COL issues or "My head is going to explode!"

[flynlr]

TO get right to the point ..

After reading multiple reloading manuals and the full suite of tools needed
to start Reloading, I am now in production mode using the following
components for my Rock River AR15
AA2230 24g
Hornady 55G FMJ/BT
CCI #41 Primers
And once fired LC05 Brass which was XM193 ammo I purchased and used.
and trimmed to 1.750

I have had no problems getting the Lee 1000 setup for this chore nor
the Lee Classic Press I used for Primer Pocket Swaging and de-capping.

Reading the 2 books I have on hand Lee Vol2 and hornady's latest
Not to mention the data from Accurate and what came with the lee pacesetter set I have come to realize that I have about 5 choices for COL
now I know the MAX COL is 2.260
the data with my dies said 55g using aa2230 the COL is 2.230
the data from hornady for the bullet I am using says 2.200
there are a couple of others that mentioned 2.220
Now I am leaning towards the Hornady data as they made the bullet.
but why the big spread in Min COL?
I measured the XM193 I still have on hand and it is at 2.247
HELP!!!
I have hundreds of cases prepped primed and ready to go but the minimum COL has me flabbergasted with all the choices!

 

[Bullet]

Your probably seeing the OAL the different sources used when collecting their data. Are the powder charges all the same? Probably not since the OAL’s are different. I’d go with the data from the company that made the bullet your using.

 

[Idano]

flynlr,

The reason for the different OAL is due to the head space of their test fixtures or guns that they used to develop the load. I also load .223 for an AR and I use and OAL of 2.260", the rounds just fit in the magazine and feed fine. Here is my recommendation; load up 10-20 rounds with at 2.260" and see if the feed without an issue if so start developing your load at that length, but if they don't feed shorten them up to 2.250" but no more. Two things to remember if you seat your bullet deeper you increase the chamber pressure for the same load and your bullet also has farther to jump before it contacts the rifling which affect accuracy. Ideally you want your bullet to just contact the rifling but in an automatic that is not practical so you have to stay within the constraints of your magazine so you get consistent feeding. I read once that the M14 and M16 were designed with a head space that was longer then what the magazine could hold so that when they got dirty in the field feeding wouldn't be an issue and helped reduce chamber pressure also supposedly that is why they used .223 bullets in instead of .224 bullets. I don't know if its true or not just what I read.

I hope this helps.

 

[Bullet]

You might want to try some Sierra Match Kings. Better bullets generally shoot better. You might look here for some AR info –

http://www.6mmbr.com/223rem.html

 

[flynlr]

thanks bullet and idano,

oddly enough I had settled On 2.225 as that was the depth that visually matched the XM193's depth of the bullet. I wonder why Hornady said the COL
should be 2.20/ when I tried that the bullet was seated beyond the crimp ring.

the 2.225 looked perfect.

the reason for using the hornady FMJ was to closely match the XM193 I had been using,.

 

[rg1]

I think Hornady listed such a short O.A.L. for the 55 fmj because they could be loaded in short throated bolt action varmint rifles. Anyway, I load the Hornady 55 fmj bullet at 2.225 for my AR's. Works fine and shoots good. If you had left the case length at 1.760 the cannelure would be even deeper past the mouth. Hornady 55 fmj/bt's have a different nose profile than military 55 fmj. They are blunter and not so sharply pointed and the o.a.l. will be shorter. Just for curiosity, put the factory loaded XM193 in your press and lightly screw the bullet seater punch down to just touch the bullet. Then seat a Hornady 55 fmj leaving the seater at where it touched the XM193. I think you'll find that the Hornady 55 fmj will be at about 2.230-2.235. That's a good way to compare o.a.l numbers using factory loaded ammo as a guide. Usually book recommended overall length with book recommended charges is the way to go. Since I crimp for my autoloaders, you have to seat the Horn. 55 fmj's longer than Hornady's recommendation. Generally I use Hornady's recommended length for pistols and bolt action rifles but for this bullet and for AR's I leave them longer.

 

[flynlr]

Thanks RG that does explain it a bit better

 

[Gnarkill]

Another guide for bullets that don't seem to follow the manual is the crimping groove. You want it partially exposed, but only a little bit. I find that w/ "oddball" bullets the crimping groove gives a good indication of where it should be.
JUST MAKE SURE that the COL isn't absurd, my little tip isn't perfect.