Ramshot Big Game

[Sockeye66]

Curious if anyone has results in the 6mm ARC with Big Game oowder.
Seems like a good fit for the cartridge in regards to case fill and burn rate.

[Hurley88]

Bolt action or gas gun? I have half a pound, wouldn’t mind running it for ya just to see. But mine is a bolt action.

[Sockeye66]

Bolt action or gas gun? I have half a pound, wouldn’t mind running it for ya just to see. But mine is a bolt action.

Should’ve clarified, my bad, I have a 20” CMMG upper mated to a PSA lower. Typically, I shoot from 85gr to 108gr projectiles. I’ve got about a half-lb also. Just seems like it might be a strong unknown powder for the 6 arc. Any help is appreciated.

[Hurley88]

Never know til you try! I’d work up using Lever & StaBALL 6.5 as maximums, see what velocity you get. Then back off a touch and shoot for accuracy. Might be a week or two but I’ll run them in half grain increments up to what I’d guess would be gas gun maximums.

[Sockeye66]

Been a bolt gun person for a long time, easy to know where one is at pressure wise, the gas gun takes some guesswork which can be dangerous in the reloading realm, just trying to be safe but also get the most performance. LVR seems to be the go to for many, been trying not to go there solely for the temperature instability, here in Montana we definitely have extremes in weather. So far, N540, H4895, TS15.5, and Varget have been what I’ve tried and they seem to do pretty well, I am going try the StaBall 6.5 for sure.

[CZ527 Guy]

Might be surprised if big game worked, well in the 6mm ARC. Defiantly on the slow side.

[Sockeye66]

Might be surprised if big game worked, well in the 6mm ARC. Defiantly on the slow side.

It’s right next to LVR on the burn rate chart and faster than N540, also definitely faster than StaBall 6.5, my issue is knowing where the pressure is in a gas gun.

[grayfox]

Both lever and CFE are not good examples to compare against, as their pressure curves and makeup are far different than standard powders. They are more rounded so while pressure does not get as high on peak, the area "under" the pressure/distance graph is what delivers the energy and acceleration. Powder "burn rate", therefore, is not the be-all for these guns. If a powder is too slow (ie, like one for a magnum) you might not get enough powder in the case, or the push to get the bullet out and the bcg to cycle back... These cartridges for the AR15 are somewhat limited on overall case capacity. One way to attempt to discover before you load is to get quickload or GRT... I've got GRT and use it as a decent guide - not perfect, it takes some tweaking, but better than loading blind with a new powder.

The other difficulty in both the grendel and the 6 Arc is their brass base is larger so max allowable pressure is limited to 52 ksi in a gas gun, which is below the point where case swipes, sticky lifts and flattened primers tend to occur.

So it is a good observation to be wary of "max" pressures in these cases.

[grayfox]

Edit to add: with all that being said, I do have one berger 105 load in my version of GRT, one of my 20's gas gun, with Lever. Translating that over to a 108 eldm over Big game, it does appear possible, at least on this modelling, to work up to about 28.7 and upper 2400's in MV (which is low for a 20"). Of course, this is only for my gun-model, ymmv, I assume no liability, do your own workup from lower if you choose...
The powder burnup is only 85%, which is not to my liking, personally.

OTOH, your MV sticking with Lvr would be somewhere low 2600's. Lever for me has worked from about 84 Deg down to about 40... but admit it is not for the desert sun, nor for the frigid winters (spent some great time stationed in Idaho, I do love the mtn west but not the long cold winters!).

[Sockeye66]

Did get to test a few loads over the chronograph this afternoon, Big Game 28.3gr 87gr VMAX 2450fps, StaBall 6.5 90gr ELDX 2510fps (.7” at 100yds), 28.1gr Shooters World Long Rifle 87gr VMAX 2505fps (.8”), 27.3gr N540 90gr ELDX 2764fps (1.1”), for comparison this rifle (20” CMMG gas gun) shoots the 108gr ELDM factory loads at 2640fps under an inch.

[BD1]

Did get to test a few loads over the chronograph this afternoon, Big Game 28.3gr 87gr VMAX 2450fps, StaBall 6.5 90gr ELDX 2510fps (.7” at 100yds), 28.1gr Shooters World Long Rifle 87gr VMAX 2505fps (.8”), 27.3gr N540 90gr ELDX 2764fps (1.1”), for comparison this rifle (20” CMMG gas gun) shoots the 108gr ELDM factory loads at 2640fps under an inch.

Just a quick look at Quickload using the default parameters with 28.3 grains of RS Big Game under an 87 gun V-Max from a 20" 6mm ARC barrel yields 2552 fps at 37866psi.  This shows a 91.7% fill ratio.
From this I think we can draw 2 conclusions:
1.As your velocity is 100fps slower than the Quickload prediction, I would say that this powder in this cartridge does NOT model well in Quickload. If we used the actual parameters from your load and rifle we could see if it refines into something closer to reality.
2. According to Quickload, you do not appear to be anywhere near "overpressure". 100% fill ratio would be 30.85 grains at COAL 2.260 an the pressure predicted would be 49651psi. QL's predicted max load would be 31.2 grains yielding 51563psi, 101.1 % fill ratio).

A note of caution: QL shows pressures going rapidly over max with more compressed charges of Big Game in the 6mm ARC. So I would suggest working up slowly and staying away from any compressed charges

The Shooters world Long Rifle powder models much better. QL predicts your load of 28.1 gr under the 87 grain V-Max would yield 2497fps at 38434 psi. Being within 10 fps of your real world results would lead me to have some faith in QL's ability to predict pressures using Long Rifle. However, velocities will be significantly lower than several other choices.