6XC Load Data – N550, RL-23, H4350, IMR-4166

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. 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 leave it in a comment and I’ll be sure to approve it for publishing.

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. Meters 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. 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 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

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