6mm Creedmore & 105 gr hybrid

[Stats Shooter]

I have finished load development for a Bergara 6mm creedmore with 26 inch barrel. I used H4350, Lapua small primer and small flash hole brass, cci 450 primers, and the Berger 105 gr hybrids. Since it is a newer cartridge I thought I would share.

First off, I either have a hotter lot of 4350, or the cci 450’s give higher velocities than standard large rifle primers. I achieved what quickload says is max velocity with about 2 grains less powder.

I first did a modified version of Berger’s jump test. I started at 0.010” and went home out to 0.150” in 0.030 increments using 40 gr powder. The best groups were 0.010” and 0.100” off the lands (8 shot groups). I then checked 0.020, 0.030, 0.090” and 0.110.

Groups were best at 0.020 and 0.090”, both about .9 moa at 200 yards. I selected 0.020” since I prefer more space in the case if it will mag feed, and it will in bergara’s mags.

I then began working with powder charge. I use a Labradar btw for velocity.

I began at 40 grains and worked up to 41.6. I tested in 0.3 gr increments, initial testing was round robin 8 shot groups.


CAUTION: The following post includes loading data beyond or not covered by currently published maximums for this cartridge. USE AT YOUR OWN RISK. Neither the writer, The Firing Line, nor the staff of TFL assumes any liability for any damage or injury resulting from the use of this information.


40 gr: .93 moa, ES 20, SD 9.6, 3070 FPS

40.3 gr: .66 moa, ES 13 , SD 5.7, 3102 FPS

40.6 gr: .78 moa, ES 13, SD 4.9, 3113 FPS

40.9 gr: 0.8 moa, ES 19, SD 6.4, 3130 FPS

41.2 gr: 1.25 moa, ES 13, SD 4.4, 3138 FPS

41.5 gr: 1.41 moa, ES 20 , SD 6.3, 3147 FPS

Above 3130 FPS had pressure signs, extractor wipe marks and 3150 had a heavy bolt.

I then re shot 40.3, 40.6, and 40.9 to try and find a difference, 3x5 shot groups each. 40.3 and 40.6 were best averaging .63 and 0.68 moa respectively.

I then tested them both at 500 yards, 25 rounds each. Wind 5 mph from 180 degrees.

40.3 had a velocity on that day of 3107, ES 21, SD 5.5 and 3-4” 5 shot groups at 500 yards. Velocities numbers for all 25 rounds counted as 1 series.

40.6 had a velocity of 3119, ES 19, SD 4.7, 3-3.5” groups at 500 yards.

So I have settled on 40.6 gr, 0.020 jump at approximately 3120 from a 26” barrel.

Some have suggested 42.5 gr with this combo, but that would be awfully hot with my combination based on my observation and labradar data.

Hope this is informative.

[Unclenick]

Thanks for sharing. My old Hodgdon manual says the canister grade IMR powders have their burn rate held to ±5% and not the ±3% held by their Extreme line of powders. In QL is that enough to account for the difference?

[Stats Shooter]

Nick,

I adjusted the burn rate in QL for H4350 and it comes pretty close to accounting for the difference. You say hodgdon notes +/- 3%. lots of people claim this bullet performs best at around 3100 fps, which is usually achieved between 41.5 gr and 42.5 gr 4350. QL confirms this. Also, generally using 24 - 26" barrels.

So, if 42 gr is the average required powder to achieve OBT, then 3% less powder is 40.7 gr. I'm sure it isnt a perfectly linear relationship though. I adjusted the Ba in quickload up 3% and it comes within a few fps. Close enough anyway.

[std7mag]

Stats,
That's some decent speed with H4350 and a 105gr bullet.
The Hybrid isn't supposed to be as critical of seating depth as the VLD.
Seems the VLD likes it right up against the lands, (my case) or way off the lands (not my case).

Something you might want to try with those 105gr bullets is RL26.
Did really well in my wife's 243 Win with 24" barrel and Hornady 105gr Match.
I was using Fed 210M.

Keep on shooting!
Maybe one day we'll match WendyJ's Tikka in 7mm-08.

[Stats Shooter]

Thanks for sharing. My old Hodgdon manual says the canister grade IMR powders have their burn rate held to ±5% and not the ±3% held by their Extreme line of powders. In QL is that enough to account for the difference?

One thing with QL Nick, if I adjust H4350's Heat of Explosion / potential number from 3760 (the default) to 4100, I get QL to track very closely with my observed velocities up and down the ladder. I doubt I can trust the pressure number it comes up with as they are lower, but at least I can track the velocities.

The load I have chosen, at 3110 - 3120 fps is right near 62000 psi, which is max for the 6 CM,at 42.8/9 gr of H4350 using the standard Heat of Explosion potential.

My OAL is 2.832, Trim 1.90, barrel 26" using the 105 berger hybrid if you want to try it. And QL states overpressure beginning above 3120 fps, which my observations confirm.

[hounddawg]

I use the 107 SMK's in my 6CM with considerably less powder and of course lower velocity down in the 2700 - 2800 range. I only shoot to 800 right now and get good accuracy. Here is a 300 yard target with 17 rounds at around 3/4 MOA group

[Stats Shooter]

Nice shooting. 3/4 @ 500 yards is tough. Gotta have favorable conditions.

@ 1,000 yards I'm usually thrilled with MOA, especially in the horizontal. It gets tough with the mirage at those distances to hold consistently. I have to use florescent paper with a high contrast bullseye like white. Otherwise in the summer it gets awfully fuzzy and I'm down to 20 power

[hounddawg]

I still need to do a lot of work on my technique and wind/mirage skills. At matches I just seem to overthink all the time. Only been competing a couple of years though and have seen improvements. Loading good ammo is the easy part

The 6CM is a dream cartridge to load for anyway

[Stats Shooter]

I still need to do a lot of work on my technique and wind/mirage skills. At matches I just seem to overthink all the time. Only been competing a couple of years though and have seen improvements. Loading good ammo is the easy part

The 6CM is a dream cartridge to load for anyway

It really is...just like the .243. You can almost just pick a load a go with it. For me to take an $800 rifle and come up with an honest .6-.7 MOA load, at 500 yards, no modifications, is pretty impressive by Bargara as well which is who made the rifle.

keeping in mind again, that I report the worst groups as the accuracy. I have shot several sub .5 moa 5 shot groups since, but mostly they are .68, .65, .72 etc.

[hounddawg]

I have shot several sub .5 moa 5 shot groups since, but mostly they are .68, .65, .72 etc.

once I think I have the seating depths and powder charge where I want it I like to do a couple of ten and fifteen round targets at 300 - 600. The wind was kicking on that test but it was pretty steady, I shot the group when the flag was at about a 45 angle, over correcting of course

Only thing I have against the 6mm CM is the barrel life. Now that I have a load for it I will just shoot that load till the barrel burns out and replace it next spring