New Chrono surprises

[wrangler5]

I've been reloading for about 25 years, but just got my first chronograph last week (Shooting Chrony.) Today I shot some commercial 9mm Speer 115g Gold Dot rounds across it and got some astonishing speeds. This is not marked as +P ammunition, but the slowest round (out of 10) was 1249 fps and the fastest was 1320, with an average of about 1280. This is considerably faster than I can reload using any of the data books at my disposal (Accurate, Hodgdon, Hornady, Lyman, Winchester)

I think my chrono setup is probably OK, as other (reloaded) 9mm rounds that I shot across it matched pretty well the velocities predicted in the manuals on which the loads were based. The first screen was about 7 feet from the muzzle. Pistol was an FN Hi Power.

Is it common for commercial ammo to be substantially faster than one can reload using published data? I know the Hi Power can handle +P loads, but I'd rather not push the envelope any further than I have to. My objective is to be able to load some rounds equivalent to the commercial Gold Dots (I have the bullets) and practice with them some, saving the commercial loads for carry purposes. Reloading saves a bunch of $ on these kinds of rounds, even though the conventional wisdom is that 9mm is barely worth bothering to reload at the plinker/practice end of the spectrum.

Thanks for any experience others may have here.

 

[~z]

When I got mine, I was surprised to find my loads were moving much faster than book values (75-125fps faster). From your post, I could not tell if you have chronoed your reloads or just compaired the factory velocities to book values listed for your reloads. Can you clarify?
~z

 

[wrangler5]

I have chronoed some of my own reloads and they were within the range I expected from the loading data I used (not exact, but then I wasn't using the same brand of case or the same brand of FMJ bullet, and my barrel was of slightly different length.)

The ones that were surprising were the commercial Speer rounds which were so much faster than anything it looks like I could load myself using any of the published data that I have for standard pressure loads. I haven't seen 9mm +P data published anywhere, although there obviously are +P and +P+ rounds loaded commercially. But I have the impression that the factories have access to powders that we can't buy by the pound, and so presumably they can come up with loads that we can't match at home.

 

[callgood]

I've reloaded for 9mm. Wallyworld Win 115gr FMJs are around 12 cents each. New 9mm brass is around 10 cents each. For 2 cents I can get my brass, plus any other good looking brass I might be given at the range. With this I can reload for around 6 cents a round.

I also reload 124gr Gold Dots for around 1150 fps in my HiPower. I don't have the figures here, but when I compared my chrono results with the figures in the Speer manual and my Sierra manual, the results were dead on with the Sierra. I was using American Select. There was a good difference with the Speer manual. The factors in my loads were closer to what Sierra was using.

The Wallyworlds were a bit faster than 1200 fps, IIRC.

 

[wrangler5]

I too have used Wallyworld as a source for (pre loaded) 9mm brass, although I bought a box of mixed brass from Midway recently that I use for IDPA competitions where I just "leave it lay" after the match. I haven't shot any of the Winchester white box over my chronograph yet - maybe next time. It will be interesting to see if its velocity is in or out of line with my own 115 FMJ loads.

 

[RugerOldArmy]

You have to read between the lines a bit with the reference manuals and their velocities. Specifically the barrel length used. Case in point:

Speer No 13
Power Pistol
Max listed at 6.4 Gr 1157 fps
GD-HP 124 Gr, 1.12 OAL
CCI 500 primers
4 inch barrel


My Test load
Power Pistol 6.3 Gr
Montana Gold 124 Gr JHP
1.12 OAL, WSP primers
CZ-75 (4.7 inch barrel)
Min 1215 fps, Max 1257, Avg 1241 (fps) SD 14.93, ES 42

My take on it is the 4.7 inch barrel, and the hotter WSP primers resulted in a bit higher velocity in actual testing with my Chrony, although I used a little less powder.


Another case:

Speer No. 13
Test Gun/barrel Sig 220 (4.4 Inch)
185 Gr GD-HP
Power Pistol 9.5 Gr (Max) 1047 fps
CCI-300 primers, 1.200" OAL


My test load:
9.4 Gr Power Pistol, WLP primers
Nosler 185 Gr JHP, 1.21" OAL
1911 Govt. (5" Barrel)
Avg 1172, Min 1156, Max 1215, SD 13.49, ES 59

Longer barrel, higher velocity again. Even with .1 Gr less powder, and a slightly longer OAL

Just my $.02

 

[wrangler5]

Thanks for the experience, RugerOldArmy. I do see that the Accurate, Hodgdon and Hornady data are all from a 4 inch barrel, and mine is just under 5 inches. I've loaded up a set of rounds using new brass and Speer Gold Dot 9mm 115 grainers, in steps from the minimum to maximum using Accurate #7 and the Accurate data book. It looks like #7 gives the highest velocity at lower pressure than other loads. Will go shoot them over the chrono once the clouds (and presumably rain) from Rita are gone, sometime next week. Will be interesting to see how close to those rocket level commercial loads I come.

 

[RugerOldArmy]

AA #7, eh? I have a pound of that yet to try. To my understanding it was designed for 9mm. Let us know how it works. I know I'd be interested, I haven't tried AA powders yet.

 

[anonanon]

Barrel length is not the major cause of velocity difference, especially the difference between 4" and 4.7". The barrels themselves make a difference -- for instance, my 6" .357 shoots faster than my 8". The lots of powder used make a difference -- I've chronographed reloads made at the same time with all the same components except powder lot, and recorded an average 50 f/s difference.

 

[Moondoggie]

I bought my first Chrony last fall after reloading for 23 yrs, kinda like your situation, Wrangler.

The results were surprising!

All of my reloads chrono'd 75-125 fps faster than I'd figured based upon the reloading manual and my calculations.

I haven't chrono'd any factory stuff...I rarely shoot any.

 

[dmftoy1]

I doubt if you made the stupid mistake I made my first time with my Shooting Chrony, but one thing that happened to me was that I didn't fully "unfold" it and my speeds were quite a bit higher than I expected. I think it made maybe 1/8 - 1/4 of an inch difference between where the "eyes" were that read the bullet passing over, but I think it dropped my speed down around 100-150fps (if I remember right . . . .not as good as it used to be. )

Have a good one,
Dave

 

[wrangler5]

Well, I managed to get to a close-by range this afternoon and shot the 9mm 115g Speer Gold Dot loads that I made up last night using Accurate #7. My reference was Speer's own ammunition loaded with this bullet, which yesterday showed an average velocity of 1282 fps in a range from 1248 to 1321. No 115g load listed in any of my loading books was this fast, but it looked like Accurate #7 might get closest with pressures slightly below #5. Now this is just a guess based on Accurate's data for a 115g Hornady FMJ, not a Speer JHP (Speer doesn't put its data online - you gotta buy their book.) Hodgdon gives data for the Speer bullet, and their load with HS-6 is even a bit faster than #7, but I have the #7 and don't have any HS-6, sooooo . . .

New Starline nickel plated cases, WSP primers, powder metered with a Redding 3BR measure, 10-round batches in 0.3g steps from the lowest to highest shown in the Accurate book, plus one load at 0.3g over max (i.e. 9.1g.) All were seated and crimped in the same press, so I think things were as uniform as they are going to get, apart from the powder charges.

Anyway, average velocities ranged from 1146 (7.9g of powder - almost 100fps faster than the Accurate book lists for this charge behind a 115g FMJ) to 1235 (8.8g) with the 9.1g (over)load coming in at 1271. All of the primers looked about the same, with a slight bit of breech face marking (so did the Winchester White Box loads that I also shot) while none of the cases showed breech face marks - all examinations with a 5x loupe. Fired case diameters were all within 0.001 inches for all of the cases fired, including the Win White Box, so I'd guess that none of the cases were stressed beyond normal (is this a reasonable conclusion?)

I didn't have a target set up, I was basically shooting to avoid the skyscreen support rods. My aiming point was a clod (or cavity) of dirt on the 100 yard berm, probably about 6 inches in diameter or so. I was pleased to see that I was either hitting right at it or close enough to give it a good scare, particularly with the lower power loads. BTW, I gather that consistency of loads is desirable, even in handguns (I know it's crucial in long range rifle loads), and was pleased to see that the 8.2g load, with an average velocity of 1182, had an extreme spread of only 28 and a standard deviation of 9.21. I'm not exactly sure what SD tells me, but this is as low a number as I've seen yet in the dozen or so loads I've measured so far.

In the interest of minimizing stress on all elements of the shooting system (including my wrist) I'll probably load up some of these bullets at the 8.2g level, for occasional practice use. These will be about 100fps slower than the Speer brand loads, but should be safely within the range of acceptable pressures. They also seemed to be very accurate.

Anyway, I'm very pleased with the kind of information that a chrono is giving me. My only question at this point is whether 10-shot strings are enough to base decisions on, or should I fire more? (The Shooting Chrony only keeps a maximum of 10 shots in a string for statistical purposes - I know I can shoot 2 or 3 strings and easily pick out the high and low, calculate the extreme spread between the two, and averge the averages. But how would you compute the SD for 3 10 shot strings - average the SDs, or is there more to it?)

 

[CB900F]

Wrangler5;

What's the screen spacing on your chrony? Typical is 1 foot, I believe. As a previous poster alluded to, screen spacing is critical to accurate measurement. He hadn't fully unfolded his screens & the fraction of an inch made a substantial difference in the readings.

If you were to test those same loads over a 2 foot space, it'd be typical to see a measurable change in velocity, usually slower. Not because the bullet actually slowed down that much, but because the wider spacing allows a 100% greater sampling area. Works like this, the clock in the chrono can supposedly get in twice as many ticks over the two foot screen. Therefore, a one tick difference in time results in 1/2 the difference in measured speed from a one foot spacing to a 2 foot spacing.

As I'm not a statistician, I'm sure somebody's gonna correct my layman's explanation. but I hope you get the idea.

900F

 

[wrangler5]

Shooting Chronys have fixed sensor spacing - they're mounted in a fold-out chassis. You unfold the unit fully, mount it on a tripod, put up the sky screens, turn it on and start shooting. No adjustments available.

I'm assuming that the "consumer grade" chronos that we can buy for a few hundred bucks (like the Shooting Chronys) are best thought of as relative measuring devices rather than absolute precision devices. So Speer Gold Dot 115s may not actually go 1321 fps and my reloads with the same bullets may not actually go 1271 fps, but the two are probably close to those speeds and approximately 50 fps or so different.