Anamoly

[jonaddis84]

I found my new Savage 308 load to be

44.2 varget
Lapua brass
175 smk
210m

This load is jammed .010" (2.292 ogive).

The action was just trued and re-headspaced so I know its not a headspace issue.

I decided to mess around with some lighter loads to see how much velocity I would lose to make it safer for the brass.

Loaded 43.8 and 44.0 at same length, and loaded 44.2 jumping .010".

All three loads had pressure problems (ejector marks and heavy bolt) yet I have no issues whatsoever with 44.2 and jammed!?

Crazy part is the 44.2 runs 2615 avg, the 43.8 was like 2550 avg and was still having pressure issues.

All brass is FL sized, shoulders bumped .003", neck turned, bushing sized, US cleaned, as close to 100% consistent as I can make it.

Thought maybe rifle was dirty, but loaded 10 more at 44.2 today and not one of them had even the slightest ejector mark. It seems the ejector is the first sign of pressure for my setup.

 

[McCrazy]

Re: Anamoly

Several people have mentioned loads with higher amounts of powder "smoothing out" compared to lower charges. Effects are smoother, more consistent ignition resulting in better accuracy and less pressure indications.

Some shooters run upwards of 48 grains of Varget with no apparent ill effect. I run 45.6grs of Varget in Lapua brass pushing a 155gr Scenar and had no pressure signs until I seated .050 off the lands and apparently compressed the load.

 

[Brutas]

Re: Anamoly

Does it have a tight neck chamber?

 

[jonaddis84]

Re: Anamoly

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Brutas</div><div class="ubbcode-body">Does it have a tight neck chamber? </div></div>

No, I size with a 0.333 bushing, after firing I think it measures 0.342

 

[bohem]

Re: Anamoly

The extra pressure is coming from the bullet obturating when it hits the lands. This is the same reason why "safe" loads in a 44mag lever gun show very high pressure in a revolver.

The jump to the lands means the bullet starts to move and then stops, pressure builds to get the bullet to engrave, then it moves again.

 

[former naval person]

Re: Anamoly

Could still be a headspace problem...When you jam the bullet you are holding the case back against the bolt face. With a jump, if the case datum line (shoulder) is back too far, the primer can back out a bit until pressure builds and slams the case back against the bolt face...that gives flattened primers and pressure signs. Try reloading the fired brass without that much shoulder setback...you may need to readjust your FL die since the work on the rifle was done. Then refire with a jump and see if that doesn't cure the symptomatology. JMHO

 

[Mike Casselton]

Re: Anamoly

Bohem hit the nail on the head. If you could see the pressure curve on a print out, you would see the initial build up and then the spike of it trying to get the bullet moving again.
With the bullet jammed into the lands, the pressure curve is predictable and without the high pressure spikes.

As FNP alluded to, If you want to run your loads off the lands you will need to fit your brass to your chamber better and work the load back up. Just remember that as you shoot your brass, it work hardens and pressure indicators do not show up as easily.