6.5CM--Berger 140 HT--H4350--BR4 Primers--Laupa SR

[Yerman]

Hey guys, thanks for reading and helping me out.

Custom 700 - Trued and blueprinted
6.5 Creedmoor, 6.5 Berger Reamer from LRI
26" Bartlein Barrel 1:8 twist
Berger 140 Hybrid Target
Hodgdon H4350
BR4 Primers
Lapua Small Rifle Primers
20 thousand off lands
Magnetospeed V3 running the latest firmware
82 degrees, low humidity, 4350 ft Elevation

Below you will find the raw data from a recent load development session at the range, and the same date with the min and max removed.

It consist of 5 rounds of 0.2 grain increments of charges from 41.6 grains to 43.0 grains.

Here are my thoughts. Please let me know what you think.
- It looks to me like the flattest velocity spot is right around 42.5 grains
- Even though the SD and ES is better right at 42.0 grains, I'm thinking the lower speed increase between 42.4 and 42.6 is more preferential.
- Based on the data I see out there, it seems like I am running really fast compared to others running the same loads. Any thoughts on that?
- Where would you focus your next batch of loads?

Thanks again.



RAW DATA

MIN AND MAX REMOVED

 

[Stpilot12]

Yeah, thats fast in a 26" tube. My load with 42.5gr H4350 averages 2918 from a 30" tube. Same charge with RE-16 is 2959, both with 140 ELD-M and
Berger 140 HYB. Did you do any comparison between primers? Ive been using 450's but I have some BR4s to try next. I started seeing pressure at 42.7, 42.5 is the sweet spot anyway. SD usually 3-5 and shoots .5 or better (when I dont suck)

 

[Yerman]

What brass do you run and what’s you neck tension?

I wonder what is causing the speed. I’m going out in the morning to get more time with the load.

I have not tried any other primers yet. Do you think that could be causing the high velocities?

 

[XLR308]

If you are not seeing any pressure signs and your not running an excessive charge I wouldn't worry about it.
Some barrels are just faster and some are on the slower side.

If you have a blade Mic have you measured the case web before and after firing to check for expansion ?

 

[Stpilot12]

Im running Norma/Prime brass and just started with some Lapua. I generally run a 289 bushing and an expander mandrel. Same powder charge is within 10 fps in either brass. Although, the Lapua is not as accurate as the Norma brass, I suspect neck tension is the culprit there. Unless your Magnetospeed is messed up (doubt it) It sounds like you have a really fast barrel. Im using CCI 450's in the Lapua brass, I doubt BR4s are gonna give you more velocity.

 

[nfngun]

Id focus the next load on the batch that's grouping the best ... Velocity, SD and ES are all irrelevant if the group isn't 1/4"

 

[Yerman]

Hey guys, I finally got back out to the range and did some followup testing, this time with neck tension and seating depth.

All 9 of these loads are running 42.5gr of H4350.

Here are the 9 different loads in this test. Note, I like the idea of running different size expanders from Whidden Gunworks vs running bushings. My theory is that even if you neck turn, because you are pushing from the outside of the case neck, you are still introducing uneven pressure on the bullet due to unevenness in neck thickness. By running the Whidden Gunworks expanders, it should theoretically be more consistent neck tension. The expanders listed below are from this kit https://www.whiddengunworks.com/product/expander-ball-kits-and-sets/

0.261 Expander (3 thou neck tension)
1 - 0 thou off lands
2 - 20 thou off lands
3 - 40 thou off lands

0.262 Expander (2 thou neck tension)
4 - 0 thou off lands
5 - 20 thou off lands
6 - 40 thou off lands

0.263 Expander (1 thou neck tension)
7 - 0 thou off lands
8 - 20 thou off lands
9 - 40 thou off lands

Here are some of my thoughts:

1. I was surprised to see very consistent velocities between loads with different next tension
2. I was expecting higher spikes of pressure when at zero jump
3. I don’t seem to see any consistency between a certain amount of jump although there is a pretty significant difference with the 0.261 expander

 

[Smokey3]

Did you go with #3 ? That group will be tough to beat.