Base of .38super cases bulging, why?

[Trina]

Hi all, I was wondering if anyone can give me clues as to why after years of no problems with them just recently my .38 super rounds are causing jamming issues due to the base of the cases bulging?
Details are:
5gn of AP50 (ADI powder)
125gn projectile
Dillon RL 550B press

The cases have been reloaded too many times to know, but I discard any with signs of wear and tear.

I haven't changed a thing for years and never had an issue like this before. I am leaning towards a problem with the resizing die, but not sure what to look for or how to rectify.

Thanks for any ideas

 

[rcmodel]

5 gn of AP50 (ADI powder)

I know nothing about the powder you are using.

But, did you just buy a new container of it???

Perhaps they have changed formulas or burn rates recently?

Or perhaps the newer powder is more dense so your powder measure is throwing more at the same setting?

Have you weighed the charges on a powder scale??

???????
Just guessing here.

But I doubt it has anything to do with your dies.

rc

 

[murf]

i would measure the diameter of the sized case and find out where the sizer stops on the case. maybe your dillon is out of adjustment or something and is not fully sizing the case. you can also use a sharpie and paint the lower portion of a sized case, put the case in your barrel, turn it around a few times, pull it out and see where the sharpie is rubbed off (or not). that should tell you if you have a sizing problem.

luck,

murf

 

[Mal H]

According to the ADI website 5.0 gr of AP50N is half a grain over their suggested maximum for that weight of bullet. Where did you find the 5 gr load information? You might want to use a slower powder such as AP70N.

Also, please define "bulging". How much is it bulged out from a normal base dimension, and how did you measure it? If a case is bulging at the web, even a little, it is most often a sign of over pressure.

Which pistol are you shooting them in?

 

[Trina]

Hi rc, the powder is a medium burn and Australian made. No I didn't get a new batch and I always weigh my powder loads as I use various rates depending on the match I'm shooting. I would also notice any major difference in recoil if I'd messed the powder up.
There is still air space in the case after seating the projectile.

 

[Trina]

Thanks everyone, wasn't expecting so many replies Murf- I will try out your ideas. Mal H - Half a grain, hmm, never been an issue before, guess I have just rounded it off to keep it simple. 100% certain it's not a powder issue.

The sides of the case closest to the base is where it's "bulging" - larger diameter than the rest of the case. The slide does not close due to the round not fully in the chamber. Kimber semi-auto.

 

[Trina]

Sorry Mal, on checking what I load I do load only 4.5gn. I use a 5gn load in my other gun

Problem might be solved though mystery still remains. On checking how far the case goes into the resizer/de-primer it stopped short of exactly where the bulge starts. I have screwed it right down so that it hits the shell plate now.
The nut was not loose and I have loaded hundreds of rounds in that position with no problems for years???

 

[Walkalong]

Tired brass finally bulging a little? Got by with the sizer up too far until now? Does the sizer remove the "bulge" now.

A pic of the "bulge" would be helpful.

 

[243winxb]

Old brass thats not sized by the die expands a tiny bit after each firing when loading close to maximum. It may work hardens the brass. Could be less spring back after firing? Time for some new brass, if screwing the die down more doesnt fix it. Tungsten carbide sizing dies may crack or break if in hard contact with a shell plate/shell holder.

 

[ReloaderFred]

Dillon sizing dies have slightly more radius at the mouth of the die to facilitate feeding on a progressive press. This leaves a small amount of the base area unsized, even when the die is screwed all the way down. Over time, after many reloadings, this can be exacerbated by a maximum loading for the caliber and cause bulging. An unsupported feed ramp area in the chamber makes this condition worse.

Hope this helps.

Fred

 

[Trina]

Thanks guys, yes it does get rid of the "bulge" now I have made the adjustment. Interesting info Fred. If I still get jams I will get new brass

 

[billybob44]

How much old brass do you have??

http://www.egwguns.com/index.php?p=product&id=846

^^^This works well to sort out the oversize cases.
Be sure NOT to mistake an extractor "Nick" for a bulged case-nicks can be filed.

Save the oversize until you get another FL size die-Lee, RCBS, etc., and then run all the oversize through this size die.
I would side line this brass for Min loads ONLY...Bill.