Small Base or NM size die for .308 AR

[MontanaHick]

I will be paying off a DPMS SASS in the next few days. I'm pretty much going to start hand rolling for this gun from the get-go.

I currently own a Forster NM Size/decap die for .308. Am I better off going with a Small-Base size die or will the NM FL die work ok?

Thanks in advance!

 

[Bennybone]

Re: Small Base or NM size die for .308 AR

You will find after multiple reloads that rounds will not chamber (jam) if you don't full length size with the small base die.

I'd estimate you could get away with 3-4 reloads just neck sizing before you see issues.

Of course if you are loading hot then you might have functionality issues after once fired...

 

[MontanaHick]

Re: Small Base or NM size die for .308 AR

Benny,
I hear you on the small base vs. neck size issue. Is a NM-FL die the same thing as small-base, or am I better off getting an actual small base die?

Also, why is a small base die necessary if a round extracted from a chamber to begin with? Why would it not re-chamber after re-shrink during firing cycle?

 

[K_4c]

Re: Small Base or NM size die for .308 AR

you don't need a Small base die.... just a FL die.

I've been using Redding S type FL bushing dies from the get go for my OBR and MWS with no issues to date (and I'm on my 5th reloads).

Stick with what you got..... size a few and see if they chamber without any issues. I'm sure they'll work fine.

 

[ORD]

Re: Small Base or NM size die for .308 AR

+1 on K_4c's advice.

I wouldn't go buying small base dies yet. Your FL/NM sizing die should do fine for you. Should you experience any troubles (which again...is doubtful), then you can invest in different dies at that time, but for now I'd keep running the dies you are running and invest in primers/boolits with the money saved.

 

[9H_Cracka]

Re: Small Base or NM size die for .308 AR

Lots of bad info provided here above.

First off, your factory DPMS chamber is going to be on the generous side in both body and headspace dimensions.

The two dies you ask about are designed to do different things. The small base is a tighter body dimension die. The "NM" is capable of pushing the shoulder back further than a standard die.

Neither die is required for your rifle.

 

[K_4c]

Re: Small Base or NM size die for .308 AR

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: _9H_Cracka</div><div class="ubbcode-body">Lots of bad info provided here above.
The "NM" is capable of pushing the shoulder back further than a standard die.
Neither die is required for your rifle. </div></div>

You say the NM die is "capable" of bumping the shoulder back further than a standard die.... how much more? and are they adjustable to the point of negating competition shell holders?

thanks for the feedback...

 

[9H_Cracka]

Re: Small Base or NM size die for .308 AR

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: K_4c</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: _9H_Cracka</div><div class="ubbcode-body">Lots of bad info provided here above.
The "NM" is capable of pushing the shoulder back further than a standard die.
Neither die is required for your rifle. </div></div>

You say the NM die is "capable" of bumping the shoulder back further than a standard die.... how much more? and are they adjustable to the point of negating competition shell holders?

thanks for the feedback...

</div></div>

From Redding's site:

"Now you can control headspace. The new Redding Competition Shellholders are packaged in five piece sets in .002” increments (+.002”, +.004”. +.006”, +.008” and +.010”). "

Notice there are no "-" headspace variants of the shell holders.

 

[bustin]

Re: Small Base or NM size die for .308 AR

A few years ago something similar came up. I called the die companies to ask how they manufactured the dies in relation to the chamber diameter spec. RCBS FL dies size the dia .002 below min chamber dia, their SB dies size .004 below.
All of Hornady's dies size .004 below making them small base more or less. Forster is like RCBS .002 below. Redding would not give me any information but from what I can tell they size .001-.002 below but I had a set that would not size the dia of the cases down enough to feed reliably in a AR. I replaced them with a set of RCBS that took care of the problem.
IMO the shoulder of a round used in a semi auto should be pushed back .004 from the fired case size for reliable feeding.

 

[K_4c]

Re: Small Base or NM size die for .308 AR

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: _9H_Cracka</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: K_4c</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: _9H_Cracka</div><div class="ubbcode-body">Lots of bad info provided here above.
The "NM" is capable of pushing the shoulder back further than a standard die.
Neither die is required for your rifle. </div></div>

You say the NM die is "capable" of bumping the shoulder back further than a standard die.... how much more? and are they adjustable to the point of negating competition shell holders?

thanks for the feedback...

</div></div>

From Redding's site:

"Now you can control headspace. The new Redding Competition Shellholders are packaged in five piece sets in .002” increments (+.002”, +.004”. +.006”, +.008” and +.010”). "

Notice there are no "-" headspace variants of the shell holders. </div></div>

I understand what comp shell holders offer.... when do you not want to bump the shoulder back? Is that an attribute (a "-" headspace) to the NM dies that others don't offer?

 

[9H_Cracka]

Re: Small Base or NM size die for .308 AR

The Forster NM die in 308 was made specifically for match gas guns with match chambers cut to minimum SAAMI headspace dimension.

Here's what happens. Let's say you are starting with new brass, which is typically .001" -.002" UNDER SAAMI on many dimensions, including headspace. You fire it in the gas gun. even though the chamber headspace is at .000" over minimum, three things are at play. One, brass springback. Two, brass growing beyond chamber dimension in the course of the rifle cycling while there is still some case adhesion to the chamber at the start of extraction. Three, in gas guns you need to size the headspace to be .002" under chamber dimension when done, which also has to account for brass springback during sizing.

Put all of these things together and you need a die that is capable of sizing the brass as much as .005" under SAAMI minimum headspace, particularly when not starting with new brass rather are using brass fired from something with a more generous chamber....

The other solution is to simply have a machinist chuck your die up in a lathe and take a few thou off the bottom of it.

 

[K_4c]

Re: Small Base or NM size die for .308 AR

I appreciate the feedback.... both my .308 gas guns work fine with FL redding "s" type bushing dies. I only bump the shoulder back .002"-.003" and haven't had one issue....

I suppose this is where my knowledge ends. Again I appreciate your input 9H.

 

[MontanaHick]

Re: Small Base or NM size die for .308 AR

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: _9H_Cracka</div><div class="ubbcode-body">Lots of bad info provided here above.

First off, your factory DPMS chamber is going to be on the generous side in both body and headspace dimensions.

The two dies you ask about are designed to do different things. The small base is a tighter body dimension die. The "NM" is capable of pushing the shoulder back further than a standard die.

Neither die is required for your rifle. </div></div>

Cracka, is this statement also true about their SASS rifle? Are all their chambers cut the same?

 

[9H_Cracka]

Re: Small Base or NM size die for .308 AR

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: MontanaHick</div><div class="ubbcode-body">

Cracka, is this statement also true about their SASS rifle? Are all their chambers cut the same? </div></div>

The only claim I would make about a mass produced rifle from DPMS, regardless of what letters and numbers they use to describe it, is you can count on inconsistency more than you can consistency from them.

I will say this - chambers cut at or near minimum dimension are going to result in more customer service claims and calls then those cut closer to no-go, hence the information above regarding minimum dimension match chambers as being the drivers behind the detailed responses and the lack of detail in the first response.