Faster bullets?


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MovedWest
April 14, 2009, 07:33 PM
I've noticed that my 210gr SJHP's leave a nice crisp hole punched in my targets whereas my 240gr SJHP's make a tattered hole. These are fired from the same 44 magnum pistol.

I noticed in another thread that made mention that Golden Sabre bullets have less friction because they're a smaller diameter. They also made mention that this allows you to push them a little faster.

My 210gr bullets are .429 while my 240gr bullets are .430. Could this be the reason for the crisp printing? The attached shot is an example of the 210gr .429 bullets.

-MW

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ReloaderFred
April 14, 2009, 07:58 PM
How ragged the hole in the target is has more to do with the shape of the bullet than with velocity. If your 210 grain bullets have a sharp shoulder, they will cut clean holes. If the 240 grain bullets don't have a sharp shoulder, they will leave a ragged hole in the target.

This was one of the reasons for wadcutter bullets, and semi-wadcutter bullets. They leave holes in paper targets that are easier to score in matches.

Hope this helps.

Fred

MovedWest
April 14, 2009, 11:02 PM
I thought about bullet shape as a possibility, but if I lighten up the charge in my loads the holes become ragged. Hotter charges yield an slightly cleaner hole yet, but I lose accuracy.

I've attached a shot of the bullets I use for comparison. Left to right in the rear 300gr XTP reload, 240gr SJFP, 240gr SJHP Remington factory load. At front center is the 210gr SJHP.

Of all these bullets, the only one that cuts clean holes is the 210gr bullet, which doesn't seem to have an edge that's much different than the others. It is the the only one that is .429 diameter though.

-MW

Shoney
April 15, 2009, 06:16 AM
The smaller diameter bullet actually was used and develope by the Germans in the early 1900's (Big Bertha). The principle is called Free Boring.

The small sized projectile is pushed thru a small length of rifling. The rapidly expanding gasses escape past the sidewall of the bore, creating a vacuum in front of the bullet (Bernuli's Principle which is also the reason for lift in airplane wings.)

The powder charge can be greater with freebored weapons, because the gases are contantly flowing past the projectile, relieving pressure build up, and pushing and sucking the projectile faster.

Ben Shepherd
April 15, 2009, 10:03 AM
Shoney-

Thanks. Neat thing to know. Don't think Ill try it with cast slugs though.:D

MovedWest-

Any difference in how your targets were hung? Bullets from different makers?

As Fred mentioed, nose profile makes a huge difference.(that's why a FMJ 9mm leaves a hole that can be hard to tell from some 22 rounds.)

rcmodel
April 15, 2009, 11:03 AM
No mention of the powder charge used.

But if all are loaded up to max velocity for the bullet weight, it can be assumed the 210 grain loads are going faster then the 240, or 300 grain loads by as much as 100 - 300 FPS.

The faster the bullet is going, the less time the paper has to get out of the way. So it cuts instead of tearing.

The difference between .429" and .430" isn't doing it.
It's the higher velocity of the lighter bullet.

rc

jfh
April 15, 2009, 11:20 AM
And then there is that variable of paper quality--i.e., how the paper is made. "Regulation" (NRA-approved, for example) targets are made to specs that provide for clean tearing.

So, add in a "commercial"--i.e., not "competition" target--to velocity difference, and the bullet hole may well be different.

Jim H.


Jim H.

MovedWest
April 15, 2009, 04:59 PM
No mention of the powder charge used.

rc - you should've seen this one coming from a mile away:
8.7gr green dot :p

Any difference in how your targets were hung? Bullets from different makers?

Ben - The targets are all hung on the same hanger and the distance is 25yds. All the bullets shown are Remington with the exception of the 300gr which is a Hornady XTP. I use 2400 in my 240gr SJFP and 300gr JHP rounds. The 240gr SJHP rounds are Remington factory loads.

jfh - I usually use the same targets for each session. It's not uncommon for me to even switch calibers on the same target at times. I would consider the targets a constant, not a variable.


I'm online with rcmodel's line of thought that the higher velocity is the reason for the clean edges. But could the bullet's diameter cause less friction which would contribute to the increased veolcity?

Shoney had an interesting note about Bernuli's principle. Not sure if .001" would be enough to have that affect though.

-MW

rcmodel
April 15, 2009, 05:03 PM
In general, a loose bore seal will get you gas blow-by and lower velocity.

Not the other way around.

This is especially true in a revolver, because of blow-by in the chamber throats.

Free Boring, as used in this country, was pioneered by Roy Weatherby. It consists of an extra long, full bore diameter throat in front of the chamber, with no rifling.

It allows the bullet to get a running start before hitting the rifling friction, and helps hold down pressure.

Don't know about the Bernoulli principle adding speed by "sucking" the bullet along faster though.
Gas loss is gas loss!
Less gas is less pressure.
Less pressure is less speed.

Weatherby made up for the loss by using a bigger case with more powder then most cartridges of the time.

I believe the German Big Bertha cannon did too.

rc

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