Anyone ever see pressure test results like this?

[Desert Dan]

Wondering if anyone has seen results on a pressure test during load development like those posted below. I fired two 10-shot groups to identify pressure and to pick out where the nodes are on my new 6.5 creed today - one with H4350 and the other with RL16. Components other than powder were all identical and both strings were loaded from Berger minimum charges, increasing in .4 grain increments until I hit pressure, which I did with neither. The 4350 shaped up pretty much as expected but the RL16 was a surprise. RL16 was shot first so loose scope components was ruled out, and that was confirmed by checking after I got home. To be clear, all shots were fired at the top target in the respective pic. I did not switch points of aim, despite what it looks like in top pic. RL16 is the top pic and H4350 is on bottom. Thoughts are appreciated.

 

[archp625]

How far was the target?

 

[Str8shtr]

Small sample size. Could repeat with rl16 and see what the results are....or just roll with the 4350.

 

[Cahunter805]

Did you chrony the shots? How far off the lands? RL 16 test is interesting for sure.

 

[Desert Dan]

How far was the target?

100 yards.
Shooting a similar string again this morning with the 16 to try to find pressure so I’ll see what happens

 

[83cj-7]

Might seem like an odd question, but tell us some details about the rifle. Particularly barrel type and contour, suppressed/naked, muzzle device, stock etc.

This type of loading problem intrigues me.

 

[prm]

I’ll toss out a guess that the RL16 produced a much great change in velocity across that range.

 

[archp625]

100 yards.
Shooting a similar string again this morning with the 16 to try to find pressure so I’ll see what happens

With what you are trying to do you need to move the target to at least 300 yards. The further the better. I would say more in the 500 yard range. You will get more separate and will start to see the loads with the least amount of vertical.

Don’t worry about horizontal at this point. You can work on that with bullet seating depth.

 

[Desert Dan]

Might seem like an odd question, but tell us some details about the rifle. Particularly barrel type and contour, suppressed/naked, muzzle device, stock etc.

This type of loading problem intrigues me.

Yeah this is a weird result especially when the 4350 was fired right after it.
The rifle is a Bergara HMR Pro in 6.5 creed shooting 140 Berger hybrid targets 20k off the lands with 1X ADG brass. Suppressed with SiCo harvester.

 

[Vandy321]

Change #3-5 of 4350 had steady vertical. Assuming those FPS are probably within a 10-15 FPS spread? You could load up a seating depth test with charge weight #4 for each and see what tightens up the horizontal and call it a day, should give you a nice, stable load.

Or, try Cortina's method. No reason to repeat the same test again and expect different results.

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[Desert Dan]

With what you are trying to do you need to move the target to at least 300 yards. The further the better. I would say more in the 500 yard range. You will get more separate and will start to see the loads with the least amount of vertical.

Don’t worry about horizontal at this point. You can work on that with bullet seating depth.

No argument that moving back would clarify the results but in my opinion one can usually pick out the nodes at 100, or at least narrow down the range to identify where to focus on going forward. For me 300 yards plus is over an hour drive away while 100 is 10 minutes.

You could load up a seating depth test with charge weight #4 for each and see what tightens up the horizontal and call it a day, should give you a nice, stable load.

Pretty much what I was thinking. I am going to load up a few more and run the top 2/3 of that test again plus a few more until I actually reach pressure and see how that shakes out, but unless I find another node toward the top I anticipate starting with the #7 shot (38.9 grains) and dialing it in from there. I think had I shot just a little better the vertical would be tighter with 6, 7, and 8.

In the meantime, the RL16 pretty much repeated itself this morning so I'll go with the H4350 and save the 16 for my .243 or another bullet. Looks like some sort of node around 42.0 grains but that was at the top of the pressure limits so I' may play around with it later but no sense wasting barrel life and components that are in short supply trying to force it to work when 4350 looks more promising. The target from this morning is pictured along with the charge weights. I started with what was shot number 6 yesterday. Encountered mild but definite pressure signs on 7 and 8 (which is .4 grains above Berger's listed max) so I wouldn't be going past that even if I were to continue with the RL16.