Question on resizing with SAC die

[AFancyPenguin]

I am sizing 1x fired Peterson 6.5CM brass shot from an American Rifle Co CDG. For die setup, I usually find a piece of brass that I barely can start to feel tension on the bolt handle and zero my comparator on that, then set the die to bump 1 to 1.5 thousandths back.

I've never used a SAC sizing die before now and I set it up per their video instructions, adjusted to get my shoulder bump and now the resized brass is noticeably more difficult to close the bolt on. It chambers fine it just feels like I added brass length. I am at a loss to why the sized brass with a shoulder bump fits tighter in the chamber. All the measurements I've taken with my calipers show the brass is smaller other than length, but I confirmed with my borescope the brass length is not bottoming out at the end of the chamber. What am I missing? Any tips?

 

[spife7980]

How much longer is that piece you are testing with than the average of the other pieces?

 

[Rio Precision Gunworks]

This all sounds way more complicated than it needs to be.

Strip the bolt and size a piece of brass down until the bolt almost drops freely, then size down another .001 and the bolt should fall completely free with gravity. Set that piece of brass as your "zero" and just set your die up to to size all your brass to that same size. No need to look for a piece of brass that barely chambers as you're now at the mercy of how consistent that piece of brass is.

With a stripped bolt falling free, you'll have room in the chamber for any inconsistent shoulders that are slightly longer and never have to worry about anything else.

 

[AFancyPenguin]

This all sounds way more complicated than it needs to be.

Strip the bolt and size a piece of brass down until the bolt almost drops freely, then size down another .001 and the bolt should fall completely free with gravity. Set that piece of brass as your "zero" and just set your die up to to size all your brass to that same size. No need to look for a piece of brass that barely chambers as you're now at the mercy of how consistent that piece of brass is.

With a stripped bolt falling free, you'll have room in the chamber for any inconsistent shoulders that are slightly longer and never have to worry about anything else.

I understand that and maybe I didn't explain this well. When I have a piece of brass that chambers without resistance and I resize it, it will now chamber with resistance. It's not length increase and all dimensions I measure with my calipers are smaller after resizing.

 

[AFancyPenguin]

How much longer is that piece you are testing with than the average of the other pieces?

Are you referring to overall length or base to shoulder?

 

[KnowNothing256]

Are you referring to overall length or base to shoulder?

Both please

 

[AFancyPenguin]

How much longer is that piece you are testing with than the average of the other pieces?

Both please

OAL 1.907 +/-0.001" before sizing; after sizing 1.911 +/-0.001"
Base to shoulder: 1.488 to 1.4885" before sizing; after sizing 1.486 to 1.488 since I was messing with the shoulder bump to try to get the bolt to drop nicely. Every sized brass so far has difficulty chambering.

Measured with starret caliper and SAC comparator set.

Also an update: I got the brass to chamber nicely at 1.4835 to 1.484" base to shoulder. I am concerned with the 0.004"+ bump required to get these to chamber. Won't this be a recipe for short brass life and case head separation?

 

[Chris1972]

SAC with or without a mandrel?

Lube inside your neck better. I’ve actually had it make brass longer.

 

[AFancyPenguin]

I've tried both ways with the same result.

 

[Mudflap621]

Sharpie a case and see where the issue is, it might not be the shoulder.

 

[Eric_F]

Hey. I'm not sure what's going on, if it's not lengths I'd look at widths/diameters (neck, shoulders).

But on the 0.004" bump for new brass (if that ends up being needed), if you're concerned you could anneal *after* the first sizing and that ought to be addressed. Further resizing can just be 0.002" or whatever you choose.

 

[AFancyPenguin]

Sharpie a case and see where the issue is, it might not be the shoulder.

I tried that but didn't see anything definitive.

 

[TheOfficeT-Rex]

I tried that but didn't see anything definitive.

Get it really dark with the sharpie, chamber, and post a couple photos. I'd look at the case mouth, shoulder, shoulder/body junction, and around the .200 line. If it's stiff chambering, you should see something on one of those areas.

 

[AFancyPenguin]

Get it really dark with the sharpie, chamber, and post a couple photos. I'd look at the case mouth, shoulder, shoulder/body junction, and around the .200 line. If it's stiff chambering, you should see something on one of those areas.

I've resized all my brass now, so when I do it again I'll try that.

 

[B y r o n]

Don't forget to measure the diameter near the base of the cartridge. It maybe that the sizing process is making the base diameter larger during sizing.

 

[CheapBasterd]

Probably sizing the case, stretching lengthwise but the die is not set low enough to push the shoulders back.

 

[AFancyPenguin]

Probably sizing the case, stretching lengthwise but the die is not set low enough to push the shoulders back.

What dimension are you suggesting is getting larger? Brass OAL is getting larger but shoulder to base is smaller. OAL doesn't interfere with chamber. I confirmed with a bore scope.

 

[AFancyPenguin]

Don't forget to measure the diameter near the base of the cartridge. It maybe that the sizing process is making the base diameter larger during sizing.

Every dimension I could figure to measure was 0.0015 to 0.003 smaller on a sized case.

 

[B y r o n]

Every dimension I could figure to measure was 0.0015 to 0.003 smaller on a sized case.

So what was the difference between the fired case and the sized case above the extractor groove?

 

[CheapBasterd]

What dimension are you suggesting is getting larger? Brass OAL is getting larger but shoulder to base is smaller. OAL doesn't interfere with chamber. I confirmed with a bore scope.

I was suggesting base to shoulder was getting longer but if your measurements say otherwise then I dunno or maybe its still not enough? I responded because this I ran into this issue myself. Same 1x fired Peterson 6.5cm but with a Forster FL die trying to .002 shoulder bump from a barely fitting case. Another 1/8 inch turn resolved the problem for me. I have my die set to what works, not going to dive into .002 shoulder bump for the next couple firings and then revisit.

In your group of once fired Peterson brass did some fit, some were tight, and some didnt, right?

 

[AFancyPenguin]

So what was the difference between the fired case and the sized case above the extractor groove?

Every one I measured was 0.0025 smaller.

 

[AFancyPenguin]

So I emailed SAC as suggested by their phone line and will see what they have to say. The only other thing I can think of is that the radius between the neck and shoulder is being changed in a way that isn't visually obvious but enough to interfere with the chamber after being sized. I am going to try to borrow a different die to see if fired brass will size differently and potentially eliminate measurement equipment and chamber issues.

 

[AFancyPenguin]

I was suggesting base to shoulder was getting longer but if your measurements say otherwise then I dunno or maybe its still not enough? I responded because this I ran into this issue myself. Same 1x fired Peterson 6.5cm but with a Forster FL die trying to .002 shoulder bump from a barely fitting case. Another 1/8 inch turn resolved the problem for me. I have my die set to what works, not going to dive into .002 shoulder bump for the next couple firings and then revisit.

In your group of once fired Peterson brass did some fit, some were tight, and some didnt, right?

That's really interesting you had the same problem with the same brass but with a different die.

There were some 1x fired that had a slight amount of drag closing the bolt but honestly the majority weren't noticable. That said I was running a light breakin load to get 1x fired brass and get my barrel sped up. Maybe thats it?

 

[CheapBasterd]

That's really interesting you had the same problem with the same brass but with a different die.

There were some 1x fired that had a slight amount of drag closing the bolt but honestly the majority weren't noticable. That said I was running a light breakin load to get 1x fired brass and get my barrel sped up. Maybe thats it?

More than likely. Especially with the lighter loads. I noticed in my once fired groups that the ones that did drag a little had a higher charger. The ones that didnt let the bolt fall were near max loads. After reading up a little and learning that it "may" take a couple firings before the brass is fully formed to your chamber. That would be the best time to take measurements and bump the shoulder back. The tape trick worked for me on a sized piece to somewhat confirm. Piece of tape added .002. Tape on no bolt drop, tape off bolt dropped freely.

 

[Rio Precision Gunworks]

I understand that and maybe I didn't explain this well. When I have a piece of brass that chambers without resistance and I resize it, it will now chamber with resistance. It's not length increase and all dimensions I measure with my calipers are smaller after resizing.

Use a micrometer and make marks in different spots on the same places on a case that fits and a case that doesn't. Exactly the same spots. Lay them side by side and make marks with pen/pencil/scribe. So that you know for sure you're measuring same spot.

Calipers aren't accurate enough to take the measurements you need to compare brass diameter. Only length.


Obviously something is larger. But you need to right tools to find it. It's likely going to be the difference of something like .001" somewhere and calipers are only accurate to +/- .001

 

[B y r o n]

Every one I measured was 0.0025 smaller.

One of these is what you need to see where your problem is.

 

[AFancyPenguin]

One of these is what you need to see where your problem is.

Why is that? That wont be a copy of my chamber.

 

[Rio Precision Gunworks]

Why is that? That wont be a copy of my chamber.

If your chamber was cut with a saami reamer, it'll be pretty close.

In theory, you'll be able to slide the brass in slowly and then visually see where you start feeling resistance.

 

[Tokay444]

Is your extractor rubbing the coned breech?
If not, trim the sized brass back to 1.907" and see if it chambers easier.

 

[B y r o n]

Why is that? That wont be a copy of my chamber.

Because if your loaded round will fit this gauge then it should fit your chamber. If it fits the gauge but not your chamber then you know there is a problem with your chamber. If there is a problem with your reloading then it won't fit into the gauge or will show where the problem is; case to long, bullet seated too long, etc..