Quickload and OBT

[jdwet1980]

Hi All,

Does quickload have a function to determine OBT on its own or do you determine your barrel time and the uses quickoad to get to that?

Regards

 

[Erik Cortina]

Barrel time.

 

[savageshooter86]

for it to be very close(accurate to the actual OBT) I think you have to alter your powder burn rate/other factors in the powder section to get Quickload to match your chronograph readings. Then you can look for OBTs for your barrel length and velocity you are getting from your rifle. I presume if you are just using it to check different powder options then you could just use what the program gives you then when you get the powder work with it after running some chrony data

 

[Nomad47]

You get the OBT nodes from a chart (or excel formula) that Chris Long provides. QuickLoad will provide you with barrel time. But you must 'calibrate' QL for everything to work.

 

[TonyR]

Hi All,

Does quickload have a function to determine OBT on its own or do you determine your barrel time and the uses quickoad to get to that?

Regards

Shoot "sleepygator" a PM if he doesn't pick up on this thread. He has done a lot of work with QL and OBT.

 

[Nvreloader]

Dave Berg, Thank you for the post/info on this OBT/QL.

First time seeing it, Just how close do you have to tune QL? for the OBT.

Does the OBT work for all bullets weights/calibers and barrel lengths?

Tia,
Don

 

[Nomad47]

As I recall, about .020ms is close enough.

You need to enter a barrel length (muzzle to bolt face) in QuickLoad. And Chris Long's nodes vary with barrel length. I use Chris Long's formula so I can enter barrel length in decimals of an inch.

For my barrels, I am trying to hit one of nodes 3, 4, or 5. As an example, for my 6XC barrels which measure 28.125" muzzle to bolt face (shooting hBN coated 105 AMax bullets), I am trying to hit node 4 which is 1.278ms. A charge of 35.02 grains of IMR8208XBR gives me a MV of 3031 fps and QL tells me that has a barrel time of 1.278ms.

If you shoot a lighter bullet, obviously MV increases decreasing barrel time, so you might try to hit node 3. But if you run into pressure signs before hitting node 3 you would have to settle with node 4.

Of interest, sometimes a particular bullet weight and barrel length just don't go well together (if you subscribe to Chris' theory). For example, for a 26" 6-284 barrel shooting 105 grain bullets, to hit one node the load is at max, and for the next node down, the load is pretty mild, not taking advantage of the 6-284's case capacity.

One more thing, due to changing burn rates with different powders, velocities will change as you adjust the charge to keep on a node. That probably doesn't make sense. Let me try it a different way. When you go to a slower burn rate powder, you will find MV is a little higher when you adjust the charge to get the same barrel time as the faster powder.

 

[Gappmast]

for it to be very close(accurate to the actual OBT) I think you have to alter your powder burn rate/other factors in the powder section to get Quickload to match your chronograph readings. Then you can look for OBTs for your barrel length and velocity you are getting from your rifle. I presume if you are just using it to check different powder options then you could just use what the program gives you then when you get the powder work with it after running some chrony data

On my Quickload the powder burn rate is grayed out how do you change it?

 

[Nomad47]

Click on that little button with the picture of the hand holding a pencil. It is just to the left of the selected powder.

 

[Erik Cortina]

If you shoot a lighter bullet, obviously MV increases decreasing barrel time, so you might try to hit node 3. But if you run into pressure signs before hitting node 3 you would have to settle with node 4.

Not true, that's why when you asked me if I use the OBT theory I said not anymore. I do use it, but sometime have to modify it such as in this case.

I have won matches with a gun shooting in between OBT nodes.

 

[Nvreloader]

Guys,
Still trying to get my head wrapped around this,

In my case,
I have a load that will shoot at a higher FPS than the last node listed (7) OBT times, (284 cal).

Can the formula be used/figured to go to node 8, to see if I can use that node's time?

Does it matter, if you are using and even number or odd number Node?

Tia,
Don

 

[Erik Cortina]

A node is a node, weather it's even or odd.

 

[Nomad47]

NVreloader, you may be looking at things backwards. As velocity increases barrel time decreases. IIRC, I was on node 4 with my 284 shooting 180 hybrids from a 28" barrel.

Erik, I agree that you may not be on a node when you find the most accurate load for a barrel. But I stand by what I said - if you are trying to get to node 3 and you run into pressure signs, you have to drop to node 4. I could add - IF you are trying to get a load on a node.

I always go for a node first, but I also don't ignore the fact that the most accurate load may not be on a node. I had one barrel that was not on a node, but when I calculated the nodes including the brake, I was on a node. So QL barrel time was bolt face to crown but OBT node was plus brake. Go figure.

 

[Nvreloader]

Nomad 47,
Do you figure the Muzzle brake length + bbl, then use the node for total overall length?

My muzzle brake is 2.5" long and I shoot an 18"bbl+MB=20.5".

Tia,
Don

So QL barrel time was bolt face to crown but OBT node was plus brake. Go figure.

 

[Nomad47]

Nomad 47,
Do you figure the Muzzle brake length + bbl, then use the node for total overall length?

My muzzle brake is 2.5" long and I shoot an 18"bbl+MB=20.5".

Tia,
Don

So QL barrel time was bolt face to crown but OBT node was plus brake. Go figure.

With the brake off, I used a cleaning rod to measure crown to bolt face, 28.125", and this measurement was entered as the barrel length in QL. Then with the brake screwed on, I measured from end of brake to bolt face, 29.875", and this measurement was entered in the OBT formula.
Hope this makes sense.

 

[Keith Glasscock]

If you shoot a lighter bullet, obviously MV increases decreasing barrel time, so you might try to hit node 3. But if you run into pressure signs before hitting node 3 you would have to settle with node 4.

Not true, that's why when you asked me if I use the OBT theory I said not anymore. I do use it, but sometime have to modify it such as in this case.

I have won matches with a gun shooting in between OBT nodes.

Me too! There are "half nodes" as I like to call them. If you look at Chris' nodes, they are about 200-250 fps apart in the 308. Most experienced competitors will tell you that nodes tend to be 100-120 fps apart. As such, there has to exist good shooting combinations approximately half-way between OBT nodes. I have proven their existence, but what I can't prove is whether they are as good of nodes as the ones Chris determined.

 

[Nvreloader]

Nomad 47

Thanks, it does now.

I just have to figure out the proper formula for node 8 on some of my loads.

My calculator does not seem to work using the formulas provide by CL,
and then again it may be me NOT doing something right etc.

I have to figure out the nodes for 14" thru 16" barrels.

I hope the OBT holds true for these barrel length/nodes to give me a starting place.

Does the caliber make any difference in the node formula??

Tia,
Don

 

[Nomad47]

Don, OBT works for any caliber. What does QuickLoad show your barrel time as being? I have a OBT tool that Chris emailed me, works in excel. For a 16" barrel, node 8 is 1.018mS. For a 14" barrel it is .894mS. And for a 15" barrel it is .956mS.

Let me do this a different way.
Here are the barrel times for nodes 3 thru 9 for a 14" barrel.
.604 .657 .722 .776 .840 .894 .957

And here are the barrel times for nodes 3 thru 9 for a 16" barrel.
.688 .746 .823 .882 .958 1.018 1.094

 

[Nvreloader]

Nomad 47
Thank you,

QL shows a BT of 1.035 ms,
284 Win/57.6 grs/Norma 205/162 Amax/2690fps,18.0" bbl,
this load does NOT show any pressure, at 80* temp, so far, may be able to go higher?? more testing will tell, this is a junk bbl, waiting for the good reamer to get here, to set up the new bbl.

I would greatly appreciate a copy of the OBT tool, I have XL, that I am using for results. reloader (AT)gbis(DOT)com, please put OBT in subject line or it will get trash canned.

Does this OBT formula REQUIRE a specific type calulator?

Tia,
Don

 

[Nomad47]

Just emailed it to you, Don. Its a "tool". You put in starting node and barrel length and it displays the next seven nodes.