Why are my chrono'd speeds WAY over the book's figures?

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Prof_Fate

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Been reloading for 8 months now, 9mm and just started with some 38 DEWC.

Finally got a chronograph and had a chance tonight after PPC to try it out.
I shoot an XDm9mm 5.25 competition model and wanted to try out what I've been shooting. Also had my 686 snubbie, a friend's 686 snubbie and 6" and glock 9mm.

OK..federal factory ammo is listed at 1120fps, out of my XDm is measured 1135.
The friend's 686 loads are 2.7 bullseye w/ 148 hollow base wad cutter, measured 830 from the snubbie and 860 from the 6".
The glock was doing 1120fps with whatever he had for it.
OK - chronograph is working fine.

Now I put 20 rounds of my load - Montana Gold 124 JHP propelled with 4.0 gr of Bullseye. Avg? 1240 fps. With a hi/lo spread of 27 fps, with most withing 15fps.

***? The max load listed in the books is 4.4 at 1059fps. I"m near min load and the bullets are WAY faster - faster than I think any 9mm load I've seen, period.

I shot 20 because I wasn't sure I believed what I was seeing. I was expecting speeds of 950 perhaps, or there abouts.

Any ideas???
 
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OAL

That does sound a bit snappy.

What is your OAL?

Is your gun setting back the bullet when chambering the round?

Fill your mag and then chamber a round. Remove the round and measure the OAL.

I would be willing to bet you are seating the bullet way short or the bullet is getting set back in the case during chambering.

I have never gotten that velocity from Bullseye.

Bruce
 
If the temperature is high, the speeds will by quite a bit higher than when it is cool. I think that it is the temperature of the powder that matters.

Rick
 
There are lots of things that change velocity.

You are using a longer barrel than the 4" barrel typically used in mosuals. The extra 1-1/4" can add 70 to 100 fps.

You don't say what data source you took the load data from but its likely the bullet used was not the Montana Gold. Some bullets jhave less barrel resistance and that increases velocity. Different components can increase velocity, esp. primers. I've had an increase of 70 fps between two .38 spl loads by using Winchester primers vrs CCI and using .2 grains less powder.

As mentioned, the outside temperature will change velocity as does increase in elevation. Bullets fly faster in thinner air.

There is just a lot of difference between guns. Some guns from the same manufacturer and model shoot fast and others shoot slow. Just the difference in their materials, machining and tollerances cause the difference.

A smaller amount of space in the case can increase pressur.

Any one or combination of elements could easily give you the higher velocity than the manual says they get.
 
Last edited:
Prof_Fate said:
Been reloading for 8 months now, 9mm and just started with some 38 DEWC.

Finally got a chronograph and had a chance tonight after PPC to try it out.
I shoot an XDm9mm 5.25 competition model and wanted to try out what I've been shooting. Also had my 686 snubbie, a friend's 686 snubbie and 6" and glock 9mm.

OK..federal factory ammo is listed at 1120fps, out of my XDm is measured 1135.
The friend's 686 loads are 2.7 bullseye w/ 148 hollow base wad cutter, measured 830 from the snubbie and 860 from the 6".
The glock was doing 1120fps with whatever he had for it.
OK - chronograph is working fine.

Now I put 20 rounds of my load - Montana Gold 124 JHP propelled with 4.0 gr of Bullseye. Avg? 1240 fps. With a hi/lo spread of 27 fps, with most withing 15fps.

***? The max load listed in the books is 4.4 at 1059fps. I"m near min load and the bullets are WAY faster - faster than I think any 9mm load I've seen, period.

I shot 20 because I wasn't sure I believed what I was seeing. I was expecting speeds of 950 perhaps, or there abouts.

Any ideas???
Click to expand...
Your data does not make sense to me. I have loaded 4.3 gr. Bullseye behind the 124 gr. Montana Gold JHP for 1050 to 1090 fps from a S&W5906 and Dan Wesson PM-9. Similarly, 4.5 gr. Bullseye behind a 125 gr. JSP or a 0.356"diameter 124 gr FMJ gave 1168 & 1108 fps. The OAL for these loads was between 1.145 and 1.160".
The old Alliant 2005 reloading guide listed the following maximum for a 125 gr. FMJ:
4.9 gr. Bullseye = 1155 fps = 32000 psi.
I chronographed the 4.3 gr. load with the Montana Gold 124 gr. JHP and I have used 3.9 gr. Bullseye with the 125 gr. Star JSP for a soft shooting load - however I have not chronographed the 3.9 gr. load. My favorite powder for 9mm is WSF which I use with both 124 and 147 gr. bullets either jacketed or plated.
 
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I did a little more research on temperature. If the cartridges are sitting in direct sun for some time, the powder can reach 130 degrees F. This has a large effect on pressure. This is a particular concern in long distance rifle shooting.

Rick
 
Are the screens on your chronograph spaced properly?? I'm assuming it's a chrony or similar and the spacing is SET, nothing to really get out of whack. Just a thought...as I had it happen years back with an old Oehler. We were off a fewinches,which really affected the readings.

Otherwise I'd agree your OCL is too short or setting back as the ctg is chambered.
 
Upon further investigation the lee beam scale is out of calibration. Not sure how/why that is, but it's reading about .6 gr lower than reality. So much for lee's claim it's idiot proof- they'd not met this idiot yet!
 
Prof_Fate said:
Upon further investigation the lee beam scale is out of calibration. Not sure how/why that is, but it's reading about .6 gr lower than reality. So much for lee's claim it's idiot proof- they'd not met this idiot yet!
Click to expand...

There are so many things that can affect pressure & velocity. You only stated bullet & (incorrect) powder charge. Was it 38 or 357 cases, std or magnum primers, ambient temperature, seating depth, crimp, well you get the idea, it's a long list. Just listing powder charge & bullet is only a small piece of the puzzle.
 
Prof_Fate said:
Upon further investigation the lee beam scale is out of calibration. Not sure how/why that is, but it's reading about .6 gr lower than reality. So much for lee's claim it's idiot proof- they'd not met this idiot yet!
Click to expand...

I was conducting an audit at a manufacturer of alarm systems. In their engineering department there was a sign:

"Those Who Devise Foolproof Systems Fail To Take Into Account The Ingenuity Of Fools" :D

Glad you found your problem and I thank you for reminding me to check my own scale calibration. You may have saved me similar grief! Thanks for sharing.:cool:
 
I think that's a good lesson learned.

I use a set of check weights before charging cases.

Not just the large weight that comes with a lot of scales.

I use weights that get as close to the charge weight I'm loading.

A couple of buck for a weight set is money well spent.
 
Prof_Fate said:
Upon further investigation the lee beam scale is out of calibration. Not sure how/why that is, but it's reading about .6 gr lower than reality. So much for lee's claim it's idiot proof- they'd not met this idiot yet!
Click to expand...

Yeah, and I'm such an idiot I could never get the Lee scale zeroed. I just bought a RCBS 1010 scale that cost more than the entire Lee 50th anniversary kit. Ha! I love that scale, though. Definitely worth the money. I usually always make sure it's zeroed before I make a batch of ammo. The other day I was in a hurry and didn't check it first, but after loading a couple of cases, I decided it's better to take a couple of minutes to ensure your scale is zeroed than have a possible situation on the firing line. :eek: It was indeed right on, but I did feel better that I checked. I suppose the last place I want to be lazy is at my reloading bench.
 
Prof_Fate said:
Upon further investigation the lee beam scale is out of calibration. Not sure how/why that is, but it's reading about .6 gr lower than reality. So much for lee's claim it's idiot proof- they'd not met this idiot yet!
Click to expand...
You beat me to it. My response was going to be, "Check the accuracy of your scale!"I once had a beam scale that was out of calibration. It was doing the opposite and indicating higher than the actual weight. I sent it back and it still wasn't right. I went with Lyman scale check weights and electronic scales. I have never looked back or had a problem.
 
Broker50 said:
There are so many things that can affect pressure & velocity. You only stated bullet & (incorrect) powder charge. Was it 38 or 357 cases, std or magnum primers, ambient temperature, seating depth, crimp, well you get the idea, it's a long list. Just listing powder charge & bullet is only a small piece of the puzzle.
Click to expand...

because the other 'factors' were not factors.
 
While I like, or at least tolerate, most Lee products for the price, do yourself a favor and get rid of the Lee scale. I use a RCBS 505 and a set of check weights. I balance out the scale with the weights matching the powder charge I plan to use. I have done this for years with no problems. Good Luck
 
^^^Prof knows this, we go back & forth on GT, but the Lee scale is a true POC & should not be on any serious reloaders bench. The scale & powder measure should cost more than any other piece of relaoding gear IMO, yes, they are that important, especially if you are attempting loads near the top end. Guessing or close will not do with many pistol powders.
 
Prof_Fate said:
Upon further investigation the lee beam scale is out of calibration. Not sure how/why that is, but it's reading about .6 gr lower than reality. So much for lee's claim it's idiot proof- they'd not met this idiot yet!
Click to expand...

Apparently we are related idiots as I've had similar problems with mine. In theory, there's nothing to go wrong; mechanically it couldn't be simpler. But every time I do a reloading session I zero it and every time it seems to be a tad low and I have to move the counterbalance back a bit. There must be a viable explanation for this but I can't figure it out.

Steve C said:
...I've had an increase of 70 fps between two .38 spl loads by using Winchester primers vrs CCI and using .2 grains less powder...
Click to expand...

Thanks for this. I remember the first time I loaded for my 5" S&W 625. I'd made up three or four progressively stiffer loads (from a reliable source, as I recall) and the velocities were quite a bit higher than anticipated; 70 fps. would be in the ball park I think. I don't recall the primers specified in the load data, but after the second level load I decided enough was enough as I was already at third-level velocities.
 
It is probably the scale problem, but it is worth mentioning that certain conditions of sunlight can cause erroneous velocity readings, and, in fact, a series of readings which can show reasonable values for extreme spread and standard deviation. This has happened to me around midday when the chrono is in the sun. It may be that reflections from the bullet trip the rear sensor too early, resulting in high readings. Earlier this summer I shot some of a more or less normal 150-gr .30-30 load and got an average velocity of 2650 fps for a ten-shot string through a 24-in. Model 94, with an ES of about 65 fps and an SD of about 25 fps. Ridiculous! A couple hours later a redo gave an average of 2385 fps. Of course, under clouds or overcast, this will not happen.
 
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