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Old January 17, 2013, 05:51 AM   #1
jabames
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.30-06 cartridge overall length

I handloaded some .30-06 180 Nosler Accubonds, they said maximum overall length was 3.340 inches, I checked my loads they were at 3.350 inches; is this not a good thing? Or should I seat them a bit further in?
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Old January 17, 2013, 06:23 AM   #2
Bart B.
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Cartridge over all length is typically set so they'll feed reliably from box magazines. If yours feeds well from a magazine and still chambers easily in your barrel, use them. If the bullets are a bit long, then just set them back with a bullet seater in your press a few thousandths.
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Old January 17, 2013, 06:38 AM   #3
jabames
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thanks
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Old January 17, 2013, 09:19 AM   #4
grumpa72
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As a relatively new rifle reloader, only about two years now, if the manufacturer of the bullet gives a maximum overall length, that is the number I would use. Period. If I understand bullet seating correctly, one part of it is magazine feeding and chamber feeding and the other part is to give the brass the correct pressure level. Too short and pressure goes up, too long and pressure goes down? Anyone care to comment on pressure levels in cases too long?

Bottom line - Accubond gave you a maximum case length. That should be the maximum in my book.
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Old January 17, 2013, 10:44 AM   #5
Ifishsum
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In large bottleneck cases, I don't think seating depth affects pressure anything like it does for handguns. It may bump up a bit if the bullet is seated far enough to be jammed into the lands of the barrel, but you probably don't want that for a hunting rifle anyway.

As long as it fits your rifle, your 3.350 is probably fine. If you have difficulty ejecting a live round or if the bullet sticks in the throat, it's too long.
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Old January 17, 2013, 11:02 AM   #6
AllenJ
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As long as your handloads are not at the maximum pressure limit for your rifle you should not have any problems. Cartridge overall length does effect pressure, the closer the bullet is to the lands the higher the pressure.
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Old January 17, 2013, 01:18 PM   #7
Rimfire5
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I just wrote this in another thread related to .308 loading but the concepts hold for your .30-06.

"The OAL you use and should use depends entirely on the chamber in your rifle. It also depends upon the ogive of the bullet - the spot where the bullet first will touch the rifling.

There is a great article in the new Berger reloading manual by Bryan Litz on page 148 that explains the subject and recommends that you adapt COAL of a load to your chamber for each bullet type (target bullets and hunting bullets are often very different).

Every bullet type has different dimensions and the ogive will be in a slightly different place (the shape of the bullet tip has a lot to do with it).
150 grain Sierra Match King bullets #2190 for example has a recommended OAL according to the Sierra Manual (5th edition) of 2.775.
However if your chamber is deep, you could easily seat your 150 SMK out to 2.810 and still not be close to the rifling.
Then again if your chamber is exactly to spec (pretty rare) you might find that at 2.810, the bullet is into the rifling and you can't close the bolt.

Sierra 150 grain soft Boat Tail bullets #2125 have a recommended COAL of 2.750. Both the #2125 and the #2190 are boat tail shapes but the #2125 has the ogive out further because the soft lead point requires a fatter tip.
At recommended COAL, both would have the ogive approximately the same distance from the rifling so the "jump" distance to reach the rifling would be the same.

From a practical standpoint, you won't know what your chamber depth is until you measure it. Most agree that you should leave 0.020 between the bullet ogive and the rifling if you don't want to increase the pressure.
BUT --- every bullet shape has a different ogive position so you really need to measure the chamber with each bullet type you use.

For example, I have a Savage 10 FP in .308 that has a deep chamber.
I can seat a 168 SMK out to 2.890 and be 0.020 off the rifling.
However, because the bullet shape is different, I can seat a Nosler Custom Competition 168 grain bullet out to 2.958 to get to 0.020 off the rifling.

My buddy's new Savage 10 FCP-K in .308 has a chamber that is much shorter and the 168 SMK bullet will be into the rifling if it is seated at 2.800 COAL. He has to load at 2.760 with the SMKs to get 0.020 to the rifling.

Both rifle shoot very accurately with their favorite loads and once we both knew the rifle's specs, we were each able to get the best out of our hand loads. We just had to load to totally diffenent COALs with each bullet type."

For your .30-06, the case is longer and the OAL is longer even for the same bullets used in the .308. However, your chamber may or may not be all that deep.
On my CZ 550 American in .30-06, the chamber is longer than spec, but is not particularly deep relative to the rifling. Every rifle is different but for most of my magazine fed rifles they run out of magazine depth before they run out of chamber depth, but my buddy's .308 is a significant exception.
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Old January 17, 2013, 01:27 PM   #8
rg1
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Nosler's 7th Manual lists a tested overall length at 3.330" for the 180 Accubond. If you're not jamming into the lands of your rifle then you should be ok.
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Old January 17, 2013, 01:46 PM   #9
BruceM
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First off, 3.340" is the SAAMI maximum over all length. The length which will work best in your rifle is unknown until you determine it yourself thru trial and error. The COAL listed in loading manuals is listed in order to qualify the conditions under which the published data was obtained and means little else. This is something people who use published loading data need to understand.

Generally, the best COAL for YOUR rifle will be the longest length which both fits in & feeds from the magazine and does NOT engage the rifling when chambered. The bullet should be set so that it sits in the loaded round, when chambered, approximately .005" to .010" back from the rifling. There are special tool you can use to determine this length. Alternately, you can load a dummy round using only a sized case and bullet. Seat the bullet out longer than necessary. Smoke the bullet using a wood match, candle or sight black. Try to chamber the round, then immediately eject. If the smoked bullet shows marks from contacting the rifling, seat it slightly deaper, re-smoke the bullet and repeat until such time as the bullet no longer contacts the rifling. After you reach the desired length, double check that the round fits in the magazine and, if so, measure & record the COAL for that bullet.

Seating the bullet just off the rifling usually, but not always, provides the best accuracy but it never hurts to experiment further if you wish. Also, if you are loading for an autoloader which produces moderate or more recoil or loading for a rifle with a tubular magazine, you will need to crimp the bullet in place in order to prevent bullet setback. In that instance, you will need to use a bullet with a cannelure and the location of the cannelure will pretty much determine the COAL. Single shot and turnbolt action rifles not not require a crimp except for very heavy recoiling rounds.

After the COAL length is determined for your particular rifle, load development can continue.



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Last edited by BruceM; January 17, 2013 at 01:55 PM.
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