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Joined: 18 Feb 2014 Posts: 30 Location: New Zealand

Greetings from New Zealand. I'd be grateful if anyone could assist with the following problem: I've just had some reloads pressure tested. The pressure was measured in kilograms on a 1/4" dia piston. The pressure readings range from 136 - 174 depending on the load. I've converted to psi with the following formula - 1/4" piston area = 1/20th of a square inch. ( actual 0.98 sq in) Multiply kg reading by 20 and convert the result to lbs by multiplying by 2.2045.

The result is psi readings in the 6 - 7,000 psi range.

In amongst my test loads are some from the Spreadsheets that I expected to fall between 10,000 and 11,000 psi. The velocities for these loads are comparable with those predicted by the Spreadsheets.

So the major anomaly is in the pressure readings. I believe some of the difference may lie in the test being done (I think) to the CIP method rather than SAAMI method. Is there a formula or rule of thumb to convert CIP readings to SAAMI?

Alternatively, does anyone know the 16ga pressure limit for CIP?

Cheers

Richard.

CIP and SAAMI, both use piezoelectric transducers to get their pressure readings. While the transducers are different the outcome from both systems will be nearly identical for all practical purposes.

I am confused by the 1/4" piston??? Was a crusher used? If so you will never get a good and proper conversion.

........here is what I am sure of:

2 3/4" 16 Gauge is listed at 780 BAR maximum average service pressure in the CIP tables.

780 BAR = 11,312 PSI

11,500 PSI is maximum average service pressure for the 16 gauge according to SAAMI

Joined: 18 Feb 2014 Posts: 30 Location: New Zealand

Thanks Mark.

Below are the actual test results. Given the apparent difficulty in correlating the pressure readings to anything familiar I’m only posting them for curiosity value. Don’t anyone go relying on these under any circumstances. A few further / cautionary points to note:

1 The stated powder values are by MEC Bush size – not grains.
2 The Win 540 is just that and not H-6. It is about 20years old.
3 The Green Dot and 800x are much newer.
4 The shot “weights” are MEC bar sizes – not weighed.
5 The bismuth shot is home-dropped by me – 95% bismuth and 5% tin. (Bismuth shot to load is unavailable in NZ).
6 The hulls are all Cheddites.
7 Test loads A-E are 2 ¾”
8 Test load F is 2 ½”.
9 All of the CB wads had the powder cups flared. In addition to this they also had the petals shortened by 50% for the load F 2 ½” loads.
10 All primers are Win 209 and all hulls are Cheddite.
11 The pressure was measured in kilograms on a 1/4" dia piston. Go figure...

Why not just use the right components and data? Because the NZ market for 16g is so small we have to make do with what we can get which is Cheddite cases and CB wads. I did luck into 1500 DR 16s in a private sale (for which I was very grateful) but no retailers import DR wads here let alone in 16g. So I am trying to work out what I can do with what I have at hand.

The reason I am experimenting with the bismuth is because although currently we are blessed with still being able to shoot waterfowl with lead shot in all gauges below 12 (those guys must use non-tox) there is talk of extending the lead ban into the sub gauges and I want to be ready for that if and when it comes. You can't buy it here so I had to source ingot bismuth and tin and make the shot myself, which was a whole other saga.

The idea behind the 2 ½” is that when the 2 ¾ “ hull wears out I can trim it down to 2 ½” and sweat a bit more life out of the case with 7/8oz target load using what I’ve got available here.

As I say, I’m just posting this for curiosity value. You guys have got access to everything you need over there to do it properly without need for this sort of mucking around.

LOAD A

Lead 7/8oz Green Dot 29 Bush DR-16

Velocity / Pressure
1179 / 119
1164 / 122
1190 / 126

LOAD B

Lead 1 1/8 Win 540 23 Bush CB10016

Velocity / Pressure
1199 / 162
1202 / 166
1178 / 167

LOAD C

Bismuth 1 1/8 Win 540 23 Bush CB10016

Velocity / Pressure
1272 / 145
1244 / 135
1265 / 144

LOAD D

Lead 1 1/8 800x 30 Bush CB10016

Velocity / Pressure
1289 / 174
1295 / 183
1286 / 172

LOAD E

Bismuth 1 1/8 800x 30 Bush CB10016

Velocity / Pressure
1356 / 164
1344 / 165
1314 / 156

LOAD F

Lead 7/8 Green Dot 28 Bush CB10016

Velocity / Pressure
1201 / 142
1174 / 131
1187 / 135

LOAD G

Clever Mirage Factory loads – 29gm. Lead

Velocity / Pressure
1147 / 125
1106 / 113
1206 / 121

Regards

Richard.

Richard - from what I can see , you need to weigh those out . Would probably be fairly easy for us to find loads that correlate to what you have and give PSI figures . If using a MEC bar for instance , you'll be 10% lite of what you think you have . Both powder and shot . (unless you are using low antimony shot in which case the bars should be fairly close .)

Richard,

The 1 1/8 oz. load of lead shot using 800-X powder should run, maybe 6,500 to 7,500 psi. I am figuring 20 or so grains of 800-X thrown by the #30 bushing.

Using unaltered MEC bars, the shot drop is between. 1/16 and 1/8 oz. light depending on what size and how much antimony the lead shot has in it.

A similar load using actual weighed charges of shot and powder. 23.0 grains 800-X and 1 1/8 oz. of magnum lead 6's runs 1275 FPS and 8,900 PSI. Using a CCI 209 which is significantly softer acting with 800-X. That load was developed and tested by me and also tested at 2 other labs. We were all within 20 FPS and 500 PSI. So I am very confident of the numbers.

I guess I don't understand the piston, as the transducer is in direct contact with the cartridge using either the SAAMI or CIP systems. Pistons are only used with lead or copper crusher systems.

Looking at the numbers I would say that possibly the conversion is a bit off? Or the system used was a lead crusher. If it was the lead crusher system, the numbers will quite likely be lower than the same loads tested with a piezo electric setup.

In either case the lab that did the testing can probably help you with the conversion.

At any rate nothing that you have done looks like an excessively hot load.

800X should be weighed, it drops poorly rendering dramatic inconsistencies.

Joined: 18 Feb 2014 Posts: 30 Location: New Zealand

Thanks guys.

I was aware that the drops for shot and especially powder would be light based on what I have read here over the years. And obviously the charge of bismuth dispensed from the 1 1/8 charge bar will weigh closer to 1oz.

Byrdog - I have read about the inconsistency of 800x. Are you recommending weighing each load or just periodically?

Mark, your info on the 1 1/8 load using 800x was much appreciated. The load I was trying to replicate was the one in the spreadsheets that calls for 20.5 gr of 800x. Hence the size 30 bush. The velocities I got were slightly slower than the spreadsheet recipe which would be consistent with the bush dropping less powder than indicated in the MEC conversion chart. I had seen the loads calling for a heavier charge of 800x under 1 1/8 of shot but was unsure about them because 20.5gr load states 11,000psi. So I was nervous about the bigger powder charges. From what you say the difference may be in the CCI 209 primer, which I can get here so that is great. Reassuring to know it has been tested a few times as well. Thank you.

The "lab" that undertook my testing is an ex Purdy's gunsmith retired to NZ many years ago who has a pressure gun. He said it was an "old fashioned" pressure gun. Would that indicate the lead crusher system you mentioned? The numbers seem to suggest that I think.

Finally, my velocities were measured at 2.5 feet from the muzzle. Is that standard and if not will they be significantly faster or slower than if they had been done at standard distance?

Thanks for the guidance and info.

Richard.

When chronographing, you try to get the the center of the skyscreens 3' from the muzzle. I still use that idea and it always works. This makes it as close to a 3' instrumental velocity as you can get.

I know what they say about the leading pellets tripping the skyscreens and causing it to read a faster velocity but, hogwash. If you have ever seen a shot charge 3 feet from the muzzle it is basically a solid mass, with no clearly defined 'leading' pellets, at least nothing that is going to give a false reading.

At one time I used a 4' skyscreens spacing and the muzzle was 4' from the center of the skyscreens. The numbers were always good with the reference ammo.

Joined: 08 Feb 2009 Posts: 1310 Location: Western WA

Richard,

Great report your load work. You have also whetted our appetite for details on your bismuth project.

Do tell, sir!

Joined: 08 Feb 2009 Posts: 1310 Location: Western WA

Also, from Doublegunshop.com, here is a reputed direct quote from Birmingham Proof House:

"The reference in the artice to the CIP service pressure of 650 bar and proof pressure of 850 bar is a reference to crushers values; the equivalent transducer values that should be used for comparison with SAAMI transducer values are 740 bar service and 960 bar proof, i.e. 10,730 psi and 13,920 psi."

That's OK as long as you are using the same loads that the Birmingham Proof house uses.

There is no direct correlation between lead crusher and current piezo electric transducer values. Each load will be different.

Please understand that the only piece of SAAMI or CIP information that we the reloader can use is the Maximum Average Pressure values.

All other SAAMI specifications for ammunition only apply to newly manufactured ammunition, not to reloads.

Joined: 18 Feb 2014 Posts: 30 Location: New Zealand

Mark

I have been in touch with the tester. As you suggested, the pressure gun employed used a crusher system. Firing the round causes the piston to crush a specially inserted piece of lead. The reduction in size of the lead is then measured and compared against published tables to give a pressure measurement. Greater pressure = greater crush = higher reading. Apparently lead is used for low pressure work (eg shotguns) and copper for high pressure. There are different tables for each.

The test is apparently "comparative". So if the testing includes a known load with known pressures then everything less than that ought to be fine. It is useful to that extent but accurate direct correlation to SAAMI (or CIP) will not be possible due to differences in the particular lead used, heat on the day, nuances of the test gun and the like.

For anyone interested, I "flared" the powder cups claybuster wads. From reading here I know that practice is not recommended but I wanted to see what would happen in a test scenario. Next time I test I will try some flared and un-flared comparisons to see if there is any measureable difference. Obviously not really an issue for you in the USA with a wider selection of components.

Brewster, I'll give a few details about the bismuth shot making in a separate post on that topic.

Thanks

Richard.

Now that explains your pressure figures.

With the crusher you do not adjust the figure because if the piston diameter. The crushers come with a tarage table. The amount of crush equals lead units of pressure. Not a direct conversion into any system of pressure as in PSI.

There are tarage tables kicking around and if you can find one and know the amount of crush of the lead crushers for each of your loads than you would at least be in the ballpark.