Do I need a small base die to save my brass? 6.5CM

[bf2junky]

I’m looking for some advice for some heavy bolt lift and extraction issues in a new barrel using brass previously fired from my old barrel. Based on all my testing and research thus far I’m thinking a small base die might be the answer to keep this brass going?

I’m getting a click at the top of the heavy bolt lift and after 3-4 shots the brass won’t extract. I have to get it out with a cleaning rod. I just got some 1x fired Lapua brass and it appears to be fine when checking it in the chamber after resizing. Here is a video.

I have always full length resized with a Redding Type S die. I'm certain the shoulder is bumping .002-.003. I have even tried bumping the shoulder back .005 and still experience the same problems.



I don't think the issue is over pressure. I'm running 42.0 H4350gr with 130gr ELD-Ms seating .020 off the lands. Here is a pic of some fired cases.

It looks like I'm getting some significant friction near the case head trying to extract the brass.

 

[Aftermath]

So...no issue with the cartridge going IN the chamber when loading?

 

[bf2junky]

So...no issue with the cartridge going IN the chamber when loading?

Nope. Chambers fine. Just clicks handle and extraction are the issues. Accuracy is sub 1/2 minute as well at 100.

 

[Maurygold]

Looks very much like your .2 isn’t being sized down from the picture. Measure a fired piece and sized piece.

I have resolved all clicker issues on .2 by going to sac dies and they size down more and farther

 

[Doom]

The rings on the brass above the case head (just above the rim and the ones higher up) lead me to believe there is something going on with the chamber. While it sounds like you are potentially having issues reusing the old brass but I would suggest buying bow of factory ammunition (quality) and see if you have issues with it on first firing and then reloaded.

 

[DeathBeforeDismount]

Either your sizing wrong, your sizing die is jacked or you have a bad chamber. Small base die wont fix either of those issues.

 

[RegionRat]

Agree with the above and will add a comment or two.

If you look close at your photo, the circumferential scuffs at the 200 line and the body-shoulder junction, when added to your clicker observations and the way the younger brass doesn't act the same, would tend to indicate your old brass and that new chamber are not going to be happy.

Sometimes this can be solved with a small base die to "reset" the body, but sometimes this also fails or is temporary. Dies only go so far down unless you get special ones. Sometimes the problem is up at the shoulder diameter and the small base dies fix it.

I would suggest you use a four place measurement (micrometer not caliper) of the brass at the 200 line and shoulder-body junction to study your issue. Take fired and sized dimensions for ones that click and ones that do not. You may find a correlation.

When brass, dies, and chambers are not coordinated, we can get issues with clickers. Sometimes the die dimensions can solve the issues, sometimes they can't or do it only temporarily.

If this starts to happen with that younger brass batch you showed on your video, or if your small base die doesn't solve it and it keeps coming back, then your chamber and dies don't get along.

If your previous barrel got along with your current dies, then this new chamber is to blame. YMMV

 

[Bacarrat]

Just get the RCBS set.

Small Base Taper Crimp Die Set â AR Series | SmallâBase Sizer & 7° Crimp for Reliable SemiâAuto Feeding - RCBS

shop.rcbs.com

I had the same exact thing happen when I swapped barrels on my AW. This also worked with a friends 6mm CM when he got once fired brass from another rifle. Cheap easy fix.

 

[stello1001]

It seems like others are having issues when using old brass on a new barrel that was fireformed in the prior one. What could this be then?

 

[bf2junky]

Thanks for all the input so far. I'm going to try some factory ammo tomorrow. If that's okay I'm going to shoot some of this 1x fire Lapua brass and see what happens.

 

[RegionRat]

It seems like others are having issues when using old brass on a new barrel that was fireformed in the prior one. What could this be then?

It isn't very easy to explain without graphics and plots, but here goes with just words....

Cartridge brass has a few parameters that explain the behavior. If we speak about the modulus, stress, strain, hardness state, yield, etc., then when the case is virgin it has a starting point that has a set of those parameters, and a dimensional relationship to the chamber (and dies).

Each firing cycle causes some of the properties at the body/head to change. Some of the dimensions also change depending on the pressure and deflection (strain). In most examples, the first cycle will be trivial to extract, but as the cycle count goes on, this can change.

When the dies work the body, there are more changes but that concept of yield and work hardening gets to dominate this particular discussion. The specific dimensions of a chamber or die are a "fixed" strain to the first order. (When we put this under the microscope, a chamber/bolt will actually do a significant amount of elastic stretching depending on the design.)

The pressure cycle forces the brass in the body to flex. The case head has a section stiffness right near that 200 line that goes from acting like a balloon, to having a thickness. Some of the flex during the cycle recovers, some of it doesn't, and all of it begins to work harden and change the properties.

When the dimensions of the dies, and the chamber are what I called "coordinated" earlier, that part of the case near the 200 line shrinks enough after firing-sizing-firing to prevent this clicker issue. But, when a chamber is larger than what those dies can handle, then we get to a point where the elastic to plastic parts of the problem start to tip over and resizing no longer "works".

In a balanced coordinated system, you can shoot (below a pressure level) almost indefinitely, or at least have the cycle count up to a reasonable level before the hardening of the case head and the primer pocket dimensions become a limiting factor.

In an uncoordinated system, or when the pressure always takes the brass beyond yield up in the case head with space to flow, we get to where dies might allow the brass to get back inside the chamber, but will still result in clickers on the next cycle.

As chamber reamers, dies, and brass/ammo, has improved, the problem is less common with more standardized designs. However, it takes time for designers, gunsmiths, and users, to iron out the newer ones.

A poor chambering job can set this problem up with any design, but even then when the chamber is borderline on a newer design and the cartridge is operated at higher than traditional pressures, we can see the clicker issues. YMMV

 

[bf2junky]

Will report back tomorrow. I got a box of Federal hunting ammo from Walmart.

 

[bf2junky]

Federal Power Shok 140gr chambered and extracted just fine. I moved on to the Lapua 1x fired stuff that I resized using the chamber test method. Every single round chambered and extracted just how I was used to on my old barrel, flawless. Precision was outstanding as well.

Now I'm wondering since I have about 450 cases of the 1x Lapua should I just move on to that and not waste the time, money and components resizing and fireforming all the old brass again. For now I'm leaning towards just putting it in some bags and save it for when I decide to upgrade sizing dies to maybe a SAC and try it again. Opinions welcome on that.

Here are the three 5-round groups from this morning, and also the brass. The .19 MOA is the best group I've ever shot.