Reducing pressure at an accuracy node?

[Shinbone]

I am shooting a .300WSM with Viht N550 powder and Hammer Hunter 124gn bullets. This thing is a laser beam for pronghorn and deer.

For my current load, neck tension is .004", and bullet jump is .027". Fill is at about 98%-99% in a Nosler case. I have found a potential accuracy node that I would like to further explore. Problem is, it is right at the charge weight where the gun pressured out. If I reduce the charge by 0.3gn, I no longer get pressure signs, but then I fall out of the potential accuracy node.

This rifle is for hunting, so I like the velocity, and would like to confirm whether this really is an accuracy node, and hunt with the load, if possible. Any suggestions on how I could eliminate these pressure signs without losing velocity, so I could safely shoot some more rounds at this charge weight to see if it really is an accuracy node? Change bullet jump? Change neck tension? Add a crimp? Change brass? Something else?

Changing to a slower powder is an obvious option, but at near-99% case fill with N550, I am not sure if I have the room to go to a slower burn rate and still hit this velocity.




Primer corner is still round, but there is a slight, although unmistakable, ejector mark. Also, I get a stiff bolt lift at this charge weight.

 

[Bill Norris]

The safe thing to do is back off of the powder charge a bit. If you change then seating depth you may see the velocity change a little because of the powder column space but you still may see the ejector mark as well. But then re-tune for seating depth.

 

[gunsandgunsmithing]

First firing on brass? New brass is usually short. It gets slammed against the bolt face and can show ejector swipe because of that. The primer doesn't show high pressure. If bolt lift and velocity numbers concur, I'd set the shoulder back .002-.003 on the fired brass and shoot it again. Orient the cases so they are not aligned with existing swipe marks and see if it does it with the fired brass.

 

[Shinbone]

Good thoughts, gunsandgunsmithing. I should have noted that this is the 3rd firing for this brass. The shoulder was bumped back .003", and it was then annealed for this loading.

I am wondering if I increase bullet jump, maybe the peak pressure will be reduced?

 

[Jager]

If you have access to an accurate chronograph, you can pair that with QuickLoad to give you a remarkably accurate view into what pressures you are running. It's then possible to model any number of load variations.

You clearly have pressure issues with the load you're exploring. Among other things, QuickLoad would allow you to understand how deeply over max you are - rifles differ in how soon they manifest pressure signs - and that information would significantly inform how you might go forward.

All that said, for a hunting load cartridge integrity is a very high priority. I wouldn't be seduced into a load of questionable pressure for the relatively small velocity increase you'd be getting.

 

[Lance21]

Is the barrel threaded for a brake? If so the EC TUNER BRAKE is your answer. Drop the powder charge, get your accuracy back using the tuner. They absolutely work. I've got 3, love em.

 

[CharlieNC]

What methodology did you use to arrive at the current charge weight? If you ran a ladder then a lower charge weight should reflect another node, as judged by stable point of impact vs charge.

 

[Clancy]

A case that size shouldn’t have a node as narrow as .3 grains. I’m not saying I don’t believe what you’re saying. I do. It’s just that I wouldn’t want to hunt with it, especially in inclement weather, if .3 grains was enough to either put me into pressure or, going the other way, diminish accuracy.

There’s likely a lower, safer, wider node. If not, it might be time to try another primer.

 

[Bill Norris]

Is the barrel threaded for a brake? If so the EC TUNER BRAKE is your answer. Drop the powder charge, get your accuracy back using the tuner. They absolutely work. I've got 3, love em.

+ 1

 

[Shinbone]

The barrel is not threaded.

Clancy - good point. I don't know how wide the accuracy node is because I stopped due to pressure.

But, you raise an important issue that I need to be able to access the full node to have a stable load. Meaning, my first thought at trying to just squeak by on pressure to barely get into the node would not be good enough for a hunting load.

The node in the photo is at about 3850fps. The next accuracy node is at about 3775fps. So, the "easy button" would be to load to 3775 and be happy. I was just wondering if there was some simple "tweak" in the various loading parameters that could get me to 3850.

 

[Homerange]

If it were me in this predicament I'd be looking at using different components resulting in lower working pressures to get to similar velocities or if not wanting all that trouble be perfectly happy with 75fps less.

You'll need to reach out a long way for that 75fps to have any impact (excuse pun) on the load.

 

[Bill Norris]

If it were me in this predicament I'd be looking at using different components resulting in lower working pressures to get to similar velocities or if not wanting all that trouble be perfectly happy with 75fps less.

You'll need to reach out a long way for that 75fps to have any impact (excuse pun) on the load.

Exactly. That's why I was saying back off a bit and work with a little lower pressure area.

 

[Shinbone]

I know. I know. I am being greedy and impractical.

It would be cool to have a 124gn load going 3850fps, though. "Thirty eight fifty" has such a nice ring to it.

 

[AckleymanII]

In hunting weather, ejector marks will probably go away. You are probably going to loose primer pockets at that pressure anyway. Sight the rifle in, hunt, verify zero as necessary, call it done.

At this time of year, You could put some rounds in an ice chest for a while in a zip lock bag, take them out and fire them to see if pressure drops.

I absolutely HATE nosler brass.

 

[Shinbone]

I absolutely HATE nosler brass.

I know! Is there another brand of .300 WSM brass than Nosler that can handle a little more pressure?

 

[Bill Norris]

I know! Is there another brand of .300 WSM brass than Nosler that can handle a little more pressure?

Hard to say. Be nice if Lapua made it.

 

[Webster]

The barrel is not threaded.

Clancy - good point. I don't know how wide the accuracy node is because I stopped due to pressure.

But, you raise an important issue that I need to be able to access the full node to have a stable load. Meaning, my first thought at trying to just squeak by on pressure to barely get into the node would not be good enough for a hunting load.

The node in the photo is at about 3850fps. The next accuracy node is at about 3775fps. So, the "easy button" would be to load to 3775 and be happy. I was just wondering if there was some simple "tweak" in the various loading parameters that could get me to 3850.

How do you get 3775 fps. The fastest load in my Berger manual is 3491 fps 125 gr bullet. You have definite signs of pressure and you are talking about trying to reach 3850 fps. Some people shouldn't be reloading ammo. Go for an accuracy load no matter what the speed is it will kill any deer.

 

[Homerange]

I know! Is there another brand of .300 WSM brass than Nosler that can handle a little more pressure?

How does genuine Winchester brass rate ?

Chaps that come here and wanna push stuff hard seek Win brass for 2 reasons, it's typically harder and higher internal capacity however no idea if the same relates to the WSM brass.

 

[Homerange]

I know. I know. I am being greedy and impractical.

It would be cool to have a 124gn load going 3850fps, though. "Thirty eight fifty" has such a nice ring to it.

No more so than a chap with a 6mm Rem here pushing 105's to 3450....some 200fps faster than you'll see anything for that weight in print....but hey, he's taking rabbits at 800+ so you need something fast to get out there.

 

[AckleymanII]

I would be all over Winchester brass, then ADG

Check those Nosler primer pockets and get back to us, please. You could have a Fire forming load, slam back on the bolt face issue as one person mentioned.