Home Forums Reloading Big Game Rifles Good 6mm AR / 6mm Grendel / .243 LBC loads

The google custom search turned up nothing for "good loads" for either 6mm AR, .243 LBC, or 6mm Grendel so I figured we may as well get one rolling. I have NO loading suggestions to offer as of yet since I am waiting for my two 20-inch barrels and likely will be still waiting five weeks from now.

I HAVE learned already that 6mm AR dies are damned hard to find, so I resorted to a Redding 6.5 Grendel FL-bushing die with a .268" TiN bushing. I have also learned that trying to neck down a fired 6.5 Grendel case using this die is likely to damage case mouths or simply be generally difficult, but FL sizing a fired case in a 6.5G die first makes it a piece of cake. I will be seating with a Forster 6mm PPC benchrest seater die.

When my rifles are built, most likely I will be shooting 95-grain Partitions at hogs...at least for starters. I may be lured into playing with slicker bullets, though...ya never know. According to QuickLOAD, the powders on my shelf that would work best are H4895, Re15, Varget, H335 (which I will NOT use for this application), and AR-Comp. Varget, H4895 and AR-Comp will get the call for starters. I'm hoping the AR-Comp does well because I have a lot of it on the shelf with no current assignment. We'll see. At any rate, it looks as though 2750 fps may be possible. I'll be doing more reading before I charge a case,elsewhere and hopefully right here.

River Rider....I'm interested in your load development. I've got a 22" 243 LBC barrel in route next week but it'll probably be another month before I get my upper completed.

The Black Hole Weaponry forum has some loads listed here and there if you want to take a look.

Dan

Thanks Dan. I think I have looked there but I'll keep checking.

My barrels should be ready about now. When I get them I will finish up assembly and see about seating depth. I have some ammo made up with bullets seated long, and I can finish seating up at that point and test the loads. I'm starting with H4895 under 95-grain Partitions.

Since I started this thread, I found a good use for my stash of AR-Comp...pushing 70-grain Accubonds in my 5.56 hunting ARs. Works good there!

I'll post results when I can.

A standard 6mm PPC sizing die (not a bushing die) is a lot better for necking down cases, and is what I use for all of my 243 LBC sizing. Just don't run the die down to the shellholder; set it up for the correct shoulder bump.

A few loads that work well in my 24" 243 LBC: (copy and paste from my load data, hope the format isn't too hard to read)

24" BHW 243 LBC 95 Berger VLD Hunting Lapua Grendel 2.235 S&B SR CFE223 32.4 2,910

24" BHW 243 LBC 95 Berger VLD Hunting Lapua Grendel 2.300 S&B SR H4895 29.0 2,890

24" BHW 243 LBC 105 Hornady BTHP Win 2.240 WLR Leverevolution 29.5 2,795

Lapooey brass,400's,Lever' and 105 Hornie BTHP ASC magfed Smooches,in all of mine.

ES/SD is essentially non-existent and Performance/Precision simply uncanny.

Hint...................

Re-15 or Varget. H-4895 does not suck either... Nor does N-140

In both 224 and 243 Grendels,it's Lever,Lever and lever...roughly in that order. Hint.

Same goes my 224 and 243 BR's. Hint.

Along with 224x45's,224 x 45 AI's and 270's. Hint.

Though I'm only talking a few dozen spouts....................(grin)

Bigstick,

Is Lever giving you the velocities like the CFE 223 is giving guys? CFE 223 seems to be the velocity king on the forums I researched.

Dan

CFE 223 is Hind Tit.

Hint.

I'm not much into fhuqking around.

Re-hint...................

Has anyone worked with the Barnes 80g TTSX ?

You'd think that would break 3000fps easy, with a 20-24inch barrel.

The 80 TTSX is a SCREAMING piece of fhuqking schit,in comparison.

Hint.........................

So, this thread is a bit old, I know. I got a 6mm Predator (same as the 243 LBC and 6mm Grendel, just different name). While messing with that (and because of that), I've started using my 6.5 Grendel for hunting again so I've been messing with loads for it. Certainly there are differences between the 6 and 6.5, but basically they're the same case and will have "close enough" loads to indicate at least a useful comparison of powders.

With that said (and this: this is about the 6.5 Grendel and presented only for reference purposes, not loading): I loaded for 95gr Hdy V-Max. I like CFE223 in general and find that oftentimes it lists with the highest published muzzle velocities for a given cartridge/bullet combination, so I tried that. I also tried 8208XBR and Benchmark. After reading this thread, I tried Leverevolution. For the 95gr Hdy V-Max in the 6.5 Grendel, 8208XBR gave me the highest velocity (2,832 FPS from a 16" barrel) with (for me) an acceptable level of primer flattening (not too much). CFE223, in the amount I tested up to, gave me too much primer flattening and not as high velocity. Same, too, with Benchmark. When I tried Leverevolution, I found a load listed online and went under that quite a bit "just in case the Internet lied". I worked up to the listed "max". With all powders I found some ejector swipes, some more than others, but I've since attributed this more to gas system timing (having shot some of the same loads in a 6.5 BPC bolt action rifle now)...except the Leverevolution...no swipes. With the Leverevolution I had rounded edges (not flattened) on the primers all the way to the listed "max". I then loaded beyond the "max" load, incrementally, to 32.5gr Leverevolution. At that amount I started seeing a little flattening of the primer and some ejector swipe (still, I think that's timing of the gas system). The muzzle velocity on the hottest load (32.5gr) was just over 2,700 FPS, about 125 FPS below what 8208XBR could give me. At 32.5 grains of Leverevolution, the case is nearly full. All loads of all powders were ignited with CCI #41 primers (per CCI, they are to be treated as "magnum" primers).

The takeaway from this: in a nearly identical case to the 6mm LBC/Predator/Grendel, 8208XBR gave me the highest velocities while remaining within my tolerance for pressure signs. Leverevolution gave acceptable velocities without exhibiting as much (if any) pressure signs. The 0.243" projectiles have 15.28% less bearing surface on their butt end than the 0.264" projectiles. That means less applied force during firing, if the chamber pressure remains the same. Therefore, acceleration of a similar-weight projectile should be slightly slower, given the same chamber pressure. Therefore, a slower-burning powder like Leverevolution, may be preferable. I say "slower burning" because, by the evidence I saw of pressure signs, the Leverevolution gave similar muzzle velocity (125FPS difference in the 2,700-2,800 FPS range is small), yet less primer flattening. Conjecture then: if 8208XBR gives better velocity than CFE223 in this load and Leverevolution gets close to the same velocity yet exhibits less pressure sign, then Leverevolution may yield higher muzzle velocity, or close enough as to make no difference, in the 6mm variants where there is less applied force (given the same chamber pressure) to the projectile hence slower acceleration while, hopefully, still exhibiting less pressure sign.

FWIW. YMMV. EIEIO.

--HC

Your assumption is flawed, and so is your takeaway.

Powder burn rate requirements for a light bullet 6.5 load are NOT the same as for heavy bullet 6mm loads. Heavier bullet (for caliber) - slower burn rate. Smaller bore - slower burn rate.
You cannot assume that the best powder in 95gr 6.5 Grendel loads is also the best powder for 105gr 6mm loads.

8208 is a great choice for light to mid weight Grendel loads. It is not the best choice for 95-105gr 6mm Grendel loads; it works but burn rate is a little fast.
Conversely, Lever is a bit slow burning for 95gr 6.5 Grendel. It is a good choice for 129/130gr 6.5 Grendel though.

Yup.

If you compare .270 and .280 (and you might have reason to do so if you want to know whaat you can REALLY do with a .280), you compare sectional density of different bullets between the two cartridges. The bore diameter is close enough to be a non-factor in that instance, and you can pretty confidently use .270 data to estimate the safety margins of the .280 cartridge by using sectional density to establish some kind of equivalency. On the other hand, you could not use sectional density similarities between .30-06 and .270 to extrapolate a 65000 psi load for the .30-06 because of the difference between bore diameter between the two.

Classy, always top shelf Classy....

No ONE on the planet can explain things that even the lowest form of intelligence on the planet would misunderstand, like Schtick can explain it.....

simple man of real simple words....

HINT....

I've been playing a bit with Hornady 105 HPBTs the last few weekends.

I tried four powders in initial workup: AR-Comp, H4895, Varget, and Re15. I did find some suggested charges on-line for H4895 and Re15 but was left to my own devices with the other two. I used QuickLOAD to find my way and try to stay out of trouble, and so far so good. The first day out with those loads showed me around 2550 fps with all powders except Re15, which was about 50 fps slower out of my 20-inch barrel. There was accuracy potential everywhere as far as I could tell, but my chronograph was causing problems...there is a rise in the ground about 15 feet in front of the bench where I was set up and that is exactly how far out front I always set up my 35P. As a consequence of that and the limited extension of my bipod I had to use a wooden box I keep in the bed of the pickup to set under the bipod to gain a little elevation so I wouldn't shoot my chronograph. It was a bit unsteady and far from ideal, but I really wanted the velocity data and I got it. I also made a mental note that I needed to enlarge the targets I was using, which I make and print myself using PowerPoint. I found the diamond shapes just a bit too small for 10x magnification.

The following weekend I tried the same four powders using the charges that seemed to be the best the weekend before, but left the chronograph at home. Nothing was really outstanding, but I was able to decide that AR-Comp and Re15 were out of the running. I also had forgotten to modify my targets, and that just really wasn't working well for me and for that reason didn't feel like I had a feel for the potential of either H4895 or Varget.

In the meantime I laid hands on some Leverevolution, which I am told is The Magic for 6mm AR.

This weekend I remembered to modify my target for better visibility when using a 10x. I loaded up some exploratory loads with Leverevolution and the same loads I had shot with Varget and H4895. Again, I left the chronograph at home. With Lever I tried 28.0 to 29.5 grains, and everything shot right at one inch for five shots. Huntable, for sure. H4895 shot the worst, with one group exceeding 1-1/2 inch (coulda been my fault, of course, but I didn't think I'd pulled the offending shot). The surprise was Varget, which turned in five-shot groups measuring 0.83 inch and 0.57 inch.

I'm not too proud OR confident to be willing to shoot some of these loads again. I've been having vision issues that I think hamper my bench shooting, and besides that I'd love to have a nickel for every time I've thought I'd found THE magic load but didn't. In the next few days I'll figure out what I want to shoot again and give it a go, hopefully soon. At this point, I can confidently say that the 105 shoots pretty well in my rifle, and I am pleased with it. I hope hogs hate it when I get a chance to introduce them to it...I've never used the 105 before and don't have any real idea whether it will actually open up on a hog at these velocities, but I am more than willing to find out.

RR, those loads seem slower than expected, bummer. H4895 at least should be able to do 2700 fps with the 105 BTHP in your 20" barrel with good brass life. Assuming that's an actual 243 LBC chamber in a BHW barrel - if it's someone else's chamber in a different barrel, maybe not. I've been noticing recently for example comparing data from several different sources for each that top loads in the 6mm Predator run about 100 fps slower than BHW's 243 LBC for the same barrel length.

Lever is certainly an easy choice though.

What's your rifle setup, and how is the upper assembled? i.e. just slapped together with a cheap loose-fitting upper, etc, or is it lapped and Loctited in the upper and other stuff like that? Asking because I've seen much better accuracy than that from all BHW barrels I've used and owned, so I'd have expected better from yours too.

Yondering, my 6Gs are built on Aero Precision uppers and lowers, and am using BHW .243 LBC barrels. I thought I recorded all the parts and sources for these builds somewhere, but if I did I just cannot locate the file. I think I bought my BCGs from PSA, but I do not recall for sure...coulda been Primary Arms. There are no Bear Creek Arsenal parts in my rifles!

As mentioned, I am having some vision issues that may be causing me problems shooting off the bench. I have rifles that shoot a half-inch or better with pretty good consistency...maybe I should take them with me when I shoot these ARs to find out how I'm actually doing. In any case I am going to make an appointment with my eye doc this week. I had an infection in my right eye early in the summer and after it cleared up my vision in that eye remained blurry, a change from 20/20 to God only knows what. Could be cataract, maybe. I hope it can be corrected because I can't shoot my handguns like I could only a few years ago. I'll admit right now that I've never really liked the ergonomics of an AR off a shooting bench and it could well be true that I just don't shoot one well enough to demonstrate its real accuracy potential.

About those velocities...I also mentioned problems with the shooting shooting position I used on the weekend I chronographed. I suppose it's possible that the readings were flawed because I was having to shoot just an inch or two over the sensors (yeah, it's a little nerve-racking). Since I never got to chrono the Leverevolution loads, I may repeat the effort and make sure I set up on another shooting bench where I can use my chrono without stressing over its welfare. For that matter, maybe I should look at the stands and see if I can modify them to set my screens about eight or ten inches lower. I do not think there's anything wonky about my barrels...my two 6Gs are identical and velocity readings have been fairly close to each other. I use two scales when loading for the purposes of keeping each one honest via spotchecking.

I'm using QuickLOAD and any on-line sources of information I can find for data---in fact I ran Lever up to 29.5 grains based on your recommendation---but I am approaching the whole thing with due caution because of the lack of published, pressure tested load data. One thing I may try is Lapua brass...I'm currently using Starline and it seems to be good and tough, but maybe Lapua would give me better results. I tried Hornady when I was shooting 6.5G, and I thought it was schitt brass and I won't use it anymore. The bottom line is, I'm not expecting high velocities with this round...I'd have built an AR10 if I was. I'd happily accept a 150 fps gain if I knew it was sanely achievable, but I'm not into locating edges of cliffs wearing a blindfold.

BTW, Yondering...do you happen to know the water capacity of your brass (I'm assuming you're using Lapua)?

Hope you get those vision issues straightened out, that's no fun.

I am using Lapua brass, among others. I don't know the water capacity though and may not get a chance to measure for a bit. I can say that while the Lapua brass has been the most consistent for me, it doesn't necessarily last the longest or handle the warmest loads; some of the other brands have done better in that regard in my rifle. (Actually, that has held true for me in both the 243 LBC and the 6.5 Grendel.) I don't push it too hard though, other than determining max and backing off from there.

If you're using the same Lapua brass and BHW barrels, I'd think your velocity capabilities should be very similar to mine, taking the barrel lengths into account. Mine is a 24", although I'll be finishing a 20" soon to compare numbers. I'd be very surprised if your 22" was more than ~75 fps slower than mine though, and more likely 30-40 fps. Do you know what velocity you're getting from 29.5gr of Lever with that 105?

Also - make sure you're not bumping the case shoulders back too much, no more than .004" or so. Excessive shoulder bump can show false pressure signs; even .010" bump can do that. FYI my new Lapua brass had the shoulders .010" back from a Go gauge, so it had a tendency to show some false pressure signs on the first firing that don't show up after that with the same loads. It did that in my LBC and the Grendel.

On the build details, the main thing I was wondering is how tight/secure your barrel is in the upper; if it's a thermo fit or shimmed and glued, or just set into a typical slightly loose fit? It's been a bit since I've assembled an Aero upper, but IIRC they were a pretty standard slip fit with a normal barrel extension, and could benefit from shimming and Loctite, or at least Loctite. (Use green 680 or 620, not just blue 242 or 243.) That can help with accuracy a bit, although it won't turn 1.5" groups into 0.5" groups.

A comment on shooting position and ergonomics with ARs - a more vertical grip is helpful for prone or bench shooting, and works just as well everywhere else. I prefer the Magpul K2 grip. The standard A2 mil-spec grip is terrible IMO; that's one of the first things I change out.
Along with the vertical grip, moving your thumb to the palm side of the grip (instead of wrapping around) and only pulling straight back with your fingers helps. Of course that goes along with setting up straight behind the rifle instead of bladed to one side.
With all of that done correctly, to me an AR feels just as natural as a good bolt gun for prone shooting, and better than a typical hunting stock bolt action.

My 6Gs have 20-inch barrels. I have not chrongraphed the Lever loads, I only clocked the initial loads with Re15, H4895, Varget, and AR-Comp. I will say that the 29.5 Lever loads did seem to fire with more enthusiasm, if you know what I mean. I'll make it a point to load up at least a few more of that load and chronograph it...I mean to chrono more of them since I am not confident in the numbers I got the first time around.




IIRC, I set up my die to bump about 0.002 inch. To be honest, I don't recall checking that with brass fired from BOTH rifles. Maybe I should revisit that...I may end up with another die because I use a Co-Ax and I detest fiddling with sizing die adjustments. I like "set-and-forget" for sizing dies (and I prefer that for my scopes too...a whole nuther can of worms!).



It has been eight months since I assembled the rifles, but as I recall the barrel fit to receiver was nice. I was able to slide them together but with a bit of resistance. I did not think LocTite would help in any way.



I think I used K2s on these rifles as well. They're Magpul, for sure. I'll try altering my grip as per your suggestion next time I shoot. I might take a look at getting set up with a better rear bag, too.

I appreciate your comments, thanks!

Yeah, Lever definitely has more flash and blast than some of the stick powders like 4895. That doesn't really translate to an indication of pressure, it's just a trait of that powder. I was thinking you had 22" barrels rather than 20", but still think you should be able to get better velocity than reported. Most of the advantage of this cartridge over the 6.5 Grendel is the ability to push velocities higher than the Grendel range for better trajectory at distance, so IMO it's worth getting the full capabilities out of it, within reason.

On the upper/barrel fit - if you can slide them together by hand, it can definitely benefit from Loctite and/or shimming. The point of the Loctite is to stiffen that joint; if it's not a press fit (or thermo fit, same thing) then the upper is only capturing the barrel at the extension flange, and can flex around the extension. With a tight or bonded fit, the upper/barrel connection is solid all the way back to the feed ramps. It's not a huge difference, but is one of the small incremental improvements that can help.

Today I was able to shoot the Leverevolution load again. I selected a different shooting position to make sure the chronograph screens were elevated to a reasonable height. My last three groups with the load averaged right at 3/4" while the first two were a little over an inch...and I am sure it was my fault as I was trying to get the hang of using a new squeezebag...never used one before today. Velocity was right at 2640 fps, a full 90 fps faster than what I measured several weeks ago.

Yeah you have to learn how to squeeze your bag. It takes a gentle touch...





I hope to have my 20" 243 LBC barrel ready to test fire in a few weeks, probably during the holidays. I'm interested to try the same loads in it and compare velocity to my 24". They are both BHW barrels and both chambered by BHW, I just have to profile and finish the 20". My 24" was a complete barrel from them (~$350 IIRC, and worth it IMO.) I'll report back here with some numbers.

RR - as promised, I did a brief velocity comparison of my 24" and 20" BHW 243 LBC barrels.

105gr Hdy BTHP
2.240" OAL
Varget 28.3gr

24" - 2794 fps avg
20" - 2709 fps avg
That's 85 fps difference.

I also tried a fireform load (for cheap x39 brass) with the Sierra 105gr SP and 4064, didn't write down the exact numbers but it ran about 2675 fps in the 20" and 2700 fps in the 24".

I need to load up more of the 105 BTHP bullet with Lever and compare those as well. I'll also be shortening this 20" barrel to 19", and will compare again. I'd be interested to hear what that same load of 28.3gr of Varget does in your barrel?

Hope that helps.

Thanks for posting this, Yondering. It's good to compare notes.

I still have not tried Lapua brass, sticking with Starline for now. I don't know how case capacity between Lapua and Starline would compare, but I suspect the Lapua brass will hold more powder. I get some ejector marks at 28.0 grains of Varget and ended up dropping back to 27.8 grains. I was getting about 2680 fps (@15 ft from muzzle) when the charge was 28.0 grains, so I'd say we're fairly close on velocity with Varget. I'm not real comfortable with the idea of running Varget at 28.3 grains in Starline brass---at least, not this batch. I think I tend to be a bit more timid when loading for an AR than a bolt gun...

I did shoot my 6G again this last Saturday, and I got results that make me happy enough. I shot five groups of the Lever load, and the average was well under an inch. With the two most errant shots taken out of the 25 shots total, the average was under 3/4 inch. I modified my bench technique a bit and it seemed to have made for more consistent results.

I also shot five 5-shot groups powered by 27.8 grains of Varget with the 105, and they shot nearly as well as the Leverevolution loads did. I'm thinking that Varget may be just as good as Lever in this application, but I'll cast a vote for Lever based on the fact that it meters so beautifully...and Lever DID beat it out to some extent.

I am going to shoot the 29.5 of Lever load a bit more just to see if I can refine my bench technique a bit more, then go back to playing a bit more with 90-grain Accubonds. I got pretty encouraging results with them early on and I think I may be able to wring a little more out of them with a little more AR practice-induced confidence. I'm really curious as to how they would like to collaborate with about 30.5 grains of Lever.

You can definitely push the velocity higher with Lever than Varget.

I set up my ARs with trued actions for full bolt lug contact, so I'm not as worried about breaking a Grendel bolt. As for pressure limits, the weak point is the Grendel case web and the primer pockets; you'll see loosening primer pockets first, and then expanding case heads on Grendel brass before you reach anything approaching dangerous pressure for the rifle; I would be using the same loads in a bolt action as in these ARs. It's pretty easy to work up until primer pockets just barely start to loosen a bit, and then back off. The first part of my load development with wildcats like this is to work up to max loads, seating fresh primers in each case after firing to test the pockets. When they get easier to seat than the first time, (using known new or once fired brass), that load or a little less is max. I've never run into any safety issues doing that, and generally try to settle on a load that gives at least a few loadings without loosening primer pockets, and that'd be a top end load.

I have not used Starline brass in this cartridge, but Lapua brass is generally accepted to be on the smaller side for case capacity. Anyway, the loads above were actually in Fiocchi x39 brass.
I can say the new barrel is showing signs of a little higher pressure (better fillout on those fireform loads) than my 24" barrel; the new barrel has less than 10 rounds through it while the 24" has been in use for a couple years. If your barrel is new, it may be more like my 20", and seem a little hotter for the same charge than my 24".