Neck Tension on 5.56 GI Brass

I have been using once-fired GI brass to reload M193 equivalent rounds, 55 Gr. FMJBT (pulled) or PRVIZI bullets. Resizing and trimming have been in a Dillon case trimmer. I do not use a case expander, just size the neck without one. Tumbling has ranged from possibly excessive (!) to much less of late, just enough to knock off the crud. In any case, I am getting a lot of cases on what appears to be second or third reloadings that have what I would consider to be insufficient neck tension on the 55 grain bullets. In most cases they have sufficient pull for practice purposes and I ensure that they have a good moderate crimp into the cannelure. They function fine and I have no problems with bullet movement. I don't consider it to be quite right.

However I don't care for this apparent light tension. Is this something peculiar to the 5.56 case, and a limiting factor on case life? I have loaded .30-06 and 7.62 for gas guns for years without running into anything like this. I would hate to think I am only going to get about one or two firings out of my GI brass with the availability and cost the way it's going.

Ideas? :sos:

Thanks.

If they work ok, don't fix 'em. How hot is your load? That is the determining factor for case life. Mind you, the crimp, that you really don't need, should hold the bullet in place. You may want to anneal 'em anyway though.

Believe it or not, there's a good reason for using a neck expander - it gives stronger, more uniform bullet tension compared to sizing without expanding (in a standard die). Brass has limited elasticity. Stretch it a little bit and it springs back. Stretch it some more and it deforms. When you seat bullets in a neck that's sized too small, the neck deforms and bullet tension is inadequate and inconsistent. Use an appropriate expander to leave the necks closer to bullet diameter and you could get more tension with better uniformity.

Successful sizing without expanding requires special dies and uniformed neck wall thickness - useful for benchrest rifles but not for the average service-style rifle, especially with cheap bullets.

Never heard of "PRVIZI." Did you mean "Prvi (Partizan)"?

Dysgraphia roolz!

just get a Lee Fact crimp Die ,,this will solve all neck tension problem
just trim all cases to same length as this is critical

I always use the neck expander and mine seem to be uniform. I have slightly crimped some .223 loads as a test for velocity and accuracy.

Joem, what were the results of the crimp test. I am considering a Lee Factory Crimp Die and wondering what effect it has on velocity and accuracy. I am interested in any results that you would care to share.

Over crimping can also cause neck tension problems. Add that to what Parashooter said...........

FWIW, most of my 5.56 cases get eaten by the grass gremlins before they wear out.