February 28, 2010, 04:15 PM | #1 |
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Strange 9mm speed.
Respected all,
I'd like some advice on a rather strange situation. Gun: HK USP 9. The "eat-all". 9mm load, 4.6 grain of Maxam's Optima A (it's one of the 9mm-suitable powders we've got widely available in Spain), OAL 1.130-1.145, crimped at 0.377 (more or less the same as factory ammo). Primer is CCI 500 small pistol. Bullet: bulk coppered 124 grain flat nose. Got to the range, set all stuff up. I previously tried with other loads: 4.2 grain -> 80% jams (not enough force to cycle the action). 4.4 grain, works just fine. No speed reading taken. I've read of some people to use up to 5.2 grain, but I don't know the rest of the parameters. Fired 5 shots of factory ammo (Fiocchi): got the advertised 1100 fps. Fired 5 shots of reloaded ammo: got 1500 fps. No higher recoil, no signs of overpressure. As a matter of fact, the action works normally. Shell casings laid out just by my side. Fired 5 shots of factory ammo again: 1100 fps. Fired another 5 of my own: 1500 fps. No signs of overpressure in spent cases. In fact, some of them have already been realoaded and shot nicely. I told a friend of mine about the situation. He took his Baikal to the range and tried the ammo. They all jammed (not enough force to cycle the action). We used the standard military ammo for contrast. Those were ejected 1.5m high. Any advice on this scenario for probable causes would be much appreciated. Best regards. |
February 28, 2010, 05:05 PM | #2 |
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Some details are necessary. The bullets: you said they were "coppered". There are two kinds of copper colored bullets. One is the conventional jacketed bullet which has a lead core. Often these are open at the base, exposing the lead, or have a cap pressed over the base to cover the lead. The other kind is a copper plated bullet. These are cast or swaged lead that has been electroplated with copper. They are evenly covered with copper all over with no separation lines. They are softer than jacketed bullets and produce lower start pressures and are normally treated like lead bullets for loading purposes.
The gun: Is this a post-1994 HK USP 9? Before 1994 they had standard land and groove rifling. After 1994 they have polygonal rifling which has compatibility problems with lead bullets and might or might not have them with copper plated lead bullets (the second type). The chronograph: How far was the chronograph from the gun muzzle? Readings that exceed normal readings can be caused by muzzle blast effect. The front of the chronograph should be no closer to the gun than about 3 meters to avoid muzzle blast causing false readings. The powder: I am unable to locate any information on the Maxam powders other than that they exist. Do you have a burning rate chart that shows where this powder burning rate places relative to some other powders made by other brands, such as Norma or Vihtavuori Oy? Is it a single-base or a double-base powder? Is it extruded grain, flake-shaped grain, or a spherical grain (either granular or round fine grains)? If the powder is on the slow side of the range for 9 mm and is spherical, it could explain high velocity, but I would expect recoil to be high, too. However, it could also exhibit erratic ignition if it is on the slow side for 9 mm and is used either with too little charge or too light a bullet (it might like 147 grain better). A difference in the throats of your gun and the Baikal could also affect its ignition consistency. Unburned slower powder blown out of the muzzle could pass the bullet and false trigger the stop screen on the chronograph, giving a false high velocity reading. Do you have a lot of muzzle flash with this powder? If the chronograph readings are inconsistent or have a wide spread from one shot to the next (say, more than +/- 25 m/s (or 75 fps) then consider trying a magnum primer (CCI 550) to try to increase ignition consistency. This sometimes works, but also sometimes causes problems in the short case by unseating the bullet too early for the powder. Overall, from the report of untrustworthy chronograph readings, light recoil and recoil that is different in two different guns, it sounds like the powder is too slow for the bullet, and a faster powder should be tried. Without more information it is difficult to tell? Please give the length of the bullet and the overall cartridge length you are loading the rounds to?
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March 1, 2010, 03:17 AM | #3 |
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Respected UncleNick,
First of all, many thanks for your time and for sharing some knowledge with me. The bullets: lead with copper electro-plating, not jacketed. The length of the bullet is 0.533, with an average of 0.175 (+-0.005) in the case. OAL is 1.130-1.145. Crimp is 0.377. The gun: Post-1994, poly rifling. The chronograph: the test distance was obviously too near. Indeed, I firmly believe that this is the source of error. I will prepare new series of tests and do them tomorrow. Afterward, I'll post the results. I'll try and shoot as directed from 3 metres. The powder: I found that the Maxam Optima A is equivalent to the Vihtavuori 3N37, based on data from other shooters. The tests were done in the afternoon, so muzzle flash wasn't fully realized. No unsual muzzle flash though. Max reading spread was about 3% of 1500 over 10 shots, that is 45 fps. Many many thanks once again, sir. Best regards. Last edited by droidw; March 1, 2010 at 11:57 AM. |
March 1, 2010, 11:51 AM | #4 |
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If you have a chrono to close to the muzzle you can read the speed of sound instead of the bullet speed when the muzzle blast shock wave passes over the sensors.
This is more of a problem with sub-sonic loads, but blast can still mess up supersonic bullet readings. |
March 1, 2010, 08:43 PM | #5 |
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Droidw,
I took a look at 3N37 in the 9 mm in QuickLOAD. The program indicates it is too slow for anything except a maximum power load. At 4.4 grains it achieved only 11,700 psi, which is below 9 mm target load pressure levels. From a 4" barrel it predicted 800 fps, and ballistic efficiency was very poor (much of the powder wasted). That would match the experience you had with recoil and functioning. The computer (not to be trusted without careful work up in .2 grain increments) thinks it will need to be at about 5.5 grains of 3N37 just to begin to achieve more reasonable pressures that would be suitable for plated bullets. If your powder is genuinely like 3N37 then you should look at creeping up the load level. 3.8 grains of a powder equivalent to VV N320 would be more typical for the bullets you have. It will burn efficiently and give you the same velocity as the heavier 5.5 grains of 3N37 would. Be careful about the equivalents, though. Powders can fool you as pressure goes up, so 0.2 grains at a step and watching for pressure signs seems prudent.
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March 2, 2010, 04:19 AM | #6 |
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Respected UncleNick,
I'll run the prepared tests this afternoon with the 4.6 grain load, just to obtain the correct bullet speed, and be able to discard "wrong use of chrony". I'll work on that, in addition with all the details you've provided, to see if this is the load I need for target shooting. I'll also post the results. And again, thank you and brickeyee for all that relevant & interesting information. Best regards. |
March 2, 2010, 04:41 PM | #7 |
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Done the tests.
Average speed 900 fps. Adequate for me, my gun and my target shooting level so far. The problem was the distance from the chrony. Thanks for all the data. Best regards. |
March 2, 2010, 06:06 PM | #8 |
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Glad that worked out. Just FYI, for your 4.6 grain load, but using VV 3N37, seated to average of 1.130" COL (from your first post), the 4" barrel prediction on the computer is 893 fps. Pretty close to what you have with Maxam Optima A. The other info is:
16,520 psi peak chamber pressure 3,656 psi muzzle pressure 80.27% powder burned inside the gun 24.0% ballistic efficiency (percent of powder chemical energy converted to kinetic energy in the bullet) So, you are likel still at about half maximum pressure for the gun with the Maxam load, giving you some safety margin. If Maxam makes a faster powder, you can get the same velocity from a lower charge weight. It will produce higher peak pressure but lower muzzle pressure. This will tend to reduce recoil, even though the bullet velocity is unchanged, and save money on powder.
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March 14, 2010, 04:58 PM | #9 |
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Sorry, I was out on a business trip.
Thank you very much once again for all the information. Very best regards. |
March 15, 2010, 05:16 PM | #10 |
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Great to find another Optima-A user
I also use Optima A. It´s one of those flake and fast powders used for both shotgun and handgun cartdriges.
I reload 9mm for a CZ75. For the bullets you mentioned my favorite OAL is 1.09 and I´ve never put more than 4.4 grains. I´ve chroned lead bullets, TC, 122 grains from same manufacturer with just 4.00 grains of Optima A and the result was a consistent 1065 fps (350 m/s) average. I believe your readings. Your pistol is prepared for hot stuff, that´s for sure, but IMHO it´s too much. Maybe a softer spring and a softer charge would be better. Ever tried Optima A with 38 Spcl.? I´d like to start reloading 38 but, as you, the only powder I can regularly find is Optima A. |
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