9mm major load free space

[garp]

Some help with understanding pressure.

 

Question,

How much does free space, the space between the powder and the bottom of the bullet, help, if any, in keeping peak pressure down on a 9mm major load. 

 

Example:  I use Berrys 124 round nose. OAL is 1.165. If I use Berrys 124 flat point and load to the same OAL of 1.165, and assuming powder charge, accuracy, stay the same, I gain about .070 inches (2 mil) of space from top of powder to bottom of bullet. 

 

Will,  the peak pressure be lowered significantly?

         the peak pressure be lowered some?

          peak pressure even change?

 

Thanks for any help,

 

[kneelingatlas]

What free space?!?

 

[RiggerJJ]

I have a bit more space with hs6...

 

Not really sure it makes much difference, as the shell is usually in a horizontal position while it's in the mag, plus the powder is sloshing around during recoil...

jj

[garp]

The free space I have when using 6.7 Auto-comp. Makes 170 PF on my crono out of CZ TS Cezechmate. OAL is 1.165/1.169 with round nose. Using the same OAL I still have plenty of round to crimp, therefor creating more space between top of powder and bottom of bullet. The question still stands as if there a pressure reduction.

 

[superdude]

As noted, when bullets are seated to the same overall length, shorter bullets will not extend into the case as far. Generally, this reduces pressure.  This applies even if the powder is compressed in both instances. 

 

I don't know if anyone has done a test of the "free space" hypothesis - that is if free space matters more than compressed in both instances.

 

0.070" will have an affect on pressure. It probably varies with different gunpowders.

[garp]

Thanks superdude. I didnt know what to call it so I used "free space." Maybe should of said "extra space."

 

[kneelingatlas]

I've been compressing powder in my 9 major loads for five years and here are my observations:  the shorter the OAL, the higher the pressure, the faster the powder, the higher the pressure, the heavier the bullet, the higher the pressure; each combination of components and length has a peak pressure after which more powder results in less velocity and I've found if you hit this point, then lengthen the round, you can push the velocity a little higher with a heavier charge.

[Banacek]

3 minutes ago, kneelingatlas said:

I've been compressing powder in my 9 major loads for five years and here are my observations:  the shorter the OAL, the higher the pressure, the faster the powder, the higher the pressure, the heavier the bullet, the higher the pressure; each combination of components and length has a peak pressure after which more powder results in less velocity and I've found if you hit this point, then lengthen the round, you can push the velocity a little higher with a heavier charge.

And what is your load of choice?

[Hi-Power Jack]

10 hours ago, garp said:

The free space I have when using 6.7 Auto-comp. Makes 170 PF 

 

 

I switched from HS6 to WAC for the same reason - have more "free space", since I didn't like

trying to cram the 124 gr MG JHP into the case with 8 gr HS6.  Plus, it tends to spill out onto

the reloading press shellplate.

 

Must be less pressure with more "free space" but 9mm Major loads are way over spec anyway.

 

Any of the powders we typically use for 9mm Major, with the 115 - 124 gr jacketed bullets we use,

are all "safe" in a gun designed to shoot 9mm Major.

 

I haven't heard that life expectancy of a STI 9mm Major depends on the "free space" - still should

be good for 50 -100,000 rounds, even though some parts will have to be replaced.

 

There is a technical, mathematical answer to your question, but I've never seen one published,

and it doesn't seem to have any discernible effect on safety or longevity of equipment.

 

You (and I ) have sensibly, in my opinion, selected the powder that increases our safety margin,

but others on BE are pushing the limits with compressed loads, to no apparent disadvantage.    

[9146gt]

Send your ammo here to have it pressure tested.

 

http://www.hpwhite.com/

 

Tom

[racer-x]

The "free space" between a resting powder charge and the bullet is irrelevant.to pressure in this application ( 9 major load).

This is controlled by the density of the powder. Besides our selection of powder , this is completely outside our control within the confines of a specific cartridge and PF goal - like 9 major.

 

The most significant part of this equation is the case volume the charge is left to work in after a bullet is seated. 

 

I general reloading, finding & using a load that fills most or all of the case is a good thing. 

- reduces any chance of a 'double charge' where you in error dump more than 1 charge into case and don't notice - kaboom.

- increases consistency of velocity / pressure since the charge can't be laying down irregular in the case when in the normal horizontal shooting position.   

* when shooting less dense powder charges in larger volume cases like 40 & 45, you frequently would see folks pointing the gun up first at a chrono stage moving powder to rear of case (when allowed) to get most velocity to make PF.

[kneelingatlas]

9 hours ago, Banacek said:

And what is your load of choice?

 

9.4gr of SP2 under a 115 @ 1.161"

 

SP2 is a French powder, made by Vectan, not currently imported to the US, but it's the best available for 9 major; 3N38 has the exact same burn characteristics but is not as dense, so it fills the case even higher.  Interesting enough, this load is exceptionally compressed and is also listed in the Vihtavouri reloading guide under 9X21, a fact which leads me to believe Jack's assumption that there:

 

31 minutes ago, Hi-Power Jack said:

Must be less pressure with more "free space" but 9mm Major loads are way over spec anyway.

 

is not based on any empirical evidence 

 

31 minutes ago, Hi-Power Jack said:

You (and I ) have sensibly, in my opinion, selected the powder that increases our safety margin,

but others on BE are pushing the limits with compressed loads, to no apparent disadvantage.    

 

Since I am one of those members "pushing the limits" I might add, the max published load for the combination I mentioned above (115gr bullets and 3N38) makes a power factor of 171, whereas the max published load for 124s and Autocomp (Jack's "sensible load") is 139 PF (5.4gr under a 124 @ 1.150).

 

I have not tested my loads in a laboratory, but I look at the flatness of primers as an indicator of pressure and I have found heavier charge of compressed slower powders to result in less flattened primers than those from lighter charges of faster powders.

 

Jack, you're a great contributor to the forum, but I wish you would stop spreading irrational fear of "compressed loads" absent of any real evidence  

Edited February 20, 2018 by kneelingatlas

[racer-x]

11 hours ago, kneelingatlas said:

I've been compressing powder in my 9 major loads for five years and here are my observations:  the shorter the OAL, the higher the pressure, the faster the powder, the higher the pressure, the heavier the bullet, the higher the pressure; each combination of components and length has a peak pressure after which more powder results in less velocity and I've found if you hit this point, then lengthen the round, you can push the velocity a little higher with a heavier charge.

+1 

This mirrors my experience exactly.

[Hi-Power Jack]

2 hours ago, kneelingatlas said:

 

Jack,  I wish you would stop  spreading irrational fear  of "compressed loads" absent of any real evidence  

 

I'm not trying to spread any kind of fear (rational or irrational) of 'compressed loads'.

 

I think it's pretty obvious from all the shooting that's been done by thousands of 9mm Major shooters

over the past decade, that although most of our loads (compressed or not) are NOT listed in any

reloading texts, there doesn't seem to be any problems  in the right gun.

 

I'm not afraid of compressed loads, just don't like them because the powder tends to spill on

my reloader (SDB) and harder for me to keep the bullet in the case with all that powder.

 

No danger, just preference, for a little open space between the powder and the bullet.     

 

 

[Balakay]

2 hours ago, kneelingatlas said:

 

9.4gr of SP2 under a 115 @ 1.161"

 

SP2 is a French powder, made by Vectan, not currently imported to the US, but it's the best available for 9 major

Not trying to sidetrack the thread but where/how are you getting SP2??

[EEH]

Jack,, just go slooow..

I bought those little rubber washers to put on the locator pins,really helped powder spills.

reloading innovations I think is th name of the company.. I started with Hs-6 and like it still use it..

[zzt]

garp, there will be less pressure and also lower velocity.  Here is an example.

 

My Major 40 load using 7.2gr Silhouette or WAC under a 155gr bullet loaded to 1.126" makes 172PF out of my CZ TS and 171PF out of my 2011.  If I load to 1.180" for my 2011, that same load drops to 164PF.  Neither is a compressed load.

[kneelingatlas]

2 hours ago, Hi-Power Jack said:

most of our loads (compressed or not) are NOT listed in any reloading texts

 

Mine is

 

[kneelingatlas]

2 hours ago, Balakay said:

Not trying to sidetrack the thread but where/how are you getting SP2??

 

I cut the horns off unicorns and grind them in my mortar and pestle

 

In 2013 I paid a king's ransom to another forum member for his mother load.

[Furrly]

35 minutes ago, kneelingatlas said:

 

I cut the horns off unicorns and grind them in my mortar and pestle

 

In 2013 I paid a king's ransom to another forum member for his mother load.

if you can find a way to get more I will take some off your hands ...

[kneelingatlas]

I sent emails to the stores importing Vectan powder asking them for SP2 a and I never heard back.

[Hi-Power Jack]

4 hours ago, EEH said:

Jack,, just go slooow..

I bought rubber washers to put on the locator pins, really helped powder spills.

 

Yeah, I started with HS6 also, but with 115 gr bullets (very nice load, but dirty).

 

When I switched to WAC and 124 gr bullets, I really liked the ease of reloading,

and found that my scores (depressing that they were) did not get worse by having

an "inferior" load -

 

seems like using SP2 or 3N38 wasn't going to make me shoot

much better    .  I'd still be a B.

 

But, I'll take your advice and get some rubber washers - thanks for the tip.

 

Jack

[Hi-Power Jack]

3 hours ago, kneelingatlas said:

 

Mine is

 

Congrats.   

 

I don't doubt the superiority of your load.    

 

I guess WAC/124 gr bullets is probably as bad as it gets, since no one

is using 147's any more.  

 

But, the small advantage of 3N38 isn't going to get me to A, I can tell ....    

 

I have much worse problems holding me back.    

 

But, if I were much younger, and could force myself to dryfire (I can't),

and I could afford to shoot 15,000 rounds/year and spend 3-4 days/week

shooting, and start attending Large Matches again, I would not only

admit to the superiority of 3N38, I would probably even give it a try     

 

Meanwhile, I shall continue to recommend 3N38 to serious shooters,

and continue to plod along with WAC.    

[zzt]

Well, I just ordered 8 lbs of 3N38, so we'll see if it's any better than the Silhouette (current fav), WAC and HS-6 I currently use.  

 

BTW, the vast majority of 9mm Open shooters at Nationals used 124gr bullets.

[kneelingatlas]

Oh Jack, you're all over the place

I'm not arguing my preferred combination is objectively better/flatter/softer than yours, you said compressed loads result in higher pressure than those with "free space" and I showed why I believe your reasoning is flawed, that's all.