Small Base Dies

[Jammer Six]

What does a "small base die" do that a normal die doesn't do?

Why and when would you use one?

 

[Bc'z]

I use a small base die for our AR's. Wifes chamber is bigger than mine.
Having a load to shoot respectfully in both was the goal.

 

[Uncle Ed]

Below three types of Forster full length dies. In a M14 type semi-auto rifle it is recommended to reduce the case body diameter by .003 to .005 smaller in diameter than its fired diameter. This allows the case to spring back from the chamber walls and extract reliably. "BUT" chambers and dies vary in size so nothing is written in stone.

Example I have a standard Lee .223 full length die that will reduce the body diameter and push the shoulder back further than my RCBS .223/5.56 small base die will.

 

[Jammer Six]

Ah, I see!

Thank you!

So it's a solution if my standard dies produce reloads that won't reliably chamber in my AR.

 

[jepp2]

So it's a solution if my standard dies produce reloads that won't reliably chamber in my AR.

Maybe, but only if it is the diameter of the base creating the issue. If you don't set the shoulder back adequately, you can have chambering problems with small base dies.

Like most things, some folks swear by them. Personally I have a set of RCBS 223 small base dies in my cabinet that have never been used. And I load a wide variety of once fired brass (plenty from the military fired in SAW's) for probably more AR's than most and have never seen the need. I shoot around 8-10K rounds a year through gas guns. So I just wonder why I have never needed them, but others have.

 

[bloc]

jepp2 - I agree completely.

I haven't loaded nearly as many of the once-fired military brass as you, but my standard FL die works fine. And, consistent with your experience, the standard FL die does just fine with brass fired in a SAW.

My SB dies just sit on a shelf too.

 

[dolek]

I have an AR that requires SB dies, so I use them. I doubt I am the only one...

 

[Bill K]

Ah, I see!

Thank you!

So it's a solution if my standard dies produce reloads that won't reliably chamber in my AR.

Could be if the base is too large after firing. However it can also be caused by case length/neck being to long and also a bullet that is not seated and bumping into the lands. 80 % of the time in the AR it will be the base diameter.

 

[MikeT49]

I have an AR that requires SB dies, so I use them. I doubt I am the only one...

My 20P and 243 bolt actions require SB dies for brass fired in other rifles. FL std dies will not size enough for those two.

 

[dolek]

My 20P and 243 bolt actions require SB dies for brass fired in other rifles. FL dies will not size enough for those two.

I have never run into that with my bolt guns,glad it's a solution for you . Makes perfect sense and you are proof it works .

 

[Liven The Dream]

Speer Reloading Manual # 8 .

Does have the Original explanation for SB Dies ..

 

[Rsadams]

Have seen a need as stated above for the use of S/B dies in both bolt and automatic.... If it's automatic I use small base dies... The only rifle brass I will pick up are crimped primer brass like lake city because I know it's once fired.... The S/B dies just insure function.... Because the action of the AR is so hard on brass or you end up losing them I don't see any difference in brass life either...

 

[Texas10]

Th

Below three types of Forster full length dies. In a M14 type semi-auto rifle it is recommended to reduce the case body diameter by .003 to .005 smaller in diameter than its fired diameter. This allows the case to spring back from the chamber walls and extract reliably. "BUT" chambers and dies vary in size so nothing is written in stone.

Example I have a standard Lee .223 full length die that will reduce the body diameter and push the shoulder back further than my RCBS .223/5.56 small base die will.

Thanks, you just explained the reason for the "bolt click" I get upon extraction in my bolt gun because I only neck size my 223 brass.

I'd thought it may be because the brass was getting too hard with multiple loadings. Now I see it's just not enough room for spring back, and nothing to worry about since I don't shoot in competition, and don't have to worry about upsetting the gun in the rest.

 

[Rsadams]

I use a small base die for our AR's. Wifes chamber is bigger than mine.
Having a load to shoot respectfully in both was the goal.

AR Chambers are definitely not all created equal....

 

[natdscott]

I have an AR that requires SB dies, so I use them. I doubt I am the only one...

Run a reamer in there, and be happier.

 

[natdscott]

AR Chambers are definitely not all created equal....

Thankfully.

 

[Stepsjframe]

Actually the small base die is also a full length sizer die. The difference between a small base and regular full length sizer die is that the small base die sizes the base of the cartridge case more than the regular die. How much more depends on the cartridge for which the die is made. Yes, the small base die does work the brass more and can lead to shortened brass life. I would start with a regular full length sizer die and only use a small base sizer die if it is really necessary. I only own one small base die. That is for my match chambered .308 bolt gun. I have to use it on cases that are once fired in another chamber (i.e. Lake City Match or M118 brass). New brass does not require a small base die to fit and once the brass is fired in rifle I can use a neck sizer die from then on. But that is a bolt gun. A semi-auto would require a regular full length die. I don't use small base dies for my Garands (I have 9) or my ARs (I have a COLT HBAR and a RRA NM). I can use the brass fired in either AR by running it through my RCBS regular full length sizer die. I can do the same thing with my Garands. Two of my Garands have tighter commercial chambers while the others have USGI chambers.

 

[Dusty Stevens]

Actually the small base die is also a full length sizer die. The difference between a small base and regular full length sizer die is that the small base die sizes the base of the cartridge case more than the regular die. How much more depends on the cartridge for which the die is made. Yes, the small base die does work the brass more and can lead to shortened brass life. I would start with a regular full length sizer die and only use a small base sizer die if it is really necessary. I only own one small base die. That is for my match chambered .308 bolt gun. I have to use it on cases that are once fired in another chamber (i.e. Lake City Match or M118 brass). New brass does not require a small base die to fit and once the brass is fired in rifle I can use a neck sizer die from then on. But that is a bolt gun. A semi-auto would require a regular full length die. I don't use small base dies for my Garands (I have 9) or my ARs (I have a COLT HBAR and a RRA NM). I can use the brass fired in either AR by running it through my RCBS regular full length sizer die. I can do the same thing with my Garands. Two of my Garands have tighter commercial chambers while the others have USGI chambers.

The die companies and others also make small base dies in addition to small base full length dies. They look like an open top pistol die and only size the base. I have some reddings and some customs.

 

[Uncle Ed]

Th


Thanks, you just explained the reason for the "bolt click" I get upon extraction in my bolt gun because I only neck size my 223 brass.

I'd thought it may be because the brass was getting too hard with multiple loadings. Now I see it's just not enough room for spring back, and nothing to worry about since I don't shoot in competition, and don't have to worry about upsetting the gun in the rest.

If you have unequal case wall thickness the case will bulge on the thin side and warp. And this can cause accuracy problems and why full length resizing eliminates the base of the case body from effecting bullet alignment with the bore.

I say this because I have seen Remington cases with .009 thickness variations that warped badly when fired. Meaning the quality of your cases will greatly effect their concentricity after firing the first time.

"a full-length sized case in which the neck is also fully sized. There is clearance at the neck and in the body of the case, the closest fit anywhere is the bullet in the throat. If the neck to bullet concentricity is good (although it needn't be perfect), then the bullet will find good alignment in the throat and the case body and neck will have minimal influence. Let's not forget that the base of the case is supported by the bolt face or the extractor to a certain degree as well; this is yet another influence on alignment. As you can see, there are several points from base to bullet that can have an effect. My procedure is to minimize the influence of those that I can control, namely the case body and neck, and let the alignment be dictated by the fit of the bullet in the throat and to some extent by the bolt's support of the base. Barring a seriously out of square case head, I don't think the bolt can have a negative effect on alignment, only a slightly positive effect from minimizing "case droop" in the chamber. Given that a resized case will usually have a maximum of 0.001" diametrical clearance at the web, this isn't much of a factor anyway.

In conclusion, I believe that allowing the bullet to find a relatively stress-free alignment in the throat by full length sizing (including the neck) and turning necks to enhance concentricity gives the bullet the best probability of a well-aligned start into the rifling."

The Rifleman's Journal
Germán A. Salazar

 

[MikeT49]

Not real heavy on small base die useage. For the 20P it looks like I will only have to use the small base die for initial case forming from 1X fired and from the on, std dies. For the new 243, I have a bunch of 2X stuff. I like to lean on stuff. What I see with this 2X brass is if I lean on it, I get stiff bolt lift usually. Virgin brass at the same charge I have zero ejection issues. Does the 2X stuff have too much "memory"? Am I stuck with a small base die for resizing this 2X sheet everytime? Mike