Initial experience loading for 6.5prc bartlein carbon barrel. Inconsistent when cold.

[ssteve]

The rifle is a defiance tenacity with a bartlein 24” 1:7.5tw carbon wrapped barrel that was built by Marc at Spartan Precision rifles. Shoots factory hornady at 1/2moa with a es of around 20fps so I am definitely happy with it so far. I live in Comifornia so I have to hunt with copper and started load development with Barnes 127lrx and H1000.

The rifle had 155 rounds down it so far till today and I loaded up 4 strings from 57.7 to 59.5gr. Two identical strings with cci magnum primers and two identical with fed 210M primers. The far left column is the first ladder on a cold barrel, followed by column 3 with 210m, then column 2 and lastly column 4. These 4 strings were all within about a 30min span so the barrel got pretty hot. Seems there was a velocity shift from the first column to the other three. Not sure if this is cause of the solid copper projectiles as I have had issues with copper in the past after shooting jacketed bullets or if it has to do with the way the barrel handles heat but the es in the other three columns is definitely a lot better after the barrel was warm and it didn’t open up a bunch on the last one when the barrel was hot either so I am not sure what to make of it all. 59.3 and 59.5 are slightly compressed so I don’t plan to go up any even though I would like more speed. Looking at the numbers I think I will load up 5 of 59.2 and 5 of 59.4 and see what it looks like unless someone is seeing something I am not it seems around 59.3 is where my node is.

This is all on once fired hornady brass, 2 thou shoulder bump, about 2 thou neck tension with a Redding type s and a SAC .290 bushing. Powder is dropped .1gr low from a Frankfort arsenal intellidropper and then trickled up to the target charge. Everything was seated 50 thou off.

 

[proff49]

Going to keep an eye on this as I have one sitting in the safe. What contour is the barrel?

 

[clcustom1911]

When doing a velocity ladder, you shouldn't be concerned about average velocity or ES... it's all about the "flat spot" and what It does on paper. You're not going to be shooting rounds with different charge weights for your real world application.

If this were me, I'd try 57.9-58 and 59.2. Those appeared to do well across all strings. One could be a winter load and one a summer load.

 

[spife7980]

You’re trying to base your es and sd numbers on strings of different charge weights?

 

[Steel head]

When doing a velocity ladder, you shouldn't be concerned about average velocity or ES... it's all about the "flat spot" and what It does on paper. You're not going to be shooting rounds with different charge weights for your real world application.

If this were me, I'd try 57.9-58 and 59.2. Those appeared to do well across all strings. One could be a winter load and one a summer load.

This
You have what appears to be two flat spots, pick one, load 10-15 and see if the ES is good then do a seating test and your done.
I’d pick the lower one and never worry about wet conditions it hot days.

You’re trying to base your es and sd numbers on strings of different charge weights?
View attachment 7616498

Lol
Just when you thought you’d seen it all,,,,,

 

[918v]

Use one of these to blow air across the barrel to keep it cool during load development. It also keeps you cool during summer.

Use larger charge increments. I would use .4grs instead of .2 in the PRC. Also, H1000 likes more neck tension than faster powders. Use graphite dry lube in the neck for smoother bullet release. Do over.

 

[ssteve]

My only objective with looking at the es was to see the shift as the barrel got hot. It’s 4 strings with the same charge weight yet the first ladder was drastically different than the other 3.

The flat spot when cold was 58.1, had I just loaded that one I’d be looking there. But if you look at the 4th string that same flat spot is at 58.7 when the barrel was hot.

I obviously don’t care about an es with different charge weights but it does show an inconsistency from cold to hot.

 

[918v]

But the problem is you first need to develop a good load that is in the middle of its node before you can test for any sort of shift.

 

[7mm-08 Freak]

View attachment 7616551

Use one of these to blow air across the barrel to keep it cool during load development. It also keeps you cool during summer.

Use larger charge increments. I would use .4grs instead of .2 in the PRC. Also, H1000 likes more neck tension than faster powders. Use graphite dry lube in the neck for smoother bullet release. Do over.

Just bought that exact fan it is great for load workups

 

[StaveyIL]

I use a rechargeable air mattress pump with a piece of tubing attached. Fast and effective barrel cooling. Something like this.