Thread: Surprising ES numbers.

Off work for a few days and the weather has been pleasant so set about completing a few chores.

One job was to mount the new loopy to the little Kimber classic 7mm08 and go and sight it in. The barrel is a bit tired on this rifle and consequently shoots an honest 1 MOA but I've never managed to get it to shoot better than that. It seems to favour the cheap and cheerful 139 grn interlocks which is good because i have heaps of them. A while ago I'd set about loading up a bunch of rounds with the intention of sighting in and having forty or so left over for hunting.

The standard brew I've settled on is free Winchester secondhand brass from a mate who doesn't reload, full length resized, some old red packet fed 210s that I was given and 49.5 grns of Win Staball 6.5. COAL of 2.780, miles off the lands but I'm stuck with a minimal length magazine.

Seeing as how I'm not using premium projectiles, secondhand non lust worthy brass and have a huge jump to the lands I figured that on that particular evening that I couldn't be arsed weighing every powder charge on the beam scales and that I'd just charge all the cases straight out the powder thrower. Dropped a few charges on to the scales and they all came up bang on or just over by point 1 of a grain according to the Frankford arsenal digi scales. Close enough i figured, it's only a close-range bush load.

Five mins later 50 rounds loaded and tucked away for the next range trip. Crikey, I thought, that sure speeded things up. But no doubt the rounds were never going to be as good as rounds I load for the WSM where I drop every charge into the digital scales and double check with the beam scales, while they settle at eye height I start on the next charge trickling up to get it perfect. Loading 50 rounds takes me a couple of hours.

New scope mounted and trued to be plumb and square to everything etc. Off I go to the range. Bore sighted it, Fired one round down range. Walked the cross hairs from the aiming point to where the round landed, fired two more. Little'll bit low and to the left, adjust and fire one more. Inch and half high perfectly in line. You beauty. Job done. Four rounds fired and finished.

Meanwhile a geezer I know turns up with one of the new fancy Garmin Chrono, give it try he tells me. Sweet, be interesting to compare to my cheap and cheerful pro chono. The pro chono reckons the rounds are going down range at about 2750 out of the 17-inch barrel.

Set her up next to the barrel and fire three measured round, usual group from that rifle. Two rounds about 15mm apart and the third an inch off group center. Pretty standard.

But what amazed me was the velocity readouts. An ES of 6.7 fps. Max 2768 and min of 2760.7 I know it's only a three-shot group and therefore useless but still... a random sample straight out the ammo box with no checking of powder weight other than initial check to confirm nothing had changed since last time I used tthrower. I was beddazzled to be fair. If it was the pro chrono i would assume it was bullshitting me but the garmin is the latest and greatest and is the new gold standard.

So... for my bush loads i will never individually weight each charge again. For the big rifle, yep, I think I'll still weigh each charge, especially since it's a stick powder and tends to hang up a but in the thrower. (ADI 2213sc)

Also, I have informed the wife that I have found my next birthday present. I now realize what has been missing in my life, the pro chono is dead to me now that I have beheld to wonders of Garmin's miracle box on legs.

As you might have guessed i have a bit of time on my hands todays so i thought I'd write up something with a bit of depth rather than the three line comments off my phone I usually put up.

The powder thrower is a Hornady match grade thrower that i picked up cheap of tardme.

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Originally Posted by Blackfern

An ES of 6.7 fps. Max 2768 and min of 2760.7 I know it's only a three-shot group and therefore useless

unfortunately: yes. This is correct. Sorry to be a downer.



Here are 5 velocities out of a string of 19 from my rifle

2722
2721
2724
2724
2729


an SD of 3 and a ES of 8!! shit it's good.


Except the whole 19 shot data set has an SD of 15 and an ES of 58. These numbers are closer to the "true" performance if I wish to describe it.


The good news is, unless you want to shoot things at 600m+, the velocity variation doesn't make any difference.



The Garmin is absolutely the best chrono I've used, by miles, though. A doppler radar in your pocket, how good is technology?