Quick Question.

[kdog70]

I do not know how to title it so I didn't sorry about that.

I am trying to find a sweet spot for seating some 120 grain B-tips in my 260 AI. I just bought the gun and I received some load data for some 139 and 140 grain bullets but I already shot them up. So how do I go about getting a seating point with out buying anything. Like can i smoke the bullets or how do i figure it all out.
thanks for the help
kdog

 

[MontanaRifleman]

You could use a sharpie and blacken your bullet ogive, or....

This is how I do it....

-Neck size or partially neck size case

-Seat bullet fully into neck up to the ogive

-Pull the bullet with a kinetic bullet puller

-Re-seat the bullet and pull, repeating this process until the neck stretches enough to seat and pull the bullet by hand with a little force.

-Then seat the bullet long, place it into the chamber and gently close the bolt on it. The rifling will push the bullet into the neck so it's just touching the lands.

-Carefully extract the cartridge, holding the the case down with one finger so it doesn't flip up. Carefully remove and measure.

Repeat the long seating, chamber and extraction steps about two more times for confirmation.

Hope that helps,

-MR

 

[cstilt]

When I did my 270 I went through the lot of brass I had bought until I found one that wasn't as uniform as the rest. Then I cut that piece of brass down the neck to just past the shoulder on each side. That way I could put a bullet in the case and still have it seat somewhat easily. Once I'd done that it was just a matter of putting a bullet in the case by hand, being sure of seating it extra long, and smoking the bullet with my trusty Zippo. Carefully chamber the round and measure the OAL after you eject the cartrige. I did this a few times with a couple bullets and took and average of the readings.

I thought this part was crazy, but it was repeatable. If I tried to use the marker like I've heard people say, I had the bullets stick in the lands a decent bit. I put oil on the bullet and this helped some, but it was hit or miss with many still sticking. When I smoked the bullet with a lighter, almost none of the bullets stuck.

 

[RT2506]

Take a case and FL size it. Take a cutting tool like a hack saw and cut a line from the mouth of the case down to where the neck runs into the shoulder on one side of the neck. Clean up the burrs good. Before use always run the case back into your size die to make sure it tightens up the neck. Now take the bullet you want to use and just start it into this case with your fingers. Slip this case and bullet into your rifle chamber and close the bolt. When the bullet ogive hits the lands it will push the bullet back into the case. Carefully remove the case from your rifle and measure the (OAL) over all length. This is your to the lands OAL measurement for this bullet. Right this length down. Now you can start finding the sweet spot by backing the bullets off the lands by seating it deeper into the case than this measurment.

You can pull this bullet out of the case with your fingers and use it to reload. Do this with every different bullet make and weight.

 

[MagnumManiac]

RT2506's method is what I use, but no one has mentioned magazine length!
If you find that the COL is too long for your magazine, and you don't want to single load each round, you'll have to work at max magazine length and work backwards to find the 'sweet spot'. This is how I do it for my hunting rifles, target/long range rifles are different.

There is another method that works easily.
Place the bullet you're going to use in the chamber, holding it in place with a 'Bic' pen or similar, carefully slide a cleaning rod with a flat end through the muzzle, until it contacts the bullet tip, mark with pointy marker flush with muzzle, remove rod and bullet.
Place the bolt back in and slide the rod down until it touches the bolt face, mark again flush, remove rod and measure the distance between the 2 marks.
This is the COL into the lands for that bullet, you can then work back from this in .005" increments until you find the 'sweet spot', but again, if this COL is longer than your magazine, you'll have to seat to that COL and work backwards.
Unfortunately, today's rifles seem to be long throated from practically every manufacturer, so a lot of rifles will never be able to have the bullet seated close to the lands due to magazine length restrictions, unless single loading is used.

 

[cstilt]

I tried using a rod when i first wanted to find the OAL when I started loading for my rifle. I wasn't happy with the results. To me it seemed a bit harder to get consistant results. I even tried using a dowel rod that fit the bore and instead of a marker I used a razor blade so I could hopefully get a better reading than with a marker. My results seemed to vary a few thou. That's when I decided to sacrafice a piece of brass and split the neck with a saw like most others have mentioned. I found my results much more repeatable like that. I have that same piece of brass put up right now so I can do it all over again for the next bullet I try.

 

[kdog70]

I ended up taking a case and taking a grinder on a dremel tool and splitting the neck of the case then de buring the work then resize and put bullet in and close the bolt on the action. With the split in the case you can pull the bullet out with your fingers and I got the same result 4 times in a row so i am going to use that and see how it works for me.