Question on 5.56 sizing (CTS Trimmer)

[Jon Road King]

Ok, so I started sizing some 5.56 brass.

After re-sizing, I set up my CTS trimmer, as the directions said, by using a *known* case and adjusting the cutting blade to the case (I used a hornady 5.56 lock-n-load case).

After I started running some cases through the trimmer, I noticed that some cases were not taking a cut. Now the crazy thing is, those cases that were NOT taking a cut, ended up short over all. I was getting readings of between 1.759 and 1.756 on the rare shortest. But none of the cases ended up long (all sized at 1.760 or shorter). And upon inspection of the case inside the trimmer, I could see that there was a gap between the blade and the tip of the case.

Just having a hard time wrapping my brain around this. Being once fired, re-sized brass, shouldn't all the necks have 'stretched' and now be longer? Will the 'short' necks cause problems in bullet seating?

[Ferrum]

Just having a hard time wrapping my brain around this. Being once fired, re-sized brass, shouldn't all the necks have 'stretched' and now be longer? Will the 'short' necks cause problems in bullet seating?

Not necessarily... Brass will "grow" at different rates depending on manufacturer, hardness of brass, the guns chamber and how hot the load is. A lot of the necks most likely did stretch, just not enough to meet rimming requirements.

Short necks become and issue when there isn't sufficient surface for proper bullet seating. Otherwise, you should be good to go! At the lengths you listed above, don't even worry about it, load away.

[Jon Road King]

Not necessarily... Brass will "grow" at different rates depending on manufacturer, hardness of brass, the guns chamber and how hot the load is. A lot of the necks most likely did stretch, just not enough to meet rimming requirements.

Short necks become and issue when there isn't sufficient surface for proper bullet seating. Otherwise, you should be good to go! At the lengths you listed above, don't even worry about it, load away.

Awesome, good news, thanks!

[damndave]

Different headstamps of brass will be totally different. For example, once fired FC brass will be around 1.745 AFTER being resized.

For trim-to lengths, 1.740 is SAAMI minimum and 1.750 is the norm.

[cpatbay]

I just trim my brass to 1.750" +/- 0.005" and call it done.