24hourcampfire.com
24hourcampfire.com
Previous Thread
Next Thread
Print Thread
Hop To
Page 3 of 3 1 2 3
Joined: Dec 2014
Posts: 8,964
F
Campfire Outfitter
Online Content
Campfire Outfitter
F
Joined: Dec 2014
Posts: 8,964
z1r, What scope is on the top rifle, in the first group of pics you posted?


Well this is a fine pickle we're in, should'a listened to Joe McCarthy and George Orwell I guess.
BP-B2

Joined: Jun 2019
Posts: 2,452
TRexF16 Offline OP
Campfire Regular
OP Offline
Campfire Regular
Joined: Jun 2019
Posts: 2,452
Originally Posted by TRexF16
Originally Posted by TRexF16
I'm looking to do some work with my newly rebored 9.3x62 with Power Pro 2000-MR, and I have been playing around with "The Rules" that John published in Appendix 1 of "Gack I" and thought I'd share it. I'll show the examples, and end up using about all the formulae.

Background. I have a 35 Whelen AI with a long throat in a commercial 98 Mauser. Speer has published some pretty game changing tested loads for the basic Whelen with their 250 HotCor and 2000-MR, specifically, a max of 66.2 gr for 2709 FPS. In my 35 WAI, the 250 HotCor and 250 partition are near perfect analogs, giving same velocities and groups with the same charges. In working up in my 35 WAI with the 250 Partition, I stopped at 65/2000-MR for 2645 FPS and sub MOA accuracy. This load in my 35 WAI produces only .0002" CHE on the first firing and then no further CHE on subsequent firings. Assuming Speer was pushing the SAMMI max of 62K PSI with their load, I figure I'm around 60K or less, the same target JB has used for his 9.3x62 loads. So I want to "derive" some 9.3x62 2000-MR loads for the 250 AB and the 286 Partition using The Rules.

My 9.3x62 has the same 23" barrel as my 35 WAI and also a long throat so both rifles are magazine limited, and I load to a 3.375" OAL in both for good feeding, and am around .200" off the lands in both.
My 35 WAI holds 65.7 grains of water underneath a 250 Partition seated to 3.375" in a once fired case.
My 9.3x63 holds 65.2 grains of water underneath a 250 Nosler AB seated to 3.375" in a once fired case.
SO, if they were both the same caliber, the 0.5 difference in case volume would cost the smaller case about 5 FPS
...65.7/65.2 = 1.00767. Divide the % difference by 4 to get the velocity gain/loss at the same pressure - .00767/4 = .0019. .0019 x 2645 FPS = 5.02 FPS (not even a standard dev of change but we'll play with it) so I'll take off the 5 FPS and call it 2640 FPS.
BUT, they are not the same caliber, the 9.3 has a greater cross-sectional area for the gas to push on. The cross-sectional areas are .1007 and .1052 respectively, so how much faster should the 9.3 go if loaded to the same pressure?
.1052/.1007 = 1.0447, or a 4.4% increase, but the 4:1 rule says we only get about 25% of the increase in actual velocity so 4.4% / 4 = 1.1% potential velocity gain (big whup, right?) so 2640 x 1.011 = about 2670 FPS.
But I need more powder to get that extra 1.1% in velocity, and the 4:1 rule says I need about 4.4% more powder, bumping the charge I'll probably need up to 67.8 grains of 2000-MR to get 2670 FPS with the 250 in my 9.3x62, and that ought to be at about the same pressure as my 65/2000-MR load for 2645 FPS in my 35 WAI.
But I want to shoot the 286 Partition with 2000-MR too. The 286 is actually .005" shorter than the 250 NAB so I will have about the same powder capacity when loading to the same 3.375" OAL. So using The Rules I add the 2 bullet weights and divide by 2: 250 + 286 = 536. 536/2 = 268. I divide that value by the new bullet weight of 286 grains. 268/286 = .93706 and use this conversion to calculate my potential velocity and powder charge.
67.8 gr x .93706 = 63.5 grains. Velocity ought to be: 2670 FPS x .93706 = 2502 FPS.

In summary, I ought to work up to ~67.8/2000-MR for ~2670 FPS with the 250 NAB, and ~63.5/2000-MR for ~2500 FPS with the 286 Partition.

How does that compare to the little bit of published data for 2000-MR? Speer's max for their 270 HotCor is 59.3 for 2439 FPS. Hornady's max for their 286 SP Interlock is 62.4 for 2400 FPS.
Now going back to Mule Deer's guidance for developing sub-60K PSI loads in the 9.3x62:
"All published 9,3x62 loading data is based on old, low-pressure standards. I have NEVER run into any sort of "pressure sign" by starting with published maximums and working up to around 2450-2500 fps with 286s and 2650-2700 fps with 250s, of whatever brand. That's with three different 9.3x62s that had 21-24 inch barrels."

Does that look about right, John?. That was kind of fun. Our local range is closed UFN due to the coronavirus but when I get a chance to shoot again over my chrono, I'll come back and update.
Thanks for "The Rules." I'm looking forward to Gack III.
Cheers,
Rex


I've actually had two range sessions with the 9.3x62 since posting the above. All the work with 2000-MR was on the first trip. Here is the short version:
- I missed the velocity predictions by about 50 FPS with both the 286 Partition and the 250 NAB.
- Pressures with both the "max" loads were about equal to the Lapua factory 286 Mega (based on CHE)
- Accuracy with the 250 NAB/2000-MR was not quite as good as that from 250 NAB/Varget that I got on the first trip to the range with this rifle.

The long version:
Attempting to use John's rules of thumb to replicate the success of 2000-MR in my 35 Whelen AI predicted ~67.8/2000-MR for ~2670 FPS with the 250 NAB, and ~63.5/2000-MR for ~2500 FPS with the 286 Partition.
I worked up to both of those as follows and the velocities, group size, and CHE are also included (I measure to 4 decimal places with my blade mic for CHE - where 5 decimal places are shown, it's from averaging 3 rounds' CHE) Cases were new unfired Lapua, primers were CCI 200, and all rounds were loaded to 3.375", which placed them over .200" off the lands in my long (standard) throat:
Bullet Charge Vel./SD Group (100yd) CHE
286 PT 61.5 2329/3 1.50" .00073
" 62.5 2396/6 3.13" .0010
" 63.5 2440/13 1.86" .0009
250 AB 66 2542/14 1.66" .00067
" 67 2594/13 1.94" .00067
" 67.8 2621/15 0.95" .0008

Of note - I also took CHE on Lapua Factory 285 Mega, and it was .00083" with 2254 FPS and SD 19.
- There were no traditional pressure signs.
- No idea what happened to the second round of the second 286 PT it landed about 2 inches at 1:00 from all the other 286 PT rounds in the three groups.
- It looks like it would take just about another grain to hit the target velocities, and I suspect the associated pressures would be fine based on CHE comparison to the factory stuff. I know CHE is not a stand-alone tool but I think it can be useful for comparisons when other factors are considered as well.

Hope this helps anyone wanting to use PP 2000-MR in the Nine-Three.

Cheers,
Rex



UPDATE for those searching for 2000-MR data for the 9.3x62:
I went back to the range yesterday with several 9.3x62 loads, one of which was the 250 AB over 68.5 gr 2000-MR. My previous math had predicted ~2670fps from 67.8 gr but I only got 2621 with SD of 15 (0.95" group). Yesterday I was surprised to see that just the addition of 0.7 gr, bumped the velocity up 2700fps, SD of 14, and 1.04" 4-shot group. Temperature was around 90F, and it was around 75F for the previous range session.

P.S. I also shot Mule Deer's two favorite loads. 60.5/Varget with the 250 AB is still lagging John's velocities by about75 fps, but the 66/BG with the 286 PT was pretty close, about 2485 fps. Both shot just fine.

And I began working up with RE-17. I'll post anything interesting I learn with that on another thread, as I didn't find a whole lot of RE-17 data and what I found was inconsistent.

Cheers,
Rex

Joined: Aug 2002
Posts: 14,440
S
Campfire Outfitter
Offline
Campfire Outfitter
S
Joined: Aug 2002
Posts: 14,440
Good job Rex, keep us posted.

Joined: Jul 2001
Posts: 59,898
M
Campfire Kahuna
Offline
Campfire Kahuna
M
Joined: Jul 2001
Posts: 59,898
Rex,

Can't remember if I mentioned this earlier, but I first tried the 60.5 Varget load in 2007, where it did get around 2650 in my rifle.

Some time after that I almost ran out of Varget, and bought another 8-pounder, which had a somewhat different burn-rate--which as I have pointed out here and there is not uncommon. With that manufacturing lot 60.5 grains got just about what you're getting. It took 62.0 grains to duplicate the early load.

For those who might be puzzled about this, there's a chapter in Gun Gack II titled "Different Batches of the 'Same' Powder" that explains why this isn't uncommon. For those who don't have a copy, most lots of the "same" powder will often vary 2-3% in burn-rate--which is only one of many reasons velocities vary with the same powder charge and bullet.


“Montana seems to me to be what a small boy would think Texas is like from hearing Texans.”
John Steinbeck
Joined: Jun 2019
Posts: 2,452
TRexF16 Offline OP
Campfire Regular
OP Offline
Campfire Regular
Joined: Jun 2019
Posts: 2,452
Thanks John - I'll give the Varget load a bump up too. It's shooting very accurately now, just not quite turning in the speed I've been persuaded to expect ;o)
Three pounds of Varget and an 8#-keg of H4350 arrived in the mail today, so I am more willing to experiment with Varget.
I'll drop the 2000-MR load back a couple tenths to get both of those powders shooting about the same and run a batch in new unfired cases to take valid CHE measurements as well for comparison.

BTW, I just received my copy of The Big Book of Big Game Hunting and am greatly enjoying it. I'm just reading it through from the beginning rather than skipping to the chapters that interest me most. So far you're sounding like quite the curmudgeon!! (kidding)

Thanks for the inputs on the Nine-Three loads.

Rex

IC B2

Joined: Jun 2019
Posts: 2,452
TRexF16 Offline OP
Campfire Regular
OP Offline
Campfire Regular
Joined: Jun 2019
Posts: 2,452
John, I bumped the Varget, with the 250 AB, up a grain to 61.5 and still was not quite to your speeds. I am guessing if I took it all the way to the extreme you mentioned of 62 grains, I'd probably be about where you were.

But the really interesting (and validating, to your "rules") news is I dialed in on the load of 2000-MR that gives the velocity I had estimated using your rules in the OP. Here's the result of the original math: "In summary, I ought to work up to ~67.8/2000-MR for ~2670 FPS with the 250 NAB"

Well , tweaking around I finally settled on 68 grains of 2000-MR. I fired 8 rounds today and the average speed was 2668 fps (with an SD of 10 for the 8 shots). So that is within 2 fps of what your rules predicted at only 0.2 grains charge different from what the math indicated, in transposing my success with 2000-MR with 250 grain bullets in the 35 Whelen AI to 250 grain bullets in the 9.3x62.

I'm thinking that's close enough for government work.
Thanks for the guidance,
Rex

Page 3 of 3 1 2 3

Moderated by  RickBin 

Link Copied to Clipboard
YB23

Who's Online Now
722 members (10gaugemag, 16penny, 160user, 12344mag, 21, 12308300, 76 invisible), 2,729 guests, and 1,334 robots.
Key: Admin, Global Mod, Mod
Forum Statistics
Forums81
Topics1,187,623
Posts18,398,611
Members73,817
Most Online11,491
Jul 7th, 2023


 







Fish & Game Departments | Solunar Tables | Mission Statement | Privacy Policy | Contact Us | DMCA
Hunting | Fishing | Camping | Backpacking | Reloading | Campfire Forums | Gear Shop
Copyright © 2000-2024 24hourcampfire.com, Inc. All Rights Reserved.
Powered by UBB.threads™ PHP Forum Software 7.7.5
(Release build 20201027)
Responsive Width:

PHP: 7.3.33 Page Time: 0.328s Queries: 15 (0.003s) Memory: 0.8300 MB (Peak: 0.9189 MB) Data Comp: Zlib Server Time: 2024-03-28 15:14:18 UTC
Valid HTML 5 and Valid CSS