[LAWMAX]

I reloaded a few 5.56 IMG (Guatemalan) once fired brass.
Used 25 grains of WCC 846 powder and 55 gr boat tail bullets from Weideners.
The powder label showed a max charge of 26 grains. The sierra folks said to use BLC(2) powder data which shows 27 grains as a max load and 25 grains as a starting load.
When I fired a few rounds (10) 2 of the 10 rounds showed no bulges but some cracking / splitting just below the shoulder, only enough to be visible to the eye.
My concern is that on these cases, when I went to clean and deburr the primer flash hole it was too small to get the deburring tool into.
I checked some Remington 223 cases and some LC brass to see the size of the flash hole. both were were larger than the IMG - same size as my flash hole deburring tool .
Don't flame me guys, but I forced the deburring tool to open up the flash hole. At the time it seemed the thing to do....now maybe not. Anyway, do you think that opening up the flash hole could be causing some excessive pressure problems or something?
My estimate is that I need to back off of the powder a little more, but the flash hole thing made me wonder.
I am going to chrono. a couple of rounds next week with a friend of mine to see if the velocity is excessive. I will also try lighter powder charges
Any thoughts or advice would be appreciated.

 

[FloridaAKM]

Take a drill bit and see what is the largest size that will easily fit the LC brass flash hole. Then do the same thing with the Guat brass. I have no Guat brass or I would measure it my self. If the Guat brass worked okay the first several times, I would leave the flash hole alone and wonder about neck / shoulder cracking instead IMHO!

 

[Finalygotabeltfed]

A few things to look at here, first, the powder lot you have may be faster than others, start low and work up.

Drop your charge a couple of grains and see what the results are.

Are you guaging your resized cases to see if the shoulder is being set back too far?

Why are you opening up the flash holes?

 

[shortround]

Shoulder and neck cracking is typical of work hardened brass. Depending on the hardness of the brass to start, it can happen in the first reload or the tenth. You can anneal the necks of your brass. Commercial brass usually does not have this problem, as the quality control is a little better. Guat is one of a few milsurp brass known for tight flash holes on some lots. Opening the flash holes up to uniform normal specs won't hurt and will save on broken decapping pins. This is one of the match prep steps. Just don't go oversize.

If it was a misadjustment of your die causing the shoulder problem, you would get the same symptoms as excess headspace which would be incipient, partial or full head separations.

 

[LAWMAX]

To clarify and answer a couple of questions:
I opened up the flashholes because it was a pain decapping due to the small flashole. The pin kept getting stuck in the cases. I didn't want the same problem if i reloaded the brass again.
The cracking is not on the neck or shoulder. It is just below the shoulder on the case. Looks like high pressure, but I am no expert. The shoulder and neck looks ok.
I used a RCBS precision Mic and set the shoulder back .004. Do you think this is too much?
I will try lighter charges to see if it corrects the problem.
My concern was more about if enlarging the flash hole could cause or contribute to the problem.
Thanks for everyones input.

 

[Roc Rat]

What do your primers look like,, do you have cratering where the firing pin cam into contact with the primer,, are the primers getting flatened out,, flush next to the primer pocket edge,, these are telltale signs of overpressure. compair the primers with unfired rounds. I have had primers "fireformed" right to the edge of the primer pocket,, sharp edge,, the normal rounded edge of the primer was gone and the dimple from the firing pin looked like a crater, with rough edges.

 

[glock357x2]

How much did you open the flash holes? If the flash holes are too large, it permits the powder in the case burn at a faster rate and can create higher pressures. If you only opened them to a comprable size as commercial brass, that shouldn't present any problems, Look @ the benchresting group, they try to insure all the flash holes are of a uniform size.

 

[mikey250r]

One more thing-
Military brass is usually thicker and heavier than commercial brass. This makes the internal capacity less for the mil brass.
Check out how much powder(or water) the millitary brass will hold and compare it to how much the commercial brass will hold. If the millitary brass holds LESS powder this will raise the pressure. If they check out the same then it's one of the problem from above, or maybe it's NOT once fired brass!!

 

[LAWMAX]

Update:
I finally had time to check velocity with the Chrono.
with 25 grains of wcc 846 velocity average is well within normal range.
at 25 grains avg = 2718fps (1 case out of 7 shows very small cracking again)
at 24 grains avg = 2570fps (only 4 rounds fired - no cracks/ splits etc.)
at 23.5 grains avg = 2540fps (4 rounds fired - no cracks / splits etc.)
I am still puzzled. 25 grains should be good to go. My only estimate is that the brass is brittle. It is once fired only and my AR headspace is good.
I plan to load a few more at 23.5 grains and see what the brass does.
If there are no problems I will load with a light charge and lower velocity and use the ammo for plinking. Does anyone see a concern with the lower charge / velocity? Thanks.

 

[mt-ac]

Split Cases and Powder

I would suggest that you do your testing again with a "known" brand of brass that you are confident of so you can eliminate that factor on trying a new load. Once you are certain of the pressure and velocity then try the new brass with the same loads and check for any signs of cracking or primers backing out of the pocket.
And yes, surplus powder will vary between lots just as all powder does. It is just with surplus powder as opposed to say IMR-3031, where each lot of IMR-3130 is blended to the same standards to coincide with reloading tables, surplus powder will vary as it is not held to the same standards.
As another example say you were to ask the Winchester staff how many grains of what powder should I use to match the factory load of a certain round, they cannot tell you. This is because they blend their powder to meet the specs now shown on most commercial ammunition boxes.
I have not used any of my WC 846 yet, so I appreciate the data you have posted here. I would like to see reloading added as another catagory on the site.

 

[Beltfire]

Split brass

I learned a long time ago that a headspace gage for each caliber you load will elliminate many questions. A lot of help for a small amount of money. The previous remarks about burn rate and case capacity and primer condition are valid observations.
My own data for 846 is 25.5gr for 55gr bullet using mixed brass. Did you weigh those bullets? Once fired brass should not be giving you problems. Get a headspace gage from Dillon or Wilson. I run into that flash hole problem from time to time so I look at the headstamp first and scrap the offenders.