129SST and the short barrel

[Kswhitetails]

When thinking about an all purpose loading for my Pistol build, shooting suppressed,I have been leaning on a heavy pill reasoning that the retained energy at medium ranges would be better than velocity. I’m shooting for a maximum of 300 yards, so lobbing a little from the short Barrel is something I’m expecting. Given the expectation of expansion down to 1200 FPS, it seems to be solid logic.

I found a guy that had 500 Midway seconds for $100 bucks shipped, so that seemed prodigious and bought them up. Add to that and the fact that Midway usually has 129 .264 “seconds” in stock, and I thought I had a good idea. Well, that was until I fired some “medium” charged loads yesterday and am seeing flat primers. (I will post pics soon) 29.5 and 30.2gr CFE out of my 18” LaRue. (Hornady X manual lists 27.9-31.7gr out of their 18” test)

Untitled by ., on Flickr

29.5 left, 30.2 right. Especially surprised by the second primer up at 30.2.

I’m also interested in a 130 SGK load for my builds for hunting, and thought this would be gaining some flags for that load development.

So, I’ll ask. Is the idea solid? Energy over velocity, not too concerned with drop for short barrel loading?

[biodsl]

At first blush, I'd think that starting with the best BC you can get makes more sense that chasing velocity in a short barrel.

[Kswhitetails]

There are two other factors I failed to introduce. Cost/projectile, and general availability.

Bio, I started at the ABLR for this, and so far haven’t found them to be reliably available. And nowhere near as wallet friendly. I know it’s the wrong reason to justify the search for a load, but this will help define my envelope.

[BCHunter]

So I was pondering similar idea. The 12.7 barrel will be used 200 yards and closer. So I wanted to be sure to have a bullet that would open at those velocities but be tough enough if I hit an twig in tight places. So I'm going to test 129 gr hornady interlock and 129 partion.

[sneaky one]

Ksw, I loaded these same bullets years back, at 2 full grains below max., wrote down wrong charge wt. by mistake.

They shot like a dream, ran through the gun just fine, and the performance on a deer at 400 yds. was awesome.

Maybe try 29.6-.8 .

[Kswhitetails]

Ksw, I loaded these same bullets years back, at 2 full grains below max., wrote down wrong charge wt. by mistake.

They shot like a dream, ran through the gun just fine, and the performance on a deer at 400 yds. was awesome.

Maybe try 29.6-.8 .

I've gotta say sneaky, your experience matches mine. Yesterday, mine performed with a smoothness I didn't expect, and never once seemed out of bounds. Not a hiccup. I think I will work a ladder from 27.5-29.5 and see what falls out over the chrony. I put three in a row on target at 270 yesterday in what turned out to be just over two inches. Deer beware. This was suppressed, which made it even sweeter, as the weight on the end of the barrel makes recoil non-existent. It was too easy, and the spotter watching said he couldn't beleive how hard it was hitting steel from an AR15 in 25+ wind. It was fun. I hit at 390, too... He was laughing at that point. He wouldn't take me up on my offer to send some for himself. I think he was worried about having to convince his wife that he needed another gun...

Thanks for the info, it adds to my confidence in developing a good load here.

[StoneHendge]

I hate to say it, but you may have discovered why Hornady considered them "seconds" and why the guy you bought them from was selling them....

[Kswhitetails]

No problem, I thought of that too. I figured they’d have discrepancies, so I started with the first box, and taking measurements they are all similar to a few thousands. No worries at 300 and in. For 20 cents a piece, I just sort them by 1/5 grain and will load them according to that. They fluctuate about a grain from 128.5-129.9. So a grain and a half. Very few are actually 129.0.

One grain difference between pills isn’t enough to make me sweat a hunting or steel ringing load.

[1Shot]

Here is something that I have been pondering on. I keep reading post of where people are working up loads and find that with one or two rounds at a below max charge and sometimes well below max charge they get high pressure and then their common since kicks in and says do not load any higher powder charge with this. But here is what has been nagging me in the back of my mind. Could it not be the powder charge causing the pressure problem? Could it actually be what may be happening during the cycling of these semi-auto actions. Could it be that the bullet is being driven back into the case some by hitting the feed ramp and when fired it will cause higher pressures? This thought began to nag at me when I was trying to get some Sierra 100 gr HP bullets to shoot. I was loading H335 and W748 and found that W748 was really shooting great groups with shots that actually fed and shot but 1 out of every 3 rounds I tried to fire would jam. What was happening was these bullets have a big HP with a wide flat point and this point was catching while feeding and it would jam the bullet back into the case quite a bit. Now if this happened and then the round actually then did go into the chamber and you fired it I am sure that there would be a huge pressure spike. Oh, and I was even using a Lee Factory Crimp pitting a medium crimp, but when I pulled the bullets from the rounds that had jammed with the hammer type bullet puller they came out pretty easy and there was no ring or mark around the bullet where the crimp was applied. I may give this bullet another try and use a FULL Lee Factory Crimp on the cases to see what happens. I have been handloading for over 40 years so my thoughts are based on a lot of experience. Has anyone had the same line of thought?

[Kswhitetails]

I’ve taken my calipers with me the last two range sessions, wondering about this very thing. Fire two, eject third and check coal. So far, about ten checks, no changes with either 120smk, 129SST, 107 SMK, 100 ELDMs. I don’t crimp my rounds, which is why I am checking this to verify my coal during live fire loading conditions.

[1Shot]

The reason behind me using the Lee Factory Crimp is that from a lot of experimenting with many different rifles I average better accuracy and standard deviation and with the slam bang loading of semi autos it just easies my mind. Where I found that the crimp really increased accuracy was when shooting old military bolt rifles that have throats a mile long. Every rifle that I have tried it with and that is a bunch, except the 96 Mauser 6.5x55 which did not make any difference one way or the other because they are just dead nuts accurate, it has greatly increased their accuracy.

[biodsl]

There are two other factors I failed to introduce. Cost/projectile, and general availability.

Bio, I started at the ABLR for this, and so far haven’t found them to be reliably available. And nowhere near as wallet friendly. I know it’s the wrong reason to justify the search for a load, but this will help define my envelope.

A load based on a bullet you can't find does you no good. And cost is always a consideration!

[LRRPF52]

Given the expectation of expansion down to 1200 FPS, it seems to be solid logic.

Change that to 1800fps with 129gr SST, as well as 123gr SST. I've never seen 1200fps expansion with the SSTs, not in 6.5mm at least.

The 6.5 Grendel Handbooks have an entire chapter showing you real expansion characteristics across the velocity spectrum with many different hunting bullets.

The pages will look like this:



You can set your maximum expansion envelopes using the data from the Terminal Ballistics Chapter, when calculating expected performance based on your bottom end of ES and mv.

[Trueblue]

KSW,
you might be thinking about the Accubond LR 129 gr that expands at 1300 fps

[Kswhitetails]

Ahhh, we’ll my memory of this reading was incorrect. Well, dang. I probably did get the ABLR numbers interjected into the discussion inside my own head. I hate it when that happens. I swear I read that somewhere though.