New Web-Based Interior Ballistics Calculator – Precise Load

[PreciseLoad]

Hey everyone,

I’m Benedikt, a reloader from Germany, and over the past 1.5 years, I’ve been developing https://preciseload.com as a spare-time project. Precise Load is a web-based interior ballistics calculator, similar to QuickLOAD and GRT, but it runs directly in your browser—no installation needed.

Thanks to Lowlight’s approval, I’m excited to introduce Precise Load here and get feedback from the community.

Key Features:

• More Accurate Simulations – On average, Precise Load predicts pressure and velocity levels more accurately than QuickLOAD and GRT.
• No Installation Required – Any device with a browser works—I recommend using something with a larger screen for a better experience.
• Public Bullet Database – Add and share bullets using Precise Load’s simple bullet measurement tool.

You can try it out here: https://preciseload.com (registration required).

I’d love to hear what you think—especially regarding usability, accuracy, and any improvements you’d like to see.

Looking forward to your feedback!

Benedikt

 

[Maurygold]

I’m shooting a 7 prc 180 grain Berger hybrid with 68.0 gn of h1000. 1:8 twist 25.5” barrel

Your calc has speed at 2785. Real world is 2930

 

[PreciseLoad]

@Maurygold:

Attached, you’ll find the table I used to verify the simulation accuracy for Hodgdon Varget. From the table, you can see that for most loads—regardless of caliber, bullet, etc.—both pressure and velocity levels were simulated quite accurately.

However, some loads have not been simulated very well so far. In most cases, this is because I have been treating all bullets as equally "hard." Obviously, the assumption that all bullets have the same hardness is not accurate. This is an open issue that I will address soon.

By the way, I tested all propellants in a similar manner. The simulation accuracy is generally consistent with what you see in the attached table.

Best regards,
Arne

PS: Calc = Calculated Values , Meas = "True" Measured Values

 

[ggmanning]

I punched in for a load of H1000, 300WM and Berger 215. It also is calculating quite a lot slower velocity than real world. Is there a way to adjust bullet/seat/jump to lands parameters?

Obviously lots of work on your part in generating the utility.

 

[PreciseLoad]

Currently, the bullet jump is calculated based on the minimum chamber dimensions according to CIP. However, I could easily add an input field to allow users to manually override this calculation to better match their individual chamber.

Maybe the main question I need to address is which calculation details should be exposed to the user to strike the right balance between simulation accuracy and ease of use.

Without having given it too much thought yet, an additional "Expert" screen could be a possible solution.

Bests
Arne

PS: Can you share the exact load you were simulating? It would also be interesting if you could hit the "Bullet Details"button and compare the dimensions of that bullet to the one you have on hand.

PPS: It was—and still is—a lot of work. But the entire process has been a great experience. From the very first calculations being quite off—having never read any interior ballistics book and only a vague memory of thermodynamics class from 20 years ago—to what you see now, it has been quite the journey.

Once I’ve finished adding all the propellants, my next step will be addressing bullet hardness. I’m pretty sure that will provide yet another boost to simulation accuracy!

 

[R_A_W]

It also is calculating quite a lot slower velocity than real world

also slow, 100fps under actual for my load w/ H1000, 143 ELDX, 210M

There are only 2 bullets in the database that I actually shoot, so I can't give you too much feedback.

Ability to toggle off all metric & use only imperial would be good.

I also only have 1 or 2 SAAMI spec'ed chambers left, so I have to edit my chamber dimensions in GRT. Ability to create custom chambers is mandatory for me.

 

[PreciseLoad]

@R_A_W

• You can add bullets to the database if you want to. Just send me a message with the username you're using in Precise Load, and I'll grant you those rights. I'm actually quite curious about any feedback, as up to now, I've entered 99.9% of all the bullets myself. You may also try the Bullet Measuring Tool.
• Adding an interface for custom chambers wouldn't be a big deal to implement. I'll put that on my to-do list.
• Regarding toggling, I need to figure out how to make it visually pleasing. The whole "visually pleasing" aspect of programming is one of my least favorite things, so... I keep postponing that request. Some German users have asked for the same thing.

 

[Dstoenner]

My 223 Rem load of 23.5 gn Varget in a bolt action 1:7 twist 26 inches long says it should be 2822, actual is 2689.

Your screens of mixed units is very confusing. Let us pick 1 set of measurements, metric or imperial. The big thing that GRT does is that it allows you to curve fit the 2 powder values that matter to you rifle/cartridge/bullet/powder as a system. Then you can get accurate projections of powder vs velocity.

David

 

[Dstoenner]

I received this from the developer who asked me to share it with the rest. This to me says he is trying to give us a better product but needs our feedback.

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Metric vs. Imperial Units​

Regarding the mixed metric/imperial units—I’ll update that. The reason it’s like this is that many Germans (myself included) use the metric system for almost everything, except for reloading, where grains are standard. It’s a bit odd, but probably because most reloading literature comes from the U.S. Also, while developing PreciseLoad, I constantly switched between metric and imperial units, so having both in parallel was convenient for me. But I guess that time has passed, and it makes sense to standardize things.

GRT’s Curve Fitting Approach​

I understand what GRT is doing with its “curve fitting” method (I also read your post about it, by the way). Implementing something similar would actually be quite easy, but let me explain why I’ve chosen not to.

The main goal of an interior ballistics calculator is to estimate pressure and velocity. While GRT’s approach does a great job adjusting velocities for a specific system, you have no way of knowing whether the pressure levels it calculates are still accurate.

To make an analogy: If you’re solving a linear equation, two points are enough. But if you’re dealing with a parabola, you need at least three points. In interior ballistics, you’re working with highly nonlinear relationships and need a lot more than Ba etc. for reasonable accuracy.

Velocity and powder mass can be linearized within a certain range—at least as long as you don’t change the cartridge, bullet, etc. But pressure? That’s a different story.

This creates a problem: Nowadays, many reloaders have highly accurate chronographs, so they see their velocity data and think, “Hey, I’ll adjust my model to match, and now my calculations are perfect!” But pressure—the dangerous part of reloading—is something most people cannot measure. And yet, they might think their calculated pressures are still correct.

From an engineering standpoint, I don’t like what Gordon did here. It gives the illusion of accuracy where there is none, which can be misleading. To put it bluntly, you could just shoot a ladder test, plot the velocities in Excel, add a trendline, and get nearly the same insights—except for the ability to compare different propellants.

On Barrel Nodes & Measurements​

On a different note, regarding the whole “barrel node” debate—whether it’s real science or just voodoo—I’m actually conducting measurements right now. Specifically, I’m measuring how barrels vibrate in response to different loads. But that’s a whole other topic.

 

[biggershooter]

It doesn't have 6mm GT or the 115gr DTAC bullets. When it does, please post and I"ll try the system.

 

[PreciseLoad]

It doesn't have 6mm GT or the 115gr DTAC bullets. When it does, please post and I"ll try the system.

I've added the 6mm GT. Could you please send me the measured case capacity (not just a value from GRT or QuickLOAD)? The current case capacity is based on a calculation.

As for the 115gr DTAC bullet - feel free to add it yourself using the bullet measurement tool in the system.

 

[biggershooter]

Sure. Tried a PM, didn't work, so: I get 45.56 grains H2O for Alpha brass, SD 0.17, fired in a chamber cut with the Alpha Legacy Reamer.

 

[PreciseLoad]

@biggershooter: Thanks! Looks like the calculated capacity (44.83 grains) wasn’t too far off after all.

Out of curiosity, I compared that cartridge using StaBall 6.5 with the 95 gr SMK, and also the 65 gr V-Max with Varget, against the Hodgdon load data. Both simulations aligned pretty well with the published data.

I’m looking forward to hearing how the DTAC simulation compares to your actual results. To add it, you really just need to measure the length and diameter, have a decent photo, and then follow the Bullet Measurement Tool. I’d say the process of adding bullets is pretty straightforward.

PS: I’m not familiar with DTAC myself, but a quick Google search suggests they’re manufactured by Sierra. If it makes sense to add DTAC as a separate manufacturer in the database, just let me know. I'd be happy to add it.

 

[SNB]

Currently, the bullet jump is calculated based on the minimum chamber dimensions according to CIP However, I could easily add an input field to allow users to manually override this calculation to better match their individual chamber.

Just tried.
It would be nice to have that option.
Personally, I always fine tune the jump and often COAL end up outside SAAMI. Since my chamber dictates the seating depth.
And my chamber is definitely not at the minimum tolerances, but rather a little outside the maximum.
- in the exterior ballistics calculator, the scope & gun input window is not active.
- also 55 fps slower than my actual load CFE BLK /208 ELDM (should be an input of gunpowder temperature here? )
- On a propellant database RS24 is stated as double base / according to the reload-swiss.com it is singl base.
This is what I saw.
I liked the interface , didn't use Quick Load before.
It is convenient to compare different loads. I plan to switch from CFE BLK powder to RS 36 for subsonic shooting due to the lower temperature dependence of the sing base powder. Comparing the graphs, I see a difference in the time of increase of the load peaks and the shape of the pressure curve itself. I would like to understand from more experienced guys how to evaluate these load peaks and their location on the graph relative to time, and the effect on shooting.

 

[PreciseLoad]

@SNB:

• Thanks for the information about RS24. I’ve updated that.
• I’m currently working on @R_A_W's request to add the ability to define custom cartridges. I started last night. Since I won’t have much time until Saturday, it’ll probably take me until the weekend to finish. I sincerely hope users won’t be frustrated by the roughly 70 parameters required to define a cartridge But I’m fairly confident that anyone who puts in the effort to develop a wildcat won’t mind that level of detail.
• After that, I’ll move on to the bullet jump topic. Currently, the bullet jump calculations are based on the minimum CIP dimensions, as these represent the tightest possible tolerances and therefore the highest potential pressure. Of course, in reality, most firearm chambers are somewhere in the middle of the tolerance range.
• Regarding exterior ballistics: my main idea here is to offer a simple way to see which bullet gives the flattest trajectory at safe pressure levels. Features like zeroing distance and range card generation will be added as well.

Overall, I believe that adding more propellants remains the top priority.
When it comes to adding bullets, I’m counting on the community to contribute. Hopefully, the bullet measurement tool will make that easier.

PS: A deviation of just 55 fps from actual measured velocity is I’d call acceptable. Even loads I’ve re-tested — both for pressure and velocity — based on manufacturer data and fully compliant with CIP measurement standards were often off by more than that.

 

[R_A_W]

I sincerely hope users won’t be frustrated by the roughly 70 parameters required to define a cartridge

custom cartridges take effort no matter what program you're creating them in

The ability to start with a parent cartridge (6gt or 6.5x47L) and edit it for the few differentiated specs of a child (25gt or 25x47L) can speed things up significantly

 

[HemiPowrd]

Shooting 300 PRC, Hornady 230gr ATIP, 76.0 gr H-1000, 1-9 twist 29" barrel. Calculated velocity is 150 FPS low. Calculated 2747, actual is 2900.

 

[biggershooter]

@biggershooter: Thanks! Looks like the calculated capacity (44.83 grains) wasn’t too far off after all.

Out of curiosity, I compared that cartridge using StaBall 6.5 with the 95 gr SMK, and also the 65 gr V-Max with Varget, against the Hodgdon load data. Both simulations aligned pretty well with the published data.

I’m looking forward to hearing how the DTAC simulation compares to your actual results. To add it, you really just need to measure the length and diameter, have a decent photo, and then follow the Bullet Measurement Tool. I’d say the process of adding bullets is pretty straightforward.

PS: I’m not familiar with DTAC myself, but a quick Google search suggests they’re manufactured by Sierra. If it makes sense to add DTAC as a separate manufacturer in the database, just let me know. I'd be happy to add it.

1) actual is 2752; PreciseLoad is 2826; QuickLoad is 2749.
So QL might as well be perfect, but a) QL has a "friction proofed" check box (these are pre-coated with HBN) b) PL says the load is touching the lands when it has .040" or so jump. I think you'll need an entry for freebore, my chamber is .170" while typical would be .120" and anyone running heavy-for-calibre bullets needs more freebore than standard.

So I assume the "friction factor" on the bullet needs some adjustment? There appears to be no simple way to do this, as it looks like I need to re-enter the bullet, which is too time-consuming for trial-and-error.

2) DTACs are designed and sold by Tubb, manufactured by Sierra. Reasonably popular in PRS. This is the variant I'm using: https://www.davidtubb.com/dtac115-boronnitride


In general thoughts, since you ask people to login, you might consider a 'save' function for some number of loads, to avoid re-entering the parameters each time the program is used.