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Discussion Starter · #1 ·
In selecting a powder to start reloading with, I'm wondering if there is a way to predict which load will be likely to reliably cycle my semi-auto. Yes, the required load varies with the model of gun, and from one gun to another within a particular model, so I just have to make some shells with a recipe and see. But is there a way to guesstimate?
Does the pressure developed by the recipe predict cycling success?​
Does the velocity developed predict success?​
Is it all higher math, i.e. E=1/2mv2 and F=ma?
 

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As a general rule -

More gas = more reliability in a gas-action automatic.

More powder generates more gas.

Higher velocity loads are generally loaded with more powder.

Higher charge weights generally require more powder.

Slower powders generally use more powder to achieve a given velocity.

More powder generates more gas.

Shoot wet with BreakFreeCLP.
 

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In selecting a powder to start reloading with, I'm wondering if there is a way to predict which load will be likely to reliably cycle my semi-auto. Yes, the required load varies with the model of gun, and from one gun to another within a particular model, so I just have to make some shells with a recipe and see. But is there a way to guesstimate?
Does the pressure developed by the recipe predict cycling success?​
Does the velocity developed predict success?​
Is it all higher math, i.e. E=1/2mv2 and F=ma?
I wouldn’t call it “predict cycling success”. I’ve always followed the following: If you stay over 9,000psi in a 12 gauge, and over 10,000psi in 20 gauge, you should be looking at 100% cycling success. Make and models and gas vs inertia, etc, will all differ a little bit. But if you’re looking at recipes. Those are the sweet spots to stay around for semi autos. If you give more info on what you’re shooting, we can give you a better idea.
 

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Discussion Starter · #10 ·
Thanks for the replies. I hadn't thought about gas v recoil. Mine is a gas semi auto that has cycled all the 1 oz factory loads I've tried (haven't tried white box Winchesters).

Many of the recipes I've been looking at have been 1 oz. at 1180-1200 fps and the pressures are often in the 7800-8800 psi range, so this info is very helpful. I may need to step up one speed notch. Using ExtraLite would be one way to get the pressure without increasing speed.
 

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It’s not the pressure for a gas gun it’s the volume of gas. A little more powder gives a little more gas. Pressure is important to get a clean burn.
 

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Yes sir! That’s what I load for my brother in 12 gauge. Claybuster 1100 (1oz) and a little over 16 grains, good pressure, good cycling and although I don’t clean his gun, he tells me it’s not very dirty after a few rounds of sporting clays. I think you’re on the right track if you want 1 oz loads in extra lite.
 

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Pressure transducers. Strain gauges.
Would you mind doing this test and reporting back to us? After all, we all have a piezo transducer with volt meter and amplifier and strain gages with a wheatstone bridge just lying around. As I am sure you do also.

Mine happens to be out of order at the moment.
 

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The Military places a lot of effort into measuring port pressure. But for the average Joe/Joesette it isn't likely that you'll find many attempting it. This however does not negate the fact that port pressure determines the difference between proper and improper cycling.
 

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Pressure transducers. Strain gauges.
That gives pressure but not volume in a gun. The only way to actually measure volume at the piston is to capture it and measure. It could be estimated but a test is easier.
 
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