2 Different Bullet Weights With Same Poi

[Paradox]

I shot my first Steel Challenge Match this weekend, WHAT A BLAST! Now I want to try some Minor PF loads...

To be more specific with my question:

I normally shoot a 180gr load at 168PF. However, I would like to try some 135gr for the steel matches (950fps - 1150fps). Is there a relatively easy way of determining "180gr bullet at 945fps has same (or really close) POI as a 135gr at XXXX fps"? I am also assuming that only the elevation changes and not windage...

Does anyone have any experience trying this?

-Justin

[Patrick Sweeney]

There is no formula, as the largest variable, the shooter, cannot be defined. there may also be some windage component, but not likely much. At the distances of the Steel Challenge or any IPSC match, you are not going to find a whole lot of impact shift. At least not in the applicaiton you're describing.

[Sterling White]

Shot my first steel match a few months back. Used the 180's, downloaded TG to 3.2, with a 8# spring in my STI. It worked but had a entirely new feel to it.

After reading the detonation theory in the OOPS thread I think I'm going to talk to more experienced smiths or shooters before doing this again.

[shred]

Technically it's generally very difficult to make heavy and light bullets shoot to the exact same trajectory (you can sync point of aims, but only at a few spots). This is because the gun starts to recoil while the bullet's still in the barrel (yes, it does, that's why this happens).

Realistically, it probably doesn't matter much. Try it and see. I find changing the bullet to change the flight path much more than changing the powder loads does. In any case, an inch or two at 25 likely won't be a problem for quite a while.

[Paradox]

Shred - I have noticed that in general the POI drops as the velocity for a given bullet increases.

I will just have to load some 135's and see where they shoot.

Thanks for the responses!

[Flexmoney]

I use the same everything for Major and Minor (same primers, same OAL, TiteGroup and Zero 180's). I just back of the amount of TiteGroup that I put in the case when I load minor. Very easy. Shoots fantastic. I think my minor load may be more accurate than my Major load.

[Flexmoney]

Sterling, I was running 3.5g of TG with the 180's for Minor, with an OAL of 1.135.

I bumped it up to 3.6g to get a bit more feel out of it.

[Sterling White]

Flex,

Your oal is a tidbit shorter - my oal's are at 1.180. Thanks for the info. Will give the load a try in practice and see what happens. Didn't like the sluggish feel so maybe that will clear it up. The match was held at Blackwater and prior to the match they announced that the PF needed to be <150....guess to preserve the steel.

The cool thing was that I didn't have to change my settup. POI wasn't an issue, same gun, same holster.....just shoot!

sw

[fishnfst]

Go to the Norma website and they have a ballistic and bullet drop calculator. You enter bullet weight, velocity, BC and zero distance and it will calculate the drop at any given distance. Use a 50 yard zero or 100 yard zero and look at what the bullet is doing at 10 and 15 yards....

[Flexmoney]

Sterling,

I'll bet that load felt "sluggish".. You are running a lots less powder...AND, with a longer OAL. I am kind of amazed the gun even ran.

[Sterling White]

I laughed when I put the 8# spring in. With some snappy jiggles I could almost get the slide to rack....lol!