Before I get slammed too hard here, let me say that I know that ejector marks on brass are a sign of excessive pressure.

Here is my problem. I'm loading for a 7mmRUM, model 700 LSS. Using new remington brass, CCI LRM primers and 175 gn Nosler Partions. I have been experimenting with IMR7828 and IMR4831.

A while back I switched from standard LR primers to magnum LR primers and backed way down on the powder and worked my way up again. I started with the IMR 7828 at 72.0 gn and IMR 4831 at 69.0 gn.

At both of the lowest charges, I noticed a very light ejector mark on the brass. Primers were somewhat flatter than new but nothing more than past experiences with this gun and a .243 Win. Being new to reloading it spooked me and I picked up a box of factory ammo, which is the first time I've done so with this gun. When I shot the factory loads,(remington's), I also noticed a very slight ejector mark on that brass.

By very light, I mean that you had to have the angle of light just right to see it.

Perhaps follishly, I worked my way up a total of one grain on each kind of powder and noticed no difference in markings.

Am I over reacting to very light ejector marks here or is there another problem? by the way, I will be seriously thinking about ordering a chrony in the near future after this experience.

Thanks in advance for your help!

I don't know of ANY firearm that don't leave ejector, extractor, or even powder marks (brass from the H&K G-3 for instance) on cases. But you are doing the right thing by being cautious. Take care.
b

Cycle a couple of new loaded rounds through the action. Do not fire them. Do they have "ejector marks"?

The ejector cut-out for the Remington 700 action is rather large, compared to most actions. As a result, it will show an ejector mark at lower pressures than some other actions. Also, Remington has earned a growing reputation for lack of proper finish in their actions, and a rough edge around the ejector cut out could help show an ejector mark.

Another factor may be the hardness-softness of the brass. If brass is not properly hard in the head area, it will show ejector marks at SAAMI pressures and below. I haven't experienced any problems with Remington brass in this respect, but a lot of posters perinnially complain about Remington brass on this forum.

As with most newly-released "super calibers", the factory loads them to a much higher pressure than calibers that have been around for a while. This is partly due to their wanting to establish a reputation for velocity claims, and partly due to their being none other than new, modern actions chambered for such cartridges, thus widening the margin of safety. (This is how they make it appear that the "short magnum" cartridges perform at the same levels as the more capacious older belted cases.) As a result, the factory loads you are shooting may be substaintially higher pressure than the brass is manufactured to handle without fatigue (head swelling, loosening primer pockets).

Now to another problem: IMR 4831 is way-the-hell too fast for any but the very lightest bullets in a 7mm RUM, and IMR 7828 is too fast for most applications, also, especially the heaviest-for-caliber 175 grainer. If you want to reap any velocity benefit out of the oversized case, you'll have to go to something like AA 8700, Hodgdon Retumbo, or better yet, a surplus powder like WC 872.

[ 09-25-2003, 19:06: Message edited by: Stonecreek ]

You really can't work out a problem like this without a chronograph. Yes, your powders are a bit fast, but your charge weights are low. The CCI primers are notoriously hard and do NOT flatten with overloads. You are right to be cautious and take the marks seriously.

Here is why. Last year I worked on a similar problem with a custom bench 260 Rem for a customer and shot it over my chronograph with 140 grain factory ammo. It AVERAGED 3220 fps!!! This is hotter than a 264 Win Mag.

Even start loads with 4350 were way too hot. We went several grains below start to calm it down to 2800 fps where it belongs. Turns out it had a very nice, smooth, hard bore that was a bit tight. It now shoots 5 shot groups into 0.35 MOA.

You really should shoot one of your light loads over a chrono and see what is going on in the velocity dedpartment. If you are getting 2800 fps or less keep working up and watch for other signs of pressure, switching to WLMR primers that flatten easier.

Thanks for the help folks, I feel a little better. I think a chrony is in my future!

I'm a little confused about IMR 7828 and 4831 being too fast though. the powder charts I have seen list them as a slower powder. what is a good chart to be checking with?

Those powders should work, as will RL25.

Check out stevespages.com

he's got a shitload of info.

Here's a trick I use that helps a lot with burn rates and powder selection.

1. Divide your case capacity (grains of water) by your bore squared.

112/.277X.284 = 1389

This is a very important number, and every case and bore has a number like this. For reference, the 308 Win is 527 and the 270 Win is 821. Anything over 1000 is getting up there.

2. Divide you velocity goal for the bullet you have in mind by #1:

3300/1389 = 2.38

The velocity goal needs to be a max velocity from a manual or factory dada for a given bullet weight. I used a 175 gr bullet here.

3. Multiply #2 by 10, and you have the burn rate of your powder expressed as a highway speed limit.

Yup, your load requires a powder held to 23.8 MPH. The 308 Win above with a 150 gr bullet seeking 2850 fps gets a 54 MPH powder.

4. As a bonus, you can multiply #1 time the velocity and raise this number to the 0.22 power and get optimum barrel length.

1389X3300^0.22 = 29.2 inches

Your 26 inch bbl is holding your loads back by 3.2 inches of bbl, or 100 to 150 fps.

NewReloader,
Ejector marks on the case head are actually a symptom of excessive bolt thrust. This is often the result of excessive pressure, but there are other causes.

If there is any oil present in your chamber, the case will not be gripping the sidewalls upon firing, and excessive back thrust against the bolt face occurs. This most often occurs immediately after cleaning the bore. Even though I use a good bore guide, sometimes a dab of solvent, Kroil, or whatever you're using can get into the chamber when withdrawing it. I keep a wool shotgun bore mop on hand that fits the chamber. I apply a quick shot of a non-filming degreaser(such as brake cleaner) to the bore mop and swab out the chamber to assure that no oil is present.

This may not be your problem, but it's something to keep in mind.

Sam, that's a good thought about oily cases/chambers causing these marks. Thanks!

My experience with Remington brass is that it's softer than most and therefore more likely to show ejector marks. FWIW.

Well, Good News! I shot several different powders/loads over a borrowed chronograph today and was very happy.

With IMR 7828 and IMR 4381 at mid range loads I was at about 2700 fps. With Reloader #25 at mid range I was at @2800 fps, and with Retumbo @ 90.0 gns I was between 3030 fps and 3060 fps. Not quite the advertised 3300 fps but in the real world I'm happy with the results. This grouped 3, 3shots groups under one inch as well.

Thanks again for all your help and suggestions!

Nice work! Now try some AA8700 and work from 92 up to 103 grs if you can borrow the chronograph again. This will put you in the 3250 to 3300 fps range.

Have you played with this load Sabot? Sounds like a real screamer to a new guy like me.

Interestingly enough, I have been playing with the program "Point Blank" balistics and found that the 7MM RUM load I am so happy about has a better trajectory than my most accurate .243 load to date.

For my .243, I've had the vast, vast majoity of three shot groups within 3/4 MOA using 70gn Nolser Balistic Tips and 38.5 gns of Varget. Not the fastest I've found from what I have been reading, (3030/3023/3030 fps on my recent Chrono experience), but very tight groups.

This brings me to two new points to make here. The first being that I've been really blessed by having such good results with the only two guns I have reloaded, especially for a newbie to reloading. Both Remington 700's, one new and one old, with no midifications made from the factory.

The second is that neither of these loads would have been working for me if it wasn't for this site and all the great advice I've been given. Thanks again to all of you who help the newbie's!

By the way, does this mean I'm doomed for failure with the next gun I try to reload for!?

No, you're not doomed. Just keep at it and have fun with it. Some day you'll be a "Master Reloader" and know it all, until suddenly a problem arises and you realize you don't know anything. We've all been there. Good luck.

You might want to try some IMR 5010.Reasonably priced and hard to over load. Might even be a little to mild.I have used it in large capacity cases with heavy bullets with some success.
You can buy it from high tech for $24.00/8 lbs.
I don't know what today's H870 is like but 33 or 34 years ago I stopped using it as it seemed to leave what looked like a Mica deposit on the inside of my barrel. Those who ran into that problem and tried to get their barrels clean again know the agony.

AA8700 is a tad faster than H870 and is not the same powder. I have put pounds of 8700 through a 300 RUM with none of the "mica" effect you mention. The loads I listed for the 7MM RUM are right out of AA's 2002 Reloaders guide. Their 8700 data for the 300 RUM was right on in my 26 inch bbl.

AA8700 seems to be notably slower than H870 in the .300 Weatherby. Just an example of how burning rate orders don't always hold up in different cartridges and loads.