129's and the Howa mini - Question

[grayfox]

So. I've run a few loads in 129 sst in my new Howa, by lengthening COALs to 2.280-2.285 I think I've kept the pressure a bit lower while loading CFE223 to 30.1 up to 30.7. In my AR I had to stop at 30.1 (2.260) due to velocities plateauing...

Now here's my question: in my Creedmoor all 3 of the 129sst, 129ablr and 130 accubond, R17 at 40.2-40.4 ie, very same loads, seem to all work great, chron within 4-5 ft/s of each other and close POI's. I don't see any load data for the 129-130 Nosler's For Grr and am wondering if the low-mid 30.x's should be ok with those 2 bullets also, like the sst here? I can load out to 2.300, even 2.310 if necessary, again which should give a little pressure relief.

I didn't see any signs of over-pressure from these loads today. The first 3 sets were new Hornady brass, the last 2 sets were 1x fired Hornady. All cci450's.
The data below is actually from 2 different days of chrono's, the first 3 about a week ago and the last 2 sets were today.

The 130 is about the same length as the sst and the ablr, while longer, I think should have "powder room" at the 2.300...

This is still a work in progress - only 2 sets of the 129 today as I also was looking at 123sst and 125 Nosler in my howa. It's turning out to be a decent little package.

129sst 2.280 in. Avg StDev
First round of tests:
30.1 2399 2403 13.0
2403
2421
2390

30.3 2394 2407.5 14.4
2400
2427
2409
30.5 2418 2418 (only 3)
2411
2427


Today's sets.
30.5 2444 2437 9
2439
2424
2443

30.7 2447 2440 5
2442
2435
2436

[LRRPF52]

If you see a plateau or not much increase in velocity between 2 charge weights that are within .3gr, that is often an accuracy node.

Pressure signs for me start with a departure in the trend line.
First round of tests:
30.1 2399 2403 13.0
2403
2421
2390


30.3 2394 2407.5 14.4
2400
2427
2409

30.5 2418 2418 (only 3)
2411
2427


Today's sets.
30.5 2444 2437 9
2439
2424
2443

30.7 2447 2440 5
2442
2435
2436

So you went 2403 to 2408 to 2418 to 2437 to 2440 with .2gr increments. Your biggest increase in velocity was only 19fps from 30.3gr to 30.5gr.

What barrel length are you using? Is it 20" or 22"? Everything appears to be well-behaved currently.

[grayfox]

It's the 20 inch Howa HB.
So, Between yesterday and today I took 2 more trips to the range, to test the 130 gr Accubonds.
On 8/21 I did just some group shots, then today I did some magnetospeed testing. Since I can load longer, to around 2.300 or even a bit more (than the AR would let me), there is more room to explore bullet velocities I think.

With 2x Hornady brass, cci450, cfe223 powder at 30.4, 30.6, and 30.8 gr, and 2.295 coal.
I pasted in the group pics for the 30.8 (left) and 30.6 (right), the 30.4 group was fairly scattered and didn't interest me. Velocities would tell me more. With the ubiquitous flyer of course!!

20170821-130AB-2.jpg


So here are the velocities, it appears to me that the 30.8 loading is the best of the lot, averaging 2467 with SD of
only 3. 2460-ish could be a node for this 20" HB.

This data also gives me some inclination to include the 129 ablr into the mix (I know I know, you said it all along!!!) in the 30.x range with cfe. Finally, I think (more gut feel than totally hard data) that the 129 sst might work out well at 30.6 or 30.7, I may even try 30.8, again in the 2440-ish range speed-wise.


130 AB
** velocity, *** Avg, *** St Dev

30.4
2426 , *** 2442, *** 11
2446
2454
2443

30.6
2461, *** 2460, *** 13
2477
2443
2459

30.8
2463, *** 2467, *** 3
2469
2471
2467


footnote: I'm also testing the 125 partition. I need to do some more testing with it, I'm not sure yet what it's telling me as I'm not getting a clear picture velocities/st-dev wise, so that's a story for another day. Somewhere 2495-2525 or so...