[RldAtlas]

So, my chosen/awarded zone for deer opens September 17th and I have a lot of work to do before then, so I'm hoping to get some keen insights from folks here and share some of my data along the way. Location will be in north-central California, up near Oregon just west of Meiss Lake; I'm going with an older friend and life-long hunter who has hunted this area several times (he is a casual/recreational hunter his whole life but never got into reloading).

One "problem" is that I have perhaps too many ingredients and need to really narrow things down without breaking the bank testing all the combinations. I plan to update this thread periodically as things develop.
My hardware is Bison SPR 18", 1:10, sold here: 18" SPR 6.8 SPC Stainless
Some technical details here: The 6.8 Bison Chamber – Bison Ops
Detail on the specific rifle is here: Finally fired my Bison barrel
Also, I have CBB modified PRI magazines, so I can load long. For reloading, I have Forster Co-Ax, Hornady button sizing die, L.E. Wilson bushing sizing die, 0.02 grain resolution digital scale, homemade induction annealer (anneal every firing).

Considerations and concerns:

• I expect to load for 100-150 yards, but I should probably "be prepared" for 50-200 yards.
• I am concerned about temperature sensitivity...I will develop loads in 65-85 degree temperatures but expect to shoot in 30-45 degrees (my guess; maybe a bit colder?). This makes me worry about certain powders, AA2200 specifically.

Ingredients (currently in possession) to choose from:

• Brass: S&B, once-fired in MY rifle; Hornady unfired; RP (LRP) unfired.
• Primers: CCI 400, CCI BR-4, CCI 450 (magnum small rifle); CCI 34 (NATO large rifle)
• Powder: FASTER: AA2200, AA LT-30, AA2015, AA5744; MEDIUM: H335, AA2230, IMR 8208XBR, Ram TAC, Power Pro Varment, VV N530; SLOWER: Leverevolution, BL-C(2), AA2520, Varget, .
• Bullets: MKZ 105, HDY CX 100gr, HDY GMX 100gr

For bullets, I am pretty much sold on using CBB MKZ...however: NOTE I don't currently have 120 gr MKZ, but given my short intended shooting range, selection of powders, and desire for temperature stability, I am thinking I should buy and use them (?). For powders, I know I'm missing some important ones for 6-8, but I really don't want to buy any more right now.
So where am I going with all this? I need to narrow things down and the clock is ticking. Range time with my work/family schedule is limited to once every 1-2 weeks at best. There is also question about cost...and crazy questions come up in my mind such as: Is there a cheaper bullet I can do a partial load development on as a proxy for MKZ bullets? Probably not, but I am curious if others have tried this.

*** After reading/researching quite a bit and with my ingredients and considerations in mind, I am thinking the following: S&B brass, CCI 450, MKZ 120gr, 8208XBR.
Anyways sorry for the long-winded post, but perhaps if you've read this far then you might have some comments/guidance to offer...thank you!

 

[ozarkpugs]

There is no reason to worry about 2200 and temp or to go to 120 s for your intended purpose . I would load 1 round of each starting at 28.0 -28.2 28.4 28.6 28.8 29.0 using the S&B brass . Put a horizontal line on a target and be sure to level it and put 6 dots along that line . After shooting each bullet you should see a pattern where 2 or 3 maybe 4 have close to the same poi along the line . If say 28.2 - 28.6 is your sweet spot base the load you settle on based on the temp that day and the expected temp when you hunt . If it was 90° that day I would work with 28.6 ( or whatever the high charge was in the node ) if it was 20° I would work up a load with the lower number and If 60° the middle number . That way you will be close to if not in the node no matter the temperature . Never work up to max in cold weather and shoot that load in hot weather no matter the powder .

Sent from my LM-K920 using Tapatalk

 

[RldAtlas]

Thank you Ozark, I will give that a try.

 

[dfleury]

I use 8208xbr with the 120mkz, S&B brass and wolf primers. I've had good luck with 8208xbr with 120 and 130 grain bullets.

 

[jimh406]

For 200 yds and below, you should be good with almost any factory hunting load for deer sized game.

If you simply want to play around and work up a load, that’s fine. I’d search this forum for more choices.

 

[leatherneck]

CBB 105s will be the ticket for sure. No “need” for 120 gr, just a different flavor.

What are the average temperature swings in your region during that time of year? AA2200 does show increased temp sensitivity compared to some other powders, but it’s fairly mild and relatively consistent. Unless you have 50+ deg temp swings, it won’t make enough a difference at your intended range to really matter about POI shift for shooting in the vitals.

I’d go S&B brass (great choice), CCI450 and AA2200. You’ll have no issue finding an accurate and effective load.

Ozark is on the money for load Development/optimal charge weight. There’s also plenty of load data shared on here to get a good starting point and expected velocity range and accuracy node. CBB has even shared their factory load data on here so you can get an idea of what they are doing.

 

[RldAtlas]

Thanks everyone for replies and also Yamaraja via PM. I did find many/most of the relevant threads including pictures of 105 & 120 expansion at various distance, etc. I do need to research temperature for mid-September in far northern California. Variation from load development temp to time-of-use temp might approach 50 degrees, but that's probably a stretch and also I can control it to some extent (hit the range early, etc.).
So, it looks like I will be in good company to develop as suggested for 105gr and AA2200, and as a back-up (or perhaps "just for fun"), develop 120gr with 8208XBR (and sure maybe AA2200 as well).

 

[leatherneck]

....Variation from load development temp to time-of-use temp might approach 50 degrees, but that's probably a stretch and also I can control it to some extent (hit the range early, etc.)......

Exactly. Develop your load of choice this summer and confirm velocity & zero when the temps get cooler.

My loads are close enough from 40F-105F out to 300 yards with AA2200 that I don't even bother worrying. I do confirm zero prior to hunting season, but that's checking the scope/rifle combo more than the load.

The safety concern is the opposite when max loads are developed in cool/cold weather and then used in much higher temperatures.

 

[chewbacca]

For your range, game and conditions, you don’t need to over complicate it. I personally would just use 2200 and the 105’s then develop the most accurate load. Which for MY rifle is 29.5. I would start at 27.5 and work up in .5 increments, groups of five. If you have more time you can fine tune from there. If not, choose the best and load away. I have done this many times when under a time crunch before a hunt.

 

[toddmack]

The Ozarkian and Chewbacca pretty much summed up what i was going to. Definitely use the S&B brass. The only difference from their loads and mine is Rem 7 1/2 other than CCI 450's.

 

[nonnieselman]

For your range, game and conditions, you don’t need to over complicate it. I personally would just use 2200 and the 105’s then develop the most accurate load. Which for MY rifle is 29.5. I would start at 27.5 and work up in .5 increments, groups of five. If you have more time you can fine tune from there. If not, choose the best and load away. I have done this many times when under a time crunch before a hunt.

Im with this guy /\
29.5gr with the 105s shoot great in all my rifles.
Its my go to load for deer and hogs.

 

[Coltdriver]

The only thing I would add to the conversation is to develop your load using a 200 yard zero.

Once you have that then shoot a 50 yd and a 100 yd target putting your crosshairs on the bullseye. Note how high (and possibly low with the 50 yard mark) you are hitting (from your 200 yard zero) and record that difference. Now you know the size of the circle you can shoot into when hunting. Depending on how high your scope is mounted above bore centerline the difference can be surprising.

While I always take an unhurried shot sometimes your target may move or shift an angle and the ideal shot may only be available for a fleeting second or three. Having confidence in where to aim without having to think it through improves your odds.

Every deer, antelope and elk I have ever taken was done with a custom load developed by me. Just my opinion but it is the most satisfying feeling to be successful with a load you have complete confidence in.

Good luck and let us know how you do!

 

[Nincomp]

The posters in this thread have a great deal of experience and offer excellent advice. AA2200 has been a favorite on this forum for long enough that its properties are well known. Nevertheless, with the kind of detail you have provided, including mentioning that you built your own annealer and plan to anneal each reloaded case, it seems you want every possible facet optimized and verified. If you absolutely cannot ignore the temperature difference issue, you can always develop a load the way Ozarkpugs suggested, then test a few rounds from a magazine that has been sitting in a cooler with ice or refrigerant packs. Heck, if you decide to go through all that trouble, you might as well shoot a few rounds that have been kept against your body for a 98.6° reference. After you do that, please report back to help others who wonder about the same thing.

 

[RldAtlas]

Coltdriver and Nincomp thank you for the helpful comments and suggestions. I will share as much (useful!) information as I can along the way.

 

[chewbacca]

The only thing I would add to the conversation is to develop your load using a 200 yard zero.

Once you have that then shoot a 50 yd and a 100 yd target putting your crosshairs on the bullseye. Note how high (and possibly low with the 50 yard mark) you are hitting (from your 200 yard zero) and record that difference. Now you know the size of the circle you can shoot into when hunting. Depending on how high your scope is mounted above bore centerline the difference can be surprising.

While I always take an unhurried shot sometimes your target may move or shift an angle and the ideal shot may only be available for a fleeting second or three. Having confidence in where to aim without having to think it through improves your odds.

Every deer, antelope and elk I have ever taken was done with a custom load developed by me. Just my opinion but it is the most satisfying feeling to be successful with a load you have complete confidence in.

Good luck and let us know how you do!

Or… you can make life simple and just do a 50 yard zero and not worry about it.
Here is my actual data from my 12.5” suppressed rifle:
105 MKZ at 2700 muzzle

 

[RldAtlas]

Thanks again for all who read and provided comment; I have done an initial round of testing.
***First thing to keep in mind: I am not a very experienced shooter (first started shooting 6 years ago, probably just about 12-15 "range days" since then), and I am shooting with bipod and bag in the back as opposed to a fixed tripod, etc. I made the deliberate decision to "learn to shoot" while also developing loads, which of course has its pluses and minuses.

Barrel is 18" Bison SPR profile.
Range: 50 yds, 75-80 degree.
Components: CBB 105gr MKZ, S&B once fired, CCI 450's sunk about 4-6 thous below-flush in a 12.5 thou (uniformed) pocket, AA 2200. COAL: variable, with corresponding CBTO (case base to ogive) of 1.83", 1.845", 1.86"
I tested single shots with powder work-up at 0.2 gr increments (6x), very much like (identical to!) Ozarkpugs' suggestion in his post above. Having read about "loading" long, I decided to do this for 3x COALs, 2.28", 2.295", 2.31" (measuring with Hornady comparator bushing "6-27" and expensive Japanese caliper (LOL)). Now, my Bison chamber has a .072" freebore which I believe is a bit shorter than the ARP that most folks have, so I wanted to be careful about jamming the bullet with longer COALs and also conscious of the additional pressures that occur as the bullet gets close. This is why I did not go out to 2.325" that I had seen in this forum as a high-accuracy COAL for this load. My (somewhat imprecise) measurements indicate that bolt face to lands is about 1.88"-1.90" in my rifle; and looking at data and calculations for various bullets here (The 6.8 Bison Chamber – Bison Ops), I believe 1.88" is closer to the truth. So, this puts my "off the lands" distances at 50, 35, and 20 thous for my 3 COALs.

First picture below shows 2x fouling shots, fired from a clean and cool barrel...felt good about those!

Next photo with mark-ups shows the shots on-paper for 6 powder charges and 3 COALs. Note the starting charge was incremented by 0.2 gr for each increment of longer COAL.

Notice the first shot, top-left corner, is high and left of the target...which is inconsistent with the 2x fouling shots that were ostensibly "identical" loads...don't know what else to say besides "operator error". Anyways, the next four shots are nicely laid out "points on a line". So, that was all pretty "feel good".
For 2.295" and 2.31" COAL, things are not so clear but I did note (and annotate) some interesting common trends with the higher charges.
Below is bullet speed data using Magnetospeed chrono.

I see a couple areas of "leveling out" of the curves that seem to indicate a couple of nodes...but I am not extremely experienced at this so I welcome commentary from the experts. It is also quite obvious that limiting COAL to 2.31" was a good decision, since the bullet speed kind of runs away above 30 gr compared to the shorter 2.295" COAL. This to me is a good indication that loading close to the lands is tricky and everyone should really get to know their rifle!
After firing these 2+18=20 bullets, I fired 6x cartridges loaded at 2.31" and 30gr. Average speed was 2769 fps, SD was 11 fps, and ES was 36 fps. I didn't measure the group but it was probably about 1.5-2 MOA.

So what have I concluded??? I'm not sure. But I'm pretty confident that 2.28-2.30" is an acceptable COAL range, with perhaps 2.29" designated as a "nominal"..but you could make the argument I should pick a single powder charge and optimize COAL within the range 2.27-2.30". I think I could make and measure some groups at 28.4 and 30.0 grains and "see what I see". Also, there is always the temperature effect to look into. Anyways thanks for reading and thanks for all the helpful comments!