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Old January 22, 2007, 11:00 AM   #1
240wby
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Adjust seating depth with micrometer accuracy.

After you get your o'all length to lands, your threaded seating stem can be used as a "mic". I measured threads per inch (TPI) on several RCBS seating stems. They were all 28 TPI. Now doing the math: 1 divided by 28 TPI equals .0357 rounded up to .036. Meaning that one full turn on seating stem gives a movement of 36\1000. 1\2 turn = .018 1\4 turn = .009 etc. This formula will work on all TPI. Most tap & die sets include a thread gauge to measure TPI, or use a ruler and count the threads per inch.
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Old January 22, 2007, 02:36 PM   #2
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Great tip! Are you an engineer? I have a friend here in CC that shoots a 240wby. I've talked to him about reloading. what gr. bullets are you shooting, and what powder is your "magic" powder?
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Old January 22, 2007, 04:27 PM   #3
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What happens when it's a metric thread?
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Old January 22, 2007, 05:52 PM   #4
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Good tip

Sounds like it might simplify the seating process a bit. Thanks. Wil try it next setup
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Old January 22, 2007, 10:24 PM   #5
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I think I’ll stay with this –

http://www.midwayusa.com/eproductpag...eitemid=200390
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Old January 22, 2007, 10:31 PM   #6
240wby
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Well an engineer I am not, but I do some machining. The .240 WBY is my favorite cal. The one I have now has a custom 1:13 twist barrel. We also removed the "free-bore" portion of the reamer so the rifling comes to the case mouth. Bullets? 65 gr. Hornady V-max @ 3864, 85 gr. Sierra hpbt @ 3710, 85 gr.Nosler Partition @ 3566. Above loads all standard rifle primers, and all H-4831 SC. Next project will be 55 gr. Nosler b-tips and will start with H-380, H-414 and WW 760. Regarding the metric question, metric threads are measured in pitch rather than TPI. Example: 1.00 pitch will move 1 m\m on 1 full turn---.50 pitch will move 1\2 m\m on 1 full turn etc. You can also purchase inexpensive metric thread pitch gauges. Thank-you all for taking a look at the tip. 240 wby
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Old January 23, 2007, 04:32 AM   #7
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Sorry for being a stickler here. .240Weatherby is not a caliber. It is a cartridge.
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Old January 23, 2007, 10:41 AM   #8
Ausserordeutlich
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While an interesting academic exercise, it's a lot simpler for me to just adjust the seating stem to whatever o.a.l. I'm loading and leave it there.
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Old January 23, 2007, 11:50 AM   #9
Crimp
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I saved this from some unknown source a long time ago:

Seating Stem Adjustment
(Manufacturer - tpi)

*Forster/Bonanza - 32
**Forster/Bonanza - 28
C-H/4-D - 20
Dillon - 20
Hollywood - 18
Hornady - 18
Jones - 20
Lee - 18
Lyman - 20
RCBS - 28
Redding - 20
Wilson - 20

* 6mm and smaller
** .25 cal and larger
-------------------------

Degrees of Rotation

tpi__90___180___270___360__
32 0.008 0.016 0.023 0.032
28 0.009 0.018 0.027 0.036
24 0.010 0.021 0.031 0.042
20 0.012 0.025 0.037 0.050
18 0.016 0.031 0.047 0.062
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Old January 23, 2007, 09:33 PM   #10
BigJakeJ1s
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You can add a micrometer head to any Hornady seating die too.

Andy
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Old January 24, 2007, 07:18 AM   #11
240wby
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To cap it off.

This has been interesting for me, some pros, some cons, which is good. Backing up a bit, how to get oal length to lands? There is a priceless tip in this forum on how to do this. Go to top of forum (Thrifty Reloading Tips) by One in the Chamber. Scroll to tip # 67. This was brought in by MRAWESOME22 via 918v. I noticed this a few weeks ago and have done a .222. I started with a sized and trimmed case....It works very well and the price is right.
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Old January 24, 2007, 09:25 AM   #12
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This is a whole different thread and I believe done before but why would you want to know the OAL to the lands? Just useless info to me. The OAL that shoots best would be useful, but knowing the OAL to the lands isn’t.
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Old January 24, 2007, 11:04 AM   #13
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240whby said "We also removed the "free-bore" portion of the reamer so the rifling comes to the case mouth." Don't you have a lot of bullet set back or hard bolt closing going on with this configuration? I would think that pressures would be way up as well. Just curious.
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Old January 24, 2007, 04:19 PM   #14
Bullet94
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Quote:
240whby said "We also removed the "free-bore" portion of the reamer so the rifling comes to the case mouth."
I never heard of anyone doing this. I'm curious too?
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Old January 25, 2007, 05:48 AM   #15
240wby
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OAL to lands is simply used as a reference or starting point. By using the dummy round described in aforementioned tip # 67 you will arrive at OAL to lands. Now, take the dummy round and adjust the seating stem to touch. If you want to seat .005 from the lands turn the stem in .005.

Weatherby stock chambers are cut with a freebore (no rifling-caliber size) area ahead of the case mouth. By setting the reamer up between centers on a lathe and using a tool-post grinder this cutting area of the reamer can be removed. Once this is done, the freebore area becomes part of the pilot and looks exactly like any other chamber reamer.

Why does Weatherby do this chamber trick? I was told to ask Roy but he's not talking.
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Old January 25, 2007, 05:25 PM   #16
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Bullet94, if you don't know MAX OAL for a specific bullet, how do you know how close the bullet is to the rifling? MAX OAL is vital information. Geezy peet. How long you been reloading?
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Old January 25, 2007, 08:32 PM   #17
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"Why does Weatherby do this chamber trick? "

It allows for more powder while not producing as much of a pressure rise.
The powder has a chance to burn before the work of engraving the bullet into the rifling must be done.
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Old January 25, 2007, 10:04 PM   #18
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mrawesome22

I start at Jam. Jam length is not the same as where the lands start. I chamber a dummy round like you except using the same neck tension as your loaded rounds. I believe if you cut a slit in the case neck you will reduce neck tension and by doing so will not really know the true MAX OAL but something less. Jam is just a starting point. I really don’t care (when I find the OAL that shoots best) where this is in relation to the lands.

I believe this is how a lot of the benchrest shooters start (at Jam), but I also believe this is not for every rifle. If someone wants to start somewhere else (just touching the lands or off the lands) that’s OK with me and may give just as good of results. One thing I might add that if your powder charge was worked up at Jam reducing OAL should be safe, but if you ever see signs of high pressure anytime while changing components (OAL included) reduce your powder charge and start again. I have measured the distance to the start of the lands and to the MAX OAL using my bullets with the amount of neck tension I use on my loaded rounds. But neither of these measurements will tell me where my cartridges OAL needs to be to shoot the best and this is what I’m after. If you want to stay away from the lands then you need to know where the lands start. Knowing where the lands start doesn’t matter if you start from Jam.
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Last edited by Bullet94; January 26, 2007 at 01:43 AM.
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Old January 26, 2007, 07:49 AM   #19
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Lands touching the bullet, not lands touching the case mouth.
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Old January 26, 2007, 09:08 AM   #20
Bullet94
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HankL
I believe you’ve got it right. I never heard of the lands touching the case mouth either.
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Old January 26, 2007, 05:56 PM   #21
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Yeah, I don't get how the lands could go to the case mouth. If you wanted any bullet jump, you would have to seat the ogive BELOW the case mouth. I guess it would work. But that would just look really weird. And you better hope every case is trimmed to the perfect length or they aren't going to chamber. Guess I'm missing something here.
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