Pressure signs in a 7mm magnum

R

Right to bear arms

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I need a little firing line help on my 7mm Remington magnum reloading. Here is my scenario. I recently acquired a win model 70 XTR in 7mm magnum. Today I test shot a few loads. I started with 60gr RL22 behind a 160 gr accubond. I worked up to 61 gr and a little extraction difficulty seemed to ensue. When I tried my 62 gr RL22 the bolt lifted OK but it took some effort to extract the case. there was little primer cratering but there was black soot around the rear of the case. My question is thus. Many manuals list 63 grains as tops. and many hand loader have loaded up to 67 gr RL22. Is it possible my gun is so sensitive that 62 gr tops it out? I would be grateful for any experienced input. thank you.
 
Clifford L. Hughes

Right to Bear Arms:

At first I thought that you rifle has a fouled chamber: however, when you said the case head, I take that you mean the head stamp portion, I'm not so sure. Soot around the primer pockets means that gas is leaking from the primer pocket. What I would do is reduce the minimun load by ten percent and work up from there. Check the chamber also to make sure that it's smooth.

Semper Fi.

Gunnery Sergeant
Clifford L. Hughes
USMC Retired
 
Chamber appears smooth. ambient temperature was about 90 degrees F. Recoil wasn't excessive. I just want to develop a successfull 160 gr accubond load I can use for all game animals. Thank you for your response gunney!
 
60 gr of RL22 behind a 160 gr accubond is enough for everything in North America. If that load is accurate in your rifle stick with it and think nothing of going for a heavier charge.

Jimro
 
Exactly, once you have a load which will do the work you want to do, accuracy becomes the issue not more fps. The game will not be able to tell the difference.
 
The XTR was made at a time when the RM was typically short throated. I had a 700 during the 70's-80's and it was short throated. If the measurement in front of the belt is more than .0005 greater than SAAMI spec, back off a grain. Black soot is bad, also.
 
I can't remember but I think RL 22 is a ball powder?

If so, it soots considerably if the pressures aren't high enough. If your primers aren't flattening and you have no pressures signs the soot can be the problem but I don't remember max. loads for RL 22 in the 7mm mag. I didn't really like it. RL 22 site gives 65 as max with 160 gr Speer bullet. If the outside of corner (radius) of the primer is not flattening your pressures are safe. That is the first thing (I've personally found) that shows when you are getting too high. I reloaded for many years and made many stupid mistakes when starting out. Some "expert" told me to watch the primers closely and that was the best information I ever received in regard to handloading.

Consider Winchester 760 or new supreme 780 powder or the new Hodgdon powder used in Hornady's superperformance ammo.

http://www.ammoland.com/2010/10/11/hodgdons-new-hornady-superformance-and-leverevolution-powders/
 
It sounds to me like it's a pressure issue, better stick with 60 grns or switch powders. Does the RL22 give you the best accuracy? I'm currently working with the IMR 4350, and 150 Nosler Partitions in my 7 mm Rem Mag, and it's loving them! I'm right at 61 grns, with no excessive pressure signs, not bad recoil, and they're accurate.:)
 
60-65 grs. is about standard for all the powders from 4350 and slower. H4350, H4831 and RL19 are also good for the 7 mag., as is H1000 and IMR 7828. You really need to tell us what you found when you measured for head space and COL. If you don't use a chrony, pressures can really sneak up on you. I've found that velocity will sometimes appear to "flatten out" just before a sharp spike when using .5 gr. charges to test between load weights. Make sure your bullet depth isn't so short that the case neck is full of boat tail!

-7-
 
Thank you for your responses. I know I'm showing my ignorance here. but how does a laymen without gauges measure headspace and how do you measure COL? Once again my primers were seriously cratered. The most prominent sign of pressure was the amount of pull I needed to exert to pull the spent cartridge out of the chamber. Right now my plan is to stop at 60 grains and be satisfied with a 2700-28-- fps bullet. I might try H1000 in the future. This gun was manufactured about '94 and has a DPM. I tested the 160 accubond until it touched the lands and shortened it about .05. to fit the magazine.
 
Many factors could be influencing your results.
For example,do you have test weights to verify your scale is really delivering 60 gr?
I do not know if Accubonds themselves run pressures up,but they do have thicker jackets,they may offer a little more resistance going down bore.
Re-22 is an appropriate slow powder,but try H-1000 and see what works best.
Do you have a chronograph,or access to one?If so,I'll make more comment.
Is this a new rifle?The bores get blued.That can run pressures up for a while.& mags can metal foul heavily.That can be a problem.
If you feel a sticky bolt,its time to stop and back up.Look close at the case head for a shiny spot indicating a little extrusion into the ejector cut in the bolt face.
Its still cool in the spring.Late July,those loads might bite you.
I recomend you size your brass so you heasdspace on the shoulder,not the belt.Set the shoulder back .002 or so.There are tools to measure this.Watch for stretch rings about 5/16 in fwd the belt,use the bent paper clip trick to check your brass inside.(see your load manual)
One other thing can boost pressures.If your brass is long or chamber neck short,the case neck is not free to release the bullet.Check case length.
If you do not have calipers,get some.
 
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I have a question. How does an individual commence reloading without essential equipment like a caliper? Measuring the case head expansion is a sure bet in guaging pressure..
 
GeauxTide:
How can I learn with out asking questions? I've been reloading for 35 years. I have NEVER bought a factory load for 16 different rifles. Incidentally I own many calipers and gauges. I'm sorry but I'm pleading ignorant of how to measure case head expansion. what is the case head? what do you measure? How do I tell if expansion indicates high pressure signs? Please don't give me any sermon about my lack of knowledge. just tell me how I can make a safe , reliable, load for a 7mm Magnum using 60-64 grains of RL22 behind a 160 grain accubond.
 
... I worked up to 61 gr and a little extraction difficulty seemed to ensue. When I tried my 62 gr RL22 the bolt lifted OK but it took some effort to extract the case...
Click to expand...
When you get "extraction difficulty", you should not increase the load. In what hand loading book did they tell you it was a proper thing to increase a load by a full grain when extraction got sticky? All the loading manuals I have read/possessed (since 1964), have stated in essence, "when extraction gets sticky, STOP increasing powder!"
 
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Case head expansion can be a useful indicator.Find it in a good reference and study it .I would guess Ken Waters would describe it ,but I do not have his book to check for you.
A hard lifting bolt handle is an equally useful indicator the somehow pressure is too high.
One thing I find interesting about the commentary,case head expansion is measured carefully with a good micrometer.It is about tenths of a thousandth.
Monitoring pressure via case head expansion with calipers ???I'll say"Not conclusive"
Not every rifle can safely be loaded with max loads.Thats why there is a start load and workup.
If you have been loading for many years,tell me about your scales.Have you checked calibration on them?
I am having a hard time with the idea you could get gas leakage around the primer with a published load.Makes me wonder .
 
Well...there's a good reason why they list START loads. That's where you start at. Which is exactly what the OP did. And he correctly noted that a sticky extraction is a great sign of high pressure. He did everything right and is now just wondering why the high pressure? I dunno either. I have used RL-22 in my 7mm mags and like it. You can try H-1000 or 7828. I like both of them as well. But chances are, you'll run into the same pressure problems down around the starting point. Nothing wrong with that as long as you're getting good accuracy. As for thinking you'll be "settling" for a lower velocity, well don't bet on it. Chances are good that if you're getting that high pressure at a lower charge weight, then you'll still be getting the velocity that you would get in a different rifle with a higher charge weight. Pressure is what gives velocity. You won't know unless you chronograph your loads. I always go for accuracy first and don't worry about velocity.
 
Thanks to everyone.

I've just discovered the true value of the firing line. Although I have been a nominal reloader for most of my life, it's never too late to learn new and safer techniques. Here are some of the suggestions I am going to implement.
1. Recheck the OAL and bring it in line with specs.
2. vigorously scrub chamber with solvent
3. Do not exceed 61 grains of RL22 until all signs of overpressure are eliminated
4. Borrow a friend's chronograph to get some real world numbers.
5. establish a pressure-safe load before attempting to optimize accuracy.
6. Probably stay away from case head expansion measurements until I get a finer caliper.
7. neck size instead of full-length size
8. test on a warmer day. RL22 shows more pressure on hot days.
just a few of the things I've learned. thanks again.
 
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