I was out at the range today testing some reloads. On firing the 7mm mag the second round after a fouler came out black on both ends, like soot. I noticed no problem chambering, firing, or extracting. During the coarse of the session I fired a total of 25 rds. The brass was new winchester, 120g Sierra hp,IMR 4831 @61.8g, col = 3.191" WLRMag primers. The case other than extremely dirty looks OK. This is not a hot load, as I fired 63.6,65.4,67.2, and 69.0 in 5 shot groups. Anyone have a clue?
Jim

I was out at the range today testing some reloads. On firing the 7mm mag the second round after a fouler came out black on both ends, like soot. I noticed no problem chambering, firing, or extracting. During the coarse of the session I fired a total of 25 rds. The brass was new winchester, 120g Sierra hp,IMR 4831 @61.8g, col = 3.191" WLRMag primers. The case other than extremely dirty looks OK. This is not a hot load, as I fired 63.6,65.4,67.2, and 69.0 in 5 shot groups. Anyone have a clue?
Jim

When a round fires, the pressure is supose to expand the brass case to make a seal to the chamber...as spressure drops, the brass contracts and allows you to extract and eject the case.

What you describe is a case that never generated enough pressure to expand and seal the chamber.

That can be from three interlinked reasons:
1. Pressure is too low
2. Brass is too hard
3. oil.grease, solvent coating the chamber (which would not only add some fouling, but retard #1 above).


As you can guess, can be a combination.

I see your point, odd that I noticed nada, except all the groups were bad. I just used this same powder on 100g Hornady and hit a magic load combo. Back to the drawing board, thanks for your reply.
Jim

Mr. R Stone has covered the "why?" part real good. I can only add that 61.8 gr. charge is on the light side for IMR 4831. I show 62.1 gr. as a starting load.

I have also noticed a difference in powder behavior with IMR as of late.

As Mr. Stone said, it could be a combination of things if it was only one cartridge of five.

Perhaps you found a good working load with a different charge level anyway?

Cheezywan

I have the Sierra #5 manual, and the starting load is shown as 61.8 for IMR 4831. I bought a bunch of this powder 30+yrs ago and if I would have saved the manual of that time the load would not have made the cut I would guess. I was trying a low to high loads for this bullet with my surplus 4831. It worked in a 100 g bullet. I realize this is probably to light for the 7mm mag but thats reloading.
Jim

My new Lyman 48th Edition shows 65.5 as the starting grains. Shows 73.0 grains max. Loading data has changed, and so has the powder to an extent.

I didn't look at the Lyman manual. Appears to be a big difference in manual info. I just ran some 223 loads on 60 g hp for Hornady and Sierra I ended up with one compromising load from the start to near max. So one may have to disregard the start load as well as the max when working up a load. Thanks for the reply I will put this bullet aside for now and go to the 139g in 7mm.
Jim

I found a old Sierra manual. I can't find the edition on the cover page? It is dated 1985. Data for a 120 spitzer starts at 61.7 gr. @2900fps and top ends with71.1 gr. @3400fps.
Sierra reports this from thier Universal Receiver with a 26 inch barrel 1-9.5 twist using Remington 9 1/2M primers.

I have a couple of lbs. of IMR-4831 that pre-date this information. It sure shoots well in the 6mm. Rem. though!
Good luck to you Jim in Iowa.
Cheezywan

I found a old Sierra manual. I can't find the edition on the cover page? It is dated 1985. Data for a 120 spitzer starts at 61.7 gr. @2900fps and top ends with71.1 gr. @3400fps.
Sierra reports this from thier Universal Receiver with a 26 inch barrel 1-9.5 twist using Remington 9 1/2M primers.

I have a couple of lbs. of IMR-4831 that pre-date this information. It sure shoots well in the 6mm. Rem. though!
Good luck to you Jim in Iowa.
Cheezywan


For what it is worth, the Lyman 46 (not the newest edition) lists H4831 as starting with 67gr. and ends with a compressed 74gr. That's changed in more modern manuals.

And it's really not the point.

Slow powders, light bullets, and minimum loads are the most likely to demonstrate case blackening. Peak pressure isn't high, and it happens later...perhaps late enough that gas has already sooted the sides of the case before max. pressure is reached (pressure that would have expaned the case and sealed if it had happened more immediately).

Much fired cases are also more likely to casuse this...they grow less ductile and less willing to expand at lower pressures.

Have a 44th Edition of the Lyman Reloading Manual (1967). For the 7mm RM, using 120 gr JSP and 4831 powder:

Start load: 68.0 gr @ 3105 fps

Max load: 75.0 gr @ 3460 fps

Jim,
Do we understand that you are using 30+ year-old IMR 4831? If that is what you are saying, then you are using WW2 surplus powder. Its burn rate most closely resembles that for today's H 4831. This may explain the low pressure signs you described.

Hey Jim, you get that 100 gr load that we discussed to work out well for you? I actually got the same thing when I loaded those light bullets early on, for me it was a really light load, i increased it and it hasn't come back with any of my handloads. I suppose it could also be if your using brass you have resized several times, since it gets work-hardened, but I'm sure its probably just a light loading.


-Martin

Slow powders, light bullets, and minimum loads are the most likely to demonstrate case blackening. Peak pressure isn't high, and it happens later...perhaps late enough that gas has already sooted the sides of the case before max. pressure is reached (pressure that would have expaned the case and sealed if it had happened more immediately).

Much fired cases are also more likely to casuse this...they grow less ductile and less willing to expand at lower pressures.

I think this quote is right to the heart of the matter.
Cheezywan

Is it possible that a .277 bullet got mixed in with your .284's? That would account for just 1 being low pressure.

You may need a magnum primer to light this powder up.

I bought the IMR4831 in the early 70's, this is ww2 surplus powder? Anywho the powder looks OK,smells OK and recently performs OK. The brass was new unfired from Sheels, full sized, wlr mag primers. I use a Pact scale and dispenser for every load. This was one load out of 25 loaded in increasing powder loads, and this was the starting load as per Sierra manual #5 est at 3000fps. I have never owned .277 bullets, however I recently bought a Tubb fire lap system for a .338, and one bullet was .308 and a Sierra, one would think!!!
Martin; the 100 g Hornady did -.75" for 5 at 100. Using the same powder we are talking about. It started out at 2.5" and came down as the load increased, then back up. medium + load, light bullet= nice group for this old sailor. Thanks for your replies I have learned in spite of my years of reloading, one can be more diligent.
Jim

I bought the IMR4831 in the early 70's, this is ww2 surplus powder? Anywho the powder looks OK,smells OK and recently performs OK.

I always thought IMR was usually newly manufactured powder. Hodgdon was the main vendor of surplus powders back in those days. If it is surplus it could be Korean war or possibly even Viet Nam surplus too, I suppose. Even if it does date back to WWII, smokeless powder has a very long shelf life if it is stored properly. Since it passes the smell and performance test, its probably just fine.

Small world you being in central Iowa... I grew up in Iowa, lived in Ames for about 13 years and then Des Moines for 10 or 11 after that before I finally got smart and moved down here... :D My parents and brother still live up there.

You might concider hoarding the powder back for another application? Just because it didn't work for you now does not mean it is old and useless. Keep the cans stored tight and dry, and you can reap the benifits later. Put the sealed cans in a ziplock bag and move on!
Ya might try IMR- 4350 or 4064 and see what happens with your 120 grainers? It is as much fun makin um as it is shooten um!
Cheezywan

My IMR 4831 is in air tight containers and my go-to-powder of the slow burners. The 338 and 7 mag consume lots compared to the 243 which shoots a 75 g fairly tight with the 4831. I may try the 4350 as I have some, with the 120 g bullet. My next test in 7mm will be the 139 and 140 gr bullets. My log shows a load for 120 Sierra using IMR 4831 that was "OK" no date, it was at 70.0g. This would have been back in the late 70's. I may try it as its the same powder as then. A little warm now in the Sierra 3rd addition the oldest I have in Sierra.
Jim

I stopped using Winchester powders for this case blackening situation about 20 years ago. My necks ended up being filthy. I did use some WW760 recently and the situation no longer seems true. I don't know about WW748, but I'm still leery. Best wishes.

Cal - Montreal