Why do we flair the mouth sometimes, but not others?


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scythefwd
September 11, 2011, 07:51 PM
On a straight walled rifle case do we also flair like we do on handgun ammo? I'll admit ignorance, but from what I have seen, we don't flair the case mouth on rifle cartridges. There are straight walled cases in rifle. Do we have to flair those as well or is there a different reason we flair the mouths of hand gun ammo besides getting the bullet to fit?

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56hawk
September 11, 2011, 08:13 PM
Yes, you have to flare straight walled rifle cases. I just went through this myself since I recently bought a 458 Lott. With a bottle necked case, there is an expander ball on the decapping pin that expands the neck of the case after it has been sized down. On straight walled cases there is no room to do this as you would be crushing the case between the sides of the die and the expander ball. Therefore you have to flare the neck as a separate step.

Walkalong
September 11, 2011, 09:20 PM
I do not flair any rifle brass. Never a problem with jacketed bullets. Some people do not flair for jacketed in pistol calibers, but most flair at least a little bit. I am one of those.

For pistol, plated bullets need a little more flair, and lead is the least forgiving, needing a good flair to keep from shaving lead and lube.

scythefwd
September 11, 2011, 09:31 PM
thanks for the clarification yall. Shows my ignorance :)

243winxb
September 11, 2011, 10:00 PM
Cartridges with thin neck walls may collapse when trying to seat a bullet. The flare/bell helps reduce the pressure on the case mouth. Also reduces lead shaving. Some cartridges like 44-40 need the bullet seated, then crimped in seperate operations. Maybe even cartridges like this 357sig. http://www.lifetimepens.com/images/crush.jpg

scythefwd
September 11, 2011, 10:24 PM
243 - what the heck did you do to that poor case? Almost looks like you ran the case into the crimp die too far and pushed the mouth back.

Lost Sheep
September 11, 2011, 11:07 PM
I flare cases only as much as required to get the bullet to fit into the case mouth. If my bullets are sized such that they fit in the sized cartridge cases without flaring, I don't. Less cold-working of the brass means longer life (for the brass). If the base of the bullet will not fit, then I flare just enough so it does fit and no shaving of lead from the sides of my cast bullets happens.

If I found cases being crushed (as 243winxb shows) I would flare or expand a little more. Might even get a slightly oversized expander mandrel, if that is what it would take the cure the problem.

The flare is just so you can get the bullet in. More than that is counter-productive. You want the brass to grip the bullet tightly and crimp (if applied) to do the same. This is for a consistent powder burn (which requires high pressure with smokeless powder). More flare/expansion of the case mouth degrades that grip.

Thanks for asking.

Lost Sheep

GP100man
September 11, 2011, 11:58 PM
The 357sig is the most frustrating round to load I`ve ever tackled !!

The case is thin & the neck so short that if you do expand it any too much the bullet will set back under recoil !!

I gave up & returned the pistol & dies to the owner & wished him luck !!!

& yes I flare or expand all my rifle cases to accept my cast boolits .

Mike Kerr
September 12, 2011, 02:17 AM
]thanks for the clarification yall. Shows my ignorance

I don't think its ignorance, I think its a question that will provide many different answers, depending on the number of people you ask.

regards,

:):):)

GLOOB
September 12, 2011, 02:25 AM
On straight walled cases there is no room to do this as you would be crushing the case between the sides of the die and the expander ball. Therefore you have to flare the neck as a separate step.
This is true. But I think there's more to it.

For starters, the expander ball expands the entire neck. It doesn't effectively put a differential flare on just the mouth. It would appear to me that the expander ball mainly ensures uniformity, in case a neck started out too small to begin with. My thinking is small bore rifle cartridges can handle this type of expansion, because the bullets are almost always jacketed and usually have a larger seating surface area relative to bullet weight. Also, cuz the bullets are longer and thinner, the seating die can get them started really straight. Large bore, stubby pistol rounds need more relative neck tension and are harder to seat straight, hence you usually want more flare on just the mouth.

Also, I think maybe chamfering the case improves seating moreso on smaller diameter bullets than larger ones. I mean, if you put the same amount of chamfer on 2 cases of different diameters, the chamfer would be relatively bigger on the smaller case. E.g., if you put a 0.002" chamfer on a (obviously theoretical) 0.002 caliber cartidge, the mouth would end up 3 times the diameter of the bullet just from the chamfering!

snuffy
September 12, 2011, 11:47 AM
The question seems to be; "can you bell/flair any case mouth whether it be rifle or handgun"? The answer is yes! The die required is the Lyman "M" die for rifle and handgun. Here's the one for 30 caliber rifles, they ARE caliber specific. That means for one bullet diameter, like this one for 30 caliber.

http://www.midwayusa.com/viewProduct/?productNumber=129697

The M die has a two diameter expander plug that expands the main portion of the neck, then puts a bullet outside diameter straight section on the extreme front portion of the neck/mouth. This allows the bullet to be placed on the mouth, it will stay put while being seated. Some just leave the mouth expanded, shooting them as is. Others crimp slightly to remove the flaired section.

Another important point is the case can be sized with a FL or neck sizer with the expander left out of the die. This eliminates the need to lubricate the inside of the necks, and eliminates the drag that can pull necks out of line and lengthen the case. Some FL or neck sizers can be used without the expander ball but still deprime. Others use the expander button to hold the decapper pin. So you might have to decap in a separate step.

Here's a much better read on the "M" die than I can write, including pics of the "plug" showing the step;

http://www.lasc.us/Brennan_LymanMDies.htm

Lee also makes an universal belling die that simply puts a funnel shaped bell on any case.
http://www.midwayusa.com/viewProduct/default.aspx?productNumber=140461

Use of one of these dies is very important when loading cast bullets in rifle cases. All important to keep from shaving lead and lube from the sides of the boolit. Also if you're loading coated bullets like the Barnes or winchester coated, this will avoid damaging the coatings.

Walkalong
September 12, 2011, 12:45 PM
RCBS makes flaring dies for rifle calibers as well, but the M die is extremely popular, and for good reason.

When shooting lead in bottle necked rifle calibers a separate expander die is a must.

popper
September 12, 2011, 02:28 PM
IMHO flaring the neck is related to the bullet, not case style. Boat tail doesn't need it. Flat base and lead need it. Flare as little as needed. Bullet then starts straight as the effective neck and case head are concentric, assuming a die is used vs needlnose pliers. I don't like the crunch sound when seating FB bullets without flaring. 30-30 looks like that 357 sig when trying to seat and roll crimp in the same step.

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