Bullet composition & velocity?


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Bullet
March 15, 2005, 07:26 PM
What does the bullets composition have to do with velocities? Say you take X amount of powder in a 357 case and use the same exact load except for using bullets of a different composition that are the same weight 158 Gr. ( lead – Bonded Core Speer – Jacketed ). What kind of velocity difference will you get do to bullet composition? I'm asking this because I've recently been using some Speer bullets for 357 (158 Gr. Gold Dots) and I can't seem to get velocities much above 1200 FPS in a 6 inch GP100 and I wondered if this was do to their composition?

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dakotasin
March 15, 2005, 11:51 PM
don't know the answer to your problem, but... i get better velocity w/ cast bullets (lead) than i do jacketed. some jacketed bullets get more velocity than others depending on their jacket thickness and hardness. dunno about bonded core bullets.

BEARMAN
March 16, 2005, 12:28 AM
My usual load for IPSC in .45 acp , 230 gr lead bullet, with 5.4 gr of WINCHESTER 231 POWDER which gives me a muzzle velocity of about 850 fps, which give me a good margin for the MAJOR POWER FACTOR. I quite often get remarks about the smoke, usually blamed on the lead. So for our NATIONALS I used the same load with steel jacketed 230 grain bullets and only made MAJOR by the averaging of all shots fired over the chrono. I figure I lost about 50 fps to 100fps because of the resistance and lack of lubrication of the steel compared to that of the lead . A prime example of don't change things before a major competition without proper testing.

P95Carry
March 16, 2005, 12:40 AM
Accepting that loads vary slightly for lead and jacket - all in all I'd say variations are rather small.

A lubed lead will IMO suffer less friction loss and so potentially come out on top. The bottom line tho to me is actual bullet weight. If loads set up right then the energy factor should be close for either jacket or lead.

Consistency is all - and so if a load ''suits'' then it suits!! Meaning - if gun cycles, performs and accuracy is what is required then all should be well - unless that is you are chasing absolute max plus hot loads - in which case I'd anyways go with jackets.

Art Eatman
March 16, 2005, 12:55 AM
Never having had a chronograph, I'm just another Mr. Hearsay. But, it seems to me that there would be less resistance with a lead bullet than with a jacketed bullet, so the lead bullet would most usually exit with a higher muzzle velocity.

But, one test = 1,000 expert opinions...

:D, Art

Bullet
March 16, 2005, 02:21 AM
Hodgdon loading manual for 357 Mag - 158 Gr. HDYXTP -

H110 - 16.7 Gr. 1591 FPS

I've shot this load except with Speer 158 Gr. Gold Dots and the FPS was only about 1250 FPS. This is around 300 FPS difference by changing bullets only. I wondered if the jacketed bullets resist movement more than the bonded core bullets resulting in this difference?

Mikul
March 16, 2005, 12:33 PM
Copper has less resistance than lead. Just look at all of the lead that gets ripped off of the bullet when it goes down the barrel. Jacketed rounds don't have that problem. Besides, if jacketed bullets have more resistance, then why don't we need to lube them? Lead bullets get lubed because leading would be ridiculously high without it. While you may get higher velocities with lead at the same powder charge, you will almost always be able to push the jacketed rounds to higher velocties because in order to push lead that hard, you'd have to send the pressure beyond the safe zone. Whenever I look at a load book, I can find loads for jacketed and lead of the same weight and jacketed bullets max out 200 fps faster than lead in 9mm.

The reason you get higher velocities with lead is because of the resistance that it gives, just like you get higher velocities by tightening the crimp. The resistance allows pressure to build. This also explains why jacketed rounds can be pushed faster, they aren't reaching maximum pressure as soon.

Remember guys, less powder does not always mean less pressure... especially when you're changing other components.

taliv
March 16, 2005, 12:55 PM
this may be a tangent, but a big hole in the center of a hollowpoint will have some affect on B.C. relative to a bullet with same weight that might have a more aerodynamic shape.

that's not going to make a big difference 15 feet from the muzzle over a chrono, but it would sure make a difference later in flight

Vern Humphrey
March 16, 2005, 03:59 PM
Ed (EC) Harris has told me, and shown me the evidence, that lead bullets actually have a higher pressure spike than jacketed. He attributes this to the lead bullet upsetting faster and sealing the bore better.

Lead bullets foul more because they are significantly softer. The fouling is a function not of friction, but of the strength of the bullet material.

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