RS70 temperature sensitivity

[EMC]

Hello

I have been reading this forum for quite some time.
It's very interesting

I use a Bergara hmr 6.5 creedmoor rifle

I am loading with lapua brass, berger elite hunter 140gr y rs70 powder.

I would like to know what experience you have with rs 70 and the temperature changes

 

thanks

[BlueBoy69]

Try this, it gives a rough estimate of the relative temperature sensitivity of Reload Swiss powders.

https://www.reload-swiss.com/en/reload_swiss/service_3/tipps_und_tricks_neu/temperaturkoeffizient/index.php

Only a small snapshot, but better than nothing.

[VarmLR]

Welcome EMC

I think that RS62 seems to be the more popular choice of RS powder for the 6.5VM which is no surprise given that it's energy is very similar to Hodgson H4350, the universal match prior to restrictions on powders coming about limiting choice.

RS powders do have some issues with temperature sensitivity but in my own experience, less so than Vhitavouri, where I've experienced some really unwanted pressure spikes with N140 in warmer weather.

The difference in MVs between a 139 Lapua Scenar and RS62 tested at 10 Celcius and again at 22 Celcius (same primers and cases) was notable .  10 degrees gave 2665 fps and 22 degrees gave 2701 fps (5 shot averages).

I don't know how this might compare with RS70 but one advantage with RS62 is that powder kernals are camphor coated to aid better temperature sensitivity. 

[EMC]

Thank you very much to the 2 for your help.

I have very good loads with rs62 and rs 70, but I had read in this forum that rs 62 is very sensitive to temperature changes.
Looking at the rs tables, it seems that rs62 is the most sensitive, but many times you can't trust that.

I have not yet been able to test these loads at high temperatures, so I was wondering if anyone has experience ...

[VarmLR]

Thing is the range of temperatures in the UK isn't that wide and the accepted wisdom is load for say a 15 degree day for load dev, allowing 15fps 5 degrees either way (RS62) which isn't out of the way.  It's when things pick up to 30 degrees or ammo is left in direct sunlight that things can become more interesting...and potentially dangerous if you continue to shoot with cases showing pressure signs.  Whilst not as much of an issue with other cals/brass which show pressure signs much more readily, the danger with 6.5CM, especially with SR primers (remember if using SR, you ought to be using magnum thickness primer cases due to the pressures involved) is that you could be well over pressure and the primers won't necessarily show this.  Keeping an eye on case heads helps.

Yes, RS is temperature sensitive.  It's 3fps per degree by my reckoning above.  What it has going in its favour though is that looking at pressure V's MV charts, it;'s velocity gain is way more uniform, as in close to a straight line, than many other powders.  Looking at some of my N140 data, it tends to show fairly stable at hott-ish loads for between 10 to 20 degrees, with some velocity gains but above this the pressure rise steepens right up with velocity creating some potentially dangerous situations.  I loaded some 175TMKs for Warminster a few years back and did the load dev at about 16 degrees.  I loaded within recommended limits and saw no pressure signs at all with any of my loads.  At an ambient 25 degrees (or thereabouts) at Warminster the first few shots seemed to kivk like a mule and I experienced a sticky bolt on the second so stopped shooting and examined the cases.  They were heavily marked with ejector marks and the primers were pancake flat.  Yes, N140 wasn't ideal but I didn't have any N150 at the time.

I switched to RS50 and despite being re-labelled TR140, having very similar bulk density and energy to N140 (load data is almost interchangeable) it shares the more uniform velocity gains with pressure I found using RS62, so I never experienced such violent pressure spikes when using it.

I still use RS62 because for most of the year it gives me minuscule ragged hole groups and I've settled on two rounds which work really well with it (139 Scenar and 140gr SSTs for hunting and vermin bashing, although I tend to use the 223 more for that).

The above relates to my own data and may not be representative of what others have found as it relates to my rifles, brass, primer choice and bullet choice, so take it or leave it with that in mind.

[EMC]

many thanks.
I'm going to wait for the summer to come in to test loads.
I'll start low and I'll go up there as speeds and pressures go.
I bought the rifle in December and I have not been able to develop loads with heat

[TacsterDK]

Whether you should use RS62 or RS70 depends on bullet weight and drag. If you want to shoot 140gr -147gr low drag bullets I would definitely go with RS70. You will most likely (estimated) get a filling of 99% or more and more than 99% burned powder out of a 22" barrel. (QL data).

Things change if you want to go with 130gr VLD's - here you would benefit from using RS62 to keep up the amount of burned powder up near 100%.

This is calculations made in Quick Load. I have used the progam in many years and it has proved to be a very effective tool when it comes to load development. Especially when it comes to choosing the right powder for the exact cartridge/bullet combination.

I will soon be developing loads with 140gr Berger VLD-Hunt and 147gr Hornady ELD-Ms for my 6.5CM using RS70. I shall post procedure, progress and data in here...

J.

 

 

[VarmLR]

RS62 works very well with high BC 140/142 grn.  Even at moderate loads I was getting decent velocities using it.  Full case loads.  It was RS themselves that did the QL for me on the RS62 and it does achieve full powder burn (99%) in my 24 inch barrel according to their predictions and seems more optimal in velocity terms than the RS70 and also is a little kinder on barrels when loading up to anywhere near full case levels being a lower energy powder.  My load was 43.6gr for 2650fps (140 SST) in SRP brass.

[EMC]

rs 70 gives very good filling.
It matches the Quick Load data very well.
For rs62 Quick load tells me that with 45gr I have 100% filling, but in reality with 43gr there is no more space.
When I tried with berger vld hunting I could get very good speeds with rs70.
My COAL with berger elite hunter 140gr is 2.940 ".
I have plenty of room for powder, so when I can see what speeds,es and sd I get with both powders.