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Same load, lighter projectile - Equal behavior?


lroy

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Currently shooting major with 200gr. Going to 165gr bullets would get me more projectiles for the same price. If I adjusted my dies to the correct oal to account for the shorter projectile and used the same powder load, would they behave the same in the gun? I know they wouldn't make major PF, but these would be strictly for training. They'd still be well over minor, so steel shouldn't be an issue.

 

It makes sense in my head, but I am not a smart man. Any thoughts?

 

 

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I would think that the recoil impulse would be similar to what you are use to and the POI should be close.   I shot 200gr with tight group for a long time, jacketed were more expensive than other bullets, in the quest for an inexpensive alternative that felt good I tried several weights, brands etc.   My favorite bullet became one that my 7 time world shoot limited champion recommended.   The 185gr Precision swagged bullet made in Kemp TX.  These make power factor with less powder and they cost less and the recoil impulse is softer than the 200gr, plus they are very accurate.   While it will get no love WST is the powder I used and still use for 40.  The trick is not to cut the coating when loading and get the crimp right, just enough to hold it solid. 

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No expert here but it would make logical sense that the recoil impulse would be less, using a lighter bullet with the same powder weight. Again, no expert but there is less mass being pushed with the same propellent. The bullet will exit the barrel quicker, expelling the gases out and causing less back pressure. Maybe that's not the exact science but I think you guys get what I'm describing. 

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Running some numbers for a 45 Auto

 

With a charge weight making 170 PF with a 200gr bullet gives a recoil of 5.2 ft-lbs.

 

Changing to a 185gr bullet with the same powder charge changes the recoil to 4.1 ft-lbs.

 

Velocity went down for the lighter bullet at the given powder charge.

 

 

 

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  • 2 months later...

Use a shot timer and measure your own split times over multiple strings, and see what the difference is for YOU.  Recoil spring rates also enter into the situation as slide momentum and muzzle rise affect YOUR time to reacquire the front sight.  The answer will not lie in calculated recoil impulse numbers.

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Going from 180's to 155's was a big difference to me. I did up the charge, and it's a LOT more flip. Lowering the charge tended to be unreliable, but I didn't mess with it much. My 180's with below min charges of WST was extremely fast to get in target! 155's are not. 

 

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