6mmAR Speeds??? Possible 18" build

[Cajuntransplant]

Hey everyone-

I love my 6.5Grendel and I've been toying with the idea of doing a 6mmAR upper build but I'm wanting to do a 18" barrel and basically copy my setup I have now. I like that the 6mmAR requires just running the 6.5G brass through a sizing die and then loading it up and shooting it. I don't want to fire form anything and am planning on trying to run the hornady 103ELD-X bullet. I run supressed all the time and really want to stick to the shorter overall length the 18" barrel will give me. Does anyone on here have some good velocity info on shorter 6mmAR builds they have done? Everything I have been able to find is the longer 22-26" barrels. Thanks in advance.

[204 AR]

My shortest is a 20" from ARP. I'm not much help since my crony crapped out and the heaviest I've gone is 87's. I shoot 70 gr nbt's, and judging by the drop figures I'm guessing around 3300 fps.

It is a great round though, for my use (coyote, pdogs mostly) it's a better fit than the 6.5.

[StoneHendge]

My shortest is a 20" from ARP. I'm not much help since my crony crapped out and the heaviest I've gone is 87's. I shoot 70 gr nbt's, and judging by the drop figures I'm guessing around 3300 fps.

It is a great round though, for my use (coyote, pdogs mostly) it's a better fit than the 6.5.

What sort of velocity do you get out of 87s? I'm getting all drooly thinking about the amount of terror I'm going to be able to rain down upon dog town from afar out of my 26" on order with the Berger 88 gr High BC FB Varminter.

[Cajuntransplant]

Thanks!! Still solid info!! Hoping someone of the members on here have 18-20” rigs setup and are running 100gr pills. Just trying to get a gauge on velocity to see if it’s worth the build cost. I think it will be. Just need to find a barrel and get the die sets.

[Kilco]

I've been playing with the Lapua 90gr Scenar and I'm getting 2911 fps average over ARCOMP absolutely no pressure from a 20" barrel.

6mmAR is my new favorite AR15 paper puncher.

I wouldn't hesitate to take it hunting either... running numbers it has just as far an effective range as the 6.5 Grendel with a MUCH better bullet selection.

[StoneHendge]

I've been playing with the Lapua 90gr Scenar and I'm getting 2911 fps average over ARCOMP absolutely no pressure from a 20" barrel.

What charge? I need to be taking notes. The thought of 3k+ with the Berger 88 Varminters has me doing a Dr. Evil laugh!

[JASmith]

One can get a pretty good idea of velocity for new barrels http://shootersnotes.com/calculator/velocity-estimator/.

Ammoguide subscribers can go to the load data and use one of the loads as a starting point.

Alternatively, start with the Grendel data on the landing page and modify the reference load data to match the 6mm AR. This should be the bullet diameter, the case volume (~1 gr less) and a reference load.

Then enter the specifics for the new load.

Iterate as much as you like!

[Kilco]

What charge? I need to be taking notes. The thought of 3k+ with the Berger 88 Varminters has me doing a Dr. Evil laugh!

I started at 27gr and worked up. 28.5 was where velocity and accuracy really made me giggle.

BTW try LVR in your 22 Nosler. 3050fps with the 77gr TMK and brass looks lovely. Bro is getting 6-7 loads out of brass before pockets get a bit loose.

[Cajuntransplant]

I've been playing with the Lapua 90gr Scenar and I'm getting 2911 fps average over ARCOMP absolutely no pressure from a 20" barrel.

6mmAR is my new favorite AR15 paper puncher.

I wouldn't hesitate to take it hunting either... running numbers it has just as far an effective range as the 6.5 Grendel with a MUCH better bullet selection.

That’s really promising!! ARComp is my favorite powder for the Grendel. I wouldn’t think that dropping another couple inches off the barrel and running the 103 ELDX would drop speeds that much.

[StoneHendge]

I started at 27gr and worked up. 28.5 was where velocity and accuracy really made me giggle.

BTW try LVR in your 22 Nosler. 3050fps with the 77gr TMK and brass looks lovely. Bro is getting 6-7 loads out of brass before pockets get a bit loose.

I've got almost a keg of IMR 4451 I bought when I did the S'more thinking it would be impossible to find H4350, and then I found a bunch of H4350. I've been wanting to give it a try with 70 RDFs in the 22 Nosler ( bought a bunch when SPS was practically giving them away) but just haven't had the time. Slower powder just makes so much sense. Also going to try cooler primers (WSRs and BR-4 vs the Feds I've been using). A switch from Feds to BR-2s in my S'more did wonders for reducing peak pressure with 140s and slowing bolt unlock across the board. If that doesn't work, I'm not going to waste H4350 on it and I don't think I'd allow myself to buy a pound of Lever just for the 22 Nosler lol. The barrel will be going in the back of the closet like the plan was before I saw Hodgdon's data

[Kilco]

I've got almost a keg of IMR 4451 I bought when I did the S'more thinking it would be impossible to find H4350, and then I found a bunch of H4350. I've been wanting to give it a try with 70 RDFs in the 22 Nosler ( bought a bunch when SPS was practically giving them away) but just haven't had the time. Slower powder just makes so much sense. Also going to try cooler primers (WSRs and BR-4 vs the Feds I've been using). A switch from Feds to BR-2s in my S'more did wonders for reducing peak pressure with 140s and slowing bolt unlock across the board. If that doesn't work, I'm not going to waste H4350 on it and I don't think I'd allow myself to buy a pound of Lever just for the 22 Nosler lol. The barrel will be going in the back of the closet like the plan was before I saw Hodgdon's data

Try RL26 is the CM.

My pet load for the 260 and CM has been 143 eld-x over 42.3gr H4350@2810 fps from a 26" barrel.

With lower pressures I'm getting a 2905 average with RL26. Thus far it hasn't displayed the temp sensativety of RL17 either.

[StoneHendge]

I'm getting 2740 over 41 gr of H4350 with 140 RDFs with no (timing) ejector marks. That's almost unheard of in a gas gun - most can't even get close to max with 140s. I cheated and worked up with the gas off. My "mild" load is 40.7 H4350 with 130 Norma GTs at 2810. Both could do < 1/2 MOA if I could. Best of all, they have almost the same POI. I spent way too long on load development before I figured out my scope was bouncing around inside of a 1.5" box due to insufficient rings, so I'm done with it!

[204 AR]

What sort of velocity do you get out of 87s? I'm getting all drooly thinking about the amount of terror I'm going to be able to rain down upon dog town from afar out of my 26" on order with the Berger 88 gr High BC FB Varminter.

Oh ya these are a pdogs nightmare! And you won't torch your barrel out too fast! 28.6 gr of 8208 behind the 87 vmax nets 3020 iirc from my 22" BHW 243lbc. I don't think I lose too much with the 20" ARP but can't really prove it. I stuck with the 70's in it for coyotes this winter.

A couple weeks ago I took a couple from Denmark out to shoot pdogs and set them up with the 243lbc. In a 15 mph cross wind they scored hits at 350 yds with those 87 vmax's. And that barrel has roughly 1600 rounds and still looks very good in the bore scope.

IMO this is the best AR round I've come across. And I've tried a bunch of them. Let's see, 223, 223AI, 6x45, 25 wssm, 243 wssm (laser like, awesome), 22 Nosler, Grendel, 204, 20P, 17-223, 243 win, 260, 300 Saum, and I probably forgot something. I still have some, some I shot out, some I was unimpressed with for various reasons. But with 6mm bullet selection, a case that barely uses more powder than a 223, and yet gets performance close to the 243 Win ar10 with twice the barrel life, it's a winner.

[K_4c]

I must have a slow barrel... my 20" McGowen runs the 95 smks at 2810 and the 75 vmax at 3030 FPS. Both on the upper end of pressure.

[454bore]

You should be able to hit 2600 fps with an 18 inch using the 103 ELD.
I'm getting 2700 fps with a 22 inch barrel using the 105 Amax.