Group size not so great…..suggestions?

[BuffaloBill]

I recently put together this rifle:

Tikka T3,
Brux MTU .236, 8T chambered in 6 Creedmoor (SAAMI spec Mason reamer) finished length 28.39”
KRG Bravo chassis
Ross 4-port brake
Warne 20MOA base
Leupold rings
Vortex golden eagle

I’ve only built a few rifles so am certainly not an expert. Yet I think I have a reasonable understanding of what’s important when striving for precision(?). Shot it over this past weekend and today, and so far nothing to get too excited about. I’d appreciate suggestions on what to try next.

The 1st target pic was shot in an attempt to find a powder node. Quickload predicted a charge of 44.07gr of H4831SC to land on a barrel time for a node at about 56Kpsi for a bit under 3100fps. Chronograph data showed the 44.0gr 3-shot group to yield the lowest ES (3019, 3020, 3020, lower velocity than Quickload predicted). The elevation signature of this page of groups isn’t very obvious to me, but chose the 44gr powder charge for the seating depth test on the 2nd trarget.

This is my first experience with the Berger 105gr VLD, and was hoping the first page results could be improved by varying seating depth. I read that the VLD can be picky regarding seating depth. I sort of followed the Berger recommended test but didn’t go beyond the 70thou jump. The groups on the second test didn’t really show me much however.

Thinking there must be something fundamentally wrong, I thought perhaps bedding the action in this chassis might be a good next step. I just tested for stress however, as the rear action screw is backed off or tightened, and measured only 0.001” deflection per the setup in below pics. I laid a piece of solder between the lug in the chassis and the slot in the action, to confirm clearance there. My solder is 16thou dia and was not squished. So the lug is not bottoming out in the action cross slot.

I’ve not yet tried another powder, primer, bullet, or scope. This powder works so well in a 243AI I built about 11 yrs ago, and I had some on-hand. Cases are Lapua with turned necks. The 1st target was with new cases. The 2nd target used these once-fired resized in a Whidden bushing FL die, to set the shoulder back 1 thou. This is the first use of the scope. I can say that the turrets certainly seem to repeat positions. The mount and ring screws have not come loose.

Thoughts, suggestions? I should have someone else shoot it to help rule out shooter error. I can say the setup/conditions for today’s seating depth testing made it easy to hold crosshair on aiming points. I took a lot of time during the machining steps to achieve the best possible concentricity. Again, take that with a grain of salt as I’ve not done this a hundred times. This is my first experience with a chassis.

 

[Dusty Stevens]

I too think your powder charge is off. Leave the chrono at home, jam your bullets .010, and find your ideal wide powder charges and your max load then start coming off the lands. There is no place for a chrono at this stage of load development, the target is what matters

 

[Bc'z]

Soooo..
You rifle read and understood what quick load was puttin down?
Do a proper load work up weather it be a ladder or OCW test and holler back.

 

[Ranger188]

If I'm wrong correct me but, I didn't see what your torque setting was
with the Bravo chassis. I think they recommend 65 inch pounds.
Make sure your torque settings are correct on the the scope, mounts
and pic rail.
Next, if you can find it, RL 16 or H4350 are better powders for
the 6 creed. They are showing up here and there.
I know people use H4831 and vld's
Try the Sierra 107g bullets. Good bullet and easy to find a tune.
I think those few things could help with your groups.

 

[spike-55]

listen to Dusty and RKS. each gun is different and don't assume what works for one will work for another.
for my 6 creed i use vapor trail V-tacs or the berger boat tail targets. bests powders have been Rl-16 or H4350
RL-16 41.1 gr should get you around 3100
H4350 41..5 gr should get you around 3150
start under and work up if you use these powders, they are a faster powder than h4831sc
stan

 

[spike-55]

i will say that I have had a couple of Brux .236 barrels that would run slightly slower and pressure a little quicker than other barrels that were .237. they shot lights out but they were always a little quick to pressure up with the same load data as other rifles with the same load data and different barrels. didn't make me not buy their barrels, I just had to keep in mind when developing loads for those barrels. or it could just be me being goofy!!!
Stan

 

[BuffaloBill]

Thank you all for the feedback. It’s encouraging to hear suggestions about finding a different powder and/or charge weight. In the past I may have just gotten luck, landing on a powder early in the process that shot well. I’ll see if I can find some H4350. I do have some Amax 105gr on hand also.

RKS,
Yes, it appears my seating depth test was a waste! I’d read about the VLD being sensitive to seating depth but didn’t know to what extent that might affect group size. It was a crude adjustment, hoping something would change the result.

Dusty,
I’ll leave the Labradar at home. Was a new toy so had to try it out. What weight increments do you like for a first wide check? These once-fired cases measure 51.1gr water. I had used .3gr increments on my first go.

Bc‘s,
Yes, my wife wonders how I can spend so much time reading on these forums. Quickload is fairly new to me. The first time I used it was for the 243AI I mentioned. I was suprised then how closely it predicted a load that my OCW result seemed to back up. That was maybe a coincidence. What distance do you suggest for testing, and what powder increment?

Ranger & spike,
I hear H4350 mentioned a lot. I’ll have to find some of that.
Yes, KRG specifies 65inch pounds and that’s what I had used.

 

[jelenko]

Quickload is fairly new to me. The first time I used it was for the 243AI I mentioned. I was suprised then how closely it predicted a load that my OCW result seemed to back up. That was maybe a coincidence.

Not Quickload, but I've been using GRT tools [does essentially the same as Quickload].
There's a tutorial on using GRT to find accuracy nodes. In it, the speaker says that about 40% of the predicted nodes turn out to not be a node. [I think the level of accuracy they consider a 'node' would be in the 1/2 MOA area].
In my experience [223 only], actual nodes are usually within +/- .2 gr of the predicted nodes.
I have had times when I had to extend well beyond the .2 grains.

 

[BoydAllen]

It is so easy to identify nodes by shooting, why even bother with software, especially given the difference in reliability? In any case, your primary reference should be your targets. If the distance that you are shooting requires excellent ES, work up an accurate load with a powder that fills the case and then see what you can to with your loading process to optimize your ES. Another tip that is not commonly tried is to do your loading at the range, shoot all shots over a chronograph, and always use a couple of wind flags. I am amazed by the number of people with expensive equipment who do not use flags. When we are working up loads the idea is to minimize variables within a given group.

 

[Bc'z]

Thank you all for the feedback. It’s encouraging to hear suggestions about finding a different powder and/or charge weight. In the past I may have just gotten luck, landing on a powder early in the process that shot well. I’ll see if I can find some H4350. I do have some Amax 105gr on hand also.

RKS,
Yes, it appears my seating depth test was a waste! I’d read about the VLD being sensitive to seating depth but didn’t know to what extent that might affect group size. It was a crude adjustment, hoping something would change the result.

Dusty,
I’ll leave the Labradar at home. Was a new toy so had to try it out. What weight increments do you like for a first wide check? These once-fired cases measure 51.1gr water. I had used .3gr increments on my first go.

Bc‘s,
Yes, my wife wonders how I can spend so much time reading on these forums. Quickload is fairly new to me. The first time I used it was for the 243AI I mentioned. I was suprised then how closely it predicted a load that my OCW result seemed to back up. That was maybe a coincidence. What distance do you suggest for testing, and what powder increment?

Ranger & spike,
I hear H4350 mentioned a lot. I’ll have to find some of that.
Yes, KRG specifies 65inch pounds and that’s what I had used.

My wife gives me guff all the time about being on the forum, but she has to admit WE have met some great folks from it including everyone you mentioned in your post.
My local range is 100-300yd to hang paper, steel out to 600.
3 shots per charge or seating depth with colored bullets at 1 point of aim.
I found AA2700 is very accurate in my 6.5cm pushing 123's. It's a lil quicker in burn speed than 4350 but a helluva lot easier to find.

 

[drover]

Quote from OP's post -
"This is the first use of the scope. I can say that the turrets certainly seem to repeat positions. The mount and ring screws have not come loose."

I would try a different scope as the first step, even though it repeats positions that does not mean that it is holding zero. Since it is a first use of the scope to me that is the biggest red flag and an easy one to eliminate.

drover

 

[Beiruty]

Quote from OP's post -
"This is the first use of the scope. I can say that the turrets certainly seem to repeat positions. The mount and ring screws have not come loose."

I would try a different scope as the first step, even though it repeats positions that does not mean that it is holding zero. Since it is a first use of the scope to me that is the biggest red flag and an easy one to eliminate.

drover

Nothing wrong with his scope.

 

[Beiruty]

Just try this load ladder in 0.3grs steps
For your 105gr VLD, try 39.8gr to 41.8gr of H4350 at 2.700", look at your targets, find where the center of the points of impacts stay at the same height and angle from POI.

There is nothing wrong with your beautiful rifle. I will get you some GRTools for your rifle.

 

[Beiruty]

Here is your actual MV and pressure model for your load at 44gr of H4831 which too slow even for your long barrel. I assumed the load is 2.700" and just lowered the initial pressure so the MV matches your observed MV.

This load is not close to OBT4 at all.

 

[Beiruty]

As per GRTools, your OBT4 is at 44.5gr and if you look at your group at 44.6gr, you notice that the center of your 3 shots group is same as point of aim. That means, that the barrel is neutral when the bullet leaves the barrel, Barrel is pointing straight at point of aim.

A seating depth test (steps of 0.010") at 44.5gr could shrink the groups size

 

[Beiruty]

Here is the OBT4 load

 

[drover]

Nothing wrong with his scope.

How can you say that there is definitely nothing wrong with it? I have seen more than one scope that had a shifting zero under recoil but they still tracked good. To me it is a simple item to eliminate and then move on from there.

drover

 

[dhagerty40]

If I'm wrong correct me but, I didn't see what your torque setting was
with the Bravo chassis. I think they recommend 65 ft pounds.
Make sure your torque settings are correct on the the scope, mounts
and pic rail.
Next, if you can find it, RL 16 or H4350 are better powders for
the 6 creed. They are showing up here and there.
I know people use H4831 and vld's
Try the Sierra 107g bullets. Good bullet and easy to find a tune.
I think those few things could help with your groups.

I think you meant 65 in/lbs on the chassis as that what the instructions say. 65 ft/lbs would probably destroy the chassis!

 

[Beiruty]

How can you say that there is definitely nothing wrong with it? I have seen more than one scope that had a shifting zero under recoil but they still tracked good. To me it is a simple item to eliminate and then move on from there.

drover

I scope that is not holding zero would shift the point of impact by 1" to 3" at 100 yards depending if the caliber is magunm or not.

 

[jelenko]

I scope that is not holding zero would shift the point of impact by 1" to 3" at 100 yards depending if the caliber is magunm or not.

How did you arrive at that?