Zero bullet jump.

V

vts

New member
Measured bullet jump using a ogive comparator from Sinclair.
Zero bullet jump is 3,600".
What do you guys use as a reference point?
Cartridge is a 30-06
 
I seat a bullet long in the case, and stuff it into the chamber with my thumb. Then I seat it shorter by a tiny bit. Each time, I point the muzzle up--when the cartridge falls out on it's own, the bullet is clear of the rifling, it's jump is pretty close to zero, and the seating die is set for zero jump.

I measure the OAL at that point, and seat it deeper to get the jump I desire (typically 0.020" for typical modern jacketed rifle bullets provided they will still fit in the magazine).


I have a comparator, but I seldom use it. It's useful for measuring how much the throat has eroded, but I keep a fairly accurate round count, so even that is of limited value.

Ha det!
 
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I'm referring to cartridge length from head to ogive using a hex bullet comparator from Sinclair.
I would like to know just to be on the safe side.
 
What do you mean reference point? I measure what the rifle will fit with the Hornady oal tool and then measure it with the comp tool. Subtract 0.030" as a std, but some rounds like Bergers in my 300 WSM like to be closer.

I need to play with this more!
 
vts, To have 3.600" you measure from base of case to top of hex which they show. If you subtract 1" for the hex, base to ogive is 2.600".

Depend on bullets I'll start .030".

I think what is confusing is your 3.600" vs COAL for 30-06 @ 3.340"
 
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I think I need to clarify.

My question is.
Is 3.600", including the hex, a reasonable measurement?
Or am I way of?
 
I think I need to clarify.

My question is.
Is 3.600", including the hex, a reasonable measurement?
Or am I way of?
Click to expand...

I have checked the distance from the beginning of the rifling to the bolt face on, it is not common to find a rifle with a long throat I have pushed bullets out of cases before the bullet contacted the rifling. One magnificent wildcat built by a friend had a throat so long the bullet traveled an additional .275" after falling out of the case neck before it contacted the rifling. The proud builder ask me how could happen and I said; "I do not know".

Because I am the only reloader that uses transfers I can not be a lot of help; seems I hate wasting time piddling with tools that are not necessary. Once I determine the distance from the rifling to the bolt face I use the tool to adjust my seating die. What does that mean? I do not have to adjust and measure and adjust and measure and adjust and measure. I transfer the measurement to the seating die when determining 'to the lands'. After that it gets very complicated if I want the bullet .030" off the lands.

The nice thing about my chambers is one I determine the length of the chamber from the beginning of the rifling to the bolt face I only have to do it once.

F. Guffey
 
Mr Guffey.
We are not on the same page. Possible due to my poor English.
My question can only be answered by some one with the same tool as I.

Now I have rechecked and this time I measured 3,601". I'm now confident that this measurement is correct. 3,600" is zero bullet jump.
I believe that 0,040" is safe distance from the rifling. So I will start there.

Now to wait for my powder scale and a bushing and the reloading may begin.
 
Vts,

You are, as mentioned earlier, getting throat contact at a point about 2.600" from the case head. The maximum case length is 2.494", so you are making ogive contact with the throat at about 0.106" forward of a maximum case's mouth position. That is a perfectly reasonable amount of throat depth to expect to find on a rifle.
 
Chamber the round, take it out and look for the land marks on the bullet about the ogive. If they aren't there your off the lands some. If you want contact with the lands by the bullet, you should reduce your load Bullet touching the lands will increase pressure to some degree. If you keep doing that, it's likely only a matter of time till you actually stick a bullet in the lands. If your lucky when you open the action, it will open pretty hard, you will pull the bullet nd dump it in the action most likely. You really should back off the lands just a bit.
 
I do not intend to shoot whit zero bullet jump.
Just establishing a reference point. If I need to reduce seating depth I will know to watch for pressure signs.
I'll back of 0,040".
 
Transfer: That would be a concept and or word that is not in a reloaders vocabulary. I transfer measurements of the chamber to the seating die to establish 'ZERO'. After I establish zero off the lands I lower the seating stem. Because the stem has threads and has a height above the die and is zeroed I am able to adjust the seater for 'off the lands;.

F. Guffey
 
Right you are.
I have RCBS Gold Medal Dies. So I note my zero in my journal and then turn it down the desired amount.
 
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