Do you really need SMALL BASE DIES?

[Innovative]

Re: Do you really need SMALL BASE DIES?

I have never needed to use a small base die. That's not to say that nobody needs one. I'm just saying that after owning almost a dozen semi auto certerfire rifles, and gunsmithing for 30 years, I've never needed one. However, I've seen too many shooters springing towards SB dies when they really don't need it.

When handloads fail to chamber, it's caused by one of two reasons. The case is either too long <span style="text-decoration: underline">at the shoulder</span> or too wide <span style="text-decoration: underline">just above the case web</span>. I quickly eliminate the case length problem by using our <span style="font-weight: bold">Digital Headspace Gauge</span>. About 60% of the time the case measures longer than the chamber (at the shoulder), and a small base die won't help that.

It also doesn't help when shooters push the shoulder back too far, because that's not safe. This can also cause cases to bulge <span style="text-decoration: underline">above the web </span>during the reloading process - making them too wide to chamber. I recommend "measuring" the chamber clearance (at the shoulder) to see how YOUR handloads fit in YOUR particular chamber . . . . . no guessing.

- Innovative

 

[Hummer]

Re: Do you really need SMALL BASE DIES?

I have one RCBS case mic and I noticed the rather sharp shoulder which is why I like the MO Gage and his is cut with a chamber reamer design and the whole shoulder contacts.
I have three of his gages and every one reads "0" with a GO GAGE.
I designed another cartridge design called a 300 Confederate Sharpshooter a couple years back so I took a section of 30 cal barrel and turned it to match the MO Gage and chambered it with same reamer I used on rifle and "qualified" it with a fired case which was my "0" point. So I have 3 1/2 MO Gages.

The DIGITAL HEADSPACE GAGE is intriging. Who makes this? You got a http for it?

Apparently from the comments the Stoney Point is iffy???

OH by the way I finally got a response from RCBS and they say they "do not release die dimensions".

Thusly we need the guys with the SB dies to measure their fired cases and remeasure them after they are fired on the base.

Also I have a freind with a M240 and he just fired off a belt and is saving the brass from this so called big chamber so I will get a measurement from them, resize them with FL dies and try them in my tight chamber rifles.
I have also obtained a NATO chamber drawing for the proof barrels for 7.62 and 5.56 and guess what, they are not JUMBO.

 

[memilanuk]

Re: Do you really need SMALL BASE DIES?

The Stoney Point gauges work just fine, but not an 'absolute' reference as most people think at first. It makes sense once you think about whats involved, but doesn't occur to most people until they get a little further along - I ran into the same deal, sitting there sputtering and unable to comprehend why my readings didn't match *exactly* what my HS gauges were marked, etc. until someone explained it to me.

The RCBS Precision Mics aren't really any better (and IMHO, over priced) - search enough and you'll find people who have factory chambers that are supposedly 'under' minimum SAAMI headspace - a highly unlikely situation.

The digital thingy is one of Larry's tools that he sells from his business 'Innovative Technologies'. It's not a bad idea at all, but again you will be getting a *relative* reference - fired vs. sized for instance, and not something referenced against an absolute - such as the 0.400" diameter datum line @ 1.630" long for a .308 Win. If you are handloading, the arbitrary reference doesn't matter that much as compared to the relative measurments.

It'll be interesting to see what the MG chamber produces... I've sized some .223 stuff fired from MGs and even with a lot of lube it felt more like I was sizing a .30-06 as I had to 'swage' the case back into size/shape. I know that sometimes even on my 'match' AR Service Rifles if I don't watch it the case headspace can stretch a bit as the bolt starts to unlock before the brass has finished shrinking away from the chamber walls. I could easily imagine that effect to be magnified when fired through an MG.

YMMV,

Monte

 

[Hummer]

Re: Do you really need SMALL BASE DIES?

Since no one responded to measuring cases sized in FL die and SB die I just conducted a little study.
Found a can of LC 76 brass off a range fired in multiple rifles and I did some measuring. Sized up 205 cases and will swage primer pockets tomorrow and put in tumbler to clean.

First off I measured base dimension of Lake City M193 and Fed Match 55 FMJBT (both new unfired).
Lake City measured .3712-.3715 .200' up from base.
Fed Comm 55Gr. FMJBT .372-.3721

Ten Cases Sized with FL die adjusted back to "0" on a Mo Gage and checked in LE Wilson Case Gage

Before Sizing After Sizing
.376 .3742
.3758 .3748
.376 .3745
.3762 .3745
.376 .3744
.376 .3746
.376 .3745
.3762 .3748
.3758 .3746
.3756 .3743

Below cases were sized in L.E. Wilson Full Length Die

Before Sizing After Sizing

.3776 .3737
.376 .373
.3758 .3734
.3765 .3736
.3762 .3738
.376 .3732
.3757 .3734
.3764 .3738
.376 .3735
.376 .373
.3761 .3735

The feel for different cases going it indicated many different size chambers.

Would someone please take a SB die and do the same test?

 

[sinister]

Re: Do you really need SMALL BASE DIES?

Define the problem first. <span style="font-weight: bold">If you're reloading for several rifles and chambers,</span> which ones are tighter and which are roomier?

This for the .223, but applies to anyone with multiple rifles of the same caliber:

Start with virgin case dimensions. http://www.accuratepowder.com/data/PerCa...%20to%20187.pdf

Know how your chamber was reamed. http://www.ar15barrels.com/data/223-556.pdf

Concur that case gages, headspace measuring tools, and calipers are absolute minimum requirements.

 

[Hummer]

Re: Do you really need SMALL BASE DIES?

Amen on that. Mic, caliper, and good case gage are the last word.

These are all being sized for any chamber.

The SAAMI drawings call for .3769 to .3789 chamber dimension. The average expanded case was .3759+ so allowing for .001 spring back after firing it appears one can expect .377-.3775 nominal chamber size for 5.56MM in ARs and commercial chambers as well.

P L E A S E
Again if anyone can document a production rifle with a chamber tighter than SAAMI specs please advise. I keep reading about small chambers for 223 needing small dies but no one seems to have small chamber.

With the exception of the bench rest boys who (like me) run tight chambers, it seems to be an imagined problem insofar as small base requirement goes. I could see ordering a reamer to cut .374" chamber on bolt gun for longer case life but that would need a die that sizes to .372" but no one has yet confirmed the dimensions of the Small Base dies.

The 7/8x14 die sized cases to an average of .3735" or .0015 larger than new cases.
The L.E. Wilson FL die sized cases to average of .37467" and I have never seen a case sized in a FL Wilson die that did not go in any SAAMI chamber.

All this is blown away if your die is not bumping your shoulder back to "0".

The LE Wilson FL die was very uniform in sizing cases to where the shoulder contact point was "0" on a MO gage with very little variation. It was harder to control the shoulder bump with the screw in die. I had it set it to size "0" and after it got warm I noticed I was sizing .-002" under so I backed it off to "0". All cases were in spec for FL resized cases on the L.E. Wilson gage.

So bottom line for you guys with small base dies please measure 10 fired cases from one rifle or better yet from several rifles measure them as I have done (fired and sized) and then size them in your SMALL BASE die and tell us what you find.

 

[JCummings]

Re: Do you really need SMALL BASE DIES?

Hummer:
I found some 223 brass I had not sized.
This was WCC Brass fired x 2.

Before sizing the base above the groove measured .374-.3745.
After sizing in a Redding Type S FL die the base still measured the same .374-.3745.
I then sized both unsized brass and FL sized brass in a Redding SB FL die. Both gave a base measurement of .372-.3725. These numbers were very consistent for 10 pieces of brass.
The headspace was set to SAAMI = 0 by an RCBS precision mic.

By the way, I confirmed that it really matters which shell holder is used. The Redding #10 shell holder sized the brass .005 MORE than using the RCBS #10 Shellholder. It is very Important to use the same shell holder unless you are going to confirm your headspace setting on the die everytime (which is a good idea to do for this very reason!)

Also, unfortunately, I do not know which of my 2 AR15s this brass was fired in, The one with the Wylde chamber or the one with the CLE chamber.

I Also measure some unfired LC brass with the same caliper. This consistently measured .371-.3715. SB sized LC brass sized last year again measured consistently .372-.3725.

 

[Hummer]

Re: Do you really need SMALL BASE DIES?

Yep makes sense. You have custom chambers cut tight which is way I like them. I will probably get a compass lake before long and will need a tight die to go with it.
Still we don't have a factory chamber reading from anyone.

 

[JCummings]

Re: Do you really need SMALL BASE DIES?

No we don't and I certainly don't expect to ever see any that are near SAAMI minimum. In my experience they generally run on the larger side. Of course you would expect that for safety purposes as factory chambers have to be able to work with anything within SAAMI spec - even if it is on the upper end.

If you do get a Compass Lake I know you will like it. Frank makes really good rifles!

 

[Hummer]

Re: Do you really need SMALL BASE DIES?

For sure. Had some friends go down to see him last week and he told them he knew me and another buddy in Atlanta as we used to shoot together along with Hugh Manus.

 

[Innovative]

Re: Do you really need SMALL BASE DIES?

HUMMER ......

You can read all about my Digital Headspace Gauge on my website. It works by inserting one of your fired cases, then zero the gauge on the case shoulder. Then just measure one of your resized cases. The gauge displays the difference - which is the clearance (at the shoulder) that YOUR handloads have in YOUR particular chamber. This information allows you to set your die height perfectly.

I like it better than the RCBS Precision Mic, because it works on ALL different calibers. I also like it better than the Stoney Point tool, because it doesn't require a collection of bushings, fittings, inserts or special tools to operate, and the readings are very repeatable.

- Innovative

 

[Hummer]

Re: Do you really need SMALL BASE DIES?

That sure looks like THE thing for all calibers.

 

[Farfyter]

Re: Do you really need SMALL BASE DIES?

Thank You!