BL-C2 Max Loads for 55gr and 1:8 Twist?

[ropsitos]

I'm working up a load for my JP 18" AR and I'd like to get a feel for where max is for most people with similar conditions.

My manuals and online data only list BL-C2 data for 55gr out of 1:12 twist guns, so I've started low and have been working my way up. Hornady lists 28.1 as max, and hodgdon lists 27.5.

I like to stay down from max because I load progressively, and while I trust the Dillon 650 powder drop, and have seen it's consistent, I like a little margin. Plus I'm using mixed cases. Also I hear BL-C2 is temp sensitive (is there a published chart or adjustment factor for it's sensitivity?). I also don't need max velocity for poking holes in paper up close. I generally use 75gr hornady's for things out past 100yds.

I'm loading Hornady 55gr spire points with cannelure (H2266) to 2.20 OAL in mixed cases with CCI 400 small rifle primers. Eventually I will switch to the hornady 55gr FMJ-bt's (H2267)...and yes I plan to check them to be sure nothing changes.

I'd like to get to around 3000 fps, because that's where my N135 loads are running at that I've been happy with, but I don't want to be on the edge to do so. I check for pressure signs, but shooting 7 rounds over the chrono and checking those cases isn't exactly a statistically significant sample. For what it's worth it was in the 80's here yesterday.

So far this is what I've checked (chart with trendline attached because I had it)

24 2491 25 2648 25.5 2720 26.1 2819

Accuracy was not fantastic, and similar across the charges, and even to my N135 loads, but I don't think I was having a really good day (and I'm using a 1-4X Burris MTAC), so I'm taking what I see with a grain of salt.

I'm going to try out 26.6, 26.8, and 27 tomorrow and see what that gets me.

Is the max charge value generally consistent across various twists and barrels and only the resultant velocity changes?

thanks

bob

[dauntedfuture]

Expectation management is the first step, that 1-4 scope is not going to help you at all; my 1-6 is not much better and I take that into consideration when I am testing ammo. You can try shooting at different size targets at range and see what happens, you will find that your groups will very based on target size; some shoot better with a big target, some with a target that's very small and only the center of the cross hair covers it.

BLC 2 is great powder for 223, its the "same" as WW 844, H335, WW 748 and AA 2230, All those powders shoot well at about 23-24g with a 55g bullet. Temperature sensitivity is not an issue for short range ammo, just make sure you are on the safe side of pressure for those hot days.

a 18" JP 1-8 barrel will handle most any bullet you put into it save a SXSP which might come apart. You will not have an issue with lighter BTHP bullets like a 52/53 and you will find that they are some of the best shooting in a 1-7 to a 1-14 barrel.

If you are shooting 75g bullets past 100 then consider a lighter 55g load, 3000 fps is doable in a 223 18" but id ask why? You will find that recoil between a 55g at 2800 and 3000 will be a notable difference and your splits will be faster.

Me, I shoot 77g SMKs at 2650 past 200 or so and 55 FMJ's at 2700-2800 for 200 and in. I want a 10 round group that's 4" or less with the 55's at 200 and 3" or so for the 77's. This is with a 6x scope shot off bags.

[Rob Tompkins]

With mixed brass I get ~2900fps with 25.5 grains out of an 18" Wilson barrel with 55gr Xtream FMJ, getting ~1.25-1.75 MOA accuracy.

[ropsitos]

I found my accuracy issue. Shooting off bipod and rear bag vs front bag and rear bag. Much better off the front bag, more like what I recalled. I had learned this lesson previously, clearly forgotten it, then relearned it.

I ended up at 26.6gr for around 2835. I got into the 2900's at 27gr, which yielded a really great grouping, but while there were no pressure signs it made me uncomfortable. It's not like the group was bad at 26.6 and 26.8, just that 27gr group was great. I'm not sure it wasn't just a case of a better better shooting on that string, or luck.

3k fps was really an arbitrary goal, based on factory ammo chrono results, and what was the results of one or two steps down from the loading books max for N135. I didn't want to dip to low to ensure I had enough gas to cycle the gun when it ends up dirty (which may not be a valid line of thinking).

thanks
Bob