Pressure signs?

[smokshwn]

I have just recently started to shoot and load for Major 9 and I have been spending a lot of time reading and learning all I can. The one question I have for you guys is will everyone please post what they think are pressure signs as they relate to an open 9mm. So far some of the descriptions seem very subjective. I would appreciate a little objective guidance, maybe even some pics.

Thanx alot, Craig

[Alan Meek]

Craig,

Unfortunately this is a difficult area at best in reloading. There are numerous scools of thought as to what to look for in determing excessive pressure. The typical area that everyone looks at is the primer itself while it does provide some indication of pressure it is not the absolute indicator. When looking at the primer some people look at the firing pin mark to see if there is any cratering/primer flow back into the the firing pin hole. This should always be suspect as if the firing pin hole is out of spec there can be primer flow with a SAAMI spec load. Flattening of the primer is another item people look for. This can be observed by looking at the firing pin mark and if there is no indentation this can be a sign of excessive pressure. Another area to look at on the primer is the the edge, if the edge of the primer is no longer rounded but has flattened out this is another sign of pressure. But now with all of that if your headspace is out of spec you can see some of the same symptoms.

I would recommend that you start with some new ammo from your favorite manuf. Fire a few rounds and keep the brass. Here is a baseline of what should be within spec out of your gun. Then as you work up a load you can compare the major 9 fired cases to the baseline and make your decisions as you progress in loads.

Now if you really want to know the pressure that your loads have Western Powders offers a test lab service. I have not looked into that as of yet but I am considering it. I don't know if they will even test a major 9 load.

Hope that helps.

Alan

[Carlos]

Alan wrote: "Now if you really want to know the pressure that your loads have Western Powders offers a test lab service. I have not looked into that as of yet but I am considering it. I don't know if they will even test a major 9 load."

As far as I know, having a lab do a pressure test on a batch of ammo is the last word in determining the actual pressure generated by a given load. Accurate, to be sure (labs use the same methods that the component and ammunition manufaturers use) but it is costly and it takes a while. I thought there was a lab conducting pressure tests as close to home as MD? Please do a Google search on something like: ammolab.com

I have heard of at least two other methods (besides visual primer evaluation):

1) internal ballistics software and

2) "pressure ring" evaluation of fired brass

The former involved plugging known variables into a program for a PREDICTION of the pressure that will be generated; I understand that while the programs are fairly accurate, the only way to be certain is to actually test a load in actual conditions

I will leave a description of the later to others. I have not tried it & cannot vouch for its supposed accuracy.

D.

[smokshwn]

Alan

Thanx, that is exactly what I was looking for. Between flat, primers, primer flow, cratering, headspace questions, I was very much looking for a place to start. The factory ammo plan sounds pretty solid.

Take care, Craig

BTW I will post Power Pistol Data sometime this week if I can get a good Chrono day.

[GvU]

Careful (case)headspace may cloud matters as well!

Last monday chrono-ed some 38 super loads with 3N38 (standard Winch. SP primers). Had some badly flattened primers with AP marked cases. Same load (same gun) with 9x23 cases was ok. Other cases (various brands and 'age') were ok. (PF about 172 from 5,5" barrel)

At home I measured case lenthgs. THe AP cases were abut .02" shorter. Headspace is probably on case mouth (haven't looked yet).

Primer type can have a big influence also. Mild fed100 may measure cup-thickness of .008" and heavy cci450 (riflemagn.) something like .023".

DVC, John

[Newguy]

Although I agree with Alan about comparing the round to factory ammo, you may be disappointed. 9 loaded to major will flatten out the primer much more than factory ammo. The amount of flattening that's acceptable is the question. I generally look at the outer rim of the primer hole to see if there's still some curvature left. But, I guess everyone has their own method and their own tolerance for risk.

[JFlowers]

Southwest Products makes a product called Pressure Trace. This uses a glued on strain guage to measure chamber pressure. A friend and I have been testing this using a number of rifles and the results have matched expectations.

The problem with this and a 1911-based firearm is there is no good way to glue the strain guage to the chamber as the slide of the firearm is in the way.

[Patrick Sweeney]

The strain gauge method is useful, but to do it properly you have to have a dedicated T/C setup, and have the chamber of the T/C reamed with the same reamer used on your 9mm Major competition gun. And you have to have a standard load that has been pressure-tested by a laboratory, as your base to extrapolate new pressures.

At the extreme margins of pressure, minor differences between chamber dimensions can create or simulate pressure signs.

One method rifle shooters use to estimate pressure is to measure the pressure ring at the base of the brass. Start with factory ammo, measure, fire, measure. then re-size the same case, load, measure, fire and measure. If you have the same amount of expansion in both firings, you have similar pressure. Problems? Brass may not expand in a linear fashion. You could find that each (for example) 5% of pressure increase causes much less than 5% brass expansion until you get to a certain pressure, and then the next 5% gets you 25% brass flow.

In this case, what good is measuring the brass expansion of factory ammo with a pressure ceiling of 34K, when to make Major you have to be running (by one estimate) 42K? The non-linear brass expansion problem means you cannot extrapolate the level of the extra pressure.

[Alan Meek]

Patrick,

To establish your baseline, Western powders offers a pressure test for ~$60. If you purchesed a specific lot of factory ammo to use as your control set and sent them the required ammo (I think it is 15rds) you would have a base line of pressure that you could then perform the initial test with this would then allow you to extropolat all subsequent tests and the reaminder of that initial lot would be your control set. While the system if not perfect you could maintain a consistency by establishing a process and following that process.

Alan

[Patrick Sweeney]

Exactly. Send off factory ammo, which you purchase a carton of, all the same lot.

Then fire pressure-tested factory ammo in your T/C 9mm barrel with strain gauge, to establish what a (pressure-test reading) pressure level looks like.

Better yet, do this with two or three factory loads, hopefully at different pressures, so you know what scale your strain gauge is operating at, to extrapolate to greater pressure.

Then load and test in T/C with strain gauge. Keep in mind statistical deviation and unavoidable spread of velocitites and pressures, when developing a Major 9 load.

And remember that all data must be re-verified if you change anything: brass lot, powder lot, primer lot, bullet lot. The next batch of anything from anyone may be enough different to put you in trouble.

All for the advantage of cheap brass. Seems like a lot of work (albeit interesting work) for a small cost savings.

[shred]

Maybe there's a market for a pro-sumer grade 1911 barrel fixture that you could slap your barrel into, attach strain gauges (or 50-yard test-targets) and fire away.

[MoNsTeR]

...small cost savings.

In lost brass country, it's a big cost savings!

[rhyrlik]

I measure case head expansion with a dial caliper referencing where the extractor groove starts. In 9mm Luger, standard loads expand to .389-.390". +P+ loads expand to .392". Some of the 9mm major loads expand to .394-.396". They are probably pushing 50K PSI.

Be Careful! I still have all 10 fingers.

[George]

Craig,

I have been running Major 9 in a modified Glock 17L for almost 2 years now. I use 9x21 cases because that is what my Barsto bbl is chambered for. The Starline 9x21 brass I use is no great shakes on the +p+ curve (seems to emulate WW 9x19 in hardness and construction robustness).

I have been relying on base gauging (like rhyrlik), primer consideration (flatness, flow, how well breechface toolmarks are left, or not left impressed in the primer) and careful brass inspection. I do initial pressure testing with new brass that has been sized and checked for spec. This gives me a good look at the brass without any previous wear marks and stretch cycles in other chambers to cloud up the picture.

I was pretty careful during my workup because I am loading short for Glock mag limits. I am running a 124 JHP at 1370-1380fps for 170ish PF. OAL is at present 1.134” (!!!). I am using FSP-100 primers and have no excessive flow signs. My guess is that I am running in excess of 52k on pressure. Probably right around where folks running 115’s in soupers are hanging out pressurewise.

Got about 6-7k on this system in two years (shoot more rifle than pistol lately) and it has not blown a gasket (yet).

Here is my read on 9Major safety. If your bbl has a fully supportive chamber, is known good in headspace and case fit, I would venture a guess (not a solid judgement) that most any 9x19 load using longer OAL (1.185, or better) in an S*I platform and at least a 124gr projectile is going to be well within the Major load safety range that we accept on a daily basis and sometimes even brag about

As always, work it up slow and keep three eyes peeled for problems.

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Happy Holidays,