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Discussion Starter · #1 ·
My USP's velocities are always quite low. I failed to make major (170) with a round that makes 175 PF in a buddy's para. I always thought that poly barrels are supposed to be faster. Mine's even a 4.9" threaded.

I was beginning to think there was something wrong with my barrel when i saw this:
.40 S&W Ammunition Performance Data

notice how rounds tested from a USP is slower:

.40 S&W 180 grain CCI/Speer Gold Dot JHP, 2/10/97: SIG P229 3.84" bbl - 982 fps

.40 S&W 180 grain CCI/Speer Gold Dot JHP, 2/4/93: H&K USP 4.25" bbl - 958 fps

.40 S&W 180 grain Remington Golden Saber JHP, 2/4/93: H&K USP 4.25" bbl - 893 fps

.40 S&W 180 grain Remington Golden Saber JHP, 1/24/93: SIG P226 4.4" bbl - 954 fps

is everyone experiencing the same?
 

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I have never bought the crap about a polygonal bore being faster. My Jarvis barrel is just about the same speed as my HK barrel, well within the ES and SD of the rounds so that no conclusion can be made one way or the other. The argument is, polygonal bores offer less resistance ergo they are faster. But if they offer less resistance, they build less pressure, which means they would be slower, not faster. Or I have also heard the argument made that they offer more resistance and higher pressures ergo higher velocity. But if they did that then you would have other problems such as flattened primers, popped primers, excessive slide velocity, short frame life, or other indicators that rounds safe in a standard pistol are unsafe in the HK. Nobody sees this. And looking at your velocities, I notice that there are no SD or ES mentioned AND that the rounds were fired on different days and therefore, likely under different conditions if they were shot outside. In February I have seen temperature swings of over 30 degrees from one day to the next and so not knowing the conditions at the time of shooting makes the data totally meaningless. All that is as important as the average velocity so as far as I am concerned the data is not complete enough to draw ANY conclusions.
From my own personal testing done on the same day under the same conditions using the same ammo from my huge sample of one (which right there makes the data EXTREMELY suspect) if they are faster or slower is in the realm of academia and has little bearing on real world performance one way or the other.
By the way, I have had different barrels by the same make, twist, caliber, and length shooting the same ammunition give very different velocities. Any individual barrel may be slower or faster than any other likewise identical individual barrel; that is why a large sample size is extremely important otherwise the data is anecdotal.
 

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Not that really means anything, as I didn't compare it to my other .40s, but I chrono'ed some ammo out of a .40 Expert and a .40 P30L, and the P30L had higher velocities, despite being shorter.
 

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Stranger things have happened. Ammo is loaded to pressure specs, not velocity, so if your barrel is "a little loose" your velocity will suffer.
 

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Discussion Starter · #7 ·
My chrono readings don't look right at all. I failed in different chronos with loads that pass with friends' para ords. I loaded 1.150" w/ 4.8 N320 and 180 gr. moly and got only 919-920 FPS (targeting 950 fps for 170PF). quickload already calls that overpressure.

Then, i loaded JHPs for carry and worked up my load from the VV N340 start load from their manual. I continued to work up from the max published load of 6.1 gr because the primers were still very healthy and i'm loading to a non standard 1.150" anyway. I got to 7.5 grains before any sign of primer flattening and cratering! i made some 7.2 grain loads and the primers were quite healthy, chronoed them @ 1100 FPS. quickload already places that load at 1290 fps and something like 60000+ psi pressure. im getting 1100 fps and normal primers with a 7.2 load! VV limit is at 6.1, sierra at 6.3 grains!

what is this? Is my barrel leaking or something? in my gun, N320 behaves almost exactly as N340 should!!! heeeeeeelp!!
 

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Although I own a USP .45, I am not a semi-auto person... But did shoot long range pistol & rifle and understand that a slick barrel is in a way slower... In shooting out to 1,000 yds. velocity spread is very important, and it was a known fact that moly coated bullets would have a bit more difference in velocity and were not used that much, also as we handloaded we knew that to obtain the same velocity with the slick moly bullets you had to use a bit more powder due to the reduced pressures from the slick moly.... Could that have something to do with the non conventional rifled barrel of the USP...???
I don't know, but was just throwing another possibility in the mix....lol...
PS-Of course Danzac & other slick coatings would probably work near the same way...
Have a good one...Tater2...
 

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Discussion Starter · #9 ·
I may have an answer to my strange mystery. I'm using quick load 3.2. I noticed that the N350 in the program behaves like N340! and N340 behaves like N320!

in QL3.2, i dialed in VV's published max N340 (6.1gr) for 180 gr bullets, and their test barrel of 5.5", but put "N350" in the powder option instead - and the result was almost the published velocity (within 20 FPS) for N340!!!

then switched the powder to N340, voila! OVER-PRESSURE! this cant be right, considering VV charts are very conservative. with my load's velocity of 1100 fps, using N350 in the program (which behaves like VV published N340) it puts me at 32000 psi. i wish this means im safe :)
 

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Yeah, that is definitely weird. The problem with "puter programs like that is that they are just "guesses" as to what is occuring in your gun. The only way to know what is happening is to run 'em over the chrony and stick to the published maximums. Hope this all sorts out for you.
This! The computers cannot compensate for temperature, elevation, and individual reloading techniques. Powders react differently and some are more sensitive to their surroundings than others. Not to mention for example, powders like Solo 1,000 that can vary so much in speed from batch to batch straight from the manufacturer.
 

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Discussion Starter · #13 ·
i have a new bottle of VV340, it looks yellower, and also seems hotter... the old one is black and acts like n 350. im getting sharp edged primer strikes now, but no flow
 
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