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post #1 of 17 (permalink) Old 01-06-2012, 11:25 AM Thread Starter
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Bullet seating question?

Reloading my .300 Win Mag and am having trouble figuring out overall length (OAL) to get correct seating depth.

I'm doing what's been suggested by several people- place bullet in brass (cleaned, deprimed), put in gun, close bolt, open bolt, measure OAL.

Supposed to be when you extract the OAL is such that bullet just touches rifling (then back off 3/1000 inch).

OAL is all over the place (I'm trying Hornady SSTs and Nosler Ballistic tips)- from 3.3 inches to 3.6 inches. I've tried it dozens of times and no consistent pattern. Tried it w/both bullets in cases that were both snug and loose.

In comparison, factory Federal Fusions range 3.287 inches to 3.294 inches out of a box of 20, and I've seen on-line OAL should not exceed 3.402 inches.

I'm thinking the bullet is getting slightly too snug in the rifling when I close the bolt. With cases that are a bit snug when I hand-seat the bullet, sometimes when I pull the bolt back the bullet is stuck in the rifling and I have to push it back out w/a cleaning rod.

I can't figger out the correct OAL using this method.

Any suggestions?

Thanks,

BH

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post #2 of 17 (permalink) Old 01-06-2012, 12:19 PM
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Re: Bullet seating question?

Close the bolt. Insert cleaning rod into the muzzle until it reaches the bolt. Mark the cleaning rod.

Place your bullet into the breach until it gets stopped by the lands/grooves. Insert cleaning rod in the muzzle until it reaches the bullet. Marked the cleaning rod. The distance between marks equals max OAL. Back off this distance until the bullet doesn’t touch lands/grooves.

If you change bullet type you may have to repeat the above due to various shapes. Cases should also be trimmed to same length.

Make sure that loaded bullet/casing fits into magazine & feeds into rifle properly. All magazines are different and some will not accept the max OAL.

Have fun. FT
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post #3 of 17 (permalink) Old 01-06-2012, 12:36 PM
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Re: Bullet seating question?


BH, are you using a case with a split neck like this?


It provides enough tension to hold the bullet, but allows it seat deeper and consistently when chambered.

Next, you want to measure the length on the bullet ogive, not off the tip.


The tips can and do vary quit a bit. The only time the OAL is important is if the ammo must feed from a magazine. With some chambers the freebore is so long its impossible to be on or close to the lands and fit a mag. It why you don't want to get hung up on published OALs.

BTW, personally I wouldn't start at .003" off. Generally I'll start at .010"-.015" and tweak it from there.

Bill
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post #4 of 17 (permalink) Old 01-06-2012, 12:51 PM Thread Starter
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Re: Bullet seating question?

Thanks for the suggestions guys!

BH

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post #5 of 17 (permalink) Old 01-06-2012, 01:05 PM
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Re: Bullet seating question?

Different guns like it different places, i have several that is seated as far as .70 000 off the lands. When you try seating deph closing the bolt you will have it normally severa; .000 mashed in te lands.
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post #6 of 17 (permalink) Old 01-06-2012, 01:23 PM
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Re: Bullet seating question?

My guess is that you will be reloading for many years so I would recommend investing in the Hornady Lock n Load guages, they're not expensive for a lifetime of use. They make finding the lands pretty easy and very accurately since they reference off the ogive.

For finding a good seating depth Berger's method is efficient. It's written for their VLD but it works well on any design.

Quote:
The quickest way to find this sweet spot is to load ammo at four different COAL. Start with a COAL that allows the bullet to touch the rifling. The next COAL needs to be .040 off the lands. The third COAL needs to be .080 off the lands. The last COAL needs to be .120 off the lands. One of these COAL will outperform the other three by a considerable margin... ...We have learned that by doing the four COAL test you will find a COAL where the VLD bullets will group well at 100 yards. Once the COAL that shoots best is established you can tweak +/- .005 or .010 to increase precision or you can adjust powder charges and other load variables. Frankly, those who do the four COAL test usually are happy with the results they get from this test alone.

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post #7 of 17 (permalink) Old 01-07-2012, 12:50 AM
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Re: Bullet seating question?

i used the bullet in a deprimed case for my .243... i tryed that with my 6.5swede and the bullet never moves!! even if its just barely hanging in the case....i might have to try the cleaning rod method

2C/2E
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post #8 of 17 (permalink) Old 01-07-2012, 01:18 AM
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Re: Bullet seating question?

Go buy yourself a hornady locknload kit. As other have said OAL is just for getting them to fit your mags, and Ogive is the way to fly for better consistency.

Your dies seat off the ogive, so measure off it too. Tips are too inconsistent.
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post #9 of 17 (permalink) Old 01-07-2012, 01:33 AM
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Re: Bullet seating question?

Quote:
Originally Posted by matt75bronco
Your dies seat off the ogive, so measure off it too. Tips are too inconsistent.
Spot On!

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post #10 of 17 (permalink) Old 01-07-2012, 02:01 AM
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Re: Bullet seating question?

Quote:
Originally Posted by m-192
i tryed that with my 6.5swede and the bullet never moves!! even if its just barely hanging in the case....i might have to try the cleaning rod method
Sounds as though the freebore is a little on the "generous" side

Its not all that unusual. Bullets on or jammed in the lands can increase pressures. Since the factories haven't a clue what someone may use they give it a little more just to be on the safe side.

Here is an example...a cartridge and a cast of the chamber for it.


Using the cartridge as a reference you can see where the case mouth would be in the chamber and the lands forward of it. The area between the two is the freebore. In this case I throated this one so the longest bullet I planned on using could be seated 10 off the lands without the base protruding into the shoulder of the cartridge taking up effective internal cartridge capacity. As a result the COAL length is 2.750" and will feed from 2.8" short action magazine.


In the case of your Swede and your positive of your measurement seat the bullet to work through the mag if it has one and have fun.

As a side note just because you can't get close to the lands doesn't necessarily mean it won't shoot accurately enough for it's intended purpose. In fact I seen some rifles shoot their best with a lot of jump.

Bill
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