has anyone ever chrono-ed the effect of COL changes from min to max in 9x19

[evtSmtx]

• does the velocity change much
• do you notice any other differences

I follow published load data and don't have a chrono(yet) but was just wondering if anyone ever experimented with that variable

 

[Rule3]

Good question, however there would be a lot of numbers/variables to crunch Pressure will change rapidly in the small 9mm more so with fast powder.

Powder type and then start and max of the powders charges.
Bullet type (lead, FMJ)
Bullet profile
Barrel length

It is so damn hot here I do not even want to hassle setting up my chronograph.

Sounds like a good project for Quick Load to get a theoretical data.

If not, I nominate bds, he likes this stuff

 

[gamestalker]

Nope, but I do know that 9mm is very sensitive to seating depth changes.

In my old Speer #10 they address this to some extent, in which they took a developed load that was producing a confirmed 28,000 cup. They then reduced oal by .030", pressure more than doubled to like 62,000 cup.

That said, if you decide to experiment with oal and 9mm, go slowly.

GS

 

[LiveLife]

It is so damn hot here I do not even want to hassle setting up my chronograph.

Sounds like a good project for Quick Load to get a theoretical data.

If not, I nominate bds, he likes this stuff

Same here. Still hovering 100F

Will gladly set up the chrono once things cool off.

Dudedog could help with chrono testing too but it's still hot in his neck of the valley too.

 

[Walkalong]

That would be a good test to do.

I'll volunteer to do the 9MM with a 124 Gr plated bullet with AA #5. I'll load 7 each at 1.060, 1.050, 1.040, 1.030, and 1.020 OAL.

Anyone else?

 

[jmorris]

I have more than once. Depends on the powder and charge for the most part, the projectile to some what lesser extent.

 

[Ironicaintit]

Anyone else?

Yeah, im down for that.
I'll do 5 each, @ 1.060, 1.050, 1.040, 1.030 and 1.020.....with 115 grain JHP atop 5.8 grains of Unique.

I'll have chrono results by next weekend.

 

[Ironicaintit]

Or maybe I'll have results tomorrow! I already have the 5 each made.

I have to be honest...i dont think I'll even end up firing the 1.020. 5.8 grains is compressed pretty tight. We shall see.

 

[gamestalker]

I'm gearing up to do a bunch of 9mm anyway, so ya, I'll run some 115 gr. JHP's with an oal variance of .030", maybe I'll run a .040" test range also.

I don't know what the starting oal will be yet though, as I don't have the bullets or the firearm yet in hand, both are in route right now. So it will probably be a little while, maybe a couple weeks. But I'm interested to see what hard effect oal produces also, I don't think I've ever run a test like this before.

I'll be using Longshot though, and can probably do some with HS6 as well.

GS

 

[LiveLife]

effect of COL changes from min to max in 9x19 ... notice any other differences

anyone ever experimented with that variable

With 115 gr FMJ and W231/HP-38, start to low charges at 1.169" would not reliably cycle the slides of my Glocks and turned them into single shot or cause stove pipes.

At 1.135" and 4.6 gr, it would start to reliably cycle and extract/eject spent cases. At 4.8 gr, it produced greater accuracy.

 

[Duvel]

Interesting.

Using QL 3.8, 115gr GD / 4" barrel.

Unique 5.8gr

1.160 29.2K - 1,215fps
1.150 30.3K - 1,225
1.140 31.4K - 1,236
1.130 32.6K - 1,247
1.120 33.9K - 1,258


HS-6 7.2gr

1.160 29.4K - 1,203
1.150 30.6K - 1,215
1.140 32.0K - 1,228
1.130 33.4K - 1,241
1.120 35.0K - 1,254

Given a starting pressure of just under 30K and an AOL of 1.160, of the handful of powders I ran this simulation on, none exceeded Pmax when AOL was reduced to 1.120.

Keenly aware of the 9s sensitivity, I would have thought reducing cartridge length by 0.04 would have raised the pressure by more than 5K.

 

[Dudedog]

I will try to get some loaded up and do some tests next weekend.
I don't want to go real short but I will run a range with the RMR 124 FNs and a couple powders.
I have been loading them to 1.10 since that fits and functions well in all my 9mm pistols.
I will see about maybe going down to 1.02 with them.

Thanks in advance to everyone else helping with this test.
It should be interesting.

 

[Walkalong]

Depends on the powder and charge for the most part,

I assumed that, so someone needs to do this with a fast for 9MM powder as well. I guess I could also do it with my 124 Gr N320 load.

 

[Walkalong]

Keenly aware of the 9s sensitivity, I would have thought reducing cartridge length by 0.04 would have raised the pressure by more than 5K.

Me too. How about running the numbers with a fast/er powder?

 

[Blue68f100]

Try using a faster burn powder like TG, it has blowup more guns than any other powder I know of recently. Try running it, it's a very moody powder.

I think you will find that fast burn powders are the ones that get spiky at the upper end. Slow burn powders do more of push than a snappy feel.

 

[Ironicaintit]

Interesting.

Using QL 3.8, 115gr GD / 4" barrel.

Unique 5.8gr

1.160 29.2K - 1,215fps
1.150 30.3K - 1,225
1.140 31.4K - 1,236
1.130 32.6K - 1,247
1.120 33.9K - 1,258

I just noticed that you ran the data using lengths of 1.120, up to 1.160.
The ones I loaded are 1.060 down to 1.020.

Could you do me a huge favor and run it again for my curiosity's sake?

 

[ArchAngelCD]

This is a very good thread. I'm going to follow it. Thanks for the work guys. If I get a chance to load some 9mms I will give Longshot a try since no one mentioned that yet. (No promises though)

 

[JDGray]

Powder position in the case makes a huge difference, way more then oal.

 

[9mmepiphany]

Powder position in the case makes a huge difference, way more then oal.

I never thought there was enough room in this case to make much difference. Granted, I use pretty fluffy powders...I can't even get an intentional double charge without overflowing the case

What has been your experience with 9x19mm cases in this regard?

 

[Duvel]

Bullseye was the fastest simulated initially.


Tite Group 4.6gr charge (115 GD / 4")

1.160 29.7K - 1,112fps
1.150 30.6K - 1,119
1.140 31.7K - 1,126
1.130 32.8K - 1,134
1.120 34.0K - 1,142

Running these models last night I didn't really process the OAL in relation to the bullet - 1.160 is long for a conventional 115gr (I used Speer's GD for the model, but have never loaded it) - At 1.160 a GD is only seated .138".

In perspective, I load Montana Gold's JHP as short as 1.096, and as long as 1.133.

Working a 95gr load up recently the model showed pretty significant pressure differences changing the OAL from 1.040 to 1.055. I suspect when the case volume starts to get pinched pressure swings are greater with AOL changes.

Regarding the comment on powder position: This is something I haven't read regarding the 9mm, only larger case cartridges using a less than 'near case capacity' charge.

 

[Duvel]

5.8gr of Unique with a OAL (Speer GD) of 1.060?

Pressure at that AOL is 45K, 10K over Pmax (MAP).

 

[Duvel]

NUTS! Must have been tired last night! After I made my comment about 1.160 being 'long' for a 115 I noticed a start OAL of 1.060 being suggested!

I'll run #s with the corrected AOL later this afternoon.

 

[murf]

can y'all include bullet length so we can figure out internal case volume? i'll volunteer on the second goaround. thanks in advance for doing this.

murf

 

[Rule3]

Good question, however there would be a lot of numbers/variables to crunch Pressure will change rapidly in the small 9mm more so with fast powder.

Powder type and then start and max of the powders charges.
Bullet type (lead, FMJ)
Bullet profile
Barrel length

I am going to quote my previous post.

The variables on doing this are extreme. Within each powder there is not only the powder charge but the actual shape and weight of many bullets. The COL is not always going to be the same measurement as the change in seating depth. It depends on how the weight of the bullet is distributed, So the interior case volume is the key.

So many many bullets would need to be tested with the same powder charge, keeping the internal case volume the same.

It is also going to vary a lot with the burn rate of every powder. Decrease the interior volume of a say BE VS that of Unique (different powder structure also and how is the pressure going to be effected?? Pressure is the real issue not velocity and FPS is not in direct proportion to pressure depending on the bullet used. Yes, generally velocity goes up with more pressure but it depends on the powder and the bullet composition.

A LSWC vs a FMJ RN, a 115 vs a 147 gr etc etc,????



As I mentioned there are so many variables.

 

[Walkalong]

Powder position in the case makes a huge difference, way more then oal.

I agree with this when there is a good bit of extra space in the case. I test revolver rounds powder forward all the time, and sometimes the velocity difference is quite big.

9MM with powders that fill the case well didn't seem to be to bad about it, but I haven't checked many.