JerryLP

Why should I resize GP-100 reloads? The rounds are going to be fired (no max loads) in the same revolver, so why exercise the brass unnecessarily?

Iowegan

You have to resized the brass in order to get good neck tension on the bullet. Without resizing, powder won't get good ignition and will leave unburned powder in the bore, reduce velocity considerably, and reduce accuracy.

leroy

Yup. ^^^^^^^^ DITTO to what Iowegan said above. Ya need a good "neck tension" on the bullet to get good powder ignition and a cleanburn. The resize the brass thing doesnt hurt the straight walled brass very bad. We have bunches of 357, 44 mag, and other straight walled cases that have been resized bunches (...probably up to 10 or more times...) with no problems.

Hope this helps a bit.
leroy

shootist

Try it and see why, you'll never ask again after they expanded once they are close to the size of the cylinder, expand again with another shot they would be so tightly stuck in your cylinders you'd have to beat them out with a hammer

JerryLP

I've always resized when I reload; but I'd never thought to question it. I figured that range brass would need the process, but I never thought about my own cases.

Thanks for the anwser(s). jp

Iowegan

shootist, That just doesn't happen ... try it sometime. Brass can't expand beyond the diameter of the chamber unless there is exceptionally high chamber pressure. With a "loose" bullet, chamber pressure is much lower than normal so unsized brass will come out the same size as it went in.

To add a little .... proper neck tension is where it takes about 50 lb of pressure or more to push a bullet deeper into a sized case (ie: hold the cartridge and push the bullet nose against a workbench). Assuming a .358" bullet, the area of the bullet base is (pi radius squared) or 3.14 x .179 x .179 = .1 square inch. 50/.1=500 ..... so it would take at least 500 psi chamber pressure to start moving the bullet. With this delay from neck tension, nearly all the powder will ignite. With an unsized case and virtually no neck tension, primer ignition generates enough pressure to push the bullet out of the case so some of the powder never gets a chance to ignite. With slow burning magnum powders such as H-110/W-296, odds are good you will have a squib where almost no powder ignites.

shootist

No can't expand beyond but tight enough to be stuck, a similar thing happened to me using loads that are to high pressure and getting them out could only be done with a wood dowel and hammer, not resizing brass would do the same thing cause it will expand again, your welcome to try it if you don't believe me, but I don't see how you could seat the bullet without resizing to start with they would just keep dropping inside the case

laidlerj

I suppose you could always neck size the brass, like some folks do with rifle cases. However, since most of the cracks I get in .357 Magnum brass are at the neck, I don't see how that would help much.

Jim

rclark

You Need to resize them for reasons said above. You should still get plenty of reloads from them anyway.

ozo

And..I will add....
I hope you have already uniformed the flashhole properly......

Iowegan

ozo, Although uniforming flash holes is not a bad idea, it really has nothing to do with sizing brass. Uniform flash holes can help make powder ignite more uniformly but mostly it is way over rated. In other words, if uniform flash holes makes your ammo notably more accurate, there's probably something else wrong with your loading techniques.

The "gauge" for performance is to chronograph a string of at least 10 rounds and look at the max velocity spreads. If your spreads (fastest velocity versus slowest velocity) are under 50 fps, you won't see any notable difference in accuracy out to 50 yards. If you weigh each powder charge precisely, weigh and cull out any bullets that are more than 1 grain too heavy or too light, use once fired brass with the same headstamp, and seat all bullets to the same exact depth, then a very token amount of velocity spread may be detected by uniforming flash holes.

tglazie

this is not an attempt to hijack the thread by any means, indeed, my question pertains to the effect of the manipulation of various components (such as sizing cases) on the overall consistency of reloads.

That said, I see this 50fps rule quite a bit Iowegan. My question is, if I am loading in the lower velocity ranges (say low 700s for .38, 900-1000fps for 9mm, 750-875fps for .380, etc) vs either max velocities for the same calibers or higher velocity calibers (like rifle loads), does the 50fps rule apply pretty much uniformly across the board? Or, for example, is a 50fps spread in an 1100fps jacketed 9mm load "better" than a 50fps spread in a 680fps .38 wadcutter load, for example?

Iowegan

tglazie, No problem ... it's all related to the OPs question in one way or another.

The 50 fps max velocity spread assumes a muzzle velocity of 1000 fps ... so 5% would be a better way to express it. The "50 fps rule" originated from quality factory ammo, which is loaded to this standard. Some of the cheap crap ammo has a hard time getting under 100 fps spreads. Here's the breakdown .... match grade ammo should have a max spread of 2.5% or less and should be capable of sub-inch groups @ 25 yards. Field grade or self defense ammo should be 5% or better on max spreads and capable of 2.5" groups @ 25 yds, whereas "plinker grade" ammo can be as high as 10% spreads and group size would be 5" or better.

Max velocity spreads are a good indicator of accuracy potential in handguns but do not always ring true, meaning ..... just because the loads chronograph really tight, it doesn't always mean the load will be accurate. On the other hand, I've never seen match grade ammo shoot mouse ear groups when velocity spreads were much over 2.5%. As we all know, reloaders have different accuracy standards. Some are very happy to hear a bang and see a hole appear somewhere in a man-sized silhouette. Bullseye shooters are the most picky where ammo and the gun must be capable of sub-inch groups at 25 yards, in fact most bullseye guys demand 1/2" or better @ 25 yds. It takes a good gun and very good ammo to do this, not to mention shooting skills.

Rifles are expected to be way more accurate than handguns so generally "MOA" is used to judge accuracy. If you were to chronograph a rifle and ammo capable of 1 MOA groups, you would find max velocity spreads will be quite tight ... typically 2~3% max spreads. It is not unusual to see match grade bench rest rifles shoot groups under .5" at 200 yards (1/4 MOA) but to do this, you need a really good rifle and match grade ammo.

So what determines how well ammo will group in a handgun? Obviously it starts with the gun itself ... and not all guns are created equally. As for the ammo, the single most important issue for consistent results is neck tension. See, I told you it was all related! Consistent neck tension depends on a properly sized case plus the the brass at the case mouth must be uniform thickness and hardness. As a case is fired and reloaded multiple times, irregularities in the brass will cause the neck to develop thin areas and will get harder with each reload, eventually resulting in splits. To get consistent bullet-to-case neck tension capable of match grade standards, about 3 to 4 times loaded is max, plus the cases need to be from the same batch. After 3-4 times loaded, max velocity spreads will increase because the thinner areas in the mouth do not apply uniform neck tension and crimp from cartridge to cartridge. This will have a dramatic affect on how the powder is ignited and in turn, a change in muzzle velocity. Many people will load cases until they split ... which is fine for plinker loads. If you want to achieve "match grade" with any ammo, your loading techniques must be as perfect as possible. This includes weighing each charge of powder to the precise weight, +or- 1%. Same goes for bullet weight +or- 1%. So for a 5 gr load of powder under a 158 gr bullet, the powder drop should be accurate to 1/2 of a tenth grain (.05 gr) and the bullet should weigh between 156.4 and159.5, which is pretty easy to achieve. Most reloading scales are not capable of accuracy better than .1 grain so it may be very difficult to achieve match grade powder drop standards. The good news is .... bullets usually weigh pretty darn close to advertised weight so the accumulated error rate between the powder and bullet is not mission impossible.

Last but not least is bullet seating depth. The faster the powder's burn rate, the more critical seating depth becomes. With fast burning Bullseye, just a few thousandths variation in seating depth can change chamber pressure by 1000 psi, which in turn changes velocity considerably. Slow burning magnum powders, such as H-110/W-296, are much more forgiving because the bulk of the burn takes place after the bullet exits the case. Besides, in handgun length barrels, H-110 / W-296 never gets a complete burn so it is almost "self regulating". That also means the powder charge weight is not critical. It is not unusual for 357 or 44 Mags loaded with these powders to produce max velocity spreads under 20 fp and astounding accuracy, even with less than stellar reloading techniques.

tglazie

Wow. Amazing info, thanks.

ozo

" it really has nothing to do with sizing brass"--iowegan

Didn't say it did.

" Uniform flash holes can help make powder ignite more uniformly"--iowegan

IF it can improve ignition ANY percentage......why wouldn't you ???