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Old December 17, 1999, 11:16 PM   #1
Cuz
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Join Date: December 4, 1999
Location: Lafayette, La. USA
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I was looking thru the Sinclair catalog, and came across a case neck length gauge...could someone tell me if keeping brass at its maximum length (whatever the gauge would say is max) has any advantages? when i load 125 gr. Sierras in my 30-06 , i cant seat the bullets out close to the lands because of the length,would this help?
Also, 1 other question, what is the best way possible to measure my chamber for c.o.l. without buying all sorts of gauges?
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Old December 17, 1999, 11:35 PM   #2
Mal H
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Well, Cuz, I think you're going to have to resign yourself to the fact that you can't get a 125 gr bullet close to the lands in a standard 30-06 chamber.

To measure the chamber length, I have used the following simple method for years with very good success. Take a fired case, no sizing, no primer, no powder, and insert a bullet that you want to determine the max length (head to lands). The bullet should be free to move in the case mouth, but not too loose. Coat the bullet up to the ogive with a Magic Marker or the like and chamber the round, bolt closed. The bullet will slide into the case when it runs up against the lands. When you remove the case, there's a good chance the bullet will stay caught by the lands. Push it out with a cleaning rod. Insert it back into the case up to the line the case made in the paint. Now you can measure the max OAL for that particular bullet type and the distance from the head to the lands (the lands should have made little marks in the paint. Obviously, this method won't work if the bullet can't reach the lands like your 125 grainer above.
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Old December 18, 1999, 12:18 AM   #3
Cuz
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thanks for your reply, i understand what your telin me. How much should i back off the max col to start, when trying to find the most accurate col? I also forgot to add that i dont only shoot 125's, I just figured the extra length of the case neck would help me reach out to the lands that much more.What do you think? Thanks again-----Cuz
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Old December 18, 1999, 12:43 AM   #4
Mal H
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That's a very good question. I am probably not the one to give you a definitive answer because I haven't tried to fully optimize a round to be the tack in a tack driver. Others may have better info. (Gale McMillan are you listening in?) I usually back off .007 to .015 assuming the bullet/case combo will allow it getting that close. Some folks seat the bullet right up to the lands and some even jam it into the lands. I would be very leary of the latter due to unknown effects on pressure.
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Old December 18, 1999, 01:36 PM   #5
Paul B.
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Cuz. You must not allow your brass to become too long. If you do, it will jam into the leade. This will prevent the case neck from expnading to release the bullet. Pressure will continue to rise until the bullet if finally pushed out, BUT, that pressure will now be excessive, more than likely to a dangerous degree. Seating bullets so that they are forced into the rifling will also raise pressures and loads must be adjusted downward accordingly.
When you are loading the longer bullets that will reach the rifling, try as close as they will go, without contacting the rifling. Load say 5 rounds that way. Load 5 more with the bullet seated slight deeper. 5 more deeper yet. Maybe 5 more deeper than those. Remember, we are talking in increments of .010 inch here. Try .010, .015, .020. 025 for starters. Say that .010 and .015 show the best accuracy. At this poiny, you could play with going .010, .011, .012. and so on. With your 125 gr. bullets, you'll just have to seat them out as far as you can without making them susceptable to falling out, or being bent when feeding from the magazine. Either that, or single load them.
Hope this helped.
Paul B.
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