223 Rem – Fire Formed Brass Question & COAL

[ExtremeX]

[mark501w]

You can do this if you wan't but, you have to develop your load for this idea. This probably isn't the most accurate. A little jump usually reduces pressure & let's you boost velocity. But, you have to decide wether you want a repeater & load for mag length or lands & groove.

[GeoffLinder]

Sometime a little jump helps accuracy, but not always. General opinion with benchrest crowd is that no jump "can" be most accurate. You will need to test to see what works best for any specific rifle and load combo.

As far as pressure, if the load was worked up with bullets touching lands and shows no pressure sign, then you are good to go. BUT, it is not a good idea to be forcing bullets into lands, you should set OAL so bullets just kiss the lands or are just short of that, they should not get pushed back in.

A .223 chamber has shorter leade than 5.56 NATO so I am not surprised that bullets hit lands in a bolt rifle in .223 chambering, just find the OAL that works for this rifle and work load up to whatever velocity you want using that OAL.

As far as trim length, general spec is 1.750" trim to. But this does not mean that you cannot trim to 1.740". If you have brass under that, give it a tiny bit of shoulder bump and then it will be longer after another firing so you can trim it to same length as the rest. It is best for accuracy that all cases are trimmed to same length, this uniforms neck tension which helps a little with far downrange vertical stringing.

[LynnJr]

Question: case length and trimming.
All the cases are around 1.739” – 1.745”... Bottom end of the SAMMI spec, because the cases haven’t been FL sized, do I need to follow a different set of rules when it comes to case length?


As you adjust your full length sizing die down your cases get longer in length.The die squeezes the body of the case and the brass moves forward.If you keep adjusting the die down it will bump the shoulder of the case and the necks will get longer.
In your situation I would fire the brass a second time then full length re-size your cases and trim to your shortest round.


Hornady manual calls out of 2.230” COAL, with light neck tension, every time I chamber a round, it’s pushed in and measures 2.195”, and this is consistent.

Is it OK to fire a round with the bullet already touching the lands, or should I seat deeper? The Speer and Hodgdon website call out for a 2.200” COAL.

I don't know what Hornady considers light neck tension to be but I stick with 0.003 on most of my rifles.

Seating depth is the most important aspect of accuracy bar none.To do it right seat your bullets long and chamber 3-4 rounds allowing the lands to seat the bullet back into the case.This is your full jam length for the amount of neck tension you are using.

If the neck tension goes up your full jam length will increase.If your neck tension goes down your full jam length will shorten up or decrease in length.
You can now adjust your seating depth in 0.005 increments looking for a tightening up of your groups.
In your case your full jam length is 2.195 inches so try 2.190 2.185 2.180 2.175 and so on until you see your groups tightening up.If you keep going they will start opening back up again then tighten back up again.

On 22 centerfires you generally see a spot 0.020 back from the full jam length which may still be into the lands of your barrel that shoots well and another spot 0.018 - 0.023 off of the lands.

Once you can see were your groups tighten up and were they loosen back up you can use smaller increments to find the exact center.Most benchrest and world team members will have all there match rounds within 0.001 of seating depth variation maximum.

Seating hard into the lands reduces your pressure a small amount.As you start to back away from that point the pressure will increase and as you keep going it will steadily drop for the rest of the way.If you start at the full jam length you only have to go one way on your seating depth and I recommend this to everyone.
Edit: Most people who reload will never see a pressure drop as they get closer to the lands.They develop there load away from the lands or mildly into the lands and as such they will never see the full picture.As they keep lengthening the over all length they will see pressure rise then quit adjusting.
Again if you are fully jammed as far as the neck tension will allow your pressure will resemble a bell curve as you back away from that point.Pressure will rise 3000-4000 psi then fall off again.

If you work up your powder charge with your bullets seated at the full jam length your rounds will always be safe in your gun as changing the seating depth will lower pressure.