Sus-Tac Bullets

59K psi is near max for most calibres. If you give more info or a GRT file then I can see what you are achieving. The longer a bullet the more friction and pressure build up. Most loads that I have calculated in QL give more speed than initially shown. Rather act conservatively and use a start load. With speed measured a much better calculation can be made that ensure safe pressures.

59K psi is near max for most calibres. If you give more info or a GRT file then I can see what you are achieving. The longer a bullet the more friction and pressure build up. Most loads that I have calculated in QL give more speed than initially shown. Rather act conservatively and use a start load. With speed measured a much better calculation can be made that ensure safe pressures.

A correction it appears the Sus-Tac bullet in question is cup and core ? info about these bullets is scarce
The given PMAX for the 300WM is 63000 - for the PRC 65000
Quite above 59000
I will PM a GRT screenshot and the recorded velocities

Save your GRT calc and send me that file. My email is my forum name plus @gmail.com I can then get the correct data without having to do any inputs.

Save your GRT calc and send me that file. My email is my forum name plus @gmail.com I can then get the correct data without having to do any inputs.

On the way ...

Replied via email.

Replied via email.

Many thanks
Unfortunately there is a slight problem ..
You have swapped the value for Case volume H2O 91.63 with Cartridge length 91mm
Each field now contains an incorrect value

Check the info you sent me. I just read in the file. Will however change the data and recalculate.

Check the info you sent me. I just read in the file. Will however change the data and recalculate.

Thanks
I notice that the burn / energy values for the powder VVN160 have been modified - did GRT do that on it's own volition ?
I am still unsure of how the indicated velocity and pressure were so incorrect ?
The observed velocity and .. guestimated pressure were way wrong ( pressure was too high )
Although 3,000fps is not unusual in this cartridge with 180gr bullets ?
I do not know if the bullet is in fact mono-metal ? There are NO "driving-bands"
Still waiting for a reply to an email I sent early this morning

IF it is in fact copper and without any driving bands that would explain the jump in velocity and pressure ?

New calculated figures.

69.85gr - 3012fps Pres 61K psi Node 4 1/2
67gr - 2893fps Pres 54K psi Node 5

In QL I adjust the burning rate. GRT has a OBT calculator that adjusts the values to achieve the mean speed of 3110fps that I gave as an input. The figures above are then calculated with the new burn rates.

Both QL and GRT use standard values for the propellants and the components. There are however many factors that can influence the calcs. Just think of barrel smoothness and diameter, friction from longer bullets or different materials, hardness of material, deviation in burn rate etc. It is therefore imperative to shoot safe starting loads and get practical load and speed data. Now the programs will give more accurate predictions.

New calculated figures.

69.85gr - 3012fps Pres 61K psi Node 4 1/2
67gr - 2893fps Pres 54K psi Node 5

In QL I adjust the burning rate. GRT has a OBT calculator that adjusts the values to achieve the mean speed of 3110fps that I gave as an input. The figures above are then calculated with the new burn rates.

Both QL and GRT use standard values for the propellants and the components. There are however many factors that can influence the calcs. Just think of barrel smoothness and diameter, friction from longer bullets or different materials, hardness of material, deviation in burn rate etc. It is therefore imperative to shoot safe starting loads and get practical load and speed data. Now the programs will give more accurate predictions.

Thanks
Makes lots of sense
I see how the changed burn rate values bring the simulation more into line with the observed results
I would suggest a starting load with unadjusted values to be no more than about 55 -56000 psi indicated pressure
I thought I was OK at an indicated pressure of 59000 when PMAX is up to 65,000
I could still lift the bolt and eject the cartridge case - a misleading indicator
Little differences can make HUGE changes
As a matter of interest what are the estimated pressures for cratered primers / primer blown out / loose primer pockets ?

I pulled all the "naughty" ones and will reload at the now indicated figures
Lets see what the new real world velocities indicate - and - how close they are to those suggested by the new values in the simulation.

Problem is .. powder is so damn expensive - to shoot lots of loads

Proof pressures are in the region of 70 to 80K psi. Blown primers as from about 75K psi.

The norm between start and max loads is in the region of 15K psi. To calculate a start load I would use QL and get the max charge that gives 60K psi in a 30-06 for example. That charge I will reduce by 10% and it normally drops the pressure to 45K psi. In some very isolated cases even that design load was over 60K psi. This is easily the case when bullets are set very close to the lands and the jump has not been declared.

Play safe and start low. With QL I have had a 375HH on a node within 5 bullets being fired. Charge versus speed is all that you need to achieve that.

I would start with the 67gr load.

Herewith photos of cases after proof shots.

One thing I have learnt in my years of reloading is that primer "flatness" is the most misleading and misunderstood sign of pressure. The reason is few people understand the mechanism that flattens the primer.

Flattened primers can be a sign of high pressure with standard headspace or normal pressure with large headspace.
You can still get primers with rounded radii even when the load is overpressure if the headspace is less than 0.002". Case in point being the third from top on the right in the picture that Tripod posted above.

By far the most reliable sign is web expansion, followed by ejector marks, enlarged primer pockets and cratered primer indentations. The problem being that most of these overpressure signs only manifest when the pressure exceeds 75kPsi. Also, cratered primer indentations can also be caused by an overlarge firing pin hole in the bolt.

Herewith photos of cases after proof shots.

Scary stuff ....

By far the most reliable sign is web expansion, followed by ejector marks, enlarged primer pockets and cratered primer indentations. The problem being that most of these overpressure signs only manifest when the pressure exceeds 75kPsi.

Please can you expand on this ...

Measure the web with a micrometer, shoot the shot and then measure again to see how much it expanded.

How the web expansion method works
Prepare and measure unfired cases:
Use new or once-fired brass from the same manufacturer/lot (brass hardness varies significantly between brands and even lots).

Use a high-precision micrometer (ideally one that reads to 0.0001" or 0.01 mm; a standard 0.001" micrometer is often not sensitive enough). Blade or ball micrometers work well for the narrow area.

Index the case (e.g., with a marker line) for consistency.
Measure the diameter at the web (just above the extractor groove) multiple times, rotating the case 180° for averages. Record the baseline (unfired) diameter. Some reloaders lightly file the rim slightly so micrometer jaws fit better without the extractor groove interfering.

Fire the load and re-measure:
Fire the cartridge in your specific rifle.
Clean the case and re-measure exactly at the same spot on the same case.
Calculate the difference (fired diameter minus unfired diameter). This is the web expansion.

Interpret the results:
Typical guidelines (these are rules of thumb, not universal absolutes):
0.0005" (0.5 thousandths of an inch) or less expansion on the first firing is often considered safe or near maximum for many loads/brass types. Some sources treat even this as a sign to back off.
0.001" or more is widely viewed as excessive, indicating high pressure. Once this level is reached, the cases are often retired from further "pressure testing" use because resizing dies don't fully restore the web diameter.
Larger expansions (e.g., 0.0015"+) or rapid increases signal that primer pockets may loosen soon, extraction may become difficult, or you're approaching (or exceeding) safe limits for that brass/rifle combination.

Measure the web with a micrometer, shoot the shot and then measure again to see how much it expanded.
How the web expansion method works

Thank you really good info
Going to use this step by step starting now
Might need a new blade micrometer ?

Just had a quick look

To make this meaningful ....

You are going to need a high definition caliper / digital / dial for 0.000 mm
You are also going to need a blade micrometer also 0.000mm
You are going to have to measure VERY carefully
The distances you are measuring are tiny

There is a cheaper way. Do not scratch the lion's balls by staying away from high end loads. Speed data is available from the propellant companies, so be conservative and avoid high pressure.

The normal reloader do not need this. Stay within the normal min-max range as per reloading manuals then you are safe.

When you want to colour outside the lines you need to pay the price; either expensive tools or run the risk of blown up guns. Most of the the more reliable signs only show when the pressures go over 70 kPsi hence the requirement for specialist tools.

When you want to colour outside the lines you need to pay the price; either expensive tools or run the risk of blown up guns.

Over and above the tools you also need skills, experience and competence in their use. Unless you have done a fair bit of high precision work, know what you don't know and what the consequences of that could be you are deep in FAFO territory.

There is a cheaper way. Do not scratch the lion's balls by staying away from high end loads. Speed data is available from the propellant companies, so be conservative and avoid high pressure.

Agreed
Use the reloading manuals start low and work up - the Golden rule
However in order to achieve 100% powder burn and above 90% case fill takes some "adjusting"
Particularly as powder choice here is very limited
Most .. magnums perform best near max loads

I would like to get the necessary tools anyway - I have a "fetish" for tools
Waiting for someone to design and market an easy accurate affordable way to measure pressure

There is this ...

But I do not have .. millions :'(

Here are some interesting remarks about absolute pressure measuring.

https://forum.accurateshooter.com/threads/how-to-measure-chamber-pressure.4097368/

Here are some interesting remarks about absolute pressure measuring.

https://forum.accurateshooter.com/threads/how-to-measure-chamber-pressure.4097368/

"Get in contact with Bill Wiseman" ...

Bill Wiseman & Co, Inc

People - Industry / Military DO test for pressure

There must be something in it ?

Even just to satisfy curiosity ... ;) :)