well beer is ok, but here in WV my 150 proof white lighting will get u there much faster. very smooth

Long wrote:

well beer is ok, but here in WV my 150 proof white lighting will get u there much faster. very smooth

robd wrote:

This is an interesting topic. When I use a dummy round to figure the max col in my .30-06 it is 3.449. No why can I load a round into the magizine at that length. I have found 3.367 to be the sweet spot for my rifle with 56gr of IMR 4350. So do the math and you'll see I am quite a bit of the riflings, but shot a 200 yard MOA today. I think I will stick with that now.

OK Rob - you are new here so I will warn you right up fron, This subject I am getting ready to address has been a powder keg in the past but we have gotten past it and agree to disagree

The OA length you are measuring is from the head of the case to the tip of the bullet. The distance to the rifling of your barrel is not really related to that distance at all. Bullets profiles can be short and fat or long and pointy. Moving back from the tip which something less than .308", the part of your bullet that is first .308" is known as the ogive. The jump that matters in barrel harmonics and accuracy tuning is measured from the ogive to the rifling. The distance from the ogive to the tip will vary from bullet to bullet even in the same lot of match bullets (up to .012"!) but the distance from the base of the bullet to the ogive is very consistent on quality bullets (.002" max usually). To control this distance you really need to use a quality seating die and a comparator tool.( Hornady makes one) The seating dies do not seat from the tip but rather some point on the profile between the tip and the ogive.

Your rifles magazine will determine how far you can seat a bullet and still run it through the bolt in rapid fire. But if you single loaded you could load a longer bullet - up to the point where the ogive is jammed into the rifling and the bolt wont close. You have determined a sweet spot that gives you MOA results at 200 yards - that is great!

To make a guestimate of your bullet jump without a comparator you can loosely seat a bullet way too long and put it in the chamber and let the bullet be seated by the rifling. You will want a cleaning rod around as you will stick a couple of them in the rifling until you get it close. When you seat a bullet tha just gets some marks on the ogive measure that oal. Then seat the bullet in your seater die that you have set up from your 3.367" dummy. The difference in the se lenghts using the same bullet will be close tou your jump distance.

Hey DawgDad that was the very best explanation I've heard!!!!

Suz

Suzanne wrote:

Hey DawgDad that was the very best explanation I've heard!!!! Suz

Thanks - its even better with pictures!

Good drawing Dawgdad,
I know one match shooter out here that seats his boolits closest to the rifling as he can to eliminate any chance of wobble or whatever. Sure his is a custom gun, rifling and all that and it works for him. But on my M700 /06, if I seat the bullet closest to the lands, accuracy suffers. Every gun is an individual, and if you roll your own, you can find the sweet spot.

My match load likes a jump of .015-.010" - No more, no less. Outdside of that range, the groups grow.

why is it called a jump? is it because of a lack of a better term? since the bullet contacts the lands before it leaves the case.

because it's unguided. It can go up or down, left or right and not entering the barrel straight in the middle. And you cannot predict how he's going to jump next time because so many things influence its flight. So it might touch the lands before leaving the case, but you cannot predict what part of the bullet will hit them first.

When I load 210 gr Berger VLDs in my 300 Ultra for targets I actually cannot put them in the floor plate of my Mod 700 LSS as they are too long, yet they do not touch the lands. For hunting loads there is no worry of getting them to touch on that firearm. Really depends on the gun and the bullets you use.

1895ss wrote:

Bushmaster wrote: Actually 1895ss. One can not predict just what each individual bullet will do. This is true...

Yet I had the same problem with Federal ammo with Sierra bullets. Tracked many-a-deer before I got wise to that little problem. In my most humble opinion (noticed how I spelled that out rather than abbreviated...rebel) Sierra's jacket is too thick. Although, as you all know, I like a bullet that explodes like a grenade.

Ballistic Tips TC !!!

Thank you Dawg.
I understand what you are saying and will work on that and post again when I have a ogive number and the number of the jump I am now using.
Thanks again.

Long wrote:

why is it called a jump? is it because of a lack of a better term? since the bullet contacts the lands before it leaves the case.

Not true grasshopper...when the powder ignites and pressure us generated inside the case it causes the mouth of the case to expand and release the bullet so the bullet is truly in freebore for a microsecond or two... This is why concentricity, neck thickness and neck tension of a round is important to the match and bench rest shoters so it releases uniformly and the bullet does not hang up on one spot or another and cause it to pitch or yaw off of the axis of the bore. (Also why a uniform crown is crital to good precison shooting as to release all of the bullet at the same instant.)

not ture? i did not say the case does not expand. expand or not the bullet does contact the lands before it leaves the case.. grasshopper? Ive been loading for 35 yrs and own 27 rifles that I load for. I am also a gun smith and do alot of chambering and recrowning.jump, leaveing point A and contacting point B without being at both places at the same time.