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Discussion Starter #1
I reload 4 different calibers: 9mm, 45 ACP, 5.56/223 REM and 308 Win.

By my way of thinking, assuming all else remains the same, the deeper you seat your bullet, the higher the pressure will be. Leading off of that, the higher the pressure, the higher the velocity.

Is this correct, or is my thinking just off base?

Thanks.
 

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Seating deeper will increase pressure but if you are tippy toeing around with max pressure seating too deep may result in dangerous over pressure. It is better to stick with the recommended seating depth to insure proper feeding and keep pressures in line with recommendations.
 

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Personally I would not want to mess around trying to get more velocity by seating bullets deeper. I would rather find powder that creates velocity using a reloading manual. I prefer the ones put out by the bullet manufacturers. I might then work up to the max loads with that powder/ There are a lot of guys on here with way more experience than I have that might feel comfortable with doing something like that but I would not.
 

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Actually some pistol ammo has less pressure by seating the bullet down on the powder charge but not crushing the powder. We don't do that much because it causes feeding problems. The reason it lowers the pressure is there is no extra room to work as an expansion chamber. As the burning powder expands into a gas the bullet accelerates up the smooth brass case before it hits any resistance at the barrel. DR
 

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I agree with the theory of using a different powder for higher velocities-I have reloaded since 1980 and have never seated deeper to get higher velocity.
In fact I have had self defense ammo get bumped into the casing from random feeding-I will normally pull the bullet-dump the powder and reuse the casing.
 

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Danger Danger Will Robinson, There is no way to know what your going to spike the pressure to. As stated use a different powder or graduate to a magnum. Faster doesn't always mean more accurate. Most reloader conduct latter tests to see what the best load is.
 

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Discussion Starter #9
Thanks everybody for the feedback.

To make things a bit clearer, I am not trying to "hotrod" my loads, or to get any additional velocity as a result of adjusting the seating depth. And, my loads are well below the max for my bullets. I was just trying to get some clarity on my thoughts regarding seating depth.
 

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For .45 and 9mm, I've played with bullet seating depth to optimize cartridge feeding in the 1911s. For any given load, plus or minus 0.050" created a barely measurable difference. These are modest-pressure cartridges and as long as you're not loading near the limits, they're very forgiving.
 

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If I want higher velocity, I use a powder that produces more energy. I DO NOT play around with the seating depth. Some of the newer powders develop more velocity while lowering pressures. I would take that route. I also do not shoot someone else's reloads!
 

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Thanks everybody for the feedback.

To make things a bit clearer, I am not trying to "hotrod" my loads, or to get any additional velocity as a result of adjusting the seating depth. And, my loads are well below the max for my bullets. I was just trying to get some clarity on my thoughts regarding seating depth.
If you are well below the limits, Playing with seating depths may give you some interesting results.
I live in CA and have to hunt with Lead Free bullets. when I first made the switch to copper bullets I could not get much accuracy from them. But after some reading I found that they needed to be 60 thou off the lands! In my gun they shot best 75 thou off the lands! My once upon a time tack driver is back to shooting sub min of squirrel brain! I guess the harder copper needs a little run up to speed before hitting the lands!

In pistol ammo most of my seating experiments have centered around feeding issues. I have't noticed seating depth affecting accuracy much at all. Good Luck. DR
 
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