Loaded up 300 PRC for first time

[waveslayer]

That speed is about right.. what's your barrel length? I'm getting over 2900 with 230gr. But I'm running a 28" barrel out of my DT.

My wife thinks I only have 3 guns

[croue]

[ShaunBrady]

QL doesn't think you should be having pressure signs with those charges and velocities.

The top 212 load:


Not even 60 ksi. The start pressure required to true up the velocity is kind of high. I tried some data from the Hodgdon website to see what that was about.





The high start pressure was also required there. I think it has something to do with how QL models those powders. The QL estimate for the peak pressure required to make that velocity is also out of bounds.

Velocity is pressure, but pressure doesn't always turn into velocity. Peak pressure has the strongest effect on velocity. Using a lot of a slower burning powder keeps the average pressure down the barrel higher, but it's a weaker effect and has consequences.

This is the primer from a 300 PRC load that has a QL pressure estimate near yours:



This is what happens to Hornady brass at ~68 ksi:



If the brass is showing more pressure than this, I'd check how much the fired case neck expands. If that came back OK, maybe try a box of factory ammo in it. Running the gun at lower velocities isn't great, but it happens. Data from another powder would also be interesting. Your velocity spreads look great, but QL suggests that powder is too slow.

[ShaunBrady]

The 190 model:



It's the same story as the 212. Lots of start pressure required to match the velocity, but peak pressure is low enough you shouldn't be seeing pressure signs.



My current 230 ATip load:



The break in load I used:

[croue]

[ShaunBrady]

Thanks Shaun!
When I get a chance to look at this on a big screen I may understand better what it’s telling you.

The 85 grain load flattened the primers very completely in many cases and blew holes in several.

I thought to fast a powder was what gave high pressure vs speed?


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Too much powder gives high pressure.

In a given product line, there might be 3 powders that'll work reasonably well.

The slowest powder in that lineup will just fill the case as pressure is reached. It'll give the highest velocity because it'll maintain the highest pressure for the full length of the barrel. Velocity spreads with this powder will frequently be good but not really good.

The middle powder won't give as much speed but will frequently give better velocity spreads.

Here are the first 5 of the R26 225 ELDm break in load. The velocity increased with each shot except for the 5th with was faster than the 3rd but slower than the 4th.




The next 10 shots. Now the barrel is fouled and we have a much better idea about how the load is performing. It helps to show up for matches with 5 shots through a cleaned barrel. I do the same thing with hunting loads. You can clean the barrel again after the season.




The final H4831sc 230 ATip load, ready to try one of Lynn's 2K matches.



The fastest powder still works reasonably well but isn't the best at anything.

The next slower powder above these won't build enough pressure to max out velocity and probably won't burn cleanly. Trying to over fill the case leads to erratic seating depths and can damage bullets.

QL provides clues on where a powder is going to land in that lineup with the Z1 line. It's the point where the powder's burning characteristic transitions from progressive to digressive. A progressive characteristic means it burns faster with higher temperatures, digressive is the other way. If that Z1 line is a little before peak pressure, it's more likely that the velocity spread will be low.

Factory barrels often need lower start pressures than custom barrels to line up the model with the observed velocities. The lower start pressure can drive the optimization to faster powders. Lighter bullets also tend to drive the optimization towards faster powders. If it looks like you're caught in between powders, the start pressure can be driven up by jamming the bullet 5 or 10 thou or down by jumping 20-25 thou. Primers are another way of moving the start pressure up or down. With single base powders used at temperature above about 40 degrees, better velocity spreads can sometimes be found with large rifle rather than magnum primers.

The lineup of some powder brands has smaller steps than others. With the 300 PRC using the Hodgdon Extreme lineup, it's H4831, H1000, and Retumbo for heavy bullets and high start pressures. The steps in the Reloder double base lineup are R17, R26, and R33. R26 is really the only choice. Fortunately, it works pretty well if the temperature sensitivity isn't a problem.

I use a similar approach to yours when starting out with new guns, cartridges, bullets, and/or powders. I switch the size of the steps though. The lowest charge is 2 grains lower than the next one. Sometimes I'll load 10 of those instead of 5 because the first 5 are throw aways as a clean barrel fouls. For something the size of the 300 PRC, a couple 1 grain steps, then the last 2 are half grain steps.

I assumed blown primers meant a sooty shart around the perimeter of a very flat primer. A primer puncture somewhere in the strike could also be a firing pin problem. If the cases that had those punctures still had reasonably tight primer pockets, it's more likely a firing pin problem than pressure.

Your next steps might be make sure we're on the same page with pressure by checking those primer pockets. Either way, I'd still check the fired case neck diameter because that's something that's good to know about a gun as soon as you can.

[croue]

Interesting stuff.
The blown primers were truly blown, not a firing pin pierce.
Some gas jetting around the edges even. Ended up tossing those brass as the pockets are compromised. And now my bolt is less pretty. But the marks are quite tolerable as far as performance goes.

I found some OK loads with the LRT. Not likely to be my favorite powder once H1000 comes fully back and easier to find.

Once I get a load, I'll order the custom dial from Leupold, so need to make sure I get a load that works really well before I commit.

I do hunt wintertime in MN and CA, so temperature sensitivity down to below freezing is a concern.

I love H4831SC in my 270's. Very accurate powder for that round.
Maybe I'll try 4831 in the 212 gr bullets cautiously. That's the 'light side of heavy' for sure in the 300, but long bullets when it's non-tox.

Magnum powder arriving today, will try with both 190 and 212. Suggestions for approach? Knowing that my barrel (Christensen Arms Traverse rifle) seems to run a little higher pressure than expected.

The necks expanded to 0.3410" using Peterson brass, second firing and neck formed only. I didn't have heavy bolt lifts really, but a few seemed to 'catch' and I worked the bolt down and up to release. So neck may be tightly expanded into chamber, but not the body it seems. Figure 1-2 more firings and then anneal and full length sizing.
I screwed up and ordered dies that don't take neck bushings even though I ordered the neck busnhings. May need to buy another set to get things really dialed in.

[ShaunBrady]

You might try a minimum load of H4831SC with the 190s to see where that lands. Faster powders for lighter bullets. In this case, lighter bullets for faster powders.

What is the neck diameter of your loaded ammo before firing?

I full length size everything every time. I'll use a one piece sizer if I'm going to neck turn, generally a bushing die otherwise. With the bushing die, even with turned necks, I size a couple thou under the final target and then expand with a Lyman M die. I haven't been annealing for the last few years. I let the necks go full hard after a couple firings. The primer pockets are usually gone in 8-10 firings and I'm not splitting necks. Aside from pinning the neck tension at a consistent value, it also saves readjusting the sizing die bump each loading. I have a Bench Source annealer I still use for some things. I'm revisiting annealing my precision loads with an AMP annealer. I'm after lower seating force to prevent damaging fragile long range bullets.

I'm using the 300 PRC for targets beyond a mile and the effort that goes into that ammo would be ridiculous for a hunting load. Some of that is going to bleed into this discussion for background. It's not intended to be advice on how to load hunting ammo. Maybe other than if I don't care about the last bit of velocity, maybe it won't really affect your hunt either.

Are we working with jacketed bullets or nontoxic solids? With the blems, you might cut one in half with diagonal cutters to check. The solids will likely run at higher pressures and have no sense of humor about tight bores or bullet release issues. The weight, length and tip color usually give it away, but being sure is better. If they're solids and that's what's required to hunt in NorCal, it is what it is. Figure out what velocity is there for reasonable pressures and move on. The animal will never know the bullet was a little slower than you'd have liked.

The Barnes site has some solid hunting bullet loads that might give useful perspective.

Please post your results. I'm interested in where this goes.

[croue]

[baih777]

Is there a 99 cent store near you.
Get a magnifying to check the primers.
I keep one in my range bag and another on my bench. And third one. Its only 99.cents.

[croue]

[croue]

[ShaunBrady]

Or the gun. It could be tight in the neck, freebore, or bore.

If it's the neck, it'll get worse the more times you fire the brass. The reason for the 4 thou difference between fired and unfired suggestion isn't that much clearance is required to actually release the bullet. Thats the number I've found makes it likely unturned brass won't give you problems. Sometimes the variation in thickness from side to side creates problems, sometimes the brass comes with premade donuts that get worse with each firing. Even if you have a nominal 4 thou clearance, 3-4 firings might be all it takes for donuts to start. That might be before you even need to trim.

Fliers are harder to stop with a magnum rifle, but they may not be you. All of the brass isn't going to change exactly the same way at the same rate, especially if you've been doing pressure ladders.

How are you determining your target OAL for each bullet? Using the Hornady setup with the modified cases can tell you if the freebore has enough diameter. That dimension goes down the more a reamer is used.

My guess is probably not but testing with factory ammo will probably be required to send the gun back for warranty work.

[croue]

[croue]

I have the Hornady gauge now and will try it out. I did the old school sharpie marker already and have clearance at my seating depth. So not jamming into the lands.


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