Setback Problem Dangerous Situation Help

[BulletFactory]

Im loading .308 for an M1A, SOCOM 16.

SMK BTHP
4895 41.5gr
Win Primers
2.050 Trim
New Brass

I dont know why, but there have been a couple rounds that I have removed from the chamber that had been set back in the case a loooong ways from just being chambered. I was then able to pull the bullets out of the case by hand, albeit with some effort.

Im using RCBS dies, they were new, and I only used them a couple thousand times. Small base X dies.

I have seen this with the new brass, I don't remember seeing a once or more fired brass with this problem, but am unwilling at this time, to say it's a new brass only thing.

Im not sure where to start looking for the problem.

Thanks. Neil.

[RickinTN]

I have some new R-P 7mm-08 brass that does not have enough neck tension to hold a bullet. I use Redding type "S" bushing dies. I have to run these through my die before I can load. If you can pull the bullets by hand you don't have enough neck tension. In my experience the neck wall thickness of 308 Winchester brass varies considerably. I have 3 seperate bushings for sizing .308 brass depending on the brand and lot. Run a piece of your brass through your sizer and measure the outside of the neck, then seat a bullet and measure the outside of the neck again. The measurement after seating the bullet should be at least .002" larger than the sized case, thus giving .002" neck tension on the bullet. More is not bad but I wouldn't want more than about .006" or so.
Hope this helps,
Rick

[nhrifle]

First thing I would do is disassemble the sizing die and give it a good cleaning. Brass particles can build up on the expander button and cause it to over expand the necks. You might also try polishing the expander. Chuck the stem in a drill and spin it in some steel wool until it gleams. I polish the expander in all my dies and it makes a huge difference.

Make sure the insides of your case necks are clean before sizing. The crud that builds up in there is never completely removed during tumbling and causes the same problem I mentioned above. I put a 30 cal bore brush in a drill, and spin it into and out of the necks of each case I size to both clean and polish the brass. This allows the expander to pass through the necks almost effortlessly.

You didn't mention the brand of brass you are using, and some are better than others. Might be worth a shot to anneal the necks unless they show some discoloration from the factory. Hard necks won't provide proper bullet tension and can cause the set back you are experiencing.

Lastly, especially with the M1A, M14, M1 Garand, I have found crimping to be necessary. The SMK you are using do not have a cannelure, and I would advise using a Lee Factory Crimp die. I would apply just enough crimp to lightly mark the case mouth and hold the bullet in place. Load a dummy round when adjusting the crimp to test bullet tension. You should be able to put the bullet tip on your bench and press on the base of the case firmly and the bullet should not move. Adjust the crimp accordingly.

If none of this works for you, might be time to start analyzing before and after results of the sizing die and perhaps try a different make of brass. And I doubt the bullets are undersized, but measure them just for grins and be sure to use a micrometer, not calipers.

[Larry Gibson]

If the expander is expanding the inside of the necks as the case is with drawn from the die remove the expander and try some with just the necks sized but not expanded. If that works the expander can be honed down to give proper neck tension.

If the "new brass" is Winchester then that is one of the reasons it is not recommended for use in the M1A; it is thinner. M1A chambers specs are for 7.62 NATO cases which are much thicker.

Also if none of the above works and a new die is needed get the RCBS standard X die. The small base die is not needd for milspec chambers; the brass is being oversized and over worked with the SB X die and will lead to early case failure.

Larry Gibson

[tomme boy]

I have had this happen too. Winchester brass. It has the thinnest necks I have found yet.

Also take out the expander and measure it. I received some dies recently from them that had the wrong expander in it. Yours should measure 0.3065-0.307" 0.307" is actually pushing it for me. I would want a little more for a autoloader.

[BulletFactory]

I'm not using an expander in the die, I have one mounted in a single press that i use right before I do the neck trimming. The thickness is at .12, I grabbed a bag of new brass, measured a bunch of them, and that was the average.

[BulletFactory]

If the expander is expanding the inside of the necks as the case is with drawn from the die remove the expander and try some with just the necks sized but not expanded. If that works the expander can be honed down to give proper neck tension.

If the "new brass" is Winchester then that is one of the reasons it is not recommended for use in the M1A; it is thinner. M1A chambers specs are for 7.62 NATO cases which are much thicker.

Also if none of the above works and a new die is needed get the RCBS standard X die. The small base die is not needd for milspec chambers; the brass is being oversized and over worked with the SB X die and will lead to early case failure.

Larry Gibson

It's mixed brass, but the new stuff seems o be consistently an issue, and the new stuff is in fact, Winchester. Hmmmm.

I do anneal after the second firing, I guess I'll have to pull a bunch of these things to be safe.