RL-17, 285 gr. Privi, 9.3x62mm Inquiry

[Puddle]

Finally got some RL-17 in and planning to work up a practice load using the 285 gr. Privi SP in my 9.3x62mm

GRT predicts ~62 grains would get me ~2450 fps MV from a 24" barrel and stay easily under max pressure. This is based on case volume of 75 gr. H2O.
I'm planning to start at 58, 59, or 60 grains - somewhere around there.

The chrony won't lie, but still, anyone BTDT? Too low, that's easily fixable. Too high, well that's a problem....

 

[112Savage]

You aren’t too high but proceed with caution. My lapua brass measures 75gr H20 capacity (PPU brass has 76.0gr capacity) and with the Norma Alaska 285 gr I hit 2500fps with around 67gr at a longer than spec OAL around 3.362” the Norma Alaska is a unique SMP bullet with a very short full diameter shank as compared to say a Swift A-frame.

this is obviously over book and I very carefully worked up to this from around 60 grains. I advise all reading this to do the same.

 

[Puddle]

You aren’t too high but proceed with caution. My lapua brass measures 75gr H20 capacity (PPU brass has 76.0gr capacity) and with the Norma Alaska 285 gr I hit 2500fps with around 67gr at a longer than spec OAL around 3.362” the Norma Alaska is a unique SMP bullet with a very short full diameter shank as compared to say a Swift A-frame.

this is obviously over book and I very carefully worked up to this from around 60 grains. I advise all reading this to do the same.

Good info. My lapua brass arrived at the same time as the RL-17 did. That's the brass I'll be using.
Now thinking I'll load starting sets at 60 & 61 grains and see what the chrony tells me.
If RL-17 is anything like RL-15 that I use in .375 H&H I'll be expecting good SD's and ES's.

 

[Desperatezulu]

I think you'll be good - GRT characterises RL-17 well in my experience with the 9.3x62. RL-17 is a match made in heaven for this cal!

I used Sako brass which has a case capacity of 76.2gr H2O.
With Norma Oryx 285gr and an OAL 3.307" (84.0mm) I got:
62.1gr RL-17=> 2355 f/s
63.0 gr => 2399 f/s

The 63.0gr load comes out below 50k psi according to GRT.

 

[Puddle]

More good data for me to store away. Thanks!

 

[Desperatezulu]

Shout if I can help with any other data! Happy to share

 

[shark_za]

What primers are you using for your loads?
Have you seen any difference between large rifle and large rifle magnum?

 

[112Savage]

What primers are you using for your loads?
Have you seen any difference between large rifle and large rifle magnum?

I have see. No real accuracy changes, but velocity changes and pressure differences with the 286 gr A-frame of about 23 fps

 

[Puddle]

I wouldn't consider using magnum primers with the 9.3. For all my LR primer use I pretty much stick to Fed GM 210M primers.

Quite a ways back a Hodgdon Rep told me a rule-of-thumb about when to consider using magnum primers. He said as a load approaches 80 grains you might want to consider using a magnum primer. Below this charge a LR primer will likely deliver better results. Of course, this was in the context of Hodgdon's single-base powders.

I decided to test this out with one of my existing .375 H&H loads - a 300 grain bullet and 77 grains of H4350. One batch using Fed 210 LR primers, and the other batch using Fed 215M primers. I shot these batches over a chrony at ~65 degrees F and ~1,500 ft elevation.
The results were measurably and visibly different. The LR primers produced far more consistent velocities shot-to-shot vs the magnum primers, and the LR primer batch produced a group .25 MOA smaller than the magnum primer group.

When might I use a magnum primer with this load? When it's early November and it's time to fill the freezer with a cow elk. At 7,000 ft elevation it's already in the 'teens and that doesn't include the wind chill factor. Then I might go with magnum primers just for that little extra spark. Out to 200 yards on a 400lb - 500lb animal the difference in POI doesn't matter to me.

HTH

 

[shootist~]

Similar results when I chronographed 9.3x62, RL17 with 250 gr NABs. F210 standard vs F215 magnum primers.

Lower SD with the Std F210s and about the same velocities. Warm weather test, IIRC.

 

[Desperatezulu]

What primers are you using for your loads?
Have you seen any difference between large rifle and large rifle magnum?

Mostly CCI250s. I agree that normal LR primers are suited to the 9.3. I used the 250s because I had an old batch that I want to use up. I found minimal difference between CCI 200 and 250 with RL-17. Can't say I tested extensively but my load worked fine with the magnum primers so I carried on.

Fed215 are the hottest magnum primers. CCI 250 are pretty mild by comparison.

 

[Puddle]

Well, this is what I've figured out from using RL-17 for the first time in conjunction with using GRT for load calculations.

The latest GRT (2021.1980.nightly) is a bit optimistic with MV predictions for my 24-inch barrel. However, after working up 3 different MV loads using the 285 grain Privi SP, the calculated vs actual MV's revealed an interesting pattern.

If I change barrel length in GRT from 24-inch to 20-inch then adjust powder charge to a targeted MV, all three load predictions were within 2 fps of actual. So, at least with RL-17, all my future load ponderings will be based on a 20-inch barrel setting.

 

[Desperatezulu]

Apologies if you're already aware of this but the 'correct' process is to tweak the powder burning parameters til the model matches your MV. With these internal ballistic models the old maxim "garbage in = garbage out" applies absolutely.

There are many variables in your set-up that may be slightly different from standard - barrel diameter could be slightly different, powder scale could be marginally out, chrony accuracy could be slightly out, measurement of internal volume of cases could be out etc etc. Hence trying to use accurate as possible data points and minimising the variables you adjust. Details are important.

One thing I would say with confidence, the reason GRT's estimate and your measured data are different is NOT because their algorithm has an error with muzzle length. (And I know you're not suggesting this)

By the way, version 2021.1980 is not the latest version, although I doubt the version makes much difference but there might be more refined powder data in the latest version (.2030)

Just because something works by coincidence doesn't make it good practice - I don't think you'll have issues modelling with a shorter barrel from a safety perspective (fudging by using a longer barrel than your actual length I would worry about). The powder burn calc and OBT will be totally out of the window because the barrel travel/residence time is very dependent on precise barrel length. This of course may be unimportant to you.

One of the great strengths of GRT is that users can easily submit their empirical data back to GRT and they can use the data to fine-tune their powder algorithms, which all users benefit from.