6XC Load Data - RL23, N550, IMR-4166

[BallisticsGuy]

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 (Coach and I) will be using the same load in both of our rifles; as 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 too but so far, I haven't made a test load I would feel bad about using in a match. I'm not sure these rifles will seriously dislike anything we put in them.

Peep out the data below and enjoy. I did this mostly to see if there was benefit in other powders. N550 indeed looks pretty sparkly. Note in groups below, called flyers are excluded from groups for purposes of measuring. I was on a pretty uncomfortable platform and was having a hard time rebuilding my position after each string.

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

Chamber: 6XC (CIP chamber w/ tight neck)
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
Dies: Exact Shooting Custom sizer w/ .266" bushing, Redding micrometer seater.
Press: Sizing - RCBS Rockchucker, Seating - Dillon RL550
Rifle - Savage 10FPSR home-build: Columbia River Arms 3-land polygonal 8-twist, .800" muzzle, LSS chassis, US Optics 3.8-22x58mm

Atmospherics: 65F, 29.0inHg, 90% RH, overcast, light to no wind.


H4350
38.5gn: 2929 average, 13fps SD, .75" group
39gn: 2964 average, 15fps SD, .71" group
39.5gn: 2977 average, 2fps SD, .33" group (approaching max)

RL-23 (Reloader 23)
38gn: 2837 average, 28fps SD, .65" group (VERY SOFT LOAD)

N550
36.5gn: 2892 average, 12fps SD, .2" group (VERY SOFT LOAD)

IMR-4166
TOO HOT by at least a full grain but promising. Reduce >2 grains before attempting to use. We got brass flow into the ejector hole with this load. The above noted, this is looking like a honey waiting to happen. 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. Copper fouling eliminator and temperature stability are listed on the can as features.
37.5gn: 3086 average, 2fps SD, .53" group

 

[Canhunter35]

Concerning temp stability, how does N550 compare with h4350?

I've used n140 but the cost and temp instability has me moving away from it

 

[BallisticsGuy]

About like most nc/ng powders. ~1fps:deg until about 80-90F or so then things get interesting. That's based on my more extensive use of N550 in a 7BR.

 

[98Vandal]

Have you tried any other bullet weights? I'm building a 6XC and recognize that the 115gr bullets are likely the best but was curious about the other options.

 

[BallisticsGuy]

In a variety of 6mm chamberings we've gotten roughly identical velocity performance with 108 ELD-M's to 115 DTAC's with the same powder charge. DTAC's are a bargain when you count that you can get them HBN coated for the same cost as uncoated (and not much different cost to ELD's) and Tubb has a pretty good price on them anyway. ~30 cents a bullet. I got a little vial of Tubb Dust free with my last order. They're a pure target bullet for sure. The closed points would be terrible on game of any kind. Just pencil on through probably. they're darned near as long as a pencil.