Ok, I am putting this in reloading as Larry's rifle issues are related to reloading.

So I go with a friend that has an Accuracy International 300 WinMag 27" barrel 1-11 twist, to rearrange the paint on the 600yd gong. Did some paper shooting also after some very unexpected results from both his 300 and my 308. It seems that a week ago Larry was provided info(from a fellow from AI)to load his bullets out to maximum magazine length. His previous OAL was 3.53. New OAL 3.62. Powder charge the same 79gr H1000, bullet same Hornady 208gr A-max, same magnum primer. The difference at 600yds was .6 MOA. The ballistic calculator used previously for range development was based upon chronograph measurements of 2888fps@muz. It showed +3.1 MIL at 600 from 100yd zero. The only way we were able to come up with numbers that matched the range results(+2.5 MIL)was to increase velocity to 3150 in the program. Did he really gain 262fps merely by increasing OAL by .09? The bullet is still not touching the lands.

With my 308 I was shooting RBCD 126gr around 3400 muzzle 5 inches high at 100yds. I expected there to be some drop at 300yds. NIL, Nada, Neitz! Still 5" high at 300. I was able to consistantly ring the 600yd gong by bracketing it with the horizontal and verticle center of the reticle--basically aiming +5in and 5"left..the wind was blowing about 9.3 mph with gusts to 12.9. My 308 is a Remy 700 Varmint, slightly modified. Barrel cut back to 20 inches. It is 1-12 twist. It was funny how the bullet holes from 308 were oblong at 100yds and perfectly round at 300yds. Am I to assume my 308 was not stabilizing these rounds until they "slowed down a bit"?

It was a most interesting day and it has left both of us shaking our heads.

Anybody got any guess as to what we just witnessed?

Andy

First off, let me say, a lots of folks would be better off if they left that @#&%!! 'puter at home and let their rifles and hands-on experience tell them what is going on.

Working with theory only, if you move the bullet further out --not touching the lands-- without changing anything else, you are increasing the combustion chamber without adding more fuel. In a minute amount, this should lower the pressure and decrease the velocity.

Regarding your rifle, IMO, the bullet weight, the twist, and the velocity are all wrong. You are indeed over-driving the light for calibre bullets. Other than the "boyhowdylookwhatIcan do" velocity, you'll find that a 150 or better yet a 165 will catch up with your bullet at 500 yards and out perform your bullet in carry up at 500 yards and will give away very little as far a trajectory goes. You may ring the gong at 600 but you surely wouldn't tump over the 500 Ram.

The questions were more for Larry than me. He does not do the "internet thingy". His use of a ballistic program was merely a starting point as he had no friends shooting long range. Why not take advantage of available technology?!?

In the past I have been completely satisfied with the 100-200yd performance of RBCD(Proprietary loaded ammo) and had no place to shoot it much farther. I was 2" high at 100 and just for grins cranked it up 3" more. As far as "over driving" a light for caliber bullet please go to gscustom and actually read the info on light for caliber monometals. I am not a metal target shooter silhuette whatever ya'll call yourselves. When I set up this particular 308 I had no intentions of ever shooting an animal living or metal past 200yds and in that application it has worked fantastic. This was merely an opportunity to try something different so I did. I am just trying to figure out what was actually taking place.

Andy

Drew
You/he are assuming that the "release harmonic point" (where the barrel is in its vibration cycle when the bullet exits) remained the same, when in all likely hood it didn't. IOW he could well have been releasing at the lower point in the cycle with his old OAL, and at the upper point with his new OAL.
What really matters is the group size, once that's at minimum he can adjust his sights/drop chart to match his shooting results.

quote:

Originally posted by wasbeeman:
Working with theory only, if you move the bullet further out --not touching the lands-- without changing anything else, you are increasing the combustion chamber without adding more fuel. In a minute amount, this should lower the pressure and decrease the velocity.

Actually wasbeeman, the opposite is true. As you increase OAL to the lands, the greater the velocity and pressure.

RC, not seating to the lands, with the same powder charge how can the pressure and velocity go up??
gscustom is in the business of selling bullets. I am not.

quote:

Actually wasbeeman, the opposite is true. As you increase OAL to the lands, the greater the velocity and pressure.

As long as I stay out of the lands and I'm not talking .00001". Far enough that I'm not causing a pressure spike I've found if I leave the powder charge the same then my velocity drops as I increase OAL. But being a person to no leave empty case as I move the bullet forward I increase powder and ussually get a pressure increase.

In the 300mag case above that OAL move per QL drops pressure 3100psi and 36fps. The change in harmonics could make that bullet then hit higher or lower than before.

We've discussed this around here before and woods posted a chart that showed how OAL effected velocity and pressure. Maybe he can post it again here.

With the same charge as you seat the bullet deeper in the case, in general, velocity decreases and so does pressure.

I've seen it first hand while chrono'ing loads during seating depth tests.

If I remember the chart right, it differed between extruded and ball powder.

From the Hornady website:

quote:

To illustrate the effects of variations in bullet travel before the bullet enters the rifling, we'll compare a standard load with adjustments made only in the bullet's seating depth.

In a "normal" load with the bullet seated to allow about one 32nd of an inch gap (A) between the bullet and the initial contact with the rifling, pressure builds very smoothly and steadily even as the bullet takes the rifling. Pressure remains safe throughout the powder burning period (B), and the velocity obtained - 3500 fps - is "normal" for this load in this rifle.

Seating the bullet deeper to allow more travel before it takes the rifling, as in these next two illustrations, permits the bullet to get a good running start (C). Powder gases quickly have more room in which to expand without resistance, and their pressure thus never reaches the "normal" level. Nor does the velocity; with the same powder charge it only comes to 3400 fps (D).

When the bullet is seated to touch the rifling, as in the accompanying illustrations, it does not move when the pressure is low (E); and not having a good run at the rifling as did the other bullets, it takes greatly increased pressure to force it into the rifling. As the rapidly expanding gases now find less room than they should have at this time in their burning, the pressure rise under these conditions is both rapid and excessive (F). Velocity is high at 3650 fps - but at the expense of rather dangerous pressure. Many rifles deliver their best groups when bullets are seated just touching the rifling. Seating bullets thus can be done quite safely if the reloader will reduce his charge by a few grains. The lighter load will still produce the "normal" velocity without excessive pressure.

Here is a ladder I did at different seating depths keeping the powder charge the same, and I was very meticulous on the seating depth



Here is a chart on pressure relationship to seating depth



Read "From the Lab" about 1/2 way down this page from Barnes.

quote:

Once our cartridge selection was made we worked up loads which were below SAAMI maximum pressure, but within a few thousand pounds of the maximum pressure to account for variation and drop-off within a given sample. We set our first distance at 0.025” off the lands, then continued to move the distance out at 0.025” intervals for five separate groups. Our one exception was the .300 Weatherby Magnum. We started at SAAMI maximum length for the cartridge and moved back in 0.050” increments.

*Note: beginning on the left with shot No. 1, distance is closest to the lands, and ends with shot No. 5 on the right, which was seated at the greatest distance from the lands. This applies to all charts.

quote:

In the overall perspective, we can say that generally pressure will decrease as the bullet is moved farther from the lands. Generally, we can say that velocity will decrease as pressure decreases the farther the bullet is seated from the lands. And generally, we can say that accuracy is depending on bullet placement from the lands dependant on the rifle the bullet is fired from.

This demonstrates some individual anomalies but generally it can be said that pressure decreases with an increased jump to the lands.

Who can argue against all those pictures and charts but I'm still very skeptical.
It's too wet and cold to do my own test.

Essentially what that is saying is that the "combustion chamber" stays the same but the bullet gets a running start. The brass is not much of an impediment to the kind of pressure in the chamber and once it expands to the chamber walls and the bullet hits the lands, that defines the combustion chamber. That doesn't change.

Hornady has a good read down at the bottom of the page.

BTW yesterday it was 83 degrees but we had a cold front blow through and it may get down to 46 degrees tonight!

Group size did not change. Only point of impact.

The only way you ould increase muzzle vel by that much is ramming the bullet into the lands & upping pressures significantly & even then, I doubt it's more than 100fps. Sometimes the paper numbers just don't match real worl shooting. POI can change when ever you change a load variable as yo uchange the harmonics of the load.

As well presented by the graphics, the seating of the bullet most likely did not provide what you describe. As also mentioned the ballistics programs and the real world often vary to a considerable degree due to untold variances in the actual field experience. For elevation and 223, 308,'06 calibers, rule of thumb for elevation with 100yd zero would be some 3 moa per 100yds out to 700yds. These are not intended to put you in the X ring, but shall we say, "on target." Preferred come ups would be 2moa from 100 to 200, 3moa from 200 to 300, 3moa from 300 to 400, 3moa from 400 to 500 and 3moa from 500 to 600yds. Total of 14moa to target.
Believe you mentioned that your friend's rifle/300WinMag was some .6mil higher than had been predicted and in reality that is not that much when you consider all the variables involved.
The 300WinMag is a high performance round and will require less elevation adjustments than those above. AMU considers the 300WinMag a superb long range match round and it is indeed, lesser calibers can shoot as well, just requires more "knob turning" to do the same thing.
Have not shot the light bullets you mention in the 308 and nothing wrong by using them, but not the ideal bullet weight for extended ranges. You will hear experienced shooters refer to the phenomenon of bullets "going to sleep" and they are talking about becoming stabilized at a given range. Your bullets at 100yds w/ keyhole impact would indicate your bullet has not stabilized or had not "gone to sleep" as they say??
Your estimated wind speed was some 9-12mph or an average of 11mph and at that distance with a "normal" bullet, my windage input would be some 4moa unless I thought it was a "full value" wind. Keep in mind that if the wind was at full value, direct from 3 o'clock or 9 o'clock it would be more and I would use 6moa. Each clock face direction requires different adjustment other than 6 o'clock or 12 o'clock which has little impact on the bullet's flight. Reason I selected 4moa is that I apply a simple formula for windage taking into consideration wind direction which has worked for me over the years. Might point out that the wind coming from right to left or reverse also will have an impact on elevation due to the rotation direction of the bullet itself. With right hand twist, right to left wind will tend to raise the bullet in flight and left to right wind will tend to lower the bullet in flight. Not much, but it is there. Now, with all this "stuff" why don't I shoot all X's at 600 to 1000yds??
Answer is the weakest link in the chain, me, the "trigger puller" plain and simple.

I won't begin to argue against pictures.

I never tried moving the bullet and checking pressure back when I had the equipment to measure it. On the rifles I saw a drop maybe my throat was so long the capacity increase was enough to offset. Don't know. Only know what I wrote down.

As to the program (QL) it will ASSUME the starting pressure will remain the same as you move the bullet forward thus larger capcity same powder less pressure. That is the way it works. You can override starting pressure(effect of bullet jump) but you would sure have to be smarter than I am to know how much to change it.

As to my own rifles I build them with a custom throat. I seat the bullet as long as my magazine will allow. Select the bullet I'm planning on using and cut the throat to match. Since I blow out cases and move shoulders forward why leave free capacity on the table.

All I can say is that I would have bet money on longer OAL less velocity. While I have not fully into the other camp I'm for sure into the camp of I'm not sure and all bets are off.

assuming less than super critical high pressure and in no case is the bullet touching the rifling.

with the same load but longer OAL, the bullet should go very slightly slower, as you effectively increase capacity of the case

THIS IS NOT A SAFE EXAMPLE FOR LOADING
if one put the charge for a 308 win with a 165 at 2500 it would go SLOWER if placed in a larger .308 caliber case.. for example, something with 10% more capacity

would it result in 5% more velocity? unlikely .. if one received 1/4 of the gain in capacity for a gain in velocity, AT THE SAME PRESSURE, it would require 20% more capacity .. however, in the same load, pressure would likely be lower, due to a tiny increase in usable capacity.

setting the OAL shorter can result in more pressure .. i recall an article on the 9mm, that .01 shorter resulted in over saami pressures from known safe loads/lengths

and all of this boils down, simply, to pressure does NOT equal velocity

Damn! I stayed awake half the night thinking about this.
To use Jeffeosso's example, if the facts of this post are correct, then it would follow that if you put a .308 load that would generate 2500fps with a 165gr bullet in a 30-06, you would get higher pressure and higher velocity. And then, if you put the same load in a .300WM, your pressure and velocity would be greater yet.
I, of course, am not arguing with charts and pictures, I'm just saying.....

IMO the brass case is not the "combustion chamber" as it presents very little resistance to that pressure. The combustion chamber would be all the volume inside the chamber from the bolt face to the beginning of the lands minus the volume the brass material of the case. IOW, the thickness of the case head is not compressible and does reduce the combustion chamber volume as does the thickness of the brass of the case body, shoulder and neck. These get pressed to the steel chamber walls.

The only way to change the combustion chamber volume would be the very minor variations in case head dimensions and brass thicknesses.

There are many variables that will reduce velocity such as particular barrels, chamber size etc. But all other factors being equal, velocity will decrease in almost all cases with a longer jump to the lands. I have seen this over and over and over again. Thought this was pretty much a given understanding.

I suppose once you get a good distance from the lands then the bullet jump variance will exhibit a proportionally smaller increase in jump speed and the velocity may stabilize or even go back up.

Think of the Weatherby calibers. They are known for their long jumps from .150" to .275" in guns that I have measured (think larger combustion chamber). Yet they have high velocity. The reason is that Weatherby puts a stronger charge of powder in the case. I have read repeatedly about not short throating a Weatherby caliber and then shooting factory ammo. The reason is that you have reduced the combustion chamber size in the short throated chamber and thus you will get an overpressure.

Take my 338RUM which I had rebarelled off a 338 win mag action. I sent a dummy cartridge to the gunsmith (Westpac who did an excellent job) and had him set the throat so that I could reach the lands and still fit the mag. Anyway my combustion chamber is smaller than a typical 338RUM factory chamber. I can not shoot max loads or I lose the primer pockets. Max load it 98 gr RL25 with 225 gr bullets and I am down to 94 gr or I lose the brass.

Of course it is risky to state absolutes in reloading but expect a longer jump to reduce velocity in the same chamber.

In jeffe's example of a 165 gr 308 win put in a larger caliber you are increasing the size of the combustion chamber which is a different variable than the seating depth variable. So beeman your hypothesis that putting it in a 30-06 or 300 win mag would not create more pressure but would rupture the case and the pressure would work on the action and escape out of the chamber through other avenues rather that exerting all the pressure behind the bullet and out the bore. IOW the smaller the combustion chamber the greater the pressure and velocity (if the pressure is controlled) so in the larger combustion chambers you would lose velocity with less pressure, again as long as you control that pressure.

I wasn't suggesting that you fire a .308 cartridge in a 30-06 and a .300WM; I was saying that if you used the same powder charge and bullet in each correct case. I see where the combustion chamber would be from the head of the case to the lands but I still can't see how enlarging the "primary" combustion chamber is gonna encrease pressure/velocity. You have more room that must be filled before the bullet starts to move.
Pretty today, couple more days to dry out and maybe I can shoot some.

Finally got a chance to shoot across chrony. New OAL load same powder charge was actually less than 100fps difference.

2888 original;2973 longer OAL. When scope re-zeroed at 100 elevation to 600 is now 2.9 instead of 2.5/3.1, see original post for better explanation.

Now to just pull 5000 loads .090"

Are you saying that in the same cartridge and powder charge but with the bullet seated out further, you go higher velocity??

I've got some brass I need to fire form, I have some loaded up with different lengths to see. hopefully, I can shoot later this week.

quote:

Originally posted by drewhenrytnt:

2888 original;2973 longer OAL.

Sounds like it beeman

And drew if you are pushing the 208 gr bullet at 2973 fps out of a 300 win mag even with a 27" barrel that is smokin!

Not that I don't believe you but chronos are not always right

What's true for auto pistol cartridges with their fast powder and small capacity doesn't necessarily translate to rifle cases and slow powders. The 9MM example is true; so are Andy's results.

So speaketh the Bubba...so be it the truth.

Okay, finally got to do a little shooting. I have a XR-100 in .223 with a brand new Douglas barrel on it. I wanted to fire form some brass for it so I loaded up 3 groups of 10 and fired them acrost the Chrony.
Dakota match brass
Rem 7 1/2 BR primers
Horn Match 53gr HP
26gr H335
The groups were seated to 2.30", 2.315, and 2.330"

The average for the shortest cartridges was 3398.2fps
The 2.315" group averaged 3344.8.
And the longest, 2.330", averaged 3340.1

A small test and a small sample, and, in truth, a small velocity spread if you were shooting anything except targets for score. But enough to convince me that when you seat the bullet longer without contacting the lands, and if everything else is the same, the velocity goes DOWN! Despite the graphs and charts.

quote:

Originally posted by wasbeeman:
Okay, finally got to do a little shooting. I have a XR-100 in .223 with a brand new Douglas barrel on it. I wanted to fire form some brass for it so I loaded up 3 groups of 10 and fired them acrost the Chrony.
Dakota match brass
Rem 7 1/2 BR primers
Horn Match 53gr HP
26gr H335
The groups were seated to 2.30", 2.315, and 2.330"

The average for the shortest cartridges was 3398.2fps
The 2.315" group averaged 3344.8.
And the longest, 2.330", averaged 3340.1

A small test and a small sample, and, in truth, a small velocity spread if you were shooting anything except targets for score. But enough to convince me that when you seat the bullet longer without contacting the lands, and if everything else is the same, the velocity goes DOWN! Despite the graphs and charts.

Sorry wasbeeman, I don't know what you were seeing, but WRONGO!

Also if you check wood's charts, ball powder acts a tad differently

quote:

Originally posted by rcamuglia:
We've discussed this around here before and woods posted a chart that showed how OAL effected velocity and pressure. Maybe he can post it again here.

With the same charge as you seat the bullet deeper in the case, in general, velocity decreases and so does pressure.

I've seen it first hand while chrono'ing loads during seating depth tests.

If I remember the chart right, it differed between extruded and ball powder.

I have no insight into this but what I'm hearing is that as the chamber dimensions increase so does the pressure?

Ken....

Not really.

It has to do with how far the bullet moves without resistance before it engages the rifling. If it jumps less, pressure builds quicker and velocity increases.

Conversely, the more jump, the longer powder is burning pushing the bullet before it can encounter resistance in order to build pressure...therefore velocity suffers.

quote:

Originally posted by Heat:


I have no insight into this but what I'm hearing is that as the chamber dimensions increase so does the pressure?

Ken....

There are several variables here, chamber size, bullet jump, powder charge, long throat, short throat, bullet weight etc.

But if you keep all the other variables constant then as chamber size increases, pressure and velocity decrease.

Now you could say (again keeping all the other variables constant); as the volume inside the case increases (because you are loading closer to the lands leaving more powder room), the pressure increases.

quote:

Originally posted by woods:

quote:

Originally posted by Heat:


I have no insight into this but what I'm hearing is that as the chamber dimensions increase so does the pressure?

Ken....

There are several variables here, chamber size, bullet jump, powder charge, long throat, short throat, bullet weight etc.

But if you keep all the other variables constant then as chamber size increases, pressure and velocity decrease.

Now you could say (again keeping all the other variables constant); as the volume inside the case increases (because you are loading closer to the lands leaving more powder room), the pressure increases.

Get that cigar out of your mouth!
Close, but no cigar!

quote:

Seating the bullet deeper to allow more travel before it takes the rifling, as in these next two illustrations, permits the bullet to get a good running start (C). Powder gases quickly have more room in which to expand without resistance, and their pressure thus never reaches the "normal" level. Nor does the velocity; with the same powder charge it only comes to 3400 fps (D).

Just because the chamber is effectively larger and there is more powder room, pressure does not increase.

Pressure changes with changes in seating depth because of what happens when the powder is ignited. How far the bullet moves without resistance before being forced into the rifling initially as pressure builds.

Hey woods,
You're gonna have to make a target load for that .264 WannaBe Mag or get a target gun. How can a guy stop shooting till October because of the heat and still be happy?
You'll also get out of practice loading and shooting and forget stuff then start posting wrong like you just did

quote:

Now you could say (again keeping all the other variables constant); as the volume inside the case increases (because you are loading closer to the lands Leaving more powder room leaving less bullet jump), the pressure increases.

That's better!

quote:

Originally posted by rcamuglia:

quote:

Originally posted by woods:

quote:

Originally posted by Heat:


I have no insight into this but what I'm hearing is that as the chamber dimensions increase so does the pressure?

Ken....

There are several variables here, chamber size, bullet jump, powder charge, long throat, short throat, bullet weight etc.

But if you keep all the other variables constant then as chamber size increases, pressure and velocity decrease.

Now you could say (again keeping all the other variables constant); as the volume inside the case increases (because you are loading closer to the lands leaving more powder room), the pressure increases.

Get that cigar out of your mouth!
Close, but no cigar!

quote:

Seating the bullet deeper to allow more travel before it takes the rifling, as in these next two illustrations, permits the bullet to get a good running start (C). Powder gases quickly have more room in which to expand without resistance, and their pressure thus never reaches the "normal" level. Nor does the velocity; with the same powder charge it only comes to 3400 fps (D).

Just because the chamber is effectively larger and there is more powder room, pressure does not increase.

Pressure changes with changes in seating depth because of what happens when the powder is ignited. How far the bullet moves without resistance before being forced into the rifling initially as pressure builds.

Hey woods,
You're gonna have to make a target load for that .264 WannaBe Mag or get a target gun. How can a guy stop shooting till October because of the heat and still be happy?
You'll also get out of practice loading and shooting and forget stuff then start posting wrong like you just did

You're gonna have to read more carefully grasshopper! I very specifically separated the chamber from the case. The case is not the chamber. The brass causes very little resistance to the pressure and will expand readily to the chamber walls.

quote:

Originally posted by rcamuglia:

quote:

Now you could say (again keeping all the other variables constant); as the volume inside the case increases (because you are loading closer to the lands Leaving more powder room leaving less bullet jump), the pressure increases.

That's better!

Same difference!

OK Sensei...

Got it!

My thought was it doesn't matter how much powder room there is, the cause of higher pressure and velocity is due to the bullet's proximity to the rifling.

Sorry,I am truely intimidated by all of the charts and graphs but what I posted was the results of my ACTUAL test.
I'll have to refer you to the bumblebee.

Just keep it in mind beeman. Most of the time we do truly live in a gray world, not black and white. One test, one range session, one set of loads does not always give the correct answer.

If you shot the 10 loads from the shortest first and then proceeded to shoot the middle length group and then the longest last, the difference in the cleanliness of the barrel could make that much difference and more. Or the other way around. External temperature can change during that much shooting.

Not sayin it's so, just sayin. I look for trends to form hypotheses and repetitive experiments to form convictions. I do believe in the graphs and pics above because I have seen it over and over again.