RS62 Burn Rate

[NigelM]

I spent yesterday developing a load for 145 ELDX in 270 Win.

Modeled it all in Quickload first and found a nice safe 51k psi OBT node that QL suggested needed 54.2 grains of powder and would give us 2780 fps. Checked against the RS load data which although didn't list the 145 ELDX suggested that this might be fairly close to their max load, which admittedly was only 55k psi against a CIP max of 62k psi.

Worked our way up to be safe but at the 54.2 grain QL recommendation we hit 2900 fps and not the predicted 2780.

We had measured everything including case H2O capacity for QL, so all the input data was spot on. I had even set the powder temperature to match the day. I can only conclude that the burn rate factor for RS62 in QL is incorrect. I adjusted it from 0.411 to 0.445 and the velocities matched up.

I'm going to be developing an RS62 load in the 6.5 Lapua shortly and will be very careful about starting loads.

Has anyone else experienced similar?

 

[Lateral]

I have found that internal barrel diameters can vary a lot, within a calibre, particularly noticeable when cleaning, where the same jag, and patch size will easily go through one 30 cal barrel, but is really tight through another.

I generally assume the tighter barrel creates more pressure, and higher speed ? I very rarely getting matching speeds to QL, some higher, and some lower.

 

[bowji john]

I've gone through my load development for RS62 and 143 ELDx in 6.5 (but 6.5 swede)

I'm happy with the results but my actual MVs bear little resemblance to those predicted in QL despite adjusting H2O case size and barrel length etc

 

[Triumph_Dave]

I spent yesterday developing a load for 145 ELDX in 270 Win.

Modeled it all in Quickload first and found a nice safe 51k psi OBT node that QL suggested needed 54.2 grains of powder and would give us 2780 fps. Checked against the RS load data which although didn't list the 145 ELDX suggested that this might be fairly close to their max load, which admittedly was only 55k psi against a CIP max of 62k psi.

Worked our way up to be safe but at the 54.2 grain QL recommendation we hit 2900 fps and not the predicted 2780.

We had measured everything including case H2O capacity for QL, so all the input data was spot on. I had even set the powder temperature to match the day. I can only conclude that the burn rate factor for RS62 in QL is incorrect. I adjusted it from 0.411 to 0.445 and the velocities matched up.

I'm going to be developing an RS62 load in the 6.5 Lapua shortly and will be very careful about starting loads.

Has anyone else experienced similar?

Yes, I found exactly the same as you for my 30.06. My velocity measured by Chrono were over 100 Fps faster than QL predictions. I also checked and adjusted all QL inputs such as H2O, case length, bullet length etc. I ended up making sure the temp on the day was correct and adjusting the burn rate. Since then the Chrono has fairly agreed with QL. I do not have my reloading data to hand at the moment but can send you the info if you require.

 

[NigelM]

Yes, I found exactly the same as you for my 30.06. My velocity measured by Chrono were over 100 Fps faster than QL predictions. I also checked and adjusted all QL inputs such as H2O, case length, bullet length etc. I ended up making sure the temp on the day was correct and adjusting the burn rate. Since then the Chrono has fairly agreed with QL. I do not have my reloading data to hand at the moment but can send you the info if you require.

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.

 

[Selous]

I wonder what the batch to batch variation is as the QL burn rate must be an average based on standard temperatures and pressures

 

[NigelM]

I wonder what the batch to batch variation is as the QL burn rate must be an average based on standard temperatures and pressures

Now there's an interesting thought. I would like to think that batch to batch didn't cause an additional 120 fps over average, but it might be the cause. I will probably have the answer after loading for the two 6.5 Lapuas and the 7mm08. Will have bought another tub by then.

 

[User00033]

What weighting factor did you use and how did you calculate it?

 

[NigelM]

What weighting factor did you use and how did you calculate it?

0.42. Obtained from here...

 

[User00033]

@NigelM

I've just plugged in basic .270 Win assumptions with the March 2019 updated data, and using RS62 Quickload returns a velocity of over 2900fps.

Obviously don't have your specific case capacity, or COAL. Used a 24" barrel assumption.

 

[foggy]

I’ve had exactly the same scenario
With RS70 in my 7 mm Rem SAUM.

Burn rate factor had to be altered quite a bit. I can only assume RS powders have changed significantly from the ones used during quick loads development. ?????

 

[User00033]

 

[User00033]

What barrel length, COAL and H20 capacity did you use?

 

[NigelM]

@NigelM

I've just plugged in basic .270 Win assumptions with the March 2019 updated data, and using RS62 Quickload returns a velocity of over 2900fps.

Obviously don't have your specific case capacity, or COAL. Used a 24" barrel assumption.

COAL 3.490"(yes, I know it's longer than SAAMi but that's where the lands are), H2O at 69.8 gr (measured) and 22" barrel.

Try it again. Bet you get the same answer as me!

 

[NigelM]

I’ve had exactly the same scenario
With RS70 in my 7 mm Rem SAUM.

Burn rate factor had to be altered quite a bit. I can only assume RS powders have changed significantly from the ones used during quick loads development. ?????

It's very odd. First time I've seen this scale of difference. With IMR7828, H4350, RL15 & 17 QL has always got it to within 30 fps or so providing I have input all the right data, including powder temperature. RS 60 works well, the RS 62 is miles out and it sounds like RS70 is too. Just as well we don't trust QL 100% and work loads up the old fashioned way!

 

[User00033]

Yup, exactly the same.

Me and Alan recently re-modelled all of our loads across a dozen or more cartridge and bullet combinations. What we found was that for the loads that were close to SAAMI spec in terms of COAL, brass capacity etc, with ADI / Hodgdon powders, Quickload was very close to observed velocity. For my .308 for example, it is exact.

As soon as we started using highly modified COAL, new long for calibre bullets, small primer brass and new Alliant powders, things went a bit pear shaped.

 

[NigelM]

Yup, exactly the same.

Me and Alan recently re-modelled all of our loads across a dozen or more cartridge and bullet combinations. What we found was that for the loads that were close to SAAMI spec in terms of COAL, brass capacity etc, with ADI / Hodgdon powders, Quickload was very close to observed velocity. For my .308 for example, it is exact.

As soon as we started using highly modified COAL, new long for calibre bullets, small primer brass and new Alliant powders, things went a bit pear shaped.

I have been fine with 6.5mm 129 ABLR and 7mm 150 ABLR using RL15 and RL17 as well as 160 STMK's with 7828, so I'm not sure it's VLD bullet related. My 129 ABLR's and 123 Scenars are well over SAAMI COAL's and still modelled very well, so I have no evidence COAL is the issue. It's just this RS62 that has thrown a spanner in the works of a very tried and tested method for me.

More work to do before I prove anything, but I do suspect they have got something wrong on the BR factor for that powder.

 

[User00033]

@NigelM

Been thinking about the bullet. The ELD-X is known to produce much higher pressures than the ELD-M, for example, due to the thick jacket.

I do not know if Helmut builds this kind of variable into his algorithms, I suspect not.

N Foster wrote about it in his books. Hornady wrote about it to in a technical paper which I can't put my hands on right now.

This phenomenon was proven beyond doubt by one of our forum admins who loaded ELD-M and ELD-X side-by-side so to speak, and found excessive pressure with the ELD-X far earlier than the ELD-M. That was in .260 Rem.

This might be part of the equation that QL is struggling with.

 

[NigelM]

@NigelM

Been thinking about the bullet. The ELD-X is known to produce much higher pressures than the ELD-M, for example, due to the thick jacket.

I do not know if Helmut builds this kind of variable into his algorithms, I suspect not.

N Foster wrote about it in his books. Hornady wrote about it to in a technical paper which I can't put my hands on right now.

This phenomenon was proven beyond doubt by one of our forum admins who loaded ELD-M and ELD-X side-by-side so to speak, and found excessive pressure with the ELD-X far earlier than the ELD-M. That was in .260 Rem.

This might be part of the equation that QL is struggling with.

Could well be.

The next load development is the Sierra 150 MK in a 6.5 Lapua using RS62 which should load at about 97% and 2600 fps. It will be very interesting to see whether or not I get the same issue.

 

[Selous]

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