Bullseye-L Forum
Would you like to react to this message? Create an account in a few clicks or log in to continue.

Looking for the collective wisdom to help understand a ballistics issue

+2
james r chapman
straybrit
6 posters

Go down

Looking for the collective wisdom to help understand a ballistics issue Empty Looking for the collective wisdom to help understand a ballistics issue

Post by straybrit Mon Sep 16, 2019 1:14 pm

I was playing with new loads over the weekend to see just how light I could go for a 45 indoor load. Looking through load information here and elsewhere I was struck by something that I've never really understood.

Why does a heavier bullet (e.g. 200g SWC) get quoted as (typically) 3.5g BE for an indoor load where a lighter bullet (say 160g) gets quoted with a hotter load - typically 4.0g BE? My simple mind thinks that a lighter bullet would need a lighter load to achieve the same velocity. What am I missing here?

straybrit

Posts : 389
Join date : 2012-09-05

Back to top Go down

Looking for the collective wisdom to help understand a ballistics issue Empty Re: Looking for the collective wisdom to help understand a ballistics issue

Post by james r chapman Mon Sep 16, 2019 1:20 pm

Not about velocity, it’s about enough pressure to cycle the action I believe.
james r chapman
james r chapman
Admin

Posts : 6372
Join date : 2012-01-31
Age : 75
Location : HELL, Michigan

Back to top Go down

Looking for the collective wisdom to help understand a ballistics issue Empty Re: Looking for the collective wisdom to help understand a ballistics issue

Post by straybrit Mon Sep 16, 2019 1:41 pm

Ah - yeah - that would make sense. Thanks Jim.

straybrit

Posts : 389
Join date : 2012-09-05

Back to top Go down

Looking for the collective wisdom to help understand a ballistics issue Empty Re: Looking for the collective wisdom to help understand a ballistics issue

Post by Wobbley Mon Sep 16, 2019 1:42 pm

Not so much pressure as it is momentum. The 1911 operates on a delayed short recoil. The slide has to have all the momentum needed to cycle the gun by the time the bullet leaves the barrel. By calculations, the slide gets all of its oomph in the first .050 to .090 of its travel. When you lighten the bullet you have to raise the velocity to get the momentum. That takes a hotter load. Often people who shoot 160 grains claim the recoil is less but it’s “snappier”.
Wobbley
Wobbley
Admin

Posts : 4803
Join date : 2015-02-13

Back to top Go down

Looking for the collective wisdom to help understand a ballistics issue Empty Re: Looking for the collective wisdom to help understand a ballistics issue

Post by Olde Pilot Mon Sep 16, 2019 1:44 pm

At ignition, lighter bullet begins to move before a heavier bullet. So, there's less time for pressure to build in the cartridge case. Even with increased powder charge versus that used with a heavier bullet, felt recoil MAY be less.

Olde Pilot

Posts : 315
Join date : 2015-07-27
Location : Apopka Fl (Central Fl)

Back to top Go down

Looking for the collective wisdom to help understand a ballistics issue Empty Re: Looking for the collective wisdom to help understand a ballistics issue

Post by S148 Mon Sep 16, 2019 3:08 pm

Even with the same powder charge, light bullets tend to go slower than heavier bullets.

See figure 2 at this link:  https://www.shootingtimes.com/editorial/power-factor-recoil-bullet-weight-gives-edge/99399

S148

Posts : 319
Join date : 2017-07-04

Back to top Go down

Looking for the collective wisdom to help understand a ballistics issue Empty Re: Looking for the collective wisdom to help understand a ballistics issue

Post by Olde Pilot Mon Sep 16, 2019 3:54 pm

Correct. Because the pressure build-up in the case is less.

Olde Pilot

Posts : 315
Join date : 2015-07-27
Location : Apopka Fl (Central Fl)

Back to top Go down

Looking for the collective wisdom to help understand a ballistics issue Empty Re: Looking for the collective wisdom to help understand a ballistics issue

Post by Allgoodhits Mon Sep 16, 2019 5:07 pm

If it is accurate at 50 yds, it is accurate at 50 ft. The reverse is not true. Load accordingly.
Allgoodhits
Allgoodhits

Posts : 901
Join date : 2017-09-17
Location : Southport, NC

Back to top Go down

Looking for the collective wisdom to help understand a ballistics issue Empty Re: Looking for the collective wisdom to help understand a ballistics issue

Post by Sponsored content


Sponsored content


Back to top Go down

Back to top

- Similar topics

 
Permissions in this forum:
You cannot reply to topics in this forum