**6 Creedmoor**

[kyotekiller25]

Gotcha! I kinda figured the 107s were a little shorter, thus the shorter OAL length.

I haven't played with mine a whole lot either since getting my custom built 223 wylde and getting it broke in.

I'll probably wait until I have 100 rounds through the 6 creed and get all my brass fireformed before I really start getting serious with my load development. As it is, I feel it's pretty close. Gonna be somewhere around 40-40.2g H4350 at 2.795" or so. I plan to load in .1g increments and shoot at 300 yards to find the right charge, and then see if tweaking the depth a little shorter will change anything. And lastly, trying a couple different primers after I've nailed the charge/seating depth.

 

[Coyote777]

18” 1-8t X-Caliber
88g Berger FBV
CCI 450 Magnum Primer
H4350-45g
BSD-2.130 (.15 jump)
COAL-2.819
Avg FPS-3180

 

[blksno]

26" Proof Prefit
Peterson - CCI 450
RL16 - 115 Dtac
3100 fps

 

[Old Corps 8541]

How much RL 16 ?

 

[diggler1833]

Guess I got it as good as it will go for the 107 SMK / H4350 in this barrel (26", 1:7.25 Bartlein). I had two distinct plateaus in velocity for groups (not a single shot). I usually don't believe in that stuff, but this barrel has shown it enough that I'm starting to drink the "flat spot" kool-aid * in this barrel.

I beat myself about the head and neck trying to get good accuracy out of that slightly higher charge weight. 1/2 - 3/4 MOA...no better or worse.

Loaded back down to the more promising charge weight that gave good results earlier. I did not do as well as last time, but I had more wind today too (excuses, excuses). Loaded one last group and shot it at 300...it held up rather well in the wind. Guess I'm done.

Today's tests:

I tried to move the dime far enough away that somebody wouldn't think I was trying to cover anything.

Whole target:

What I was trying to duplicate and failed:

^ This is 40.0. I ran 39.9 and 40.1 over a chronograph and had an ES and SD average of 25.5 and 8.5 between the two. Velocity is going to be right at 2,950.

 

[TheOfficeT-Rex]

Just dropping a little more N160 data, as I don’t see a lot and VV powders are becoming the cheaper option…

22” suppressed, Lapua cases/CCI 41/N160/105/2.7” OAL

This was shot left column down, then back up the right. The rifle was allowed to “cool” between strings (about as much as you can in with a little shade, no wind, and high temps). The differences in velocity (in red) for 5 shot strings are… something.

I’ve suspected N160 in this cartridge of being a little temp sensitive when it’s hot for a while now. My previous outings with virgin brass at 70*F averaged 2760 on two different 69*F days, same charge with once fired nets about 2823 at 89*F… unless it’s the last group of the day, then the same charge on a hot barrel averages 2865. I haven’t quite wrapped my head around it yet, but I’ll probably be vacuum sealing some rounds to do some temp testing next time out.

It could have been that the barrel was late to speed up (200 rounds then vs 275 now), 40 rounds of fouling, or maybe the difference in sizing/mandrel/the humidity while I was loading – hard to say. I honestly expected a small drop in velocity once everything was fireformed/resized, which is why I added more powder from the baseline of 41/2760.

Considering the total of 40 rounds aggregates under 1” with a .21” mean radius (and the fact I know that I possess neither diggler's oustanding marksmanship nor penmanship), I think I’ve reached the ‘stop messing with it’ phase- I’d just like to have a good temp sensitivity input to load into the kestrel and to add a little more confidence.

Thanks for coming to my ted talk.

 

[TheOfficeT-Rex]

I’ve suspected N160 in this cartridge of being a little temp sensitive when it’s hot for a while now.

A quick follow up: Sometimes I’m wrong.

TL;DR – in my testing, N160 in the 6 creedmoor produced a gain of approx .77 fps per degree F temp increase, in line with the .75fps/1*F I’ve seen listed elsewhere.


I vacuum sealed four 5-round packets and placed half in a thermos with 60*F water, and half in a thermos with 110*F water. They were allowed to normalized for three hours before shooting. I used a food thermometer and recorded the water temp in the thermos. Speeds recorded over a lab radar. While I am certain there is error both in how I estimated round/powder temps, experimental setup, and low round counts, it is in line with what I should have expected. I’m dropping the issue and going back to focusing on basic positional shooting. This was likely the last bit of load development and testing I’ll do in 6CM - this is my last barrel and I don't see myself coming back to the cartridge.

 

[Cody S]

load data for my last 3 6 creed barrels was split between two loads, the higher of which I advise you not to try because I had a custom chamber and gain twist barrel
all loads with 115 dtacs and Federal 205m and lapua 6 creed srp brass
40.5 H4350 with dtac at 2.8" gives 2977 currently and usually around 2950 for me
41.4 H4350 for 3125fps (and excellent accuracy) at 2.8"
fwiw that is about 20-30 thou off lands for us.
barrel contours have been M24 or heavy Palma, 28 inch finish with a 8.5 transitioning to 7.5 left hand gain twist.
only downside to 6 creed is the 1000-1500 ish round barrel life

 

[diggler1833]

You aren't kidding about barrel life . I went away from the 6CM because of that, but came back again. It is hard to argue against that midrange trajectory/deflection, along with achieving it with so little recoil.

Was cleaning my latest 6CM barrel and a 6.5x47L this weekend. Stuck a borescope down both tubes to verify that I was back to bare metal. The 6CM barrel with exactly 240 rounds on it had more fire cracking and erosion than my 6.5x47 with 625 rounds on it. Granted, I'm not standing on my x47 barrel (123gr @ 2,815 FPS).

Since I don't shoot comps, and 10 shot strings over 2 minutes is as fast as I'll ever take her, I'm planning on 1,400 rounds before I pull it for good (preemptively). That's about how long my last went.

 

[Cody S]

I should have mentioned we basically only use our 6 creed barrels for comps so pretty much only 10 shot strings in about 30 seconds give or take, then the barrel could down completely before the next stage. and if we go with a normal, "sane" load I expect 1500 before she gets squirrelly or gives up the ghost.
we broke so we usually run them right up until they won't shoot under 3/4moa with tuned loads.

 

[Cody S]

I no longer borescope my barrels, it's too scary.

 

[diggler1833]

I no longer borescope my barrels, it's too scary.

Definitely the #1 source for made up barrel problems .

I still do to check my cleaning and for carbon ring development.