I'm reloading .284 Win fired in a M77 Ruger. My fired cases mic 2 to 3 thousandths over SAAMI specs in the shoulder area. After resizing in RCBS FL dies they mic 2 to 3 thousands under specs. Is that typical for other cartridges? Seems like I'm working that brass a lot.

That would likely be acceptable in a lever action or autoloader to ensure trouble free cycling. In a bolt action I would back the die out of the press about one full turn so the case is only partialy re-sized and perfect headspace is maintained.

Snowman has a good, cheap, answer for your problem. However, you may have runout problems with this solution. Buy a set of Redding's match shellholders. These are built slightly taller in increments so that you can try sizing with the die turned down against the shellholder, minimizing runout.

when resizing the best way to set your die is to screw the die in but dont let it touch the shell holder,usually the thickness of a dime is a good starting point.Now take a lighter or a candle and hold the neck and shoulder above the flame to get a coating of smudge on it. now put it in the press and keep adjusting the die until you see it touching the shoulder(you will have to resmudge the case a few times)then if you know how much you have to bump the shoulder back you can adjust to what you need.this can also be used to neck size also.I only flr about the third firing. hope this helps

I don`t know if there is enough taper in the 284 case to reduce the sizeing of the wall by backing the die out a turn or two. I only see .026" difference from shoulder to base at the extractor grove on a drawing. I`d send a case or two to RCBS or Redding and have them make a die that fits my chamber and insure it`s right.

I have a theory that I'd like some feedback on:

I bought these dies back in 1970 when very few bolt action rifles were chambered for the .284. I believe at that time RCBS only offered one type of die in this caliber. Now they offer it in both regular and small base varieties for lever action and semi-autos. Would be likely that the old dies were purposely small to function in the Win mod 88 and 100?

In other words perhaps the newer regular dies size to SAMMI specs.

Allan, all of the ideas mentioned above are good solutions. If it were me, I'd buy a new die and shellholder(from the same manufacturer). This will insure headspace is maintained.

packrat

I don`t know how much difference there is between reg and small base dies but you might want to call RCBS and ask their opinion. You may have your answer.

1-800-533-5000, RCBS tech line

The tips about Redding shell holders and die adjustments are good. I also have something for you to think about before contacting the die manufactures.

Firearms manufactures will chamber their firearms to fit the majority of commercial rounds available. This means they will generally tend to be on the plus side of the cartridge specifications. Die manufactures on the other hand will produce dies that resize to fit tighter chamber specifications, which means the minus side of the specs. This is why you end up with the difference you are seeing.

There is probably nothing wrong with the gun or dies. To get maximum case life the sizing die just needs to be adjusted so the fired case will chamber, about .001" less than fired size. If you don't want to opt for the Redding shell holders you can use a shim, with parallel surfaces between the shell holder and die when you lock the die in place, this will also keep things in proper alignment.

As Ol' Joe pointed out, there isn't much taper to this case. To make up 3 thousandths I'd have to unscrew the die .20 inch. The neck is only .285 long leaving just .085 inch of the neck resized.

I just found out that Redding makes a body sizing die for using with their neck sizing dies. I still have a old Lee Loader in .284. Maybe this is the combination I need.