Increase in charge but not in velocity

[Toolhand]

Been reloading for awhile but never worked up a load with no book data so looking for a little help. The load is 26 nosler with a 160 Matrix vLD bullet loaded over RL50. Looking to find pressure range as I can't find any load data on this setup. I used load data for 140 grain vld bullets to come up with what i thought to be a starting point. Using once fired nosler brass fired from my rifle fully prepped and trimmed to 2.850 with shoulders bumped .002 with federal 215M primers.
So went to my range today and setup my lab radar and shot 3 bullets
The first 64 grains of RL 50 - 2639 FPS
The second 65 grains of RL 50- 2646 FPS
The third 66 grains of RL 50 - 2628 FPS.
Weather was clear and 44 degrees

Lab radar was used for multiple other rifles with consistent readings I also was using 50 BMG powder in the 26 with the same setup as described above and it showed 50-60 FPS velocity increase with 1 grain of powder increase. Worked 3 loads from 2759 up to 2860 and haven't hit any pressure signs yet with the 50 BMG so looking promising there.

Am I starting to low with the RL 50 and that causing the lack of increase in velocity or should I just drop the RL 50 all together and work strictly with 50 BMG.
Thanks in advance - Jason

 

[Kansaswoodguy]

In my 6.5 Creedmoor and 223's I look for flat spots in the velocity and load for the middle of them. I've never seen one a full 2grs wide before but my case volumes are much smaller than your talking about maybe someone that shoots larger volume calibers will chime in.

 

[dok7mm]

If you just shot one round of each charge, they won't tell you much, compared to the average velocity of 3 shots. Several things could influence your Chrono numbers on one shot....... like barrel condition or temp and the fact that one fireforming will not usually expand your brass fully to chamber dimensions. I would suggest firing 2-3 foulers and then shoot groups of at least three rounds for average velocity with the same wait between shots.

I don't bump shoulders until after 2 firings, unless the brass won't chamber. This way, I just have to set up my die adjustment one time.

 

[Toolhand]

The shoulders I had to bump back due to very tight chambering. I see what you are saying about shooting three shot groups to get an average instead of single shots. I was trying to save some powder and projectiles thinking that there should be some sort of consistency as to powder increase and velocity but apparently not always the case. I shot two foulers with a known load before firing the three shots and waited about 5 minutes between firings Barrel is a carbon six bull barrel profile so it doesn't heat up much after one shot anyway. Thanks for the responses.

 

[Lefty7mmstw]

rl50 is a pretty large kernel powder for a 6.5mm bore. I'd look at a slightly smaller kernel powder to keep the bridging to zero and burn more uniformly. Retumbo is significantly smaller kernelled, and rl33 is a bit smaller while nearly as slow as rl50. Also, as stated earlier, you'll need to shoot at least a few shots at each charge to get a true idea of speed generated.

 

[Dean2]

You are shooting a case that is way over bore. Like the 7 RUM, they do not react well to light loads. These are not the cases to be messing around with. If you read published load data almost all of it specifically warns you not to go below published minimums, and in many cases for certain powders there is no min, only one published load. Unless you have pressure trace equipment I would not be winging it with 26, 28 Nosler, & 7 RUM etc. I would consider RL50 and even BMG too fast a powder for that heavy a bullet in that case. Look at the 150 and 140 grain Nosler data, notice how much lower the velocity is than the other two, slower burning powders listed 896 and LRT, and you are going up another 10 and 20 grains in bullet weight.

 

[Dmagna]

You are shooting a case that is way over bore. Like the 7 RUM, they do not react well to light loads. These are not the cases to be messing around with. If you read published load data almost all of it specifically warns you not to go below published minimums, and in many cases for certain powders there is no min, only one published load. Unless you have pressure trace equipment I would not be winging it with 26, 28 Nosler, & 7 RUM etc. I would consider RL50 and even BMG too fast a powder for that heavy a bullet in that case. Look at the 150 and 140 grain Nosler data, notice how much lower the velocity is than the other two, slower burning powders listed 896 and LRT, and you are going up another 10 and 20 grains in bullet weight.

Think he figured it out over the last 3 years?

 

[Dean2]

Think he figured it out over the last 3 years?

Well ****, that was a big waste of time. This came up in the new threads section, never even noticed it was from 2019.

 

[villagelightsmith]

Yep. That'll happen.

 

[jessej]

Well ****, that was a big waste of time. This came up in the new threads section, never even noticed it was from 2019.

But interesting none the less. I'd like to hear from the op to hear how this has turned out