Perplexed Results

[MustangMike]

Just started to load some 185 gr TTSX bullets in my 338-06 using CFE223 powder, F210 primers and necked up LC 68 brass.

I loaded 3 each with 57.5 grains of CFE223, 58.0 grains and 58.5 grains.

Velocity and SD were as follows, respectively:

2,896.6 FPS SD 8.4 (most accurate, 1.5")

2,872.9 FPS SD 10.8 (worst accuracy, over 3")

2,886.4 FPA SD 10.2 (1 5/8")

I'm perplexed why the increase in powder charge did not provide any increase in velocity. Is it because the charge may be slightly compressed? I have a 24" barrel.

Based on my results, I'm going to try 57.0 grains of CFE223, with 2 different seating depths, and the 57.5 also with a shorter seating depth.

Any thoughts, comments, recommendations would be appreciated. Temps were in the mid 40s and virtually no wind.

I full length size but expect the next loading of this brass to be a little more accurate, as it was previously not fired in my gun (scrounged it at the range).

 

[MagnumManiac]

If it is showing a plateaus straight off the start, it is either a poor burn, or at the beginning of proper burn needing a rise in pressure to get going.

The groups suggest to me that the powder choice is not a good match, however, without knowing the rifles history and traits, it's just an unfounded observation.
My own 338-06 prints sub half MoA with most bullets in it's Hart 24" barrel.
I find best powder to be H4350 in mine, with 760 a close second pushing 200g Accubonds to almost 2800fps.
I use 210g Partitions in mine 90% of the time with H4350 pushing them at 2750fps.

Cheers.

 

[MustangMike]

Max load per Hodgdon with this bullet + powder is 59.2 grains, but that is with Winchester brass, and I think the LC-68 brass is thicker so I'm trying to stay off the max.

With 200 gr SST and 210 Gr Barnes TTSX I've had good results with H380 and IMR 4350.

 

[MagnumManiac]

Max load per Hodgdon with this bullet + powder is 59.2 grains, but that is with Winchester brass, and I think the LC-68 brass is thicker so I'm trying to stay off the max.

Well, it just might be running very near to max in this case, or has already surpassed it if it plateaus across that spread of charge weights.
I only ever see this when max has been passed.

What do fired cases show?

Cheers.

 

[MustangMike]

Primers were equally flat with all 3 loads. No difficulty with extracting cases. I just can't see adding more powder if it does not do anything.

FYI, my gun is a Ruger American Rifle with a Shaw 24" stainless spiral fluted barrel.

They have 3 lug bolts, and I think the actions are pretty strong. My 30-06 does not show any excess pressure signs in loads that other guns don't like.

Will try to get back to the range next week. As I'm a tax preparer, after 2/1 I won't have any time till after 4/15.

 

[med358-boise]

A couple comments: 1) An SD based on 3 rounds does not provide meaningful information 2) Even average FPS based on 3 rounds is only slightly more meaningful. Consider an extreme spread of 35 FPS and what if your 3 shots of 57.5 were all at the upper end of a theoretical 20 shot string and those at 58 were all at the lower end of a theoretical 20 shot string.

I would start over at 56.6 and load in .4 increments upto 58.6 I would load 6 rounds of each and run two OCW round robins. Look for two adjacent charge weights that have a similar POI to POA. Split the difference between those two charge weights and then refine for seating depth.

 

[MustangMike]

I'll keep that in mind when I do more loading, but I hope to work it out with less rounds than that. If what I'm planning to do does not pan out, I will re-test.

 

[Tiny Tim]

Without more data, it's hard to tell for certain, but I often fine similar "Plateaus" when approaching max.

If accuracy is not what you are requiring, I'd likely follow @med358-boise's advice. Back off and work up. I'd probably also switch powders, but admittedly, I have zero experience with CFE223.

 

[MustangMike]

I don't use CFE223 in the 223 because I think it is intended for the heavier bullets, but it works very well in my daughter's 308 with 150 grain bullets, pushing them over 2,900 FPS from a 22" barrel with VG accuracy.

 

[ShtrRdy]

If you were to plot all the individual velocities versus powder charge I would suspect that the velocities would look all mixed up.

 

[MagnumManiac]

Erratic velocities mean erratic pressure.
That is the whole point of my answers above, just didn't word it that way.
Most likely a poor burn.

Cheers.