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Old September 19, 2008, 02:47 AM   #1
BurkGlocker
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Seating off of the lands...

I have been searching for a how to find out how far a bullet(s) [ogive] is seated off of the lands. Whats the best method for finding this out?

I've been loading 150 gr SSTs and 168 gr BTHPs in my .308 Win and I have shot .375-.500" groups with the 150s, but the 168s have hovered around 1-1.
5".

Right now the OAL is @ 2.825", .025" over what is recommended with the powder I am using (H4895), but they are already getting to be pretty long for my rifle's magazine. Should I just keep them @ the length that they are already @ and play with the amount of powder or maybe play with the OAL some more?
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Old September 19, 2008, 07:13 AM   #2
wncchester
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"Should I just keep them @ the length that they are already @ and play with the amount of powder or maybe play with the OAL some more?"

Keep them at that length (mostly just as a starting/place for reference) and play with small changes of powder untill you get best accuracy.

Then play with seating in maybe .005" changes until you get best seating depth.
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Old September 19, 2008, 08:27 AM   #3
Alleykat
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I use the Stoney Point tool with the dummy case and a comparator with calipers.
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Old September 19, 2008, 10:38 AM   #4
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Rights to the Stoney Point tool were bought by Hornady, so it is now called the Hornady Overall Length Gage. You use it with adapters to make the determination you are after. To make it exact, you need the gage, a specially drilled and tapped test cartridge case (sold by Hornady), a caliper adapter base, the aluminum insert for your bullet diameter, the aluminum insert for measuring case headspace in your chambering, one of the bullets you want to load, and, of course, the caliper itself.

The process is to screw the test case onto the gage and with the probe rod way back, drop sample bullet into the case. You remove the bolt from your rifle and push the case adapter up into your chamber. (Note that if you have a gas gun that does not allow a clear shot when the bolt is removed, such as an M1A, you need the angled version of this tool.) You then push the bullet against the ogive and use the thumb screw to lock the gage's probe rod in position. you then put the ogive adapter on your calipers and measure the length from the ogive to the caseheas. Note that the caliper adapter's body has its jaw offset to compensate for the offset in the gage, so it has to be installed on the correct side of the caliper jaw.

After you have that measurement, remove the test case from the gage. Install the headspace measuring insert and measure the headspace of the test case and that of several cases from your gun that you have already sized (however you do that for reloading; full-length or neck only). It your cases have greater headspace, add the difference to the ogive length measurement you made, and keep that number your standard. If they are shorter, subtract the difference and keep that result for your standard. Now all that remains is making loads to the new ogive length standard, minus however far off the lands you want to be?
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Old September 19, 2008, 01:50 PM   #5
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I used a method suggested here. I slit the throat of a sized cartridge. Then just started a bullet into the throat. i then gently placed it into the chamber a slowly closed the bolt. I was then even more careful removing it. I measured OAL, subtracted .010in and built some rounds. So far they are showing to be very accurate. This may not be the exact proper method but appears to have been adequate.
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Old September 19, 2008, 01:59 PM   #6
tINY
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Or, you could take one of the prepared cases (you may have to cut a slit inthe neck with at cutting wheel on a dremmel tool). Then seat a pill long and chamber the "dummy". You want to be careful and probably want to remove the ejector if it's a plunger style.

What happens is that the bullet runs up against the lands and gets forced back into the neck. When it comes out, the length will be propper for the bullet to be seated into the lands.

WARNING "Never do the following" (blah blah):

Some bench rest shooters with really strong actions will seat the bullets long and actually press the bullet into the lands as the action closes. This makes for zero jump and better consistancy - at the cost of a bigger pressure spike on ignition.



-tINY

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Old September 19, 2008, 02:48 PM   #7
texastweeter
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I do just as tiny said, but i smoke the bullet first so i can tell when it is actually making contact. then back it out from there.
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Old September 19, 2008, 07:33 PM   #8
Slamfire
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I would just shoot those 150's and be happy.

You will find, that the throat wears with use. It takes about 1000 rounds to increase a 308 throat by "1" on the throat erosion gage. So you can expect to be chasing the throat as it erodes away.
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Old September 20, 2008, 05:14 AM   #9
BurkGlocker
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I went out today and did some target shooting, and to my delight, the 168s actually did pretty well. All three of my groups were right around .625", so I think that I will be playing with the charge weights a little more, but I think I hit the nail on the head with everything right off of the bat. Thanks for the input guys...

Brad
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Old September 20, 2008, 06:55 AM   #10
hodaka
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I have always struggled with the empty case/smoked bullet method. It seems the bullet moves too often on me. Alternatively, I take a cleaning rod and measure the distance from the muzzle to the bolt face, then drop a bullet into the barrel until it seats into the lands then once again use the cleaning rod to determine the distance to the bullet tip. The difference, of course, is the max OAL for any specific bullet type. A bit crude but pretty accurate. I've intended to get the Stoney Point device, but never did.
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Old September 21, 2008, 03:51 AM   #11
REDTAIL
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Seating Bullet Test

Cover the tip of the bullet with a black magic marker then chamber the round then extract the round, there should be a mark on the bullet tip shown on the magic marker how deep the bullet is seated works every time and is less expensive than buying gauges etc
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