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Finding Max OAL for specific bullets

 
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  #1  
Old 10-01-2013, 09:51 PM
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Join Date: Oct 2013
Posts: 4
Finding Max OAL for specific bullets

This is my first post, I've been gathering very useful information as I started reloading and begun to shoot long range, so thanks for helping me not blow myself up!


Anyways back to the post, so I've been trying to find the best way to measure OAL for each bullet and haven't found anything really consistent till I started playing with my caliper. I know I'm not the first but let me know it this is an accurate way of measuring out to the lands. Ill be using a Nosler 165gr BT chambered in .308 as an example:

- Remove bolt, Drop a bullet down the barrel (wiggle it around) then measure from a set point on the bolt entry to the bullet (needs 6"+ caliper)- 6.606"

- Drop a fired casing in and measure from the same point to the rear of the case- 4.822" (this number will not change between bullets)

- so now subtract these two numbers (1.784") then add in the length of the bullet (1.215") which gives you a final result of 2.999 for max OAL

I've tried the marker,smoke, and loose bullet techniques but this is the only way I got the same number everytime. Let me know if this method seems accurate. And also where should I start my load length at? I always hear " back off a little" but could use some actual numbers, thanks



Measurements done on Remington 700 ADL .308 SA 26" barrel
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  #2  
Old 10-02-2013, 12:44 AM
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Join Date: Jul 2008
Posts: 41
Re: Finding Max OAL for specific bullets

The method you describe should work just fine. Seems like a lot of work, but reloading is just that! I use the RCBS Precision Mic for measuring jump to the lands. It has a dummy cartridge that you chamber and the dummy bullet is pushed back as it contacts the lands. You then remove the cartridge and place it in a device that measures from the cartridge base to the point on the ogive where it hits the lands (it does not measure from the bullet tip). You then make a note of the measurement and seat your bullets down until they give the same reading on the device. It's simple, quick and you can double check whenever you feel like it. The kit also comes with a tool for measuring case length from base to shoulder, which is very useful when body sizing or full length sizing to get just the right amount of shoulder bump.

There is no magic number for how far off the lands to seat. Anywhere from .120 off to .010 into the lands may work. Just be aware that pressure could go up significantly as you get really close to the lands, so definitely use starting loads and work up. Try a few maybe .010 off, .050 off, and .090 off and see how they perform.
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Old 10-02-2013, 08:35 AM
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Join Date: Oct 2013
Posts: 4
Re: Finding Max OAL for specific bullets

Thanks for the reply, ill be picking one of those up soon. But curious if this was an effective way for guys first starting to reload, $30-40 doesn't seem like much But after you buy bullets,powder, reloading equipment , etc etc. it starts hitting the pocket book hard
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Old 10-02-2013, 09:03 AM
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Join Date: Mar 2008
Location: SW Idaho
Posts: 1,148
Re: Finding Max OAL for specific bullets

Most of the other ways to do it involves measuring from base to bullet tip, which isn't the way you want to do it if you want to get the tightest groups. Measuring from base to ogive gives you the same amount of jump to the lands as it measures off the bearing surface.

Scot E.
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  #6  
Old 10-02-2013, 09:15 AM
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Join Date: Aug 2008
Location: east central fl. /n.c. pa.
Posts: 633
Re: Finding Max OAL for specific bullets

back in the old days we just took an empty unprimed case and partialy seated
the bullet. then put it in the gun and closed the bolt causing the bullet to be fully seated. then by turning the stem on the die you can get the exact seating
depth desired. using a sharpie or smoke from a match will tell you when no
land contact is made. when your happy with the seating depth keep the sample for future reference. that way if you change bullets you can easily reset your die back to that one.
no tools involved at all.
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  #7  
Old 10-02-2013, 09:34 AM
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Join Date: Jan 2013
Location: Tucson
Posts: 51
Re: Finding Max OAL for specific bullets

Hmm. I just close the bolt, run my cleaning rod down the barrel until it hits the bolt face, and mark the rod, in relation to the end of the muzzle, with a piece of tape. Then I remove the bolt and put a bullet into the lands and hold it in place while doing the same with the cleaning rod. The measurement between the two pieces of tape is the oal for that particular bullet. Of course, we're more concerned with ogive length, so measure the total length of that bullet and measure the length of the base of the bullet to give and subtract that value from the bullet length. Take that value and subtract it from your oal. This is your ogive length to the lands, and it is the same value regardless of the bullet you use
t
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