A buddy in Grants called me with a problem he is having with his .38/55. His reloads are bulging causing a great deal of difficulty to chamber in his Marlin 336 Cowboy and his H&R Buffalo Rifle. He said he is using virgin, .38/55 brass and cast bullets specifically cast for the .38/55. These are 250 grain bullets he buys in bulk from a company in Phoenix. He loads with seven grains of Trail Boss powder. Marty said when he does shoot the load, it barely has enough velocity to make it to the target. His problem is, when he seats the bullet into the case it is creating a bulge the entire length of the portion of the bullet that is seated into the case. Marty said less than a half inch of bullet is seated in the case and the bulge is along the entire seated portion of the bullet. I immediately thought that maybe he had like a caliber larger than he was supposed to have, but he said the bullets mic out at .380 even. He said his barrel slugs at .380 as well. I also told him to check out the wall thickness of his cases. Does anyone have any other suggestions. This rifle has been shot before and all of a sudden begins having this problem. Again, any suggestions as to what is going on? Thank you ... Tom Purdom

It sounds like his brand new, unfired brass might be on the skinny side, and as you suspect, the wall thickness might be a bit over norm. Has he put a mic on the new brass, and compares it to fired brass? Also, has he measured a loaded round?

If he has used this gun before, and reloaded for it too I imagine, and then buys a bunch of new brass and starts having trouble that is a good place to start. Has he tried loading a different case yet using these same components?

If his bullets and his bore are 380 that is good for accuracy. Since it is not chambering that is bad. This is a complaint I have heard about the NEF rifles. I have a Marlin 375 and I don't think it would have a problem with a .380 bullet in its huge chamber.

The cures are:
1. Smaller bullet that will probably be less accurate
2. Ream the chamber with a larger reamer -- there are gunsmiths that already know how to handle this problem.
3. Turn the brass---38-55 brass is already pretty thin so this may not be such a good idea.
4. He might blow out some 30-30 Winchester brass and get thinner cases.
5. He may have burrs on the case mouth or crimping problems or lack of crimping that might cause chambering issues also.

quote:

Originally posted by 7x57mm:
...
1. a great deal of difficulty to chamber ...

2. when he seats the bullet into the case it is creating a bulge the entire length of the portion of the bullet that is seated into the case...
3. the bulge is along the entire seated portion of the bullet....the bullets mic out at .380 ...
even.
...Tom Purdom

The cases are most likely to be sized for reasonable tension on jacketed bullets (.375"), hence the bulge.

If they don't chamber (.380 + 2x wall thickness + .001 or .002 (MINIMUM) clearance SHOULD = chamber diameter.

The solution has been stated - open up the chamber or use thinner brass.

What is the inside diameter of a sized case neck? His expander plug may be to small.
Also, what happens if he does NOT crimp?
Sounds more like he is bulging the case outwards below the base of the bullet, can he place a straight edge between the rim and the bullet base, and if so is there any light visible between the case and straight edge?