I am handloading .300 Wby with the recommended load in the IMR data: 180 grain Nosler ballistic tips, 85 - 86 grains of IMR 7828 on Federal #215 magnum primers.

The load shoots well, but the primers are all showing significant flattening, which I understand is a sign of excessive pressure. What can I do to reduce the pressure aside from reducing the charge - anything? I'm also loading them quite a bit longer than the OAL specified - would this make a difference?

Thanks,
Jason

If you're close to the lands, pressure and MV will likely be higher. Backing the charge off wil bring it down, reducing the OAL can too. If I run 'em up to the lands, I usually back the charge off from the book max for this reason.

Watching MV using a chronograpgh will give you a good indication of what's happening.

Cratering of the primer around the firing pin dent is often another good indication, as is brass extruding into any other recess in the bolt face, stiff bolt lift etc. All of these indicators should be used, not just a single one.

Another thing would be to back off on your sizing die until your just barely touching the shoulder.
Excess slop in the headspaceing will also flatten the primers.

Is it a Weatherby Mark V Rifle ? If not , it might not have the freebore , designed with the Weatherby cartriages . Another thing , What brass are you using ? Some nickle brass from Federal has shown higher pressure than standard Norma Weatherby brass .

Some primers flatten more easily than others.

There are a lot of commercial loads that show significant flattening.

With many kinds of primers, flattening starts to be noticeable around 50 KPSI, which is well below max for most rifles.

The Weatherby Vanguards have the freebore as well as the Mark Vs.

The reason for that freebore was to reduce pressures with the crazy hot loads of IMR 4350 Roy Weatherby used to stuff into those things, and it probably also minimizes pressure differences from rifle-to-rifle dimensional tolerances. It certainly makes small differences in seating depth or bullet ogive shape noncritical. As has been discussed at length in threads on non-freebored custom Weatherby caliber chambers, you can't use the maximum book loads (or factory loads) safely when the freebore's significantly reduced. (Which seating the bullet out long, close to the lands, does.)

It is a Mark V (SBGM), and I've been using both Federal and Norma brass. The brass I've noticed this most on is the Norma. I think I'll back off the OAL a bit and allow the freebore to do its thing. I've read several places that people go up to 3.60 or longer, so that's what I did. I'll back it up 3.58 or so and see if I get any improvements.

Thanks,
Jason

Jason:

What brand of primers are you using? I would look at that. Remington and Winchester primers are much softer than Federal and CCI primers.

I use the latter two, and when I have flattening, I know my pressure is getting up there with them.

Good luck on figuring it out tho.

I actually find the federal primers to be softer than the others.Lee actually recommends that you don't use their autoprime tool with federal primers because of a concern that they may accidently be detonated because of this.

[ 12-02-2003, 09:08: Message edited by: stubblejumper ]

I've been using nothing but Federal #215 primers. Wonder if they're just soft. The brass shows no sign of excessive pressure, and there is no cratering around the firing pin dent. When I get around to it, I'll post some pix of the fired primer.

I've given up on trying to judge pressures by checking the primers (but, out of force of 30 years' habit, I still look ). Lot to lot variation in cup thickness and/or hardness can cause excess hair loss. Throw the wild cards of different internal case capacities from various mfrs into the mix, and it starts coming out in clumps.

Unless you have some pressure testing equipment, the only way to even get close to maintaining a comfortable safety factor is to use a chrono and compare mfr's data (preferrably taken from a SAAMI standard pressure barrel) for a given charge weight/bullet combo, while, hopefully, using the same brand of cases and primers as they did, with what you're seeing on the chrono. Otherwise, you're pretty much flying blind.

As to your specific application, it is quite possible your primers are soft. I've run into this numerous times with Federal and others. Let the chrony be your guide.

R-WEST

AZ: I wouldn't be troubled about your primers flattening. Federal makes the softest primer cup of all the manufacturers -which is why Lee doesn't want them used in their tray tool. I've used Federal factory handgun ammo, and use their primers in my handloads. The factory stuff flattens out so that there is almost no radius around the edge. Enjoy your loads and rest easy.

Flattening may or may not indicate too much pressure. Excessive headspace due to oversizing the case can also cause it.

A good test is to size and prime a case, then fire the primer in the rifle. Eject the case and look to see if the primer has backed out of the pocket at all. If it has, you are moving the shoulder back too far for the chamber, and should ease your sizing die up a hair to compensate.

In the event that this isn't happening, then flattening indicates higher than normal pressures. Also look for "cratering" around the firing pin dent, and if you see a bright ring around the ejector hole in the bolt face you are WAY too high for that gun.

I had a Winchester 88 in .243 that would give all of these signs with any 100-grain bullet load, even factory due to very tight chamber and throat dimensions. I had to back all my loads off at least 10% off starting loads with 100-grain bullets before I was comfortable with them, but with 80 or lighter could run up to full manual max without any signs of pressure.

Every rifle is a law unto itself.

I run a Rem sendero in .300 Wby, but I don't have much info on 180g bullets. We always use 200g Sierra soft point boat tails. We also use H870 for the powder but that might be to slow for the 180g bullets. It works great with a 200g very impressive numbers over the chrony, 200g bullet at 3060fps. I seat to mag length, fire form and neck size only, nothing special. I always have used Fed no.215 primers, they are always fairly flat with that load.

[ 12-07-2003, 07:10: Message edited by: bearcat ]

Lots of advise out there and its good but your problem is that you are 4 grs over book max for IMR-7828!! I expect that would flatten a primer or two....

82 grs. is book max. in most reloading books and I have found that to be about sure nuff max in most of the 300 Wbys I have loaded for.....Many of them really did better with 80 grs.

Flattened primers can be from a myriad of causes, and IS A TOTALLY UNRELIABLE MEANS of determining if your pressures are excessive. If your loads are shooting accurately, your decision as to whether you need to cut back on the load should be based on how many times you can reload the cases before you have to discard them. If you have a good chamber and a properly adjusted resizing die, you should be able to reload your brass 8 to 10 times (or more!!) before it is worn out.....

If you can't get at least 8 reloadings out of your brass, it might be that the load is too hot. But there could be other problems causing that, too!!

The fact that your load "is over book maximum" may or may not be of any significance, because you don't know anything about how the manual publisher decided what a "maximum load" is.....

[ 12-08-2003, 20:04: Message edited by: eldeguello ]

I agree with Tailgunner. I have a 300 weatherby mag and had similar results. I started sizing the brass so that the die barely touched the sholder. This allows the brass to head space on the sholder not on the belt. Doing this will allow greater brass life as it slows down the brass streching due to excessive chamber demensions. I don't necessarily like the idea of head spacing on a belt when there is a perfectly good sholder to work with.