Need Coaching Interpreting Range Data

[Badbob]

Folks, I went to the range this weekend to do more load development. I'm basically a beginner shooter. I need help interpreting my range results. Target is attached.

6x47 on a R700 trued action Sightron 8-32x scope
H4350 BR-4 primers Lapua Brass (2nd firing)
105 Berger Hybrids
.005" off the lands
Weather 55, wind 0-3mph, 5600ft altitude
No turn neck. 090" freebore

My big questions are: What should I do for my next trip to the range. My goal is a PRS gun. Velocity must be under 3200fps for matches. The gun is a repeater so I really want to stay out of the lands.

Which nodes look good? Why did the speed jump at 40 and 40.5 grains (see attached spreadsheet)? Bad Chrony?

Thanks BB

 

[LitLBoy]

38.5 and 40.0 seem to have good water line. I'd work with those two areas. go up and down 2/10 grain on both of those. back off the lands in .003 increments till you are .020 off. Guys with more experience will help also.
LitLBoy

 

[Badbob]

LB, thanks for the reply. What do you mean by waterline? Vertical consistency?

So, then would it look like this: 38.3, 38.7 and then 39.8 and 40.2, 3 shots each?

I notice many shooters are using CCI450 primers with H4350. Should I just stick with the BR-4 until I find the best node?

Thanks, BB

 

[Bbear]

Badbob, LitLBoy's comment about a 'water line' is meaning that those two groups were on the same vertical, or nearly the same vertical, line with each other. As for loads to check next, I'd suggest 38.5, 38.8, 39.1, 39.4, 39.7, 40.0, 40.3. 3 shots each. Allow the barrel to cool as close to ambient temp as you can. Run those on your target and over your chronograph and look for a series of loads that show little change in velocity and roughly the same vertical line through the center of each group.
If, for example, you find that 38.8, 39.1 and 39.4 have little change in velocity and are on the vertical line together, you can pick the 39.1 load and play with seating a bit to see if you can tighten up your group.
Check out OCW (Optimal Charge Weight) on google to get better detail on what I'm talking about.

 

[Sniper338]

yep. your loads 38.5-40gr... play in that area... BR4 primers are fine, keep with them and see what you find, then try 450s and see what happens.. never know. seating depth can be played with too... the further out you shoot, the easier you can tell what its doing.

 

[Badbob]

any idea why the speeds jumped up 40 and 40.5? Just curiuos

 

[Drop Port]

My 6.5x47L groups looked like your 40 through 42 groups with BR-4's a swap to 450's cut the groups in half an seating depth pulled it into one hole over a two grain spread. Most (MOST) 6 and 6.5x47's I've worked with showed a strong preference to 450's with H-4350.
A quick primer swap will tell you.

 

[Keith Glasscock]

First things first. Back away from the lands. Your ES numbers are showing that there is something wrong. I suspect that you are so close to the lands that one is jumping and the next touching. In general, I start with hybrids .015" off.

I don't think the powder will change any significant amount as a result.

As for primers, 450's might be advantageous in this application. They certainly are in a 6 Dasher (similar)

 

[pat fulghum]

What barrel? and how many rounds?

How are you determining your lands? Stoney Point (aka Hornady) tool?
If you give me your Overall Length and Length of your 105 Hybrid - I will be able to compare to mine.
Mine is: COL 2.691, BTO 2.076 Using Hornady Ogive tool.... but I don't know what your chamber looks like.

I agree with Keith, I only run CCI 450's in my 6mm's...they handle the pressure.

In my 6x47....

Bartlien 30" 8 twist (no need to go 7.5 twist for 6x47 velocities)
39.9 gr H4350
Hybrid .015 off the lands
3175 fps

20-Shot ES < 15, with SD < 6
Shoots great, but barrel life is about 800 rounds.

Looking at your data, the ES is way too big for this cartridge something is wrong....
What are you using to measure velocity?
How do you measure your powder?

Did you shoot in round - robin? or 1,2,3, 1,2,3,.... Any barrel heat? ... a 6x47 has a lot of heat and you can't just blast away.

Double check that the fired round neck diameter is a minimum .003 bigger than loaded round.

Looks like you had some foulers... so how much carbon/copper came out last time you cleaned. I have found that I do get pressure issues with this cartridge if I don't bore scrub it every 300-ish rounds.

When chambering a round.... does the bolt close the same (ie are the cases all head spaced the same and bumped .002?)

lots of things to check ... I know... but something is wrong to get that wide a spread of ES
-- pat

 

[urbanrifleman]

It appears the nodes are 38.5, 40, and 41.5. 1.5 grains apart. Just like they should be.

 

[Badbob]

My 6.5x47L groups looked like your 40 through 42 groups with BR-4's a swap to 450's cut the groups in half an seating depth pulled it into one hole over a two grain spread. Most (MOST) 6 and 6.5x47's I've worked with showed a strong preference to 450's with H-4350.
A quick primer swap will tell you.

Ya, I see a lot of folks reporting using the 450s. My knee jerk is just to jump on those and start using them. But won't that just complicate my data because I've introduced to many variables?

Shouldn't I just work the nodes and then look at seating depth and finally play with primers?

Many thanks for pointing this out. BB

 

[Badbob]

First things first. Back away from the lands. Your ES numbers are showing that there is something wrong. I suspect that you are so close to the lands that one is jumping and the next touching. In general, I start with hybrids .015" off.

I don't think the powder will change any significant amount as a result.

As for primers, 450's might be advantageous in this application. They certainly are in a 6 Dasher (similar)

Good point--I'm .003" off. Should I just move them back to .010" off for my next trip to the range or wait to after I do another powder work up, explore the node, and THEN play with seating depth.

I guess I'm asking what the right order of changing variables should be? Thanks BB

 

[Badbob]

What barrel? and how many rounds?

Criterion--26" 7:5 Varmint Contour. 50 rounds through it.

How are you determining your lands? Stoney Point (aka Hornady) tool?
If you give me your Overall Length and Length of your 105 Hybrid - I will be able to compare to mine.
Mine is: COL 2.691, BTO 2.076 Using Hornady Ogive tool.... but I don't know what your chamber looks like.-- pat

I'm using a Stoney Point tool 3-24, touching the lands is 3.077" I removed the firing pin and plunger and seated the bullet until the bolt was just ever so loose.
chamber is .104" free bore, .273 neck reamer drawing attached.

I agree with Keith, I only run CCI 450's in my 6mm's...they handle the pressure.

In my 6x47....

Bartlien 30" 8 twist (no need to go 7.5 twist for 6x47 velocities)
39.9 gr H4350
Hybrid .015 off the lands
3175 fps

20-Shot ES < 15, with SD < 6
Shoots great, but barrel life is about 800 rounds.

Looking at your data, the ES is way too big for this cartridge something is wrong....
What are you using to measure velocity?
How do you measure your powder?pat

Chrony Alpha Chronograph on a tripod. 6 feet from the bench.

Did you shoot in round - robin? or 1,2,3, 1,2,3,.... Any barrel heat? ... a 6x47 has a lot of heat and you can't just blast away.pat

I was not really watching this. I shot 3-shots in each charge level at one target and then moved on to the next charge level

Double check that the fired round neck diameter is a minimum .003 bigger than loaded round. Looks like you had some foulers... so how much carbon/copper came out last time you cleaned. I have found that I do get pressure issues with this cartridge if I don't bore scrub it every 300-ish rounds.pat

I carefully cleaned the bore as I broke in the barrel--about 25 rounds. I fully cleaned the bore--using Butch's--before I went to the range last weekend. I did not clean while I was there.

When chambering a round.... does the bolt close the same (ie are the cases all head spaced the same and bumped .002?)pat

Yes--until I got to 42 grains and experienced pressure signs--flat primers, tight bolt. Other than that the rounds chambered the same.

lots of things to check ... I know... but something is wrong to get that wide a spread of ES
-- pat

Pat, thanks for all the questions--I hope it helps you help me diagnose any problems. BB

 

[Keith Glasscock]

@Badbob

I'd suggest that the seating depth can cause difficult reading of testing data. I'd work that variable first. I have learned the hard way to get a safe seating depth before doing any in depth tuning.

.010 to .015 would be safe. The change is minor enough that you should be able to move forward with the powder testing as planned.

 

[pat fulghum]

The nodes are somewhat tied to barrel length (not necessarily contour) due to harmonics.

You said only 50 rounds....

Barrels will change speeds drastically in the first 100 rounds.... I really don't do much tuning before then.
I have seem barrels jump 150fps.... (there is another recent thread here that discusses that),

If it were me, I would just try again.

Wait until you get 100 rounds, get CCI450's / H4350 (A proven combination) and try again..... I bet it will be a lot different than the first 50 rounds.

 

[Badbob]

Ok, so next range trip I will make the following adjustments:

Set bullet seating depth back to .010"
Switch to CCI450 primers
Try these loads in an effort to hone the node: 38.5, 38.8, 39.1, 39.4, 39.7, 40.0, 40.3. 3 shots each
Allow barrel to cool between each 3 shot group.

Great thread and huge help, thanks!

 

[jimmymac]

Hopefully you are using a good front rest and rear sandbag setup, or you'll end up chasing your tail trying to figure out powder and seating depth combinations.

38.5 and 39.0 both have two bullets touching then a flyer with each group. That could easily be a gun handling problem. Food for thought.

 

[Badbob]

Hopefully you are using a good front rest and rear sandbag setup, or you'll end up chasing your tail trying to figure out powder and seating depth combinations.

38.5 and 39.0 both have two bullets touching then a flyer with each group. That could easily be a gun handling problem. Food for thought.

Eagle rest with 3" front bag. My stock, At-One Boyds has a custom 3" wide forearm. Large brick style rear bag. Attempting free recoil. Am I an experienced shoot at the bench? Not really.

I'm hoping more time shooting will help. Also, the wind was puffing 0-4mph at the time I was shooting.

BB

 

[jimmymac]

Eagle rest with 3" front bag. My stock, At-One Boyds has a custom 3" wide forearm. Large brick style rear bag. Attempting free recoil. Am I an experienced shoot at the bench? Not really.

I'm hoping more time shooting will help. Also, the wind was puffing 0-4mph at the time I was shooting.

BB

I'm not familiar with that stock, but if it has a flat bottom you should be good to go.

I'm a long time shooter (old guy ) but have only been shooting a bench gun for less than a year. That said, this is what I'd do.

My first order of business would be to stabilize the gun with a better rear bag. After that is accomplished, the groups should tighten up and become easier to interpret. At that point, all the hard work you are putting in will be more meaningful and you will be rewarded for your efforts.

You will be better served with a rear bag that has ears of some sort for shooting free recoil. Even if you don't shoot free recoil, a brick bag isn't helping your effort. Ears are a good thing. A nice inexpensive choice is a Protektor 13A with heavy sand. That bag is even better if you add their bag stabilizer. Alternately, get in touch with Protektor and tell them what you have and let them make a recommendation.

If I'm way off base here I'm sure someone will be along to poo-poo what I'm saying, but that's what I'd do before I tried to do a formal load workup.

Good luck to you sir.

 

[Badbob]

Heres my rig. Bullet front rest and homemade rear bag. Looking a little saggy. The rear stock, butt, has a horizontal piece added sol the gun free recoils horizontally. I added a new forarm that is 3" wide to ride on the 3" wide front rest upper. But again, I'm not a skilled shooter so those flyers could be me! However, I shot a .093" group on my 6mm br and a .143" group on my dad's 6ppc, so I'm not that rickety!