Help analyzing 6.5 Creedmoor results

[paraman1]

I took my 6.5 out yesterday and did some load testing with what I would call “odd” results. Components used were as follows, Nosler 140 RDF, lapua SRP brass, H4350 powder and Federal GM205M primers. I shot at 200 yards as it was a super calm morning. I lost the first 5 round group but found 3 of the shots at about 1.9 inches for a group. I have posted the results for the other 4 groups below. What I found “Odd” was how quickly it went from 1.9 inches to just over a half inch and then back out to 1.9 inches with just .6 grains of powder difference. Anyone else find this strange? I’ve loaded some more rounds up at 40.5 , 40.6 and 40.7 grains to take back out and see if the .570 group was a fluke and if there are any gains to be made.

 

[ShtrRdy]

I'd say what you're seeing is possible. I'll be curious what your next test shows. You may have a narrow sweet spot.

 

[DMP]

May be attributed to equipment. Not necessarily the load

 

[BuildingConceptsllc]

I would try a different bullet unless you are heavily invested in that one. I was sent those bullets by a supplier to test out a few years ago and could not get the kind of consistency I get from several other bullets with 2 different rifles. I know some like them but the consistency of groupings just wasn't where it needs to be for me compared to several other options.

 

[paraman1]

I am doubtful on the equipment issue as I shot a 5 round group of Hornady match before and after the session and it shot a 1.5 and 1.75 inch group respectively which is where it usually shoots that ammo.

Hopefully I can get back to the range next week and try it again.

 

[straightshooter1]

I would try a different bullet unless you are heavily invested in that one. I was sent those bullets by a supplier to test out a few years ago and could not get the kind of consistency I get from several other bullets with 2 different rifles. I know some like them but the consistency of groupings just wasn't where it needs to be for me compared to several other options.

this ^^^^

I've had issue with Nosler bullets in the past, thinking they'd do at least as well as Sierra's. . . .not! But that was ~6 years ago.

 

[kthomas]

RDFs are incredibly inconsistent.

I remember when I was doing bullet seating depth testing with them (back when I wasted my time on that nonsense) that I could produce some sub 1/10 MOA 3 shot groups. Load that same recipe up and shoot 5 round groups and I don't think I could get it below 1 MOA.

There's a reason they earned the moniker 'random damn flier'.

 

[Doom]

Looking at the groups I'm guessing this is a fairly lightweight barrel on a hunting rifle. Actually it appears you found the OCW node and the scatter node. It seems that nodes appear about 3% apart (1.2gr) and the scatter node is about 1.5% (.6 gr). You would need to re-shoot around the 40.6 to verify (40.4, 40.6, 40.8).

 

[paraman1]

Looking at the groups I'm guessing this is a fairly lightweight barrel on a hunting rifle. Actually it appears you found the OCW node and the scatter node. It seems that nodes appear about 3% apart (1.2gr) and the scatter node is about 1.5% (.6 gr). You would need to re-shoot around the 40.6 to verify (40.4, 40.6, 40.8).

It’s a 24 inch Sendero profile fluted barrel so while not a MTU profile it’s also not quite a sporter weight. I have 40.5, 40.6 and 40.7 loaded up to try next range day. Do you think I should load the 40.4 and 40.8 to shoot at the same time?

 

[LR1845]

It’s a 24 inch Sendero profile fluted barrel so while not a MTU profile it’s also not quite a sporter weight. I have 40.5, 40.6 and 40.7 loaded up to try next range day. Do you think I should load the 40.4 and 40.8 to shoot at the same time?

Might as well...and bring your target into 100yds.

 

[Doom]

I would. I shoot 308 and usually do .3 gr initially and .2 gr on verification loads. Nothings wrong with .1gr.

 

[wyliecoyote]

You're shooting almost the exact same load I've been using for 2200+ rounds in my AIAX 6.5 CM (140 Nosler RDF, 40.6 gr H4350, Lapua SRP, CCI 450). There's nothing inconsistent or wrong with the RDFs, especially at shorter to mid ranges. See the pictures below for proof. Those bullets and that load shoot like that all the time. What you're probably seeing in those results at 200 yards, is the normal dispersion profile of your system. Shoot more groups at 100 yards and quantify it. You'll probably find 3/4 MOA is as good as it gets. It is for me. I'm happy with it and it works.

I used to chase my tail like in circles like you're doing, playing around with 0.1-0.2 grain movements in powder charge and OCW tests, but no more. The stuff the Hornady guys put out in their group size and sample size podcasts pretty well proves the futility in that. It'll save you a lot of time and frustration by just picking a load, shooting a good sample size, and applying those results to your intended use case.

 

[KYAggie]

Interesting. I loaded 140 RDF’s with H4350 and REM 7.5 in Starline brass and got similar results. 40.4 to 40.6 grains seemed to be a sweet spot as long as I seated them .04 or a little more off. If they were seated less than .04 or .07 and more, the groups opened up to an inch or more.

What’s your seating depth? How far off the lands?

 

[paraman1]

Interesting. I loaded 140 RDF’s with H4350 and REM 7.5 in Starline brass and got similar results. 40.4 to 40.6 grains seemed to be a sweet spot as long as I seated them .04 or a little more off. If they were seated less than .04 or .07 and more, the groups opened up to an inch or more.

What’s your seating depth? How far off the lands?

.010 off the lands. I checked all the bullets and they all measured within .001 of each other on the ogive. I’ve seen some posts that indicate these liked more jump (like .030) but given these were the first loads for this rifle I started there as a baseline.

 

[straightshooter1]

.010 off the lands. I checked all the bullets and they all measured within .001 of each other on the ogive. I’ve seen some posts that indicate these liked more jump (like .030) but given these were the first loads for this rifle I started there as a baseline.

Given my freebore could be a lot longer than your, that .010 from your land could mean your cartridges could be .060 off my lands. What's the COAL are those cartridges? I can get a better idea what your cartridge seating depth actually is with that info.

 

[paraman1]

Given my freebore could be a lot longer than your, that .010 from your land could mean your cartridges could be .060 off my lands. What's the COAL are those cartridges? I can get a better idea what your cartridge seating depth actually is with that info.

2.905 COAL

 

[Doom]

You're shooting almost the exact same load I've been using for 2200+ rounds in my AIAX 6.5 CM (140 Nosler RDF, 40.6 gr H4350, Lapua SRP, CCI 450). There's nothing inconsistent or wrong with the RDFs, especially at shorter to mid ranges. See the pictures below for proof. Those bullets and that load shoot like that all the time. What you're probably seeing in those results at 200 yards, is the normal dispersion profile of your system. Shoot more groups at 100 yards and quantify it. You'll probably find 3/4 MOA is as good as it gets. It is for me. I'm happy with it and it works.

I used to chase my tail like in circles like you're doing, playing around with 0.1-0.2 grain movements in powder charge and OCW tests, but no more. The stuff the Hornady guys put out in their group size and sample size podcasts pretty well proves the futility in that. It'll save you a lot of time and frustration by just picking a load, shooting a good sample size, and applying those results to your intended use case.

OCW was never about smallest group sizes but looked for the POI that was insensitive to small changes in load/velocity. When you dig deeper into what is going on its the barrel is moving slower at the nodes as we call them. At 100yds for consistent POI with different velocities the barrel must be pointing in the same line of sight.

As for what the Hornady guys are saying is that group sizes for a given load are likely to be closer to each other than what our typical testing indicates. From what I remember most of thair discussion is centered around PRS shooting and rifles. While I have never tested their conclusions I think that if you pick a reasonable load (case fill, burn rate, consistent primer, etc) and with consistent quality components the round should provide consistent results as Honrnady claims.

 

[paraman1]

After messing about all summer changing everything and dialing in my load on this rifle I finally settled on the 140 grain Berger Hybrid and 43.1 grains of Vihtavouri N555 in Lapua SRP brass and GM205M primers. The barrel has sped up a bit once I got it over 200 rounds and the load runs around 2720 FPS with ES around 10FPS and SD around 4 or 5. Here’s a 3 shot group I shot today to confirm zero before moving out to 200 yards.

 

[ShtrRdy]

Man, that looks good!!