6XC Load Data - IMR4166, N550, RL-23, H4350

[ballisticxlr]

There doesn't seem to be quite enough variety out there. 6XC can do wonders with quite a number of powders. It's not all H4350's world (well, sorta). Coach and I did some experimenting and we have some helpful results. We'll be doing some more testing with other powders in the coming weeks.

This data came from our initial efforts at load development for my new 6XC barrel for my prone/PRS match rifle. So far it looks like we'll be using a 39.5gn charge of H4350 to get just shy of 3,000 FPS and single digit SD's with groups at about half an inch. It was a very tight decision as I would normally have chosen the actual winner which was N550 in a slightly lighter charge. N550 is super expensive compared to H4350 and we have several 8lbs jugs of H4350 on hand and only about 3lbs of N550.

Since we'll be using the same load in both of our rifles (don't forget there's a 2nd new 6XC barrel identical to mine ready to go onto Coach's gun), we will of course have to make sure the load performs acceptably from that rifle but so far, I haven't made a test load I would feel bad about using in a match.

Peep out the data below and enjoy. If you have some data you'd like to share, be sure to do so.

The 38.5 group was actually fired at the CML dot. FYI.

Chamber: 6XC (CIP)
Brass: Norma Large Primer, .013" neck thickness, .003" neck tension
Primer: Federal 210
Bullet: 115gn DTAC RBT HBN coated jumping .040"
Barrel: Columbia River Arms P3 (Polygonal 3 land) 25.5"
Muzzle Device: N/A

H4350 (well we did test it a good bit)
Brief: 37-40gn seems to be a decent window. Known solid performer. 3000fps is probably pushing pressures a bit for maximum brass life. Getting the case as full as possible seems to help SD's but pressures rise rapidly at the end of the capacity limit.
38.5gn: 2929 average, 13fps SD, .75" group
39gn: 2964 average, 15fps SD, .71" group
39.5gn: 2977 average, 2fps SD, .33" group

RL-23 (Reloader 23)
Brief: 37-40gn seems to be a decent window. Likes a full case. SD's really open without a pretty full case (including the bullet). Meters 100% terribly. Burns clean. We estimated we could pop 40gn in the case and get 2950fps. More testing coming but this was a very soft load pressure wise. RL-23 is super slow burning.
38gn: 2837 average, 28fps SD, .65" group

N550
Brief: 35-38gn seems to be a decent window. Expensive powder but turned in a stunning pair of development groups at .1" and .2" with single digit SD's. Pressures were mellow and it was a very quiet shooting load. People should start looking closer at N550. We started very soft.
36.5gn: 2892 average, 12fps SD, .2" group

IMR-4166
Brief: The load listed below is HOT by at least a full grain or two. Reduce 2 grains minimum before attempting to use. We got brass flow into the ejector hole with this load. The above noted, this is looking like it could be a stunner. Low SD's have been routine with this powder in every overbore case we've tried it in with a heavy bullet. Might be better for slightly lighter bullets than we tested.
37.5gn: 3086 average, 2fps SD, .53" group

 

[ballisticxlr]

Analysis Time

This little case seems to really like being as full as possible and/or run a little hard and put away a little bit wet if you get my meaning. We broke in the barrel with 15 shots but as you can see from the data below, around shot #6 things stabilized. By round 10 I had warmed up the barrel a bit and was vacillating between baking rounds in the chamber while I wiggled around trying to get a natural point of aim and firing quickly when I was already at a good NPoA.

All discussions of load data and charge weights come with the "don't copy me and hurt yourself" disclaimer. Don't just run my loads, work up to them. These are all on Norma brass, F210 primers, 115gn DTAC bullets and COAL at 2.8".

Around shot #6 things pretty well started to stabilize. Inconsistently going between firing quickly and baking rounds in a warm-ish chamber widened the ES a bit around shot 11.

After grinding out the first 15 rounds to break in the bore and establish a zero; this was a BRAND NEW barrel after all, we took a little break and went to check the target. The new barrel shot to such a different POI than the prior barrel that it took quite a few shots just to get on steel at 100yrds. By round 10 we were on steel at what seemed like pretty close to POI=POA. Enough to move to the BoxToBench Precision 100yrd Load Development Target and dialed the zero in on the cold zero aiming point. 5 rounds at the cold zero put us at 15 shots and we were already seeing each set of 2 bullet holes (because: adjust, fire 2, adjust) either touching or very close to it. We're pretty excited about the performance we're seeing so far.

After the first 15 shots and letting the gun cool down I settled in to go for groups for record. Starting off we did the Coach's match load (CML) which is 38.5gn of H4350. Then the RL-23 was run followed by N550 and IMR-4166. To wrap things up we came back to the H4350 and did the 39.5gn load then finished out our paper punching with 5 at 39 grains. After that I had 5 rounds left and wanted to drop a shot on the 900 yard target so we went up there and I rang the gong for 5 rounds of 38.5gn. There's a called flyer (obvious) on a couple of the aiming points. I wasn't in the most stable position and I knew it.

Polygonal Rifling vs. Enfield Rifling - Mini-Test
My velocities are a solid 150fps above what Coach gets from his Enfield rifled barrel of the same length with the same load. Ok, to be completely transparent, it's not EXACTLY the same load. We do actually seat the bullets about .100" deeper for my new barrel than Coach's barrel but I can't see 150fps difference from that. This is the polygonal rifling in full effect. Less friction because you're not engraving the bullet, you're swaging them and then twizzler-ing them, if only ever so slightly.


Powder Testing Results:
So now on to the powder results. H4350 you see the curves change shape as you fill the case up. To my eye it almost looks like someone's grabbed on to the right side and started pulling the string taut. Group sizes went down as powder charges went up but we're talking about going from a .75" group to a .71" group to a .3" group. The academic in me is crying out to be let loose with a scale and all of my reloading supplies to do a 1/10th grain at a time experiment. But, that's expensive and I have other matters to attend to. The experienced rifle shooter in me says, "You do realize that any one of those is sufficient for the 1000yrd stuff you're doing with this rifle right?" The competitive rifle shooter in me says, "Take the 39.5 and let's go home and load ammo before you change your mind again."

This is Coach's match load in my barrel. Featuring a tight standard deviation from my gun and a not disappointing .75" group this load showed promise. I just don't want to tune it. In Coach's gun this load runs 150fps slower, has a 32fps SD and turns in the same .75" groups.

The group size collapsed on this load down to .4" until I popped a flyer into it (which I called) that took the final group to .71". 40fps ES is a bit on the broad side for me out of a 5 shot sample size.

When we give it 39.5 grains the dissonant came into harmony and it made a .3" group with 2fps SD's and 5fps ES. It's running mild pressures and making within a gnat's ass of 3,000 fps where I'd draw the velocity line anyway. 2900-2950 was our target and we're there with a solid load.

Onward and upward. We still have loads to analyze. Everyone that knows me knows that after my experience with it in .243AI and 6.5x55AU that I'm a big fan of Reloader 23 despite the poor metering. It's sloooooooow burning and has been returning impressive velocities with reasonable pressures from very heavy for caliber bullets in relatively long bores from very overbore cases... as you would expect it to do if you are at all familiar with Boyle's Gas Law. We had no idea how much to start with so we did exactly what Coach did with it for my .243AI. We filled the case up to the body:shoulder junction, dumped it out and weighed it and put that much into 5 cases. It came out at 38 grains with no drop tube, just a funnel and a weighing pan.

Reloader 23 showed me with my .243AI that it likes a full case (I'm sensing a trend here with these slow burning magnum powders) and that it's pretty hard to put enough into a 6mm case based on a .473 case head to blow the damned thing up if you're seating to SAAMI/CIP lengths. 38 grains produced pretty nice velocity. A testament to the efficiency of the 6XC case setup. Still with 28fps SD's, 66fps ES and a .68" group of 5, it would "do" but I'd want to develop it more if I were to use it. We did find that RL-23 is a great option. Somewhere around 40 grains should give high 2900's at reasonable pressures even when seating bullets deepish.

That right there is porn star sloppy.

Pressing on, we have N550. A double base NG/NC powder known for being a little temperature touchy after 90F and for being pretty darned expensive. 36.5 grains of N550 gave us a nice narrow 11.95fps SD's on ES's of only 29fps. Still a little tall but velocities were touching 2900 and pressures were VERY low. It also grouped a .2" group of 5 shots. Oh man am I tempted to increase my powder budget by 25%. We figure we could fill the case on this stuff somewhere around 39 grains at 3,000fps. But, I don't want to develop a load; much less an expensive one, if one jumps out at me elsewhere, and that H4350 load at 39.5 grains is hard to beat even with stupid tight groups.

Some promise in this one. Stupid quiet load.

Now we cross into "Coach style load" territory. So far we've been on the very slow side of the slow side of the rifle powder spectrum. Now we're going to cross the street where the Beatles fans turn into Stones fans and start dragging their knuckles. Not really. Just making fun of Coach. The defining line between a "Me" style and a "Coach" style of handload is I like my powder to burn all the way down the barrel giving as consistent pressure all the way as possible without a hard spike of pressure in the case itself. My way is easier on brass but harder on barrel throats because there's more grit coming out of the case neck this way. Coach likes his pressure to form in the case, for all the little events to happen in that space and then to use the built up pressure. He also tends to jam bullets rather than jump them where I jump them at least a little bit normally.

Making a Coach style recipe means you know you'll see pressure sooner or later in your experimenting. That being the case and the fact that there was no data for IMR-4166 (which is around Varget/IMR-4895 burn speed) we elected to hot-foot bloody educated guess it. I calculated that 37.5 grains was about the most we'd want to try and so we tried that. When I say calculate I mean I used wild approximations, esoteric rules of thumb and plain old guesswork. It came back hot enough to imprint my ejector hole on 2 of the 5 brass cases so that's at least 1 full grain too much juice. It did however make 3080fps with a 2fps SD and a 6fps ES for 5 rounds. Drop a grain or two and you're right up around 2950-3000fps. What a smoker though! Too bad the pressures were simply too high. I kinda wonder if 4166 doesn't have a bit of a self dampening capacity.

If it wasn't running north of 70,000psi This would be my new load.

Below you can see the velocities as they came out of the gun during testing. You can see it took about 5 rounds to season the bore during which time the rifle sped up by 50FPS and then it's pretty much standard load development induced wavy gravy until you get to 2 very specific sections whose extreme flatness gives away that something very cool happened there and needed to be paid attention to.

So while N550 turned in the best group and ok SD's, the extremely tight SD's and the super tight group out of the 39.5gn load of H4350 has won the day. I might mess with bullet jump a little but really, I'm happy. Best not to waste barrel life.

On the topic of barrel life. Common wisdom is somewhere north of 1500 rounds but under 2000 before it's smoked. Well that's about a year and a half or 2 worth of life. That's from a conventional Enfield rifled gun. I run Columbia River Arms polygonally rifled barrels which have been giving me very long barrel life and I used only HBN coated bullets for the last 1000 rounds (it's at well north of 1300 rounds now). I shot that thing hot all the time too. Repeatedly doing things like 10 shots in 2.5 minutes basically every time it came out of the safe. After 10 rounds of 6XC my barrel was warm but not hot like the .243AI was.

My .243AI still runs like a laser. I only took it off because seating depth was longer than my magazine, but there's plenty of bullet still in the case yet. I could take it another 500+ rounds if I was willing to single feed. Pushing 115's at 3200 can't have been gentle on it and the expectation was that by 1000 rounds it was going to look like 5 miles of rough road down the bore but, it's not. It's smooth as glass still and makes tiny 1000 yard groups. So if we take this barrel life thing to mean the point at which the boat tail is up inside the neck of a loaded case when seated equals cooked, my .243AI will have gotten something like 1800 rounds before its death. Thanks to some combination of the HBN coating and the polygonal rifling.

 

[Frankr]

GO to the CCI BR2 primer ...try RL26 and RL17....RL17 is my favorite. Although I have heard great thing about superformance and one of the N powder not sure if it is N550 or not. But I am happy with RL17. been shooting it for years in the XC. RL26 does real well in warm temp. maybe the best. I had not problems getting 3,150 FPS from a 26" barrel in bug holes with a 115 Berger.

 

[urbanrifleman]

I can't imagine why N160 wouldn't be ideal and would be much easier on barrels.

 

[ballisticxlr]

I wanted to try RL26 and go for 3050fps. I knew I could easily get that but all I had was RL-23, which I know if I went up a few grains it would have really shined. They're both getting some stunning velocities in overbore cases. Unfortunately it wouldn't have been as helpful as baseline data for the barrel life comparo we're doing now. N550 has a lot of promise. Something a little more energy dense with the same basic burn speed would probably do better. I surmise that N160 might just be that thing.

The powder choice for us is already set for our match loads. We have kegs of H4350 from the same lot on hand with too many reasons that using it makes sense or is actually necessary; we do long term experiments with our match rifles & for these barrels it's necessary, and we're not needing to speed demon them. I wanted 2900fps & super low SD's and we got it.

Coach and I have opposite philosophies on loads. He's from a more different competition world than I am which explains it. I like a little slower powder, a heavier bullet and a longer barrel. He's more of the mid-range on all 3 type. He's from a world of 220-550yrd shots at targets that are 4MOA or more while I cut my teeth on >1000yrds with 2MOA targets. It's been an adventure getting him to accept that there's a reason for my way in the longer range games that run smaller targets.

What I really see is that now that I get a fresh look is from 38.5-39.5gr of H4350 it almost doesn't matter how much I put in, it shoots to the same point of aim, groups fine and makes an aggregate SD of about 25fps. That's just stupid stable.

 

[urbanrifleman]

Tubb shoots H4350. His load is 39 grains with the DTAC.

 

[STOMP442]

39.5-40gr of H4350 has always been a sweet load for the 6XC. The last few I have done I have switched to R16 and seen the same great accuracy with a bit added speed as well. In my personal rifle I am running 40.5gr of reloader 16 with a 110SMK and getting 3070fps with an SD of 7. I am using Norma brass and CCI #200 primers. Brass is still going strong on its fourth firing now and will consistently print half inch or less at 100.

 

[urbanrifleman]

R16 IS SWWWEEETT STUFF.

 

[urbanrifleman]

Alliant powders are sweet across the board really.

 

[ballisticxlr]

Yep. Very aware of David's findings. I used a variation of his spec reamer print, modified for a slightly tighter neck that matches perfectly with what the Exact Shooting dies I'm using and neck turned brass are turning out.

 

[Frankr]

Yea RL16 is a powder I would like to try. What about the story of RL17 which I know just switches out to H4350 loads with 100 FPS more velocity but what about the story that it is easier on throats due to the way it burns and that you could expect longer barrel life with it. I really don't know if there is any truth to that or not. That is what I have read. The RL17 has been the powder I have shot mostly in the one I have now. I have shot a good bit of H4350 and a few other powders in it and I run a hot load. 105 HVLD 40.0GR RL17 Norma brass CCI BR2. Pac Nor SSM #3 sporter 26" I get 3,150 FPS. I have around 1,800 rounds through it and have not bore scoped it. Throat does not seem it moved out much and still shoots sub 1/2 MOA on a good day. I'm a big fan of the 6XC, it is just right. often imitated never duplicated. Best 6mm class cartridge out there.

 

[Willow]

39.6gr of H4350 seems to work reasonably well in my rifle (MPA chassis off an Atlas bipod) - weight sorted Nosler RDFs are actually holding the 6 ring (10 ring in the US) which is a surprise.

 

[TroyG]

I'll second VV160. When I started shooting 115gr Dtacs in my 6x47 I needed something in between H4350 and H4831. 41.5 grs in my 6x47 gets me 3065fps with 5fps extreme spreads. Barrel is a 236 Bartlein 28" long. 105 freebore. 205M primer.

 

[ballisticxlr]

We've taken some more measurements and charted the measurements taken of the last couple years and done the math and it looks like we have some interesting throat erosion rate data. It looks like backing down from 2950+fps to </=2850fps netted a ~25% reduction in the rate of throat erosion. That data should be doped by the fact that the sample size is very small. When I plug the numbers into my handy little calculator they come out right. The real change on target at 1000yrds is half a mil. The windage change is .1mil. Some food for thought. You can seriously extend the life with just a little dunk in speed.

 

[ballisticxlr]

So wait, you're refuting the statement, "You can seriously extend the life with just a little dunk in speed."? I have that right? Or are you refuting the fact that the measurements we took showed a slowing of throat erosion when the speed was pulled back? Or are you refuting the open admission that the sample size was indeed very small and that the information should be taken with a grain of salt? Which part? Sometimes trying to poke someone in the eye just makes you look well....

 

[urbanrifleman]

He does that a lot.

 

[Baer45]

I’d like to know the h4350, 115 dtac loads w/uncoated bullets. I think with6xc especially, it would be good to state whether we are shooting coated or uncoated bullets. I appreciated one of the earlier post specifying Moly....

 

[Baer45]

Tubb shoots H4350. His load is 39 grains with the DTAC.

Remember he is shooting coated bullets

 

[eric32]

can anyone confirm if that is the load for his 6XC Precision ammo???

 

[Baer45]

39.5-40gr of H4350 has always been a sweet load for the 6XC. The last few I have done I have switched to R16 and seen the same great accuracy with a bit added speed as well. In my personal rifle I am running 40.5gr of reloader 16 with a 110SMK and getting 3070fps with an SD of 7. I am using Norma brass and CCI #200 primers. Brass is still going strong on its fourth firing now and will consistently print half inch or less at 100.

Are these with coated bullets?