Compressed loads - pressure increasing explosevly?

[Jayjay1]

Hello gents,
if you are making compressed loads with a real slow burning NC powder (for the round you are loading), can it be, that the pressure rises extremly and uncontrollably?

I´m loading the 6.5 Creedmoor with a real slow powder and am at roundabout 107% load density now.
No pressure marks so far at all.

I´m wondering if I can increase the load without getting my rifle blown.

 

[XLR308]

Run a ladder in .2 to .5 increments until you see any pressure signs or most likely run out of case volume.
I did something similar last month in 65CM with H1000 and the 147eldm.
The highest charge I made it to in new Lapua brass was 48 grains and no hint of pressure.
At 48 grains using a long drop tube to settle the powder column my seating depth had to be increased by .010".
Obviously it is up to you to work up your own charges to find what is max and back off from there if you see any pressure, also you didn't state what powder you were using.

 

[Ryridesmotox]

My experience was with IMR4064. I was running 46 gr in a jagemann case with q 175gr nosler. My sd and es were crazy low. The load was plenty accurate. Ther marmot downside was, it was hard on brass. I had no pressure signs, no heavy bolt lift, nothing. But I noticed the primer pockets were a little looser than the brass I was using at normal sane levels.

Your mileage may vary on that depending on the brass you're using. Mine was already fired 6 times.

 

[Milo 2.5]

You never said what powder, w/o the case capacity there are powders slow enough that physically cannot pressure your case up. Give us a little more info, powder and bullet.
I like case fill like the next guy, but there is a crossover point where it becomes futile. I will never vibrate cases to hold seat depth.

 

[Jayjay1]

Well, because it is a European powder I first wanted to hear any response before I get none, because you guys might be not familiar with it.

So, the powder is Vithavuori N160,
brass is Hornady with large primers,
the bullets I´m testing with are 140s from Hornady, BTHP and ELD-Match, the 147 ELD-Match and the 139 Lapua Scenar.
The one 139 and the two 140 are operating very similar with the same powder load.

According to QL I´m now at round about 107% load density with all of them, no pressure signs at all.
Velocity is still quite low, with 2680fps for the 140ish and 2560fps for the 147gr. bullet.

 

[Milo 2.5]

Well, because it is a European powder I first wanted to hear any response before I get none, because you guys might be not familiar with it.

So, the powder is Vithavuori N160,
brass is Hornady with large primers,
the bullets I´m testing with are 140s from Hornady, BTHP and ELD-Match, the 147 ELD-Match and the 139 Lapua Scenar.
The one 139 and the two 140 are operating very similar with the same powder load.

According to QL I´m now at round about 107% load density with all of them, no pressure signs at all.
Velocity is still quite low, with 2680fps for the 140ish and 2560fps for the 147gr. bullet.

Theoretically, you should be able to pressure out with N160, I have not shot it, but do know in 6.5 creed I could pressure out with N550 and a 140 hybrid.
As for speeds, what barrel length you running?

 

[Gohring65]

If your manual calls got compressed load, you’ll be fine. If you’re going in blind, then it does have a risk, although a slight one. How temp stable the powder is would influence my decision on running it or not.

 

[straightshooter1]

Beware and be aware of what temperature changes can do when your loading to a max. ?

 

[Silverjay]

Doing similar work with H1000 in a 6mm case. “Light” compression did not change the slope of powder charge Vs velocity. Drop tube and more compression changed that slope, I went in 0.1 grain increments and had pressures signs that were reasonable with powder increases. I did not see a drastic step change.

Again, this is a different powder and case. Approach with caution. As previously mentioned as well summer will increase pressures as well.

 

[Jayjay1]

Theoretically, you should be able to pressure out with N160, I have not shot it, but do know in 6.5 creed I could pressure out with N550 and a 140 hybrid.
As for speeds, what barrel length you running?

Very interesting, because the N550 was the powder I was thinking about next.
But I´ve heard N5XX are hotter (barrel gets hotter) and dirtier than the N1XX.

Did you like the N550?

Barrel length is 24".

 

[Milo 2.5]

Very interesting, because the N550 was the powder I was thinking about next.
But I´ve heard N5XX are hotter (barrel gets hotter) and dirtier than the N1XX.

Did you like the N550?

Barrel length is 24".

I myself like N550, and to me it was relatively stable. It is expensive though and have gotten away from it even though I have 8lbs of it.
By barrel length and velocity you are getting, common sense says you wont max out with N160. People claim N 160 coolest burning powder around, I cannot verify that as I have never shot it.