lighter contour. Just beware, the 22” is 1/2” threaded muzzle. The 20” is 5/8”. For a hunting gun, and because it’s easier to get brakes for my can with 5/8 thread, I went with the 20”.

[Jay]

What did it for me was the mini action for this cartridge. I like the short bolt throw and compactness of it. The cartridge is a little, stubby bastard. Not overly exciting in factory form. But still launching a long, sleek bullet at reasonable velocity. I’m hoping handloading will unlock more potential.

[Zee]

Science!!

[Jay]

I also have a 6x45 AR that shoots great. While not even close ballistically, I couldn’t see having two 6mm ARs. So, the mini action was appealing. No way I’d do this on a standard short action. That would have killed the appeal, for me.

[Wambli Ska]

Damn, that is a fine looking rig.

[Chiro1989]

Science!!

Yes, this, on a pig or a deer, coyote will be acceptable

[mitdr774]

You don’t need to rebarrel the mini action for 6ARC unless you want a different barrel. They sell the barreled action at Brownells in 20” heavy and 22” lighter contour. Just beware, the 22” is 1/2” threaded muzzle. The 20” is 5/8”. For a hunting gun, and because it’s easier to get brakes for my can with 5/8 thread, I went with the 20”.

I would be looking at 22-24" barrel length and I can get a rifle locally that will avoid the hassle of shipping to an FFL and doing a transfer. My local transfer options are about 0 right now anyways. The local place I was getting ready to take a list of items to consignment sell to, and would have used for a transfer, did not have their FFL renewed.

[jkp]

That looks like it will end up costing me some money...

[Jay]

https://www.brownells.com/gun-parts/rif ... =430102218

https://mdttac.com/oryx-chassis-system/

[Jay]

Test loads assembled this evening. Left to right, 75 grain Sierra Varminter hp hand load. 105 grain Hornady Amax hand load. Factory Hornady 108 grain ELD-M.

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[mitdr774]

Really looking forward to your results. The Hornady load data doesnt have it as far behind a .243 as I would have expected, if you stick to what the book says. I wish they would list bolt gun loads for the 6.5 Grendel like they do for the 6 ARC.

[Jay]

Using that Hornady bolt gun load data, I’m starting off just under their max load. 30.0gr LVRevolution with the 105 and 30.0gr H335 with the 75gr. Once I check those for velocity and accuracy, I’ll go from there. I’m also seating a little longer. I might be able to squeeze a little more out of it. But having no experience with the gun, cartridge and powder, I’m going to be a LITTLE cautious to start.

Hornady indicates bolt gun loads up to 62,000 psi max and gas gun loads up to 52,000 psi max. Since my hunting buddy has the AR in the same chambering, I’ve let him know we need to not have a brain fart and put my ammo in his gun.

It seems I’ll have a little spectrum of 6mm rifles to work with. 20” 6x45 gas gun, this 20” 6ARC and a 22” bolt gun in 243. The advantage of this one over my 243 is that it can be suppressed. The 243 isn’t and can’t be threaded with its current barrel. And the can very well could bump the 6ARC velocity up a bit as well.

[Jay]

Little update. I took this rifle out last weekend for a quick date. I didn’t get any incredible groups with it. So no group pics. It did shoot a couple groups around 3/4”. But not exactly what I was looking for. I’m going to work on my handloads a little more and it will get there. It’s very promising.

I had some Hornady 108gr ELD ammo and picked up one box of the Hornady 105gr “Black” hollow point ammo. Mostly just to get the brass. Neither were impressive. The 108s shot ok. Right around an inch or slightly less. But slow. This rifle apparently hates the “Black” ammo. 1 1/2” (100 yards) at best and slow. 108gr ammo was around 2600 fps. The 105s were about 2550.

My first hand load was with 105gr Amax, 30gr LVRevolition powder, Federal GM205M primers. Just over 2700fps and slightly more accurate. I can work on that load. Bolt lifted easy, primers looked perfect.

Second handload was 75gr Sierra Varminter hp, 30 and 30.5gr H335. 3072 and 3119 fps respectively. I really like that load. Just not quite as accurate as I’d like. Again, no pressure signs with the loads I tested. I’d like to have these at 3000fps, with accuracy. My 30gr load put two into one overlapping hole, and one about 1/4” away. I’m thinking a couple tenths up or down could finish that load. That also could have just been me…

General warning, for outsiders looking in, don’t take my loads as safe starting loads. I’m not pushing it yet. But I’m at the upper end. Use common sense.

[Zee]

Have you measured the chamber length with each bullet?

[mitdr774]

Based on my experiences with the 6.5 Grendel, 0.2-0.3gr charge increments have been what I needed to do during load development. These little cases have decent sized changes from small charge weight differences. I still want a 6ARC. Using published load data it can almost match published .243 data for the same bullets.

[Jay]

Have you measured the chamber length with each bullet?

Not yet. Although I do have a modified case to do so. Only reason I haven’t yet is because the rifle is limited by magazine length anyway, unless I want to single load it. So I’ve just been loading as long as I can and still fit in the magazine. Which is a tiny bit longer than book OAL.

I have more of the 105gr Amax loaded. Wasn’t able to test them last weekend due to weather.

I stopped work on the 75gr Sierra bullets for now. I’m contemplating switching to 75gr Vmax, which would make load work with the Varminter bullets kinda pointless. The Vmaxs are more readily available and 5 or 6 dollars per box cheaper. I don’t have any real world experience with either bullet. According to the manufacturers, I should be about right in the middle of the velocity window with both bullets.

[mitdr774]

If memory is correct my Howa Mini 6.5G is also magazine limited for OAL. Its the same with my CZ 527 6.5G. I want to say that I can load about 0.100" over book length with most bullets I use, with the exception of the Nosler 100gr Partition. I have to seat the 100gr Partition deeper than book to get it to fit in either 6.5G chamber.