.223 COAL for 69gr smk


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CJK8
September 2, 2011, 02:00 AM
I have some 69 gr sierra BTHP match king bullets I am going to seat tomororw. If I understand correctly, max COAL for .223 is 2.260". The Sierra manual shows COAL for this bullet to be that max of 2.260". Most other bullets I see are recommended shorter COAL. Don't I want to back off on the 2.260" max so I have some room for error and am not touching the riflings? Thanks.

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DANNY243
September 2, 2011, 02:11 AM
Max COL for .223 is however long your magazine is. In a single shot you are limmited by touching the lands, which ellevates pressures slightly (watch for cratering, head expansion etc.). I've seated out to 2.384 before having feeding problems.

ArchAngelCD
September 2, 2011, 02:51 AM
At least you are getting closer to loading some ammo and shooting it. You have moved from sizing the brass to seating the bullet.
The Sierra manual shows COAL for this bullet to be that max of 2.260".
The people at Sierra spent a lot of money to put that manual together and you are shooting their bullet. Why not believe them? SHOOT some ammo and make changes if needed, not buy guessing again.

Load just one round and shoot it and a lot of your worries will go away... ;)

cfullgraf
September 2, 2011, 09:15 AM
2.260" overall length is about the max length that fits in an AR-15 magazine. I would guess that more of the 69 grain Matchkings are shot from AR-15s than any other 223 Remington. I would also guess that Sierra considered that in their load development.

I use them for Service Rifle Matches. My die is set to seat the bullet to a nominal 2.258" just so any variation in seating depth will not give me magazine problems with my match AR-15.

ArchAngelCD makes a good suggestion.

CJK8
September 2, 2011, 11:29 AM
Thanks. Just trying to make sure I keep it safe and not push to the extremes. Hodgdon's loading data has all their OALs shorter than 2.260" from what I remember, including this one. Again, trying to keep it safe. Thanks.

CJK8
September 6, 2011, 12:30 AM
The OAL of my catridges varies from shortest to longest by .004". Is that normal? Thanks.

jelenko
September 6, 2011, 12:40 AM
I would say that it is.
I load lots of .223 rem. Hornady's 75 gr bullets vary ~ 10/1000's.
Sierra's 69gr's vary a little less than 10/1000's.
Since a seatting die seats the bullets by indexing off the 'ogive' of the bullet [i.e., not the tip of the bullet] and that the ogive is usually within 1/1000's from bullet to bullet, you will see a variation in the COAL.

CJK8
September 9, 2011, 01:01 PM
Since a seatting die seats the bullets by indexing off the 'ogive' of the bullet [i.e., not the tip of the bullet] and that the ogive is usually within 1/1000's from bullet to bullet, you will see a variation in the COAL.
The Sierra 69 gr bullets I loaded averaged a COAL of about 2.255. I then loaded some Sierra 52 gr BTHP and, without adjusting the seating die, the COAL with those bullets was .035" less than the 69 gr bullets at an average of 2.220". Is that normal? That is more than within 1/1000. As an aside, I had about 7/1000s of variation in COAL on the 52 gr bullets. Thanks.

Canuck-IL
September 9, 2011, 01:48 PM
That is more than within 1/1000
They're different bullets - why wouldn't the OAL be different?
/Bryan

CJK8
September 9, 2011, 02:00 PM
I guess I don't have a basic understanding of why a bullet seating die would seat one bullet deeper than another or if something else is going on to shorten the OAL by 35/1000s. It will kind of be a pain to keep adjust the die depending on the bullet. Thanks.

Canuck-IL
September 9, 2011, 02:18 PM
The seater die contacts the bullet at approximately the ogive - where the bullet "widens out" to the portion that holds it in the case (bearing surface). The more or less "pointy" nose of the bullet does not contact the seater die - look into the die - there's a hole in there ... so bullets with a different "nose" length will have different OALs.

Yes, you adjust seater dies for different bullets.
/B

W.E.G.
September 9, 2011, 02:51 PM
Seat it until it looks like it just clears your tightest magazine.

Then seat it 0.010" deeper.

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