OV1 wrote:

ts my understanding that at the point of ignition from the primer to the powder, the powder in (nano seconds) does not ignite all at once and reverberates back and forth against the inside of the case as pressure builds up. Air space inside the shell (compressed or not) contributes to acceleration of burning the powder, as the pressure builds up, it pushes the bullet out in towards its target. As the bullet is traveling out the muzzle, pressure fluctuates at different points up till bullet leaves the muzzle. Now on firing any projectile, the gases which propel the bullet even after it leaves the shell are still high and thats why you have to resize the the shell or neck after firing since brass with 35k lbs on up will form to outside (chamber). This is a lot more pressure then required to seat the bullet and crimp it. Just have to remember the minute the bullet hits the rifling, you have friction which will keep pressures high till the bullet exits.

My head hurts.

I handload 'em, I put 'em in the boolit box, I push 'em into the chamber and I squeeze the trigger after aiming wiv me dodgy waterlogged eyeball (soon to be fixed I hope). Whatever happens after that is outa my hands and into the realm of physics...a subject in which I am not even remotely qualified...dumb as a box of hammers some would say. You guys keep at it...with some luck I will learn something.

However...my loads are always within Minute of Critter, so I am happy.

Cheers, Vince

Here you go, I like this info:

www.the-long-family.co..._paper.htm

I am with you Vince- let just see how many angels can dance on the head of a pin and eat Yak butter while we are at it.

It is all semantics but as we ever strive to understand what makes a good rifle better...enquiring minds want to know.

The nanosecond and few thousands of an inch we are discussing are really a minor piece of the whole accurate rifle puzzle . But it is one that many try to contol as a way to eliminate any source of error. What Long and I are disagreeing on is the amount of neck tension required to resist sliding friction as the bullet begins its journey to the target. It is a matter of words where I say since it is moving in the case neck and the case neck brass is expanding under pressure it is unsupported, Long says that the neck tension still guides the bullet to the point where it engages the rifling and starts down the barrel like a piston in a cylinder sleeve.

Maybe it is a solution in search of a problem but regardless of how we say it... Some bullet/rifle combinations have very specific sweet spots of bullet JUMP that make drastic improvements in precision down range.

marty, in my 300 wtby it does shoot a better group seated at 0.10 off the landing, BUT at that lenth they will not fit into the mag so i load them as long as I can so that they just fit the mag. it still shoots a 1/2 group at 100yds. I load the 125gr nosler with 89gr of RL22. it will destory the shoulders on WT,MD OR ELK just anit much left of the shoulder meat but that is why I shoot da big gun.

lol Hi Guys & Gal. I have not found a site that i like as much as this one.Some very interesting idea's and it seems as also a LOT of knowledge about weapons and their workings.But if this gets any deeper i'm gonna start playing golf.I have a terrible headache trying to follow this 8O.keep up the good stuff.I'm kinda like vince if it drops when i pull the trigger i'm happy.

Pumpkinslinger wrote:

Here you go, I like this info: www.the-long-family.co..._paper.htm

Hmmmm... a 20" AR match rifle uses the gold standard load of a 77SMK with 24.0 gr. RE-15 at about 2650 fps that will shoot very well in about any rifle... by this calculation that is meeting an 8th order node... In order to meet the 4th node the muzzle velocity in a 20" barrel would be 3600fps,

Node # Velocity OBT
1 4871 0.684
2 4432 0.752
3 3899 0.855
4 3609 0.924
5 3250 1.026
6 3044 1.095
7 2786 1.196
8 2631 1.267
9 2438 1.367
10 2318 1.438


Interestng to note that the OBT varies in a regular pattern between nodes the differences in velocities between nodes is very irregular...

Long- is that your web page?

Sorry Roadjockey - just trying to wrap my head around some interior ballistics..

Keep pulling the trigger - I'll keep pulling my hair out...

Since a primer alone can lodge a bullet in the lands I am going to say that the case expands enough to release the bullet (or at least push it out of the case). If you have a maximum diameter chamber and a minimum diameter cartridge then the case can only expand about .003" leaving .0015" on each side or roughly a minimum main bearing clearance for your gasoling engine. it is "guided" as it leaves the case but there can be substantial play as well. It is just a matter of degree.
The lead or freebore is typically within .003" larger than bullet diameter. on target rifles it is much less than that and on some there is less than .0005" clearance in the diameters.
In my old 03A3 the lead has a lot of clearance (over .005") in diameters and it is long enough to let a 150 grain spitzer rattle between the end of a maximum length case and the rifling. It shoots .5" groups regularly and some days a bit better. I never have groups over .75" with it.
All this proves is that ultimately a weapons accuracy depends on a lot more than what happens as the bullet begins to move.

When the powder ignites it burns from one end to the other, it doesn't combust all at once like some think. As this is occurring the pressure starts to build against the interior of the case and the seated bullet. Once sufficient pressure has built up the bullet will begin to move. Keep in mind we are nowhere near peak pressure at this time. The powder continues to burn, pressure and temperature are now rising rapidly. It's at this point that the case is expanding into the chamber sides and enough pressure has been generated to force the bullet completely out of the case and into the bore.


As far as bullet jump, bullet jam, and sweet spots !!!
It still baffles me that no can seem to figure this one out.
Simply put, you don't have to touch the lands to make a rifle shoot good groups. You can pretty much seat the bullet to where ever you want (within reason) and get good results as long as your capable of tuning a load. Some bullets by design will need certain criteria to perform to their best but that doesn't mean they don't have flexibility one way or the other.
That's one of the things I like about the OCW method. It finds the barrel harmonics for the seating depth you've chosen.

This whole issue in my opinion got started when benchrest shooters started throating chambers for particular bullets. They simply didn't need a chamber that would work for a wide range of bullet weights and profiles. All of a sudden this is the way everyone should be doing it. Seat them their bullets right into the lands. I agree with Aloysius theory of knowledge and believe on this one.

Now as for those rifles that won't shoot unless they're seated close to the lands. I ask these questions;
Are your necks square and free of burrs ?
Have you checked your re-loads with a concentric gauge ?
Have you experimented with neck tension ?
Is your bolt locking up square to the chamber ?

Dawgdad wrote:

Sorry Roadjockey - just trying to wrap my head around some interior ballistics.. Keep pulling the trigger - I'll keep pulling my hair out...

Hey Roady...we'll just sit back here throwin' a few beers into our faces while the others debate...then when the time comes, we'll just go out there and shoot a deer for the bbq mate.

Cheers, Vince

slimjim wrote:

marty, don't fix what ain't broke ... and ... don't argue with success. I've read technical articles where it is not unusual to find rifles that shoot well with the bullet more than 0.100 off the lands (like your Ruger). For your .300, is that just one type of bullet or has seating depth not mattered for several different type of bullets?

I tried three different bullet styles: 180gr HDY round-nose, 165gr Speer spitzer, and 220 (if I remember right?)gr Nosler partitions. Seating depth in the case covered a wide range since the distance to the lands depends on the ogive position, and these bullets had very different profiles. Most testing was done with the Hdy RN, as the freebore in the Weatherby is so long that the more pointed bullets (ogive closer to case) would not allow a deep enough seating depth in the case neck for bullets to reach the lands. I did first use the OCW method for each bullet to determine best powder and charge weight. (EDIT: A range of seating depths was tested for each of these bullets. I saw no appreciable difference in group sizes with any of these bullets.)

After all was said and done, I decided that the Hdy RN with 77.1gr RE 22 gives me the best groups and performance on both paper and game (whitetail and black bear). I now load all my ammo with this recipe.

Well, that's not quite true. I also have a box of ammo set aside with a different recipe I worked up (for Nosler partitions) that is a max load for long distance or heavier game. I printed out a ballistics chart for this and stuck it in the box. Maybe one of my kids will use it someday after they inherit this rifle.

what round are we in now

Been a while since I hated myslef enough to get back into this discussion...

I did a jump test last weekend using .223 75 Amax in a service rifle AR (iron sights). I did the Berger recommended jumps of 0.00-.010 - .040-.080-.120" jump three of the groups were in the 1.5-2 moa range but the .040" put six shots in 1.5" at 300 yards... I have not gone back to check if that is in an OBT node and dont really care - I found the long range load for my sons rifle.

I like the way your thinking Dawgdad, if it aint broke dont try to fix it.

If it ain't broke you're not trying!