Originally Posted by
44magLeo
toot,
The 6.5 Jap and a lot of other cartridges from other countries often spec slightly larger in case diameter than similar cases made in this country.
Here they often start with a similar case and final form it to the new case. This often leaves the case head a bit small and it will bulge a bit just ahed of the case head. Cheaper than getting new form dies to make the larger cases.
Most European case manufactures already have the larger form dies, so they get them closer to the right sizer.
I find that some European made brass for my 7mm Mauser has the extractor groove cut differently than US made brass. On some I have to use a 6.5 Swede shell holder.
In your case your 6.5 Jap may just have a larger chamber than it should be. Making a chamber cast you can get the chamber measurements easily. Then compare this to the Spec the cartridge should have,
Mil spec rifles and ammo are often a bit loose. This helps prevent jams in battle conditions. They don't care much if the cases get a bulge, as long as it functions reliably.
Even with the bulge as long as you keep loads within pressure specs you should be fine. Just watch for cases that show signs of failure.
Leo