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short throats and long bullets????

 
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  #1  
Old 04-26-2004, 09:30 PM
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short throats and long bullets????

My 30" PacNor in 300RUM was chambered for me last year. I failed to mention to the gunsmith about the bullet I would be using (200-240gr). My throat appears to be for the shorter, lighter pills,..as the base of the 210gr berger is below the shoulder/body junction slightly. This makes sense in retrospect as I reached pressure at 88gr of H1000 with the 200gr smk seated at the lands. That is far below the manual max loads. I assume the deeper seated bullet,..while still being seated at the lands,..boosts pressure with a lesser charge due to lower internal capacity.

My question is this,...should I have the throat lengthened or just enjoy longer throat life as I chase it after erosion? I use this as a 1000yd LG,..so the best performance for that useage is what I am interested in.

Thanks

[ 04-27-2004: Message edited by: JustC ]
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Old 04-27-2004, 06:00 AM
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Re: short throats and long bullets????

Dave Kiff Pacific tools and reamers, sells a tool that allows you to lengthen your throat yourself. think it is $75. Basically it is fool proof according to him. Just make a few turns (takes out about .003-.005) and remeasure.

Before you do that though, get a 210 JLK, 216 Clinch River, 210 Berger and then measure length of bearing surface with either a Buhay ogive checker or two Stoney Point comparators. You will find that there is a significant difference between the bullets. I have found that the JLK is one of the shorter. Work up loads with the shorter bullet and see what happens.

For what it is worth I like the JLK and Clinch River bullets over the Berger. Found quality is more consistent and uniform in weight and length of bearing surface.

BH
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Old 04-27-2004, 06:45 AM
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Re: short throats and long bullets????

JustC,

Not that it's apples to apples, but I short throat my 6.5x284's by .1". This puts the base of the bullet at the body/shouder junction. With my load of 49gr of H4350, I still have only about 90% load density, and it shoots outstanding.

I think that the ideal of having the boat tail start at the neck/shoulder junction has merit, but it's not a rule set in stone. You may be better served with a different powder, or less/more neck tension. This also may be a result of a slightly tigher bore.

You didn't mesnion how it shoots..

Chris...
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Old 04-27-2004, 08:21 AM
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Re: short throats and long bullets????

Bounty Hunter,..I bought 2 bags of the 216gr clinch rivers the same day I purchased the remainder of your 142gr match kings,..so maybe I will be giving them a try and leaving the bergers for another less competitive rifle. Also,..do you have the contact info for me to purchase some JLK's? I would like some .264, .284, .308, and .338's. Not that I'm greedy or anything

FatBoy, She goes .25moa at 100yds with the H1000. As soon as the new chrono arrives I will retest the remaining loads from the last match,..but I think my verticle dispersion is the result of velocity variance(extreme spread) due to H1000 being a fairly non-dense load in the 300RUM. She likes the 200gr SMK thus far,..but I want to go to a heavier bullet and a slower powder (retumbo and RL25 are next to be tested with the heavier pills) I think if I can get more load density with a heavier and more consistent bullet,..I should be able to pull the extreme spread down quite a bit (it says here in small print)
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Old 04-27-2004, 08:38 AM
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Re: short throats and long bullets????

JustC,

you may be right with the load density,, but my SD numbers are single didgit with about 85% load density in my standard Norma match chamber.(fouled by about 6 or 10) I was concerned with flash over and the 210M's, but she lights right every time and doesn't let me down.

One other thing you may look at to reduce verticle dispersion is centering and slightly enlarging your primer holes with a cutting mandrel. I'm not sure that it helped, but I know it didn't hurt.

Chris...
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Old 04-27-2004, 08:47 AM
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Re: short throats and long bullets????

Fat boy

Only 3 sources of JLKs

1. Jimmy Knox directly at (479) 331-4194

2. John Hoover in PA (814) 684-5322

3. OK Weber at www.okweber.com in Oregan

BH
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Old 04-27-2004, 10:04 AM
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Re: short throats and long bullets????

Bounty Hunter,..thanks for the JLK info,..I will order some here directly.

FatBoy,..where do the flash hole reamers come from? are they a specific tool I can order, or have you used some other type of tool for the task? thanks

And you say the 210M lights up the charge consistently? what about a ~90gr charge of retumbo or RL25? think it will still light up without flashover? what caliber were you lighting and which powder?

Thanks for the help thus far gentelmen.

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