Barrel Life, Accuracy and Velocity – Columbia River Arms Wins!

I’m running a .243AI set up by Columbia River Arms (formerly Black Hole Weaponry) about a year ago. It’s a pre-chambered drop-in with a pretty tightly necked chamber set up by CRA. I’ve got it set at zero head space so between that and the Ackley Improved case there’s zero brass growth after 4-5 firings.
It’s got just a touch over 1000 rounds down the pipe and appears to be going strong. So far I’ve only had to push the bullet out .010 and add .1gn powder to keep everything tight to my original load spec. I don’t know what kind of life the pipe has left in it. I’m running 115gn 6mm DTAC bullets at 3200fps with a modest charge of very slow burning powder (RL-23). Pressures are pretty mellow but it’s, for sure, burning that powder all the way down the barrel. This is evidenced by the fact that there’s just the tiniest bit of flash in the first chamber of my brake that’s visible in low light conditions.
Corey testing out the CRA barreled Hot-Dog Gun at 900yrds.
In a more conventional barrel I’d guess I’ve have between 100 and 300 rounds more life before it’s just not match grade anymore (based on a 1200-1500rnd life expectancy) but I would also expect substantially more throat erosion than I’ve gotten to this point if that were the case. I started with uncoated 108ELD’s and quickly went to HBN (hexagonal boron nitride) coated 115DTAC’s. The rebated boat tail and pointed tip on the DTAC’s pulls the BC up to .620 which puts me up to 1mile of supersonic range. So far it’s been as far as 1500yrds and proven itself very capable.
Out of the gate I was getting 10 shot groups like those below (these are fireforming and load development groups, the first loads out of the barrel). After a little refinement they settled down to repeatable .5-.7MOA across 10 shots with single digit SD’s (5fps across over 100 rounds loaded in 3 sessions). The thing has since then been ridiculously consistent. Once I found an optic I could deal with in matches (I hated the turrets on Vortex Razor 2’s, U.S. Optics ER-25 was just too damned big, SWFA 16×42 was too much minimum magnification, etc… nitpicky stuff) in the form of the U.S. Optics SN3 3.8-22x58mm with a custom made PRS oriented reticle and 35mm main tube, I really started to have some fun with it including punishing the rifle with 10 shots strings in 90 seconds on hot days (hey, that’s the stage on the match). I wasn’t going to take it easy on this barrel.
I crossed the 1000 round mark last month at a match and I’d thought the barrel might be toasted then due to some repeated and huge misses on otherwise simple shots. Turns out it was just me. I clearly did something wrong to make those misses. I know that because I went out again this month to teach a long range precision rifle class and demonstrated most drills and techniques with my .243AI. It started out by making a .5″ 5 shot group @ 100 yards. At the end of the class it got to be time to see what I could do under some performance pressure so I got right down into the prone with my Columbia River Arms barreled Savage 10FPSR, dialed the parallax on my U.S. Optics SN3 3.8-22×58, extended the Accuracy Solutions BipodEXT, set the Accu-Tac SR-5 bipod to 45deg forward and slapped a 6″ 900 yard 5 shot group on the steel rapid fire in direction shifting 5-15mph winds while the student body looked on.
I’m using 45.6gn of powder now. It started at 45.5gn of Reloader 23 in a very tight chamber with Hornady brass. By the book one should expect to see 3000-3100fps with 44-45gn of powder in a 24-inch barrel with 100gn to 105gn bullets. I’m getting 3200fps with 115’s and only 45.6gn in a 26″ barrel. I’d expect to see 25fps or thereabouts per inch of barrel after 24″ but certainly not 50fps per inch from barrel length alone and not with a heavier longer bullet. I’m also not even remotely pushing this round. I can go another 3gn of powder before even starting to flatten primers but 3300fps only serves to damage steel targets and is technically against the rules. 3200fps is max so that’s what I’m running. I already damage quite a few targets at 3200fps anyway so I don’t need any help in that department.
Hot Dog Gun in .243AI. A Savage 10FPSR with bits from MDT, XLR, Magpul, BipodEXT, Accu-Tac, U.S. Optics, Seekins, Weaver, and JP Enterprises. Painted to look like a Dodger Dog. Go Dodgers!

Typically as I wear out a barrel I’ll see it shoot fine, fine, fine, start to open up, plateau, fine at plateau, open up more, open up more, open up more and it’s all downhill from there. After the plateau if it doesn’t quickly plateau again it’s getting there and it’s time to start planning my next pipe. I’ve already started planning my next pipe, a 6XC to match an identical one we’ll put on Coach’s gun. Nonetheless, this barrel is still good. Question is, for how long?

I know from prior experience that I get a little longer barrel life from the polygonal rifling that CRA uses. I’ve not burned out enough to get a useful statistical value for how much longer but I can speculate. Right now, given the throat wear and grouping we’re getting on Coach’s existing 6XC; which is at 1500 rounds so far, and the expected life of that Shilen barrel being around 2200-2300 rounds, I’m estimating; and trying to be extremely conservative in that estimation, that I’ll make it to 1800 rounds or further before this pipe is really done for match work.

The difference between .243Win (right) and .243AI (left) is shoulder angle, body taper, performance, case life and barrel life. The loaded round has a 108gn ELD-M in it and 39.5gn of RL-23 for fireforming.

That’s almost 40% longer barrel life than I initially anticipated, if it gets there. We knew that the HBN coating on the bullets would help barrel life so I’m confident it’ll get to 1500. We knew the CRA polygonal rifling means no sharp edges for the burning powder plasma to ablate would help too. We knew the Ackley shoulder angle would keep the flame vertex inside the case neck and that that would help too.

It’s just with all those things helping, we have no idea where this train is going to stop. If I go on throat erosion alone, calculating how far until the boat tail is up inside the case neck, then I’m looking at almost 3000 rounds of barrel life. That’d be 230% of anticipated barrel life and I just don’t see that as being realistic given the amount of powder being burned and the rapidity with which I shoot in matches. I’ll get that barrel pretty hot sometimes.

Shooting stage 6 at my monthly match with Hot Dog Gun in its current form. Targets are on the opposite hillside from 300-700yrds away.

I get higher velocities than one might expect from less powder than one might expect. I get longer barrel life than one would expect. I get amazingly accurate and consistent performance than one might expect (especially for a drop-in pre-fit). The thing turned out sub-MOA groups with fire forming loads. It did not like 55gn varmint bullets at all though. No surprise on an 8 twist. The chamber on it is very tight. It’s meant for someone who’s willing to turn necks if necessary (my inside neck diameter on a fired case is .2435). Thankfully I don’t have to neck turn. Lucky me, everything just fits perfectly. When I ordered it I specified that I would not be put off by a possible requirement to neck turn brass if that were what their reamer would require.

Much of this situation was and is by design. When I initially decided I wanted a fast 6mm I found what my options were and then picked a chamber that would maximize performance, brass life and throat life. I picked a powder that would give maximum velocities without pressures being tall or a lot of flash. I picked projectiles that had very high BC’s and would be routinely available in boxes of 500 (including a primary and backup bullet). I set up a load that performs identically with both bullets and shoots to the same point of aim, just in case I’m unable to re-up on one I can use my backup supply of the other.  I bought all of the brass, powder and primers I expected to ever use in this barrel ahead of time (8lbs of powder, looks like I might need another 8lbs). Everything about the gun except the optic I’d settle on was decided before the barrel even arrived. Best of all, the barrel was set up to CRA’s rigorous standards which means it was done perfectly and it was under $400.

Hot Dog Gun before it was even painted. Getting some early long range testing done. Both Vortex Razor 2’s are now replaced with U.S. Optics glass. I just like USO. What can I say, they work for me.

So why am I building a 6XC now? Well Coach and I shoot together. It’s best if we have one set of ballistics DOPE and shoot the exact same load through identical chambers. It’s actually best if we share a gun but I like mine and he likes his. We find that when we can use drop and wind corrections from each other that we win more matches. Duh. If I run a stage and miss 2 of 7 shots on wind, I can tell him what the adjustments would have been and what the wind was for those misses then he can adjust accordingly and pick up those points and vice versa.

So, I’ve got 2 new barrels on the way from CRA, 27″ 6mm 8-twist unprofiled blanks which we’ll have a local gunsmith chamber, thread and profile for us in 6XC with a .267 neck (CRA doesn’t have a 6XC reamer or I’d have them do it). We’ll set them up for zero head space to minimize brass growth and then we’ll use my new ExactShooting.com Custom Collection sizing die to perfectly set the head space and neck tension of our reloaded ammo. We’ll be as close to shooting the same rifle as two guys can possibly get. If you want faster velocities, longer barrel life and one heck of an accurate barrel, you could do a lot worse than to drop Columbia River Arms a line.

.243AI Dimensions

6XC Dimensions
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