chrony question. Cast vs. Copper

[bdecker9]

hello all you casting legends. just curious but has anyone crony-ed two identical charges with similar ja-ket-tid and cast boolits? I'm just curious, as i have found my perfect target load, for my sr-9. well with j-words anyway. when i switch to cast the recoil seem a little stiffer. (mind this charge is just under the start load.) but, and i might be nuts it seems like the velocity is slower. i do know that the cast boolits are 4.5 grains heavier, but they are also loaded to a longer OAL. but never mind all that. i will find a better load for the cast. its all i shoot, 99% of the time. but its driving me nuts about the velocity. i don't care about the speed of the boolit that's not why I'm asking. I'm just trying to iron out a theory i have about accuracy and such.
thanks in advance. decker

[detox]

Higher friction and less obturation will cause the jacketed bullet to be slower than cast bullet of same weight. I am sure someone here will disagree

http://members.shaw.ca/cronhelm/TheLoad.html

[Whitespider]

Yes, I've run them across the sky screens, and the answer ain't so simple... maybe faster, maybe slower, maybe near the same.
Funny thing about recoil... "felt" recoil can be deceiving. For lack of a better descriptive, target load recoil using relatively fast propellants feels "sharper(?)" to me, full-blown load recoil using slower propellants feels "heavier".

Not everybody perceives recoil the same way; the oldest boy and I were shooting a couple revolvers last weekend,
1 - A 4-inch K38 loaded with 156-grain plain base SWC's over 5.0-grains W231 (.38 Special brass).
2 - A 4-inch King Cobra loaded with 155-grain gas checked SWC's over 6.0-grains W231 (.357 brass).
He swore the K38 recoiled more... even though, as I watched, the King Cobra muzzle was raising noticeably higher during recoil.

[Shiloh]

This is a great question bdecker9.

Been ages since I fire jacketed boolits let alone chrono'd them.

Shiloh

[blackthorn]

Scroll down and read the subject matter in this thread. Seems to me to be on topic.
" Lead bullet pressures are greater than jacket bullet pressures of the same weight "

[HeavyMetal]

If you cast weight is heavier that the jacketed load, all else being the "same" the heavier boolit should recoil more.

Now if you can actually feel the 4.5 grain difference in the two loads I have a few safes that need opening, LOL!

Seriously each gun has it's own preference in a load and I have had several that prefer Jacketed over lead and the other way around as well!

This is what makes the hobby fun, cause if I could just pour and shoot perfect groups I'd have to get a real hobby, LOL!

Keep working on this theory I want to hear it when your ready.

[leadman]

The resistance the bullet or boolit has going down the bore can make a difference in how the powder burns. I have had very soft boolits go slower than harder boolits with the same load in the same gun. Only thing I can think of causing this might be the soft boolit obturiates more in the bore to cause more friction?

It is also very easy to get a large velocity variance just by gripping the gun tighter or looser.

[detox]

Bullet fit in bore and alloy hardness can change things around.

[JSnover]

It depends... :wink:

[bdecker9]

thanks for the observatoins. yeah it's weird. the lead load seems stiffer, but seems like it takes longer to impact. my theory on why the jacketed load works is pretty simple. my sr9 has a slightly large bore. my lead boolits are 358-359. i believe what happens when i push the copper too fast it skips across the rifling, not spinning the bullet or spinning enough. drop the load down though, and groups get smaller with copper.