Quickload question

[dcali]

Keep in mind that QuickLOAD's barrel time begins at 10% of peak pressure.

 

[rammac]

The reality is that most people that bad-mouth QuickLoad don't have a clue how it works or what it's capable of. Not only can you adjust the obvious parameters (cartridge specifications, powder variable, primer variables, etc.) but you can also create your own case dimensional data to better match your loads. You can also create a detailed profile for your barrel's lands and grooves.

 

[Riky]

I did a lot of OBT calculated loads and checked them by chrono measurements with unsatisfyed results.Now i'm convinced the best way to get one hole groups and repeatable accuracy is
to find the proper CBTO length.This may happen even by different powder weights.Last week on the 7 RM round i found with the same amount of powder at .015 , .040 and 0.12 a one hole group.My reloading tactic is use quickload/chrono to check burn rate and bullet speed, the nodes can be found quickly by moving the seating depth, i don't use anymore
the barrel time calculations.

 

[mikecr]

Seating is the coarse/largest adjustment.
It is best tested for while away from your powder nodes, so I test it during fire forming of new cases, but you can back off powder and do FULL SEATING TESTING anytime.

 

[BCBRAD]

As an example, I loaded a 280AI (light hunting rifle) via QuickLoad for a temperature of 20F, The day I shot them it was 35F, loads ran ~25ft/s faster than predicted.

I came back to QL and entered the new temperature of 35F, QL 'told me' to lower powder charge 0.46gns to get back on the OBT and the velocity it should be.

Even being off this small amount ( everything else ,weights, measures and velocity as close as my tools and expertise will allow) the rifle put 5 on paper at 219 yards , 0.6 moa group.

The semantics can be argued but as has been vocalized the paper tells the story.

 

[mikecr]

QL 'told me' to lower powder charge 0.46gns to get back on the OBT and the velocity it should be.

Is this true? Did QL tell you anything about OBT? In what field did it do so?

 

[BCBRAD]

How it worked out I was 25 ft/s faster than predicted, I had already fixed the Ba from previous tests.

Prediction was 2725 ft/s with a barrel time of 1.241mS

The velocity was 2750 ft/s, the barrel time was off, the charge weight was 55gns, to get back to the barrel time of 1.241mS I must lower velocity, I do this by putting less powder in the case.

Lower the weight bit by bit and watch the OBT come back to 1.241mS and the velocity fall to 2725 ft/s, it will all coincide when done correctly.

That is for a temperature of 35F.

Now getting to the OCW, in the graph the Pmax and the Z1 lines are overlayed, the pressure peak is very broad , sort of a plateau with the Pmax and Z1 in the middle of it.

This is an excellent load, it is tolerant of small changes in charge weight, temperatures and minor variance in measure.

 

[mikecr]

I just wanted it clarified that QL does not provide OBT (nor OCW). That these are theoretical systems outside of QL.

 

[jlow]

Brakes do not contact the bullet, the inside diameter of the brake is .005" to .040" over the size of the bullet (depending on what the manufacturer thinks is most accurate and safe). Once the bullet no longer contacts the bore the barrel vibrations will not effect it's performance.

As Ned said, QuickLoad simply provides you with the time that the bullet is in the barrel (barrel time) and you can use that information to help tune the load so that the bullet leaves the muzzle around an OBT node.

This is the answer. Basically accuracy nodes refer to when a bullet exits the crown of the barrel. If the timing is bad i.e. when vibrations is at the crown, the flight of the bullet is disturbed, giving a wide group. If the vibration is at the chamber, the crown is least disturbed and as such the bullet is least affected giving a small group.

As such, if you look at the barrel where the break is attached, the crown is at the back of the brake where it is attached and so the bullet is not affected by the brake but still the crown.

Having said so, attaching a weight like a brake can still affect the bullet, not its precision but point of impact.

 

[SeabeeKen]

I assume that most people understand that any simulation software will only provide us with approximations, that seems obvious to me. But since the software's approximation is repeatable we can use it as a marker to make adjustments from. It's not perfectly accurate but it's better than a SWAG (scientific, wild-assed guess).

I agree. GRT usually gets me close if not on the node. I tested this with a friends competition rifle in 222 rem. He was on a node and rifle shooting one hole. Took his data and input to GRT and calibrated the powder model. I ran the OBT and it calculated a node .1 gr off his current load. The devil is in the details