Can someone educate / explain "small base dies" to me?

I've shot BP for 55 years and only started reloading the new fangled cartridges about ten years ago - my question is in regards to rifle dies. I'll add that I reload 30-30 and 8 X 57 but will be adding .308 and 30-06 - have the brass, dies, molds, etc. and am looking for rifles over the winter. I'm thinking a single shot 308 and a bolt 30-06.

Now to my question. I have run across "small base" die sets both in posts and have seen them listed in the S & S - IIRC - in reference to 308 and 30-06 but I'm sure they are probably made in other calibers?

My reloading - for 308 and 30-06, I picked up Lee sets that while used are really "new". I de-prime all of my brass with a universal de-priming die - FL size in the Lee FL die with the depriving/expander stem removed, expand with a Lyman M die, use a seating die and usually the Lee collet crimp die or similar.

In 308 - I've made some dummy rounds up just to try the dies and see the results. For the 308, I did buy a Hornady "cartridge gauge". My brass stash is mixed head stamp commercial brass - 1X fired and range brass. In the Lee FL die, it seems to work jus fine and the cases slide right in to the cartridge gauge like they should - so I'm guessing everything will be kosher when I actually load some up for real.

In reading, I seem to remember the "small base dies" being correlated to semi-autos of the most part.

Can someone explain the difference between (we'll use .308 dies as an example) a regular normal FL sizing die and a "small base die"? What does the small base die do to the cartridge casing as opposed to a regular die. I'm assuming that it makes the base smaller in some manner? That seems like a hard thing to do given the brass in the base of a cartridge casing at the base. Why is it necessary to use a "small base die" in relation to a rifle or rifle type? Maybe I'm misunderstanding but I'm assuming the it is the FL die that is being talked about since that is the only one that would really have anything to do to the base - but if it makes the base a tad bit smaller, what about the portion in the shell holder?

Thanks for the lesson - greatly appreciated. Been wondering the "whats" and "whys" of small base dies for awhile but didn't want to appear to be ignorant. So far I haven't run across an explanation when searching - mainly references to their use for certain rifles but no explanation why they are required.

A good link and Larry weighs in which is always a good source on information...

http://castboolits.gunloads.com/arch.../t-183983.html

A regular size die most of the time is just fine, it revolves around what the chamber itself likes. In my 06 it will only take a small based cartridge. Even factory cases are at times a snug fit, but after I fire them they'll cycle just fine when empty. The small base dies themselves will make the base of the case smaller than some regular sizing dies. Which for some works well when using someone elses 1x fired brass. Remember it's the chamber that decides the outcome.

For what your loading a 06 small base die will work for not only the 06, but also the 308 and the 8mm. The 30-30 unless you can't chamber the thing after using a regular sizer die I wouldn't even give it a second thought.

I believe that originally small base dies were designed to assure reliability in semi and full auto military weapons. I have them for .30-06, 7.62 mm NATO, and 5.56 mm, but have never found them necessary for civilian firearms.

The only firearm I have ever needed a small base die for is my 308 Winchester match chambered 98. Brass fired in another rifle will more than likely not chamber in this rifle. Once the case has been sized in the small based die and fired in the match chamber it chambers easily when sized in a regular sizer die. The blanket statement that a small based die is needed for a semi auto rifle is incorrect. None of my ARs, Garands or my M1A require the use of small base dies for reliable functioning.

Bill Barker

Well I have a 300 win mag bolt action based on a model 98 mauser that has to have its brass resized in a small base die set , I believe it is a interarms mark x . Tried 2 different full length rcbs dies and had to order the small base , chamber is tight . I have never needed any small base dies for any of the semi autos I own or have loaded for.

My experience has been that I need them to resize my range pickups that were shot in sloppy chambered autos. My Kimber chamber is tight, brass from any other gun has to go thru a small base first, then all is good. If your a "dumpster diver" like many of us, you will wind up with a set of small base dies ..

Thank you all for your kind responses - greatly appreciated.

I only ran a half dozen though my Lee FL die - all went in to the cartridge gauge just fine so I'm assuming that those particular casings would work - however . . . .

I have accumulated around 600 "range brass" .308 casings. I think my next step will be to run a hundred of them though my Lee FL die - then check and see the fit of each in the cartridge gauge. I'm thinking that will tell if I need a small base die? Unfortunately, I haven't found a rifle yet. I'm looking at perhaps one of Henry's new single shots or perhaps something like a Ruger American - I'm mainly looking for a reasonably priced rifle to pay with as far as boolit weights, etc. - I don't hunt anymore and will mainly be plinking and doing some paper punching with it. As already mentioned, the individual rifle will tell the story as far as chamber size.

Thanks again - interesting and always good to learn new things!

Jim

If I have a rifle or pistol that won’t function with ammunition that is sized to factory specifications I fix it.

If I have a die that cannot resize a case back to factory specifications I return it.

Back in the 70's I had a Browning BAR, the sporting model not the military one. RCBS recommended using small base dies on the BAR and a few others. I think maybe the BLR and maybe the Savage 99. I've shot a lot of other semi autos with ammo loaded on standard dies. M1A's, Garands, Winchester 100's, Remington 740/742's, H&K's, with no problems. The small base die is helpful if you load surplus brass that was fired in automatic weapons but they are usually not needed. There is such a small difference I doubt you will notice any loss in accuracy or case life.

The small based die are made to size to the minimum sami spes or sometimes a little under that for fire arms with little camming force, IE semi autos, lever actions, single shots, pumps. These dies size brass down more thus working it more. You may see slightly shorter brass life due to this. Let the rifle tell you what it needs

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Originally Posted by FLINTNFIRE

Well I have a 300 win mag bolt action based on a model 98 mauser that has to have its brass resized in a small base die set , I believe it is a interarms mark x . Tried 2 different full length rcbs dies and had to order the small base , chamber is tight . I have never needed any small base dies for any of the semi autos I own or have loaded for.

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I had the same problem with a Mark X Interarms, mine was in 7 mm Rem Mag. Robert

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Originally Posted by bedbugbilly

I've shot BP for 55 years and only started reloading the new fangled cartridges about ten years ago - my question is in regards to rifle dies. I'll add that I reload 30-30 and 8 X 57 but will be adding .308 and 30-06 - have the brass, dies, molds, etc. and am looking for rifles over the winter. I'm thinking a single shot 308 and a bolt 30-06.

Now to my question. I have run across "small base" die sets both in posts and have seen them listed in the S & S - IIRC - in reference to 308 and 30-06 but I'm sure they are probably made in other calibers?

My reloading - for 308 and 30-06, I picked up Lee sets that while used are really "new". I de-prime all of my brass with a universal de-priming die - FL size in the Lee FL die with the depriving/expander stem removed, expand with a Lyman M die, use a seating die and usually the Lee collet crimp die or similar.

In 308 - I've made some dummy rounds up just to try the dies and see the results. For the 308, I did buy a Hornady "cartridge gauge". My brass stash is mixed head stamp commercial brass - 1X fired and range brass. In the Lee FL die, it seems to work jus fine and the cases slide right in to the cartridge gauge like they should - so I'm guessing everything will be kosher when I actually load some up for real.

In reading, I seem to remember the "small base dies" being correlated to semi-autos of the most part.

Can someone explain the difference between (we'll use .308 dies as an example) a regular normal FL sizing die and a "small base die"? What does the small base die do to the cartridge casing as opposed to a regular die. I'm assuming that it makes the base smaller in some manner? That seems like a hard thing to do given the brass in the base of a cartridge casing at the base. Why is it necessary to use a "small base die" in relation to a rifle or rifle type? Maybe I'm misunderstanding but I'm assuming the it is the FL die that is being talked about since that is the only one that would really have anything to do to the base - but if it makes the base a tad bit smaller, what about the portion in the shell holder?

Thanks for the lesson - greatly appreciated. Been wondering the "whats" and "whys" of small base dies for awhile but didn't want to appear to be ignorant. So far I haven't run across an explanation when searching - mainly references to their use for certain rifles but no explanation why they are required.

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Google RCBS small base reloading dies. Scroll down to FAQ on reloading dies. RCBS provides the answer very adequately, and may even surprise may reloaders on this forum that not just semiautomatic actions are best served with (SB) dies, but also pump and lever action rifles too. Standard size reloading dies are meant for BOLT ACTION RIFLES.

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Standard size reloading dies are meant for BOLT ACTION RIFLES.

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Not sure what to say about this comment except the make “standard” dies in calibers they don’t make bolt action rifles in.

This will probably start a **** fight, it often does...

The common top down die does 5 things in quick succession,

1. Removes primer punching it out the bottom.

2. Squeezes the neck down to grip the next bullet.

3. Squeezes the sides of the case back in so it fits the chamber body.
-- With the shell holder sticking up the sides, and the rounded edge to guide the brass into the die, this top down does DOES NOT resize the brass all the way down, usually 1/4" or more does not get resized.

4. The shoulder of the case is set back to a specific Datum Length.
-- (Head stamp surface to Datum Line on case shoulder is Datum Length)

5. The neck sizing ball expands the neck on the way out as die is lifted.

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A 'Small Base Die' can be one of two things change in the die over 'Common' dies,
It can reach slightly farther down the case, the radius at the bottom of the die (to guide cases centered in the die) is tighter, allowing the die to reach a few thousands further down the case.

Since most rifle chambers don't support the head/web of the case, it can expand when fired and might need to be 'Bumped' to fit again, or another (different) rifle.

Some 'Small Base Dies' squeeze the brass sides in a little more so the case fits back into 'Tight' chambers.

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I suggest you find out WHY the brass isn't fitting the chamber before jumping off to new dies...

First off, DO NOT 'OVER CAM' the press!
Once the shell holder hits the dies, all sizing of the brass stops.
The shell holder hitting the die is a 'Hard Stop', and all you are doing is bending/stretching the press frame & linkages.

Stick an automotive 'Feeler' gauge (Shim Stock) between brass & shell holder,
This will push the brass a few more thousandths into the die.
Bench rifle loaders have done this shim trick for decades to get the shoulder (Datum Length) precisely correct on the brass.

You can also try different case holders, some have thicker collars than others, and most of us have several.

Some people shave off the top of the case holder and dedicate that particular holder to a specific die/rifle.
Others grind on the bottom of the common dies, but I only do this as a last resort.

Keep in mind here, ANYTIME you shove a brass further up into a die you are setting the shoulder back further.
The idea of a 'Small Base' is to keep the shoulder more or less where it belongs while reducing the diameter of the case slightly.

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Another way to tell if it's shoulder, or case diameter that's causing the stoppage...
This is .308 Win specific,

Use a .30-06 die body to size the outside of the case WITHOUT moving the shoulder.
Size a case normally, when it just doesn't quite fit, run it through a .30-06 die body which is ever so slightly smaller, and you can shim from underneath to reduces the case diameter slightly more.

If it fits, it was the diameter.
If it doesn't fit, it's probably a shoulder Datum Length issue and the shoulder needs to be set back a little more for that specific chamber.

Screenshot

Attachment 226852

To revisit this: There's a big war going on. The ammo plants are turning out our standard caliber munitions for ourselves and allies. Ourselves and the allies are using many different weapons in these calibers of different designs and different manufacturers. Ammunition is resupplied under combat conditions when the chambers of these various weapons are being maintained to different degrees, meaning many of them are in use and are dirty. Ammunition produced with small base dies is designed to fit into and work in any of these chambers.

Civilian application: Used to be that SAMMI did not exist. Ammunition specifications and chambers were not as precisely standardized as they are today. In the time period from the 1880s through the 1930s if you picked up a fired cartridge casing you found at the rifle range or in the deer woods and attempted to load it into your rifle of the same caliber it would likely not fit, whereas today it is much more likely that it would, although still not a sure thing. But the chamber specifications used by today's manufacturers are much closer resulting in the dimensions of fired brass being much closer, and the normal full length sizing dies will almost always suffice to resize the fired brass to dimensions useable in most rifles. You can find this problem with the old Lyman 310 dies that neck sized only. Despite doing everything correctly, reloaded ammo produced by these dies might fit in my rifle but not in yours, especially if the cartridge was originally fired in my rifle.

So the "take-away" from this is that small base sizing dies are usually not needed for civilian cartridge cases intended to be fired in civilian-type rifles, but still have their use in semi and full auto weapons that fire a high volume of ammunition and which weapon's chambers become increasingly dirty a they are operated. Having several ex-military and military-type rifles in my collection I load the ammunition intended for them with small base sizing dies, having the assurance that the reloaded ammo will work satisfactorily in all of them.

Well...

I shoot 'Tight' chambers, what most people call 'Tight' is actually SAAMI specification and not sloppy/oversized.

Since the average reloader can not draw brass from scratch, it's resizing currently existing brass.

The average top down die will set the shoulder back, it will resize part of the side walls, about 3/4 of the sidewalls of the case.
It will NOT resize the lower part of the case or the rim. It can't reach the lower sides of the case or the rim simply because it CANT REACH the lower sides of the case/rim.
It's that simple.

We all know that accuracy costs money, how accurate do you want to be?

What I did several years back, and do to this day, simply because it CORRECTLY resizes the rim, the lower part of the case pushing bloated brass back up the case walls where it can be dragged out the neck is a case roller.

Roll the cases between two die plates with the PROPER rim, groove & to set the proper diameter of the lower case.
This can be something as simple as a Case Pro 100 or as complicated motor powered rotary case roller.

Once the lower case & rim are sized, then you can accurately size the Datum length & size the neck.

This will produce a 100% repeatable, 100% SAAMI specification brass product,
Or,
You can produce undersized brass if that's what you choose.

Personally, I don't see US military production ammunition that's undersized.
The US made military ammo I see is exactly SAAMI or NATO sized (depending on round designation).

I'm sure if you messed around long enough you could find some defective sized ammo from somewhere...
What I see is military weapons with oversized chambers to allow standard ammo 'Fall' into the chambers when dirty etc.

Now *IF* a guy does a low enough volume,
And all a guy was looking for was to get those cases into the chamber WITHOUT a precise fit,
Then a 'Small Base' die might do the job for you...
Only the guy doing that particular job can say for sure.

Personally, I shoot a truck load of ammo, but through just a few rifles, so I'm more inclined to make a standard (SAAMI) size round, and spend a little time on each rifle getting the chamber to fit a standard round instead of trying to beat every random brass into a shape that (more or less) fits the chamber(s).

MOA - I'll take a look at the RCBS info - thanks.

I appreciate the info everyone .. . and my intention wasn't to start a conflict! LOL I asked the question as I kept seeing references to "small base dies" and was seeking an explanation of "what and why".

I DON"T have a .308 or 30-06 rifle - yet. BUT .. . I am looking . . either a single shot or bolt .308 and a decent shooting 30-06 bolt. I asked because I seem to have seen more references to small base dies in those calibers and was curious as to . . . again . . . the "what and why".

That said . .. Sunday, I had time and resized 190 + or - 1 X fired PPU 308 casings. Once again, I load 30-30 and 8mm and I remove the de-priming/expanding pin from the FL sizing die as I de-prime with a universal de-priming die and expand with a Lyman M die. For the 308 (and for 30-06) I have Lee dies.

I adjusted my single stage so that my shell holder was just kissing the bottom of the die - the same away I adjust it for all of my calibers I reload. I'm old, retired and reload for enjoyment so after lubing each casing, I would run the casing up into the die, lower the ram, rotate the casing a 1/3, raise the rame, and repeat - then toss the FL sized casing in a plastic pan. After re-sizing all of the casings, I sat and put eaten in the Hornady case gauge. Out of the 190 + or - casings - 6 would not go in all the way. I re-lubed those and repeated the sizing - they still wouldn't go in the gauge all the way - base sticking out approximately 1/16" to 1/8". Those were serrated out and marked. I measured the cosigning just above the extractor groove and all of the six that wouldn't go in to the gauge appeared to be "in spec" at that location. I ran out of time and have been busy all week, but I'm going to take a couple of those casings, rub a black felt ten over the sides and put them in the gauge to see where the "hang up" is on them. My guess is that all of the casings were shot from different guns and those six may have been shot in one with a chamber a bit big in the unsupported area of the base?

It really isn't a big deal - 308 brass is plentiful and fairly inexpensive. And, who knows? When I do find a 308 rifle - those casings may chamber just fine. I have a stash of 308 fired casings that I've collected - probably close to 500 more - so when I go to FL size them, it will be interesting to see how many don't fit in to the cartridge gauge.

I'm only going to have one 308 and 30-06 rifle so once the brass is fired in them, I will probably only neck size the brass for them a few times before doing a FL size, annealing, trimming, etc. as required. I shoot my 30-30 in two different rifles - a Winchester 94 Ranger and a Marlin 336SC - I don't load heavy as all I do is plink with them (I don't hunt anymore) and on those, I can get by with just neck sizing and the brass will work in both rifles as the chambers have to be really close. The 8mm Mauser is getting light loads as well and once I do a FL size on them for new to me brass, neck sizing is althaea is required. My Mauser is 113 years old and shoots very accurately out to 100 yards with my lighter cast loads.

Many thanks again on the lesson - it is appreciated!

Jim

A lot back in the day when 308 and 30-06 were the rounds for high power used small based dies for the rapid fire ammos for the quickest easiest functioning of the rifle. 10 rds with reload in 60 or 70 seconds dosnt leave much extra time for tight ammo or problems.

Some brass has more memory than others and a pause of 5-10 seconds while its in the die may help reduce this effect. if its neck shoulder area annealing may also help. 308 fired in the "roomy chambers" of the belt feds can be a chore to get sized back down to fit a standard chamber. Other brass that's been harder to size back is that fired in fluted chambers. Te force to size is higher doing these.

Ink up the case body ( I like dykem blue lay out ink) and see where its tight work from there. Ideally you only want to bump the shoulder back .002-.003 from fired dimension, this saves over working brass.