9mm Accuracy & Velocity

First topic message reminder :

Everything that I've read on this forum indicates that 9mm has to be pushed fast to be accurate.  Why is this when .45 ACP and .38 Special seem to perform fine at much lower velocities?    This doesn't make sense to me.

Well, 147 gr xtp's and 3.9 gr WSF(not WST!) gave me 930 fps.

contemplating how to go lower....

down to 3.5 gr's WSF, 850 fps...

OldMaster65 wrote:I was offered 2800.00 for mine. Turned it down. There were good buys on them even a year ago but they are getting harder to find.

Len


147 gr XTP. Still room to improve.

As I type this there are 6 for sale on GB. not cheap of course.

I sort of lost interest and gave up on the 952 as prices now seem to be more in line with collector pieces.  I'm satisfied for now playing around with the Range Officer in 9mm and just purchased another Pardini SP in .32 ACP for a more serious effort into centerfire.  I would still like to get a 952 but will wait for the right price one to come along.

The one I told you about is/was the best price I have seen. Adds like this one make me feel good about saying "no thanks" but wow..

http://www.gunbroker.com/Auction/ViewItem.aspx?Item=479712494

147 xtp, 3.0 gr WSF, 724 fps......need a spring, lol

OldMaster65 wrote:The one I told you about is/was the best price I have seen. Adds like this one make me feel good about saying "no thanks" but wow..

http://www.gunbroker.com/Auction/ViewItem.aspx?Item=479712494

Wow indeed!  But a pie in the sky ASKING price in my opinion.  I would turn my attention toward a Sig P210 long before reaching that price.

james r chapman wrote:147 xtp, 3.0 gr WSF, 724 fps......need a spring, lol

What platform are using for these bullets?
What kind of groups are you getting?
How low do you expect to get?

BTW  Congrats on the clean PPC 60 shot course!!!!

just in the testing phase for velocity right now. I'm where I wanted to be.

at 724 it stove pipes, so I'm waiting on some other springs n' things before I see if it has viable accuracy. It's a super light recoiling round that's for sure.

beeser wrote:

OldMaster65 wrote:The one I told you about is/was the best price I have seen. Adds like this one make me feel good about saying "no thanks" but wow..

http://www.gunbroker.com/Auction/ViewItem.aspx?Item=479712494

Wow indeed!  But a pie in the sky ASKING price in my opinion.  I would turn my attention toward a Sig P210 long before reaching that price.

MMmyeahhh.... "Collector's Dream" if you're the collector selling at THAT price.

Don't think there is anyone gullible or motivated enough for it to sell at that price for at least 3-6 months if not for years.

Dream on, you collector. In my book that seller's just a greedy, mercenary jerk.

OldMaster65 wrote:... I just ordered some 115gr SWCBB from Penn that I am going to play with and see if I can work up a load for.

Len

Len,
Any updates on the 115 gr. Penn bullets?

Beeser ,
  When they got here I sent some to DrDon. I had a full plate getting the 40 cal (bullets came at same time) working the way I wanted. DrDon is working with his prototype barrel and I was curious how they would work for him. I haven't loaded a single round yet. I did make a seating die insert that wouldn't try to make a round nose out of it and I am ready to go now. Put the dot on the 40 today so should start on the 9's next week. I hope. Maybe..

OldMaster65 wrote:Beeser ,
  When they got here I sent some to DrDon. I had a full plate getting the 40 cal (bullets came at same time) working the way I wanted. DrDon is working with his prototype barrel and I was curious how they would work for him. I haven't loaded a single round yet. I did make a seating die insert that wouldn't try to make a round nose out of it and I am ready to go now. Put the dot on the 40 today so should start on the 9's next week. I hope. Maybe..

Sounds like a full plate.  Let us know when you get around to the 9mm Penns.

Full plate here too.  I will get to the Penn 115's in the 12 twist barrel soon I hope.

Dr.Don wrote:Full plate here too.  I will get to the Penn 115's in the 12 twist barrel soon I hope.

Get to the Penn 115s yet?

Yes, I did finish my tests of the Penn 115's.  They did not do well out of my 12-twist barrel.

Re read this thread. Interesting calculations.
The 38 HBWC weighs 148 gr.. I am not surprised the 115 gr projectile did not fare well..
My 9mm testing was done mostly in 2001.. The light weight projectiles did not do well.. The 147s out of the 1X16 barrels did quite well.. We tried the 32 twist, but the shooters themselves, requested the return to the 16 twist barrels..
Convert the RPMs to Revolutions Per Second, and I think it is easier to envision. And ultimately, how fast is the bullet spinning as it passes thru the target? It's like a AA/F dragster.. The engine only revolves approx 540 revolutions light to light, but it is spinning almost 10,000 rpms light to light.. If the bullet isn't spinning fast enough to be stable, it will not be accurate in terms of ultimate group..

Not only do I not follow you, I am pretty sure that the effect of bullet travel on rate of rotation is so negligible it is practically nil--subject to mathematical calculation but so tiny as to defy in situ measurement.

I still await some more definitive testing and perhaps analysis of this. Similar bullet weights between the HBWC .38s and the (presumably) JHP 9mms, but there are opposite offsets of center of gravity and I suspect also vastly different centers of pressure on the aerodynamics side.  My suspicion since I was a pup and learned the difference between WC and SWC is that it is super-easy to make a generally cylindrical shape gyroscopically stable and a reasonably square front face minimizes any tendencies to hook or slice or whatever you want to call it from merely traveling through the air. Make it pointy and reduce the bearing surface and there arise many more opportunities for shape defects to screw up the bullet's flight, beginning with release from the case and engagement with the throat.

All nice in theory but all my attempts at seating depth adjustments in 9mm (like loading long to get closer to the lands, etc.) have had no reliably measurable effect. So I guess it's time to get a real barrel since 4 different OEM guns have failed to respond to massaging the ammo.

I even tried loading the 115 FMJs lighter, duplicated others' known loads, and still no joy. This latest with a SIG.

Well, how about a football.. A fast spinning pass is far more stable than a slow spinning wobbling pass.  The barrel gurus say the lowest twist that will stablize the projectile is perhaps the best selection, but it is better to err on the side of fast twist..
Don't know what else to say.. I have been spinning them fast for 40 years, and it has always worked in my favor...

Jerry Keefer wrote:Well, how about a football.. A fast spinning pass is far more stable than a slow spinning wobbling pass.  The barrel gurus say the lowest twist that will stablize the projectile is perhaps the best selection, but it is better to err on the side of fast twist..
Don't know what else to say.. I have been spinning them fast for 40 years, and it has always worked in my favor...

Not true according to this ...

Jerry,

I have been contemplating on this and perhaps I can share what I have worked out.  With bullets, break things into two forms of stabilty:dynamic stability, which includes gyroscopic effects, and aerodynamic.

The fact that the bullet gets sent down range pointed the way it does, along with gyroscopic forces from twisting help keep it pointed that way.

However, for aerodynamic stability the center of pressure coming from wind drag and lift must be behind the center of mass. Unfortunately, wadcutters have a very square face with no rounded corners and this causes the air to be turbulent and swirl around the front edges, separating it from the bullet and not permit skin drag from the body of the bullet. This makes the center of pressure being very far forward, so in this respect, they want to turn themselves around. This doesn't happen right away, because of the other gyroscopic forces.

The shorter the bullet (light bullet), the lower the gyroscopic forces, which is what I believe is happening with the light wadcutters poor accuracy that I asked about previously.  I think that there is some faster twist rate where one can get those lighter wadcutters to stabilize, but it seems faster than what has been reported so far, and likely faster than practical

By the way, in keeping with the center of mass being in front of the center of pressure, this seems to me a good explanation of why hollow base wadcutters remain more stable than the solid ones. Also, the gyroscopic reactions increase when you move the mass of the bullets to the outside (HBWC vs. Solid WC). 

I am like you, thinking of the conventional information that says the twist rate should be enough for the bullets you shoot, but excessively more is not always helpful. That twist rate may not be very practical for lightweight wadcutters.

In regards to long vs. short bullets, bearing surface (length) and the jump from the case mouth to the throat and rifling is not included in the above statements. :-)

-Ron 

-Ron

Ron,
I apologize for my comment here before.  It has been removed.  It was not constructive to this topic nor your contribution to it.

Yes, I suppose one can say that it is old school.  I am pretty old school now I guess ( I usually start with paper for my basic problem solving before stuffing it into the computer).  But if you have little or no drag at the back (caused by the subsonic turbulence), there are little or no forces (like what is provided by fins on a rocket or a long, thrown javelin), then wouldn't the very low forces of turbulent drag work against the desired effects?  Oh....and the blunt sharp nosed face of wadcutters is so very dominating in terms of the old-school drag that they appear very dominant in determining the center of pressure.

By the way, I am not saying it is so, but this is what my head has been able to absorb so far.  In other words, I am open to enlightenment!

-Ron

I think I need some Goody's Headache Powder....

james r chapman wrote:I think I need some Goody's Headache Powder....

I agree... some things are a lost cause..