Trimming .223 Brass for an AR-15


April 7, 2007, 11:32 AM
I bought a simple Lee trimmer when I first started reloading .223 for my Bushmaster AR-15. It worked good enough, but when funds became available I bought a nice Wilson/Sinclair trimming setup.

I usually lightly roll crimp, so I need to trim each time to keep the case lengths/crimps uniform. After sizing, the case lengths are all over the map.

Should I trim to the 1.750" trim to length recommended by the manuals each time or go a little longer (1.755")?

Is this the best way to trim for .223 in an AR-15? I haven't had any problems with uncrimped bullets. I would like to save time and effort if it doesn't compromise safety.

Any advice would be appreciated.

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April 7, 2007, 11:56 AM
I have never roll crimped my .223 Remington ammunition.

Frankly, I was not aware that it was even done.

I trim my cases 1.760" in my Bushmaster 5.56mm chambered rifle and seat the bullets to just barely clear the magazine.

April 8, 2007, 09:25 AM
Trimming to 1.75 is the suggest length. A consistent case length is essential for a good crimp.
Get a Giraud Trimmer!

April 8, 2007, 09:46 AM
The Lee Factory Crimp Die is much less sensitive to case lengths than a roll crimp type. As long as the cases are in the ballpark, they will crimp just fine in the cannelure. Trying one might save some time and frustration with your crimping.

April 8, 2007, 09:50 AM
Do yourself a favor and at least trim them once at the begining.:)

April 8, 2007, 01:50 PM
I'm strongly considering the RCBS X-die for .223. High volume trimming and deburring is a pain. Currently, I'm using the Sinclair possum hollow trimmer, which is much better than the RCBS I used to use, but still very tedious when trimming a couple thousand cases.
With the X-die, you trim once to 1.740 and supposedly never need to trim again.

April 9, 2007, 01:42 AM
Ugh. I accidentally trimmed another batch BELOW 1.750" which is the minimum. I had my trimmer set to hit it just right at 1.752, and for whatever reason, it's gone down .010"--I think it may have been a burr stuck in the mechanism. Now I've got a bunch at 1.740" and I guess i'll have to scrap them--unless it's safe to fire?

I know a round that headspaces on the mouth (such as the 45 ACP) is unsafe trimmed too short due to excess headspace. But what about this? I know I'll lose accuracy but I hate to waste the brass.

I'm strongly considering the RCBS X-die for .223.

My first batch with the X-Die was trimmed to 1.750" exactly. I resized them after firing and I'm getting around 1.754"; so far so good.

April 10, 2007, 03:12 AM

Those rounds you trimmed to 1.740 will be just fine and don't crimp .223. I shoot mine in an AR without any crimp and they shoot just fine, I also doubt you will see any accuracy differences because of under trimming them. If you are worried about them you can always send them to me, I'll let them grow back up.

April 10, 2007, 06:12 AM
When it comes to my .223, I trim them if they are longer than 1.760. If they are not, I reuse them to let them grow the next round of firings. If they are long, I trim them to 1.75 + a thousandth or two, whereever the trimmer is happy. I try not to be too anal about it. I was trimming all of them and it was getting tedious so I started measuring as described above. Saved me oodles of time and that first batch (just started reloading rifle rounds) shot very tight groups if I did my part.

BTW - 52 gr Hornady HPs with 26.5 grains of Varget were the tightest groups out of a Ruger HB 223 and a Weatherby HB fluted barrel .223 from the 25.5 to 2.62 grain work up loads that we made. Both rifles have 1-12 twists and the long barrels, 26" I think. I'm pretty happy with Varget for .223, but again, I just started and know from everyone sharing here that there are better powders to use.

Good luck and happy shooting.

April 10, 2007, 06:46 AM
I use a sinclair chamber gage. As it turns out in my rifle, my brass can be as long as 1.785. Dont do nearly as much trimming as I used to, but do keep them at 1.775 as a max.
Your results may vary. So measure your chamber.

April 10, 2007, 06:49 AM
I trim mine once, with a motorized RCBS Trim Pro and wish I had a Giraud. If I had it to over again, I'd buy the Giraud and be done with it. Best way to go on a trimmer if you have a large volume.

Once they're trimmed, I use an RCBS X-die from then on to minimize having to trim. So far, so good.


Jon Coppenbarger
April 10, 2007, 07:52 AM
I use the Giraurd but I do many thousands every year. I use the Redding S-type dies when sizing and I am able to set my neck tension exactly how I want it So I never have a problem keeping the bullet in the case as can happen.

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