Load adjustment safety question...

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kculbert2
Posts: 18
Joined: Sat Jul 31, 2021 8:43 am

Load adjustment safety question...

Postby kculbert2 » Mon Nov 01, 2021 11:52 am

Full safety disclosure: I know that the best way to ensure a load is safe is to have it professionally tested.

That being said...

Here is what I am pondering. When considering adjusting published loads, so long as I use the same powder charge and shot weight in the same size hull, regardless of how I achieve this, shouldn't my pressures and speed be the same, or relatively close?

For instance, let's say a tested duplex load calls for 1/2 oz tss and 1/2 oz steel, but I want a bit more tss. If I were to increase the tss to 5/8 oz and decrease the steel to 3/8 oz, and use spacers to make up the difference in the wad/shot cup to ensure a proper crimp, would my pressures and speed be relatively similar to the original, tested load data? Is an oz an oz, regardless of how you get there? Or am I going to lose a hand when I test these shells?

Prior to tss, I have only loaded steel, so duplexing is new to me. Any advice based upon real experience would be appreciated!



paulinkansas
Posts: 178
Joined: Fri Mar 11, 2016 11:28 am

Re: Load adjustment safety question...

Postby paulinkansas » Mon Nov 01, 2021 2:22 pm

Your logic is the same as mine. I'm typing this message with 10 fingers while looking at the screen with 2 eyes. I use published loads with pressures around 9,000 to 10,500. But I use a 3.5" gun.



kculbert2
Posts: 18
Joined: Sat Jul 31, 2021 8:43 am

Re: Load adjustment safety question...

Postby kculbert2 » Tue Nov 02, 2021 7:43 am

paulinkansas wrote:Your logic is the same as mine. I'm typing this message with 10 fingers while looking at the screen with 2 eyes. I use published loads with pressures around 9,000 to 10,500. But I use a 3.5" gun.



So, you're saying you load 3.5" hulls with published, 3" loads? Just eat up extra space with fillers?



paulinkansas
Posts: 178
Joined: Fri Mar 11, 2016 11:28 am

Re: Load adjustment safety question...

Postby paulinkansas » Tue Nov 02, 2021 1:24 pm

kculbert2 wrote:
paulinkansas wrote:Your logic is the same as mine. I'm typing this message with 10 fingers while looking at the screen with 2 eyes. I use published loads with pressures around 9,000 to 10,500. But I use a 3.5" gun.



So, you're saying you load 3.5" hulls with published, 3" loads? Just eat up extra space with fillers?


No, I load 3" hulls with 3" hull recipes and shoot them out of a 3.5" gun.



kculbert2
Posts: 18
Joined: Sat Jul 31, 2021 8:43 am

Re: Load adjustment safety question...

Postby kculbert2 » Tue Nov 02, 2021 7:56 pm

paulinkansas wrote:
kculbert2 wrote:
paulinkansas wrote:Your logic is the same as mine. I'm typing this message with 10 fingers while looking at the screen with 2 eyes. I use published loads with pressures around 9,000 to 10,500. But I use a 3.5" gun.



So, you're saying you load 3.5" hulls with published, 3" loads? Just eat up extra space with fillers?


No, I load 3" hulls with 3" hull recipes and shoot them out of a 3.5" gun.

Well, a 3.5" gun should be able to shoot 2 3/4, 3, or 3.5 inch shells. I'm talking about altering published loads by switching "ingredients" and wondering if they're still safe to shoot so long as the powder charge and shot weight is the same.



patternfreak
Posts: 41
Joined: Sun May 02, 2021 6:31 pm

Re: Load adjustment safety question...

Postby patternfreak » Wed Nov 03, 2021 11:57 am

The only thing your line of thinking isn't considering is shot column height. That has a huge affect on your overall pressure. Usually as you shorten the shot column and add spacers the pressure will go down. Usually!

Your pressure and speed will most likely be nowhere close to the published load. You will need more powder to get you there if you are shortening the shot column. How much more you ask? Well the only way to know is to pay the $25 and have them tested. Cheap, cheap, cheap insurance!



kculbert2
Posts: 18
Joined: Sat Jul 31, 2021 8:43 am

Re: Load adjustment safety question...

Postby kculbert2 » Thu Nov 04, 2021 6:01 am

patternfreak wrote:The only thing your line of thinking isn't considering is shot column height. That has a huge affect on your overall pressure. Usually as you shorten the shot column and add spacers the pressure will go down. Usually!

Your pressure and speed will most likely be nowhere close to the published load. You will need more powder to get you there if you are shortening the shot column. How much more you ask? Well the only way to know is to pay the $25 and have them tested. Cheap, cheap, cheap insurance!


Cheaper than replacing a shotgun barrel, you say? Haha. I think i will test it over the chrony, and if the speed is lower, just start increasing the powder charge one grain at a time until it comes back to where i want it. Then i'll send the load to be tested.



patternfreak
Posts: 41
Joined: Sun May 02, 2021 6:31 pm

Re: Load adjustment safety question...

Postby patternfreak » Thu Nov 04, 2021 9:18 am

I don't think the velocities will give you much of an indication of where your pressure is at. For example, when I was developing my 137/164 tss/steel duplex in 28 ga I was at 1447 FPS, 10,090 PSI with 26 grains of powder. I had around 2400 psi until I was at max pressure, so I figured I could add a little steel to lengthen the column and give some extra pellets. I added 26 GRAINS of shot, so the blend was 137/190. This required me to remove 1/8" of filler from the shot column. At the same powder charge my pressure went from 10,090 to 13,188 PSI and velocity stayed close to the same at 1436 PSI.

I realize you aren't trying to add any weight, but changing the length of the shot column is a variable that affects your pressure and can't be directly solved by velocity measurement.



continental shooter
Posts: 40
Joined: Mon Aug 19, 2019 5:03 am
Location: Edinburgh

Re: Load adjustment safety question...

Postby continental shooter » Thu Nov 11, 2021 3:35 pm

hey

I'm assuming you want to change the wad then because otehrwise you'd be having the published load LOL

if that's the case then mind that wad tickness and seal also affect pressure



derbyacresbob
Posts: 69
Joined: Fri May 27, 2016 9:29 pm

Re: Load adjustment safety question...

Postby derbyacresbob » Thu Nov 18, 2021 12:04 pm

Adding soft cork, felt or fiber filler wads under the shot lowers the pressure way more than I ever thought it would.

I took some Federal Heavyweight 3-1/2" 1-7/8 oz Turkey loads and removed the shot from them. Then I put 3/4" of cork and fiber wads under 1-7/8 oz of TSS shot on top of the soft filler wads. So these loads had a much shorter TSS shot column that was the same weight as the factory 15g/cc 1-7/8 oz load.

I sent these load off to precision reloading to have them tested and I was shocked at the results I got back. 2 of the loads had pressure just over 1,000 psi the other 4 shells were all below 4,000 psi.

It looked to me like all the soft filler wads under the shot collapsed not letting the pressure build up. Also the shot column was shorter so that also lowered the resistance and lowered the pressure.

I ended up having to add 1/4 oz more TSS shot to make it a 2-1/8 oz load and only used one 1/4" cork wad under the shot to get the pressure up to then 10,000 psi range.




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