RS62 Burn Rate

[User00033]

Good question @srvet. I should do some work now instead of fannying around on here but later over lunch I'm going to research this topic. Will probably take me through to "afternoon tea".... oops there goes another afternoon.

It struck me when I thought about Nigel's posts, that his .270 combination is very similar to a couple of the loads we are having difficulty modelling accurately. Longer COAL, higher capacity brass, and ELD-X. I'm going to read what Helmut has got to say about starting pressure, and then what the gurus have done, hopefully with ELD-X.

I've often thought Quickload would merit its own specialist forum. I love using it and learn something useful every time there's a new problem to solve.

 

[NigelM]

Would increasing start pressure also be valid for the ELDX bullet if it has a thicker jacket?

It would do. I'm never sure which parameter to change when dealing a load to a measured velocity. They have set starting pressures for different scenarios - bullet jammed, monolithic etc so I tend not to play with that. Burn Rate Factor is the one I tend to tweek but that doesn't mean I'm right.

 

[Sharpie]

AFAIK Quickload is the product of one person, with un-disclosed algorithms to predict the internal ballistics. Occasionally updated, with no information about what might have changed. Maybe, just maybe, he has tested every calibre and powder on the market under scientific conditions, or perhaps it's more of a guessing game, with the fiddle-factor adjustment to make the numbers match the chrono. I'd take the pressure figures with a large pinch of salt too.

I'd like to know which actual test barrels and chamberings he actually has, because it is quite impossible that he has everything. Everything else can only be extrapolation. Likewise powder data, presumably he has a shedfull of everything on the market, or maybe not.

Altogether a most mysterious product, that seems to be treated as fact by many, who get upset when it doesn't really work. Being realistic, it can give a decent indication of what might happen, but as always, start off low, work your way up, and trust your own measurements, not the synthetic numbers on your computer screen.

And of course, every rifle, and barrel, is different, as I think we all know.

I think RS provide a download of data for QL usage, but perhaps it's not fully up to date with their newer powders. Powder QC is pretty tight in my experience, but still varies batch-batch. Hence buy it in quantity, same batch, enough to last you long enough. Expect to have to make a fine adjustment with a new batch, if accuracy is your thing, or you have worn out your barrel a bit.

 

[User00033]

I was wondering when you were going to turn up @Sharpie.

As a helpful suggestion, if you haven't got anything positive and constructive to add to this interesting thread, don't post. You've probably still got time to delete the one above.

 

[NigelM]

AFAIK Quickload is the product of one person, with un-disclosed algorithms to predict the internal ballistics. Occasionally updated, with no information about what might have changed. Maybe, just maybe, he has tested every calibre and powder on the market under scientific conditions, or perhaps it's more of a guessing game, with the fiddle-factor adjustment to make the numbers match the chrono. I'd take the pressure figures with a large pinch of salt too.

I'd like to know which actual test barrels and chamberings he actually has, because it is quite impossible that he has everything. Everything else can only be extrapolation. Likewise powder data, presumably he has a shedfull of everything on the market, or maybe not.

Altogether a most mysterious product, that seems to be treated as fact by many, who get upset when it doesn't really work. Being realistic, it can give a decent indication of what might happen, but as always, start off low, work your way up, and trust your own measurements, not the synthetic numbers on your computer screen.

And of course, every rifle, and barrel, is different, as I think we all know.

I think RS provide a download of data for QL usage, but perhaps it's not fully up to date with their newer powders. Powder QC is pretty tight in my experience, but still varies batch-batch. Hence buy it in quantity, same batch, enough to last you long enough. Expect to have to make a fine adjustment with a new batch, if accuracy is your thing, or you have worn out your barrel a bit.

There speaks a man who hasn't used it or hasn't bothered to understand it.

QL is not perfect, but I have found it a huge benefit to load development if used properly. It has it's quirks and it's faults, but it's far better than anything else available at modelling and I wouldn't be without it.

If you don't have anything useful to add to the debate it's probably best not to post at all.

 

[NigelM]

I was wondering when you were going to turn up @Sharpie.

As a helpful suggestion, if you haven't got anything positive and constructive to add to this interesting thread, don't post. You've probably still got time to delete the one above.

Too late...

 

[Sharpie]

As it happens, I did have Quickload, about ten years ago, and spent hours "modelling" things. Then realised that I was wasting my time because actually I just chose the manufacturer's recommended powder and start load, then worked my way up. With some ladder testing. Maybe I'll dig out the old disc and see if it runs on Windows 10.

I'm really not knocking it, and can see that it is a valuable tool (possibly the only tool) to try to simulate things, which is an amusement in itself.

Back then I also used "Load from a disc", which I found rather better. But that's obsolete now (well the designer is dead).

For external ballistics I use Strelok Pro on my 'phone. That is a much more useful bit of software for me. And for the current price of QL, and update costs, I'd rather put that into a chronograph. which is of course the most important tool.

 

[foggy]

My RS 70 and 7 mm , h20 was measured and all other specifics were exactly loaded Into quick load.
This has been with 3 different rifles using 2 different reamers, all 24 inch barrels. And 2 different lots of powder ??

 

[Triumph_Dave]

It would do. I'm never sure which parameter to change when dealing a load to a measured velocity. They have set starting pressures for different scenarios - bullet jammed, monolithic etc so I tend not to play with that. Burn Rate Factor is the one I tend to tweek but that doesn't mean I'm right.

I load with Accubonds, so do not believe it's a bullet issue. I cross checked as many variables as I could on QL input and corrected temp on the day. I tweaked the burn rate after reading an article on bench rest reloading from the states. I can not recall the author, but basically it stated that if all QL variables had been checked and the Chrono result can be replicated with a known proven Chrono, then you may have to tweak the burn rate.
I my case I started working up a load and could not understand the velocity from the Chrono vs QL. And I started to see over pressure signs. When I tweaked the burn rate in QL to the measured velocity the pressures made sense and explained the start of over pressure sign. So i backed down to a lower node.

 

[Sharpie]

You can twiddle the numbers to try to make the results fit the facts. Which they often don't, initially. Assuming that you have a chrono. Then pore over the laptop playing guessing games. Once you have done that, where exactly are you ?

As I said previously, it's a useful tool to have a guess before actually trying it, and can provide countless hours of amusement, whilst not actually shooting, in the real world.

Based on using an old version, maybe it has improved since. But I got bored with it.

As for predicting barrel harmonics, optimal nodes etc, that is a far more complex thing to do. Best done by actual testing. Or ring your barrel like a bell and measure the natural frequency, that might give you an indication. Not that the bullet progresses down the barrel at a uniform speed, oh no, nevermind how straight your barrel actually is, if it was perfect you wouldn't have to worry, in reality very few are, and whip about like a snake, on a micro-scale.

 

[NigelM]

But I got bored with it.

I rest my case your Honour. There speaks a man who hasn't bothered to understand it.

 

[Sharpie]

I rest my case your Honour. There speaks a man who hasn't bothered to understand it.

In my work, electronics design, I use some of the finest simulation software available. But when it comes to testing, particularly precision analogue and RF circuits, they rarely do exactly what the sim. results predicted. I regard rifles etc. as very simple things by comparison and, having tried, as I said, got bored, quickly, because I spend quite enough time behind a computer screen, and don't really want to do that in my leisure time with clunky software which I don't particularly trust. I'd rather be shooting.

If it works for you, great.

Out.

 

[User00033]

There's definitely something to be said for upping the shot initiation pressure for certain harder projectiles. But probably only to a value somewhere between the default, and that for the hard FMJ. It won't close your gap on the 270 Nigel. I couldn't find much documented stiff that is useful, other than using a higher value for loads jammed into the rifling.

I also spent some time modelling the IQ and EQ variables for various cartridges, and found unequivocal evidence that assuming high EQ when higher IQ values are evident is incorrect, you can get a perfect match for high IQ with a very low EQ value. A classic ISTJ outcome.

 

[The deer man]

Thank you Dave, glad it's not just me. I suspect QL has got the Burn Rate Factor wrong for the powder. If my 6.5 Lapua and 7mm08 behave in the same way I will be sure of it. I'm changing from RL15/RL17 to RS62 in all the chamberings at the moment to get away from the double base powders which have been the cause of a little premature throat erosion so have a busy few days reloading to do if this rain and wind will stop.

The RS62 gives good accuracy in the 7mm-08 (with 160gr thereabouts bullets) but found the velocities are very low - and can't fill the case anymore! RS60 was rubbish and have in fact gone back to R15.

 

[Malxwal]

Think I've mentioned my low velocities experienced with RS62 and a 130gr Sierra TMK from a 24" 47.

 

[Edinburgh Rifles]

i was getting up around 3150fps with the 145 ELD-x in .270 Norma brass/CCI200 and RS70
I stopped as I was not chasing velocity but had still not seen any signs of pressure

RS on the whole give significant MV advantages over other powders of similar charge and burn rate but even then this was a massive anomoly
10% heavier AND 10% faster

 

[nun_hunter]

When I started to load my 223 with 55grain Zmax and RS40 I gave them my data and they sent me back the QL predictions.

At 10% under max I was already getting higher velocities and pressure signs than they had predicted with the max load. I had to pull the rest of the rounds and start again going considerably under minimum to keep it safe.

 

[NigelM]

The RS62 gives good accuracy in the 7mm-08 (with 160gr thereabouts bullets) but found the velocities are very low - and can't fill the case anymore! RS60 was rubbish and have in fact gone back to R15.

That's really odd! I started with R15 which I have always used in the 6.5 Lapua and couldn't get it to shoot. I went to RS60 and it is very accurate with good velocities, 2740 fps with a 150 ABLR. Now about to try RS62 in a bid to get away from double base powders.

 

[NigelM]

When I started to load my 223 with 55grain Zmax and RS40 I gave them my data and they sent me back the QL predictions.

At 10% under max I was already getting higher velocities and pressure signs than they had predicted with the max load. I had to pull the rest of the rounds and start again going considerably under minimum to keep it safe.

It looks like many of us are finding the same thing. Just need to be very careful with RS62 and QL predictions.

 

[User00033]

Batch variability.

Haven't got much detail to post now, but locally we're playing around with some H4350 / AR2209 assumptions (same powder, different brands), seems that the batch variability as measured in the field is as extreme as the values Helmut has derived in the various versions of Quickload.

I don't have a problem with tuning powder assumptions to actuals, its a necessity. That's the only way to use all the excellent predictive capabilities of the program.

Interestingly the latest H4350 QL values are an exact match for my exterior ballistics in both .243 CM and .243 with powder bought last year March, and other mates here are reporting the same. I'm modelling a new rifle today (Rem 700 with the 90gr TGK "GameChanger") using the March 2019 update and the modelled velocity is 9fps off the chrono'd average from 20 shots.

If I use the 2014 assumptions, its way off.

Just as well I bought 4kg of H4350/2209 from the same batch last time round.