COL variances for .223

[dbshabo]

This may be a stupid question, if so I'm sorry but I'm stumped. I'm getting COL variances of up to +/- .005" when loading .223 ammo. I'm using a Lee single stage press and RCBS seating die. My first thought was that my primers weren't seating flush, but I was wrong. The die is set up correctly and locked in place. Any ideas? Thanks in advance for any and all advice.

Shabo

 

[Beau]

If this is mag length ammo, anything to the right of the hundredths place (.01") is irrelevant.

For long-loaded ammo, use a bullet comparator so you can measure your seating depth from bullet ogive to the start of the rifling.

Bullet tips are not uniform in length and it is not unusual to see variations of .015" in overall bullet length.

 

[CJ6]

Variances in base to ogive length of the bullets is one place to start.

 

[waldo1979]

Get some better bullets j/k, that level of variance is normal as the tips of the bullets are uneven AFAIK due to the casting process. The front of the bullet has less to do with how straight it will fly than the base. To measure cartriage length from the ogive (seating is done base to ogive) you need a bullet comparator. Hornady sells one that works with a standard caliper.

 

[CJ6]

I was refering to the base of the bullet to ogive (sort )....not base of case to ogive (seated) although this will play a part too

 

[dbshabo]

Thanks for the replies. Yea this is an AR15 with a 5.56 NATO chamber. I'm happy with minute of pie plate @ 100yds from it, although it shoots better than that. I'm loading for mag fit so the slight +/- in COL doesn't hurt anything.

I was just curious as to why the difference in COL is showing up. I don't see how bullet length makes any difference. I mean the die is set at a specific depth and the ram goes thru a complete cycle every time I pull the handle. A difference in bullet length should mean a difference in how much of the bullet is pushed into the case mouth shouldn't it? The distance from the plug in the seating die to the bottom of the case base should be the same ever cycle right?

Shabo

 

[jlow]

What you say about bullet length not affecting base-to-ogive is indeed true, it should seat the long bullets deeper into the case.

Apart from what gstaylorg has stated, you might also look into how you seat the bullet. Seating force and speed can significantly affect seating depth, always use a light and consistent force and speed - that might help.