Learning pressure signs

[Benjblt]

Those primers are pretty, but an ejector smear on a bolt gun case head is not good. There's a slight chance your ejector spring is stout, but 99% of the time this is over pressure.

That is common in stout to over pressure loads. Common occurrence. Means a different powder should be selected.

N570 is a pretty slow powder for your application. I should think N560 & N165 will bring you on home. Interesting to see the Hornady data showing only a grain difference between N560 & N165. These two powders are currently a mystery to be solved recently on Hammer Time.

Ya'll know I'm getting serious when I'm breaking out the color codes!

The color codes are demonstrate how far you need to break it down for someone like me It's helpful though.

I'm not seeing that round smear on all four shots of each powder charge but I do see it. There's also some half arcs on some of them. I'm not sure what that is. On the lower charge weights I'm not seeing those marks.

Do you mind explaining?

N570 was a mistype. I corrected it above. I'm using N560.

 

[Steve Davis]

Reading pressure is the most difficult thing to learn. This is where I feel for the guys that are trying to learn the art of reloading without a mentor. The way I read pressure is all of the above. I personally think primers are the hardest thing to read. Although I must admit I have never looked at them after de-capping. Well built rifles will do a great job of masking pressure and making it hard to see or feel. Here are the things that I pay attention to when developing a load and looking for pressure. 1. How the rifle feels when opening the bolt and ejecting the case. 2. Watching the case head for signs of an ejector mark. 3. Watching the vel. If vel is too high so is pressure. 4. Primer flattening and cratering. 5. Primer pocket. If pocket is loose, pressure is too high. I want to start my load development with a mild start load, so I can observe all of these things, how they look and feel at mild pressure. To me this is very important to be very conscious of how all of these things look and feel when we know we are mild (low vel). Some rifles will crater the primer at low pressure and flatten the primer at low pressure and show ejector marks at low pressure. Probably the main thing that I want to feel is the bolt lift and ejection in this process. I know how it feels at low pressure and when it starts to change, I know we are starting to push the brass and therefore pushing the pressure. The brass is the weak link here and we need to pay attention to it. You keep going past the breaking point of the brass is when you will get in trouble. @Farleg used the terminology that the brass is the shear pin in the system that keeps you from breaking the tool. This is a great analogy. So, as we start with a mild load and work up, we want to be very aware of 5 points changing. Obviously #3 will be changing, we just don't want to see it hundreds of feet too fast. When any of the other 4 points start looking or feeling different than the mild load, then we know that the pressure is starting to push the brass toward the point of becoming the shear pin.

When I am in doubt whether or not I am pushing too hard, I will de-cap the fired brass and re-seat another primer and take note of how much force is needed to seat the primer. Primer falls in, we need to back down. Goes in stiff, we are in good shape.

So don't cut corners and start up into the data. You are only saving a couple of shots and you can't feel and see all the indicators at a mild load.

 

[LightTheTower]

I want to start my load development with a mild start load, so I can observe all of these things, how they look and feel at mild pressure.

When I am in doubt whether or not I am pushing too hard, I will de-cap the fired brass and re-seat another primer and take note of how much force is needed to seat the primer. Primer falls in, we need to back down. Goes in stiff, we are in good shape.

So don't cut corners and start up into the data. You are only saving a couple of shots and you can't feel and see all the indicators at a mild load.

These are excellent points. The second I just started doing… the first I’d never considered. Thanks Steve.

 

[Benjblt]

I'm farely new to reloading. I'm shooting new peterson brass, N560, 125 grn HHT's out of my Seekins 6.5PRC with a 21 inch barrel. Attached are pictures of brass from three different powder levels, 58 grains (3,140 fps), 58.5 grains (3,160 fps), 59 (3,190 fps), and 59.5 (3,120 fps). FPS are averages with some fairly wide spreads except for at 58.5 grains where there was only a 6 fps spread between 4 shots. . . . I see marks on the head around the case head, or face, whatever you call it around the primer pocket. Sometimes its the round ejector marks and some times its small partial circles near the rim. For reference it was 65 degrees outside. What are you'alls thoughts? ... BTW, accuracy was about a half inch group except for the 58.5 grain load which was closer to an inch.

So I worked up some more loads. Starting at 57 grains (where I originally experience no pressure signs) up to 58.5 grains (where I originally experienced phenomenal SD/ES). But...... I crimped, using my RCBS die. I ordered a Lee crimper but it hadn't arrived yet. My velocities increased at least 70 fps with my starting load of 57 grains. The velocities did not increase at as large an increment from 1/2 grain load increases. My accuracy was slightly worse as well. What also increase was pressure signs. All the way down to 57 grains. My original non-crimped load at 57 showed no pressure signs. Another interesting thing was that the speed at which I experienced low SD/ES was the same speed as before, 58.5 gr non-crimped and 57 crimped. Thoughts? Is this what you call a "node". It was about 12 degrees warmer this second time. Using N560 powder. I think next time I'm going to use a slighter crimp with the LEE crimper and see what happens. To remind anyone reading this, I'm relatively new to reloading. Talk to me like I'm a 2nd grader. Any advice is appreciated.

 

[ButterBean]

So I worked up some more loads. Starting at 57 grains (where I originally experience no pressure signs) up to 58.5 grains (where I originally experienced phenomenal SD/ES). But...... I crimped, using my RCBS die. I ordered a Lee crimper but it hadn't arrived yet. My velocities increased at least 70 fps with my starting load of 57 grains. The velocities did not increase at as large an increment from 1/2 grain load increases. My accuracy was slightly worse as well. What also increase was pressure signs. All the way down to 57 grains. My original non-crimped load at 57 showed no pressure signs. Another interesting thing was that the speed at which I experienced low SD/ES was the same speed as before, 58.5 gr non-crimped and 57 crimped. Thoughts? Is this what you call a "node". It was about 12 degrees warmer this second time. Using N560 powder. I think next time I'm going to use a slighter crimp with the LEE crimper and see what happens. To remind anyone reading this, I'm relatively new to reloading. Talk to me like I'm a 2nd grader. Any advice is appreciated.

You are doing great,