What will a small base die do for me?

[grubbylabs]

I am looking at getting an RCBS X die and they have them in small base. I am shooting a 308 Marlin Bolt rifle but plan on getting a AR-10 some day will the small base serve any purpose for me or should I get the cheaper one that is not a small base?

 

[R.W.Dale]

Other than costing you more money and overworking your brass

nothing at all

If you want to buy something that will actually help with loading for a semiauto purchase a SAAMI case gauge


Small base dies are a crutch for folks who refuse to adjust a normal FL die properly. Without fail anytime someone posts on a forum about possibly needing SB dies the problems leading up to the person's inquiry miraculously goes away once myself and others convince that person to adjust their FL die properly IE against the shellholder + .25 a turn. I've literally loaded for well over two dozen autoloaders, straight pulls and pumps and NOT ONCE was a standard FL die not up to the task

 

[cfullgraf]

Generally, small base dies are not required and virtually never with a bolt rifle.

Small base dies do extra work to the brass and shortens case life a little.

But sometimes cases fired in one rifle and full length sized won't fit another rifle particularly if the second rifle has a tight chamber.

I have a full length 223 Remington die that when cases fired in a 5.56 nato chamber and resized won't chamber a 223 Wylde chamber in a National Match AR.

But cases fired in the NM rifle and resized in that particular resizing die will chamber in the NM rifle.

 

[Slamfire]

I am always so amazed at the negative opinions I see on small base dies. And they are so strong!

I called RCBS and the tech told me that a small base die reduced the case head by .002” more than their standard sizing die. I don’t see how that can over work brass.

I use small base dies on every caliber that I can get a small base die. Basically that is .223, 308 and 30-06.

I have a spread of match rifles, hunting rifles, and rock busting rifles all in the same caliber. With the small base die I ensure that my ammo will fit all of my rifles in the same caliber.

I don’t know if there is anything to the “overworking of brass”. It is true that military chambers are huge, and brass fired in a military chamber is very hard to small base size. But I don’t know if that really results in lessened case life. At least for axial case expansion.

So many people reload for bolt rifles that they get used to what would be sloppy reloading practices for auto rifles.

As long as the bolt cams engage, you can crush fit an oversized cartridge in a bolt gun. That is why neck sizing is so popular and hardly any bolt gunners ever set up their dies with a case gage. They just crush fit the ammo in the chamber.

Gas guns will jam with ammo that will chamber in bolt rifles.

Garands and M1'a have the inertia to chamber slightly fat and slightly long cases. But it is a bad idea as bolt closure is delayed as the cartridge is crush fit to the chamber. In that time period, that free floating firing is just tapping the heck out of the primer, and your lugs are not engaged.
That has, and will lead, to out of battery slamfires.

Regardless of the type of sizing die, standard or small base, you should always use a cartridge headspace gage to set up your sizing die.

I own a number of Wilson cartridge headspace gages. They cost about $25.00. These work great in setting up your dies to size the case to SAAMI lengths. These gages are also oversize between the shoulder and the base, so you can drop a fired case in the gage and roughly measure the headspace of your rifle.

I also have reamer cut gages. I have asked the gunsmiths who chamber my match rifles to use their chambering reamers and cut me a dimensionally correct chamber from a barrel stub. I can use this gage to tell me if my ammunition is too fat as well as being too long.

I now can gage brass in a virtual chamber. This has lead me to the use of small base dies. In the attached oicture I found two huge fired WRA 68 cases. One would drop all the way in the Wilson gage, but the other would not drop in the reamer cut gage.


After sizing with a standard Lee sizing die, one case would not drop all the way in the reamer cut gage. After sizing with a Redding small base die, the other case would drop in the reamer cut gage.

This tiny amount of case sticking out of the gage may not seem like much, but the unfired cases on my second out of battery slamfire in a Garand stuck out that much. Maybe if the lugs had been engaged instead of the bolt crush fitting the round to the chamber that slamfire would have been in battery. I had to replace the receiver when the bolt knocked the receiver heel off.

If you search enough threads you will find bunches where some poor guy is using standard sizing dies and his semi auto is choking on his cartridges.

If you want to improve your feed and extraction reliability in a semi auto, you should use small base dies.

A couple of caveats, one is that you must set up a small base die with a cartridge headspace gage or you will set the case shoulder back too much. I think this is the origin of those statements that “small base dies oversize brass”. They will if you don’t gage your die set up. The second is that spray on lubes don’t have the lubricity necessary to small base size. You are more likely to get a case stuck in the die than to get it out with these spray on lubes. Imperial sizing wax and RCBS water soluble work just fine in small base dies and I have sized tens of thousands of rounds with RCBS water soluble.


Wilson gage with new Winchester brass.




Once fired WRA 68, one drops in Wilson gage, the other won’t drop in reamer cut gage.




WRA 68 case sized in Lee sizing die, won't drop in reamer cut gage




WRA68 case sized in Redding small base die, drops in reamer cut gage

 

[grubbylabs]

Thanks for the post slamfire1

 

[243winxb]

Seems a small base die would be a good choice. DPMS LR308 TAC 20 which is chambered for 7.62x51, read more > http://www.thehighroad.org/showthread.php?t=555065

 

[USSR]

I am always so amazed at the negative opinions I see on small base dies. And they are so strong!

That's because someone once said they are bad on the Internet, so it MUST be true and we don't have to even think about it! However, if you DO think about it, the only thing a small base die does as opposed to a regular FL sizing die, is reduce the size of the case just a little further down the case. This does not shorten case life. What shortens case life is inducing an excessive headspace condition by bumping the case shoulder back too far, which can be done with any sizing die. That being said, the only time I use a small base die is when I buy once-fired brass that may have been fired in a machinegun or a semi-auto rifle.

Don

 

[Walkalong]

What shortens case life is inducing an excessive headspace condition by bumping the case shoulder back too far, which can be done with any sizing die.

Yep

 

[grubbylabs]

So I am guessing that If I plan on getting a Semi Auto 308 I should plan on getting a small base Die. Its not really that much more so its not really that big of a deal. I have been wanting to try the X die so when I buy I will get the small base.

 

[cfullgraf]

I also have reamer cut gages. I have asked the gunsmiths who chamber my match rifles to use their chambering reamers and cut me a dimensionally correct chamber from a barrel stub. I can use this gage to tell me if my ammunition is too fat as well as being too long.

I now can gage brass in a virtual chamber. This has lead me to the use of small base dies. In the attached oicture I found two huge fired WRA 68 cases. One would drop all the way in the Wilson gage, but the other would not drop in the reamer cut gage.


After sizing with a standard Lee sizing die, one case would not drop all the way in the reamer cut gage. After sizing with a Redding small base die, the other case would drop in the reamer cut gage.

Two questions:

1. Were the oversized fired WRA cases fired in your match chamber?

2. If not, would cases fired in your match chamber and then resized in the Lee full length die chamber in your match rifle?

It is excellent that someone uses a true chamber gauge to test their cases for their rifle. I feel that too much faith is put into the commercial gauges for bottle neck cartridges except for headspace and overall case length.

I use, and will continue to use a small base die with my match AR to insure reliable function. But, I find I need to trim the brass more frequently with small base die sized brass than when using a conventional full length sizing die.

That says to me the brass is being worked more. Whether it is enough to make a difference in case life, my technical training says yes, but I have no data to support that thought.

I am questioning the need to use small base dies with my other 223 Remington rifles, both semi-auto and bolt, but the jury is still out at this point in time.

There are two camps in relation to small base dies, each with very opposing view points. My research (aka dabbling) with regards to small base dies is finding lots of grey areas.

 

[Slamfire]

1. Were the oversized fired WRA cases fired in your match chamber?

No they were range pickups.

2. If not, would cases fired in your match chamber and then resized in the Lee full length die chamber in your match rifle?

I have not determined that in all cases. New brass or once fired LC fired in match chambers do not have a problem in my 308 rifles. However once fired 30-06 brass has problems. I have sized many in standard sizing dies and the stuff drops in the reamer cut gage. You would think that is end of it, but you would be wrong. I found that once I stuffed a bullet in these 30-06 cases, I got an interference fit on many when trying to drop them in the reamer cut gage.

My second out of battery slamfire, my 30-06 cases were sized in a Bonanza Benchrest die. They dropped in the reamer cut gage without issue but stuffing a bullet in the case buckled the case. Just a little of the case head was sticking out of the reamer cut gage.

But remember, according to the brightest guys in the room, only high primers caused slamfires, right? And all my primers were below the case head, so convention wisdom was that I had no problem, right?

Well it turns out the brightest guys in the room were stupider than stumps of wood and their conventional wisdom was all crap.

I size everything that can be fired in a gas gun with a small base die. That does not guarantee that everything will fit the chamber after a bullet is stuffed in the case, but it reduces the chance that case buckling will cause an interference fit.

Now chambering oversized stuff in bolt rifles, I never felt or had a problem. Bolt rifles have sufficient leverage, like 1:7 cam ratios, to crunch the cases in the chambers.

Even rounds that have an interference fit will chamber in M1a's/Garands as the bolt has sufficient forward momentum to crush fit cartridges in the chambers. There is a limit to the amount a M1a/Garand can crush fit and it is 100% dangerous to attempt this at any level.

The point at which the bolt stops and cams down it has the highest velocity it is going to get from the recoil spring. That free floating firing pin is also at its highest velocity. Have you noticed those primer dents in the back of unfired but chambered rounds in your AR?. That is the firing pin tapping the primer. In the AR that has to be after the lugs are engaged. (Because I have never heard of an out of battery slamfire in a AR). However, in Garands, M1a's, that free floating firing pin is tapping the heck out of the primer before lug engagement.

You will read threads in which reloaders brag about neck sizing their M1a brass. They are so proud of having reduced the amount of work it takes to reload for their M1a. They just have to tell everyone how clever they are and how many neck sized rounds they have fired and never had a slamfire.

These fools are proof that some people can play Russian Roulette a long time before they put a hole in their heads. The only thing keeping them from an out of battery slamfire is primer sensitivity. It is just a matter of time till they get one that is overly sensitive and then they will have a ruined rifle. But they won’t be bragging about that experience, nor posting it, you can be sure of that.

I took one set of brass 22 or 24 reloads in a M1a. I lubricated the cases so I got zero case head separations. Early in the effort I was trimming about .003" each reload. Somewhere around reload 5 to 7, I was trimming .001" or so. The cases were being workhardened. Most of the time these cases were small based sized. I found that changing sizing dies caused trim length growth, also shooting in a different rifle. Don't know why, just had to trim more.

I sectioned brass when I got case neck or body splits. Brass flaws cause those. What I saw on high mileage cases was a spongy interior for the lower third of the case. Brass is being washed out of the sidewalls on the inside of the case each time you shoot it.

That tells me taking cases 22 reloads may not be wise as the case is thinning. But I don't know at what reload it is time to quit.

 

[grubbylabs]

Again thanks for your post, that is some good experience to learn from.

 

[Brian10]

I purchased 500 308 brass cases from a seller here. He recommended that I run them all through a small-base die once. I ignored his advice and loaded them as I would any other. About 1 in 10 ended up jamming in the chamber of my DPMS LR-308. So I bought a small base die and ran the remaining cases through. I can tell you it REALLY works the brass because some cases (probably the 1 in 10) require quite a bit of effort.

I don't know where the brass originally came from, but the seller was right in that I needed to run them through a small base die first.

 

[USSR]

If you are buying once-fired 7.62x51 brass, it is almost GUARANTEED that it is machinegun fired. Machineguns tend to have very generous chambers and the web area of the case is typically blown out of spec, and this part of the case cannot be brought back into spec with anything other than a small base die. And, yes, the part of the case near the web has thick brass, and can take quite a bit of effort. BTDT, so I don't buy once-fired 7.62x51 brass any more, unless it has "Match", "NM", or "LR" on the headstamp.

Don

 

[243winxb]

Brass Fired in 7.62x51mm NATO Chambers

Machineguns tend to have very generous chambers and the web area of the case is typically blown out of spec,

I would guess the web area is not so much the problem, but more spring back of the brass shoulder after sizing. If GI chambers are longer as shown here http://www.303british.com/id36.html Then this rule would apply when using standard dies.>

Forming vs. Sizing

Case forming dies are usually cut to size the case slightly smaller than the minimum SAAMI (Small Arms Ammunition Manufacturers Institute) dimensions, to account for the brass case's tendency to spring back after sizing.

Our full length sizing dies are cut to size the case closer to the middle of the SAAMI dimension, because that is where most rifle's chambers are made, and to size to the minimum would shorten case life. Whether or not our full length sizing die will work as a case forming die depends upon the chamber dimensions of your rifle, and how much spring back there will be when sizing the case.

I feel/guess, spring back of the shoulder is the problem, this is corrected by small base dies, much like forming dies. I have never had this problem with M16 223 brass, when using it in different rifles. When sizing 308 GI brass fired in M14s to use in 243win, the standard 243 die could not push the shoulder back far enough for the bolt action to be closed without extra pressure on the bolt handle. Belt Fed machine gun brass may produce a very different result. USSR has much more experence then i, shooting the 308. http://www.thegunzone.com/30cal.html