Tutorial of How to convert 223 cases to 20 Practical

[TheCZKid]

I'm just getting back to working on loads for my 20 Practical, since 2018. I was reviewing my process of making 20P brass from Lake City cases. Today I was sizing my cases in stages, and noticed the concentricity was good from first FL die, then went way off with first bushing. So I called Redding today to see if I was doing something wrong. They said if I'm getting 5 thousandths of runout that's really good, and should not have any noticeable affect on accuracy.
Some cases were going from about 1 thousandth to 5 to 8 thousandths. Tonight I found a method for making my cases average 2 thousandths of concentricity when final. So, I wrote myself a "how to" page, so I could review it in the future, if I forgot again.

I'm not sure how well others first converted cases are turning out, and am curious if my methods are similar to others. Here's my info I wrote, curious what you think of my "How-To Tutorial" list for myself. Thought it might be helpful for new 20 Practical reloaders too.

How to make Concentric 20 P Cases, with your first conversion cases.

Prepare cases by de-capping the primers, cleaning the cases, primer pocked uniforming, and flash-hole deburring.

1. First size once shot cases in a Full-Length Small Base sizing die, with the Expander Rod removed.

2. With my RCBS FL SB die it takes the neck diameter from outside diameter of .2520” to .2375”, and I only let the shoulder get pushed back to 1.575” or less approximately, not below 1.573” base to shoulder datum, with Hornady G240 case comparator. The concentricity from a Full Length die should be about 1 thousandth.

3. Next, with Redding S Die put in 233 bushing with the lock-nut from the expander rod on top as a spacer. Set die to NOT “bump” or set back the shoulder for this first bushing sizing, or at least not to the final shoulder bump you want for the final dimension. The concentricity might not be very good, from .002” to .008” runout.

4. In Redding die, install 225 or desired final bushing size stamping facing down, and then set the die to bump the shoulder back to 1.567” base to shoulder with AR barrel (or to your desired final dimension for your chamber). With the bushing and the bump together in the final sizing, this should bring the concentricity to .001 to .004 on average. The shoulder bump and bushing sizing both together on final sizing seems to really help to bring the neck into concentricity with the case on the final sizing. I even had the .008 runout necks go back to about .002 to .004 using this method.

5. After it’s sized, then trim necks to OAL of 1.750" or 1.755” for case, and chamfer & deburr the necks. Clean sizing lube off exterior, run a brush through the necks, and you’re ready to load.

Annealing might be a good idea after your cases are freshly converted, or at least after fired 2 or 3 times.

Neck Turning:
After the brass is shot and fire-formed to your chamber, it will be more concentric. This would be a good time to turn the necks. The sizing down of the neck from 223 to 20P tends to make the final thickness of the neck uneven, and a skim turn to bring it to uniform thickness will help in accuracy.

Keep in mind, if you turn the necks, it will make change the outside diameter of the neck, and lessen how much your bushing ends up sizing your necks, and neck tension will be less. If you use a bolt action rifle the neck tension can be as low as one to two thousandths. If you are using an AR upper you will need more neck tension to keep the bullets from sliding forward when they chamber, so you might need a smaller bushing. In an AR four thousandths or more neck tension might be minimal to be safe. So, a final bushing might be 224, or what you determine is correct for your application.

 

[Coyotefurharvester]

Case length 1.760. Annealing before neck reduced.

 

[L.Sherm]

I have a Bullberry forming die that will reduce mine to 20 cal in 1 step then I anneal and run through my FL Redding 223 bushing die.
More than one way to skin a cat though.

 

[Oso]

I would anneal before you start any of the resizing process, and then do a second annealing after the cases are fully formed. Just to clarify...

Step 1 - Full Length Sizing DIe (small base) - I am assuming this is a .223 cal die?
Step 2 - RCBS FL SB Die - I am assuming this is a .20 cal die? with the internal parts removed?
Step 4 1/2 - Run newly-formed case through an expander mandrel to open neck to appropriate dimension.

 

[TheCZKid]

I would anneal before you start any of the resizing process, and then do a second annealing after the cases are fully formed. Just to clarify...

Step 1 - Full Length Sizing DIe (small base) - I am assuming this is a .223 cal die?
Step 2 - RCBS FL SB Die - I am assuming this is a .20 cal die? with the internal parts removed?
Step 4 1/2 - Run newly-formed case through an expander mandrel to open neck to appropriate dimension.

Okay, I should have changed some stuff in the list based on your guys comments. 1 and 2 were really the same step, #1 is a FL sizing die is a 223, and step #2 is actually a further explanation of step #1, my bad.
Step #4 with expander mandrel would seem to be a better alternative of sizing from the inside. The bushings size from the outside of the neck.
I actually think a mandrel is a more precise way to size necks to consistent ID, but I haven't got any mandrels, so I'd be using the bushing to size it from the outside.
But... that always relies on the neck thickness being the same from case to case, and that's why the neck turning seems to be important with this process. I haven't started turning my 20P necks yet, as most of my brass is newly formed, and not shot from my barrel yet.

Case length 1.760. Annealing before neck reduced.

And I think that's a great idea too. I wasn't sure what the correct OAL on the case was supposed to be for trimming, thank you.

 

[Oso]

You want to use both. You are going to size down the neck a little bit below your desired neck tension. Then the next step is to use a Neck Expander Mandrel to expand the Neck (ID) to get he perfect neck tension. The other part of using the neck expander mandrel is it pushes any irregularities to the outside of the neck... nice smooth, clean, neck to seat your bullets.

21st Century Precision makes a nice mandrel die and all the the inserts that you want. Price is reasonable.
Sinclair also offers a similar product.

 

[TheCZKid]

You want to use both. You are going to size down the neck a little bit below your desired neck tension. Then the next step is to use a Neck Expander Mandrel to expand the Neck (ID) to get he perfect neck tension. The other part of using the neck expander mandrel is it pushes any irregularities to the outside of the neck... nice smooth, clean, neck to seat your bullets.

21st Century Precision makes a nice mandrel die and all the the inserts that you want. Price is reasonable.
Sinclair also offers a similar product.

I actually looked for 21st Century Precision mandrels for my 17 Hornet and 20 Practical, but their sizes say available from 22 to 338 caliber. I don't know if there's a mandrel made by anyone for 17 and 20 caliber, but I'd be interested in finding both.

 

[L.Sherm]

Porters Precision will make what you want.

 

[B23]

KM Precision Shooting Products makes them for 17 and 20 cals as well as they generally always have what you need in stock. I've used their stuff for years they make a very fine product.

Expand Mandrel for Bullet Tension

Expand Mandrels for Bullet Tension expand the case neck so the brass will spring back to the correct size needed for seating bullets.

kmshooting.com

 

[Coyotefurharvester]

I have Sinclair 17 and 20,22 mandrel. The 20 cal expander(E) measured 0.201.

 

[L.Sherm]

K@m's are spendy its why I went with Porters Precision 10.00 ea and I have no complaints

 

[jepp2]

I don't know if there's a mandrel made by anyone for 17 and 20 caliber,

You can buy neck turning and expanding mandrels for the 17 and 20 cal, will give you a 0.001" step option.

 

[TheCZKid]

You can buy neck turning and expanding mandrels for the 17 and 20 cal, will give you a 0.001" step option.

I'm new to doing neck turning, and have not used an expanding mandrel, so I'd have to get educated a bit before I purchased something. I started using my Hornady neck turner I purchased many years ago, on my 17 Hornet cases, as those necks vary in thickness a lot.
And, already have a 20 caliber mandrel for turning these 20 Practical cases. So I think I'm okay with sticking with that gizmo for turning necks.

I currently use a Redding S die with bushings for determining neck tension in my 20P cases. I'm thinking my next step is to skim turn some of the necks of once-shot (in my 20P) after I re-size them with my 225 bushing, as that's the only way I currently have to make the necks any smaller with the 20P cases.

Then, I assume I might need a Smaller size bushing to size to the same neck tension, after I turn the necks (since they have less material / thickness). And, if I want to incorporate the use of an internal expansion mandrel, than need a Smaller bushing, below the size of the expander mandrel, so the expander would determine the final internal diameter...

Sounds like some stuff to figure out: Bushing size(s) to buy, diameter expander mandrel(s) to buy, and how much neck tension am I wanting to have for my AR version of 20 Practical, so the bullets stay put in the semi-auto action?

 

[L.Sherm]

Personally if you use good brass I see no need to turn necks on 20 Prac brass unless your reamer used leaves you no choice.

 

[TheCZKid]

Personally if you use good brass I see no need to turn necks on 20 Prac brass unless your reamer used leaves you no choice.

I've had folks say, since the 20 Practical neck has bee squished down it causes the brass to not be even in distribution in the neck wall thickness, seems to make sense to me. For me, it helped with the 17 Hornet necks, because Hornady doesn't make them very precisely. The 223 brass I'm using is LC (Lake City) and I think it's really good brass, pretty uniform, I use it for my AR's. Plus I pick it up free in abundance where people go shooting in my area.
I'm thinking I'm likely to try turning some necks, see if my 225 bushing doesn't give enough tension for my AR rifle, and if I need to buy a 224 and / or 223 size bushing. Then they should have consistent neck tension.

 

[jepp2]

Then, I assume I might need a Smaller size bushing to size to the same neck tension, after I turn the necks (since they have less material / thickness).

Correct.

And I'm not necessarily suggesting you turn your case necks. Only that since 21'st Century doesn't offer expander mandrels for the 20 Cal, just another option.

My process, and I think I might have shared it with you before
- Size with a FL 223 die with the expander removed. I haven't ever needed to use a small base die. I use my 223 die (have several) with the smallest neck diameter, but it is MUCH larger than yours.
- Redding Competition neck sizing die with a .235" bushing
- FL 20 Practical sizing die (I actually have 3 with different neck diameters). I pick the one based on the brass I am using. For LC I use the one with the .224" neck. My experience across many calibers was Redding bushings create neck runout. I was glad to see they gave you runout numbers in the range I experienced. However to me 0.006" neck runout is unacceptable.

Most of my 20P get fired in an AR rifle, and I never have had an issue with sufficient neck tension to keep the bullet from moving.

Here is one of mine at work.

 

[TheCZKid]

Most of my 20P get fired in an AR rifle, and I never have had an issue with sufficient neck tension to keep the bullet from moving.

That's a nice looking rifle, and I like the bench too! Looks like you might have made that shooting table?

Yes, the RCBS 223 FL die does reduce the neck diameter excessively, to my way of thinking. Overworking the neck. I actually purchase my AR upper in good used condition, and it came with the Redding 223 REM B/FL 5T bushing die, and also the 233, 226 and 225 bushings, plus a Competition Series 204 Ruger seating die. The barrel is a White Oak Armament 24" bull barrel, and it was all for $400, so I couldn't pass on that deal. I have been mostly going by what the original owner said he did to convert the brass to 20P. It wasn't until the last couple weeks I decided to really work to get more accurate loads for this gun.

All the brass I created in 2018 I used the 226 bushing for the final OD, and I realized it was not enough neck tension, as the bullet was definitely moving right into the lands when the bolt went forward. So now I'm using the 225 and going back through all the brass and necking it down so it's safe to load.

I'm not sure if I want to neck turn, but seems like a good idea, and if I do I'll probably buy a 224 and 223 bushing. Curious what others are using??

 

[L.Sherm]

If you wanna turn neck by all means do it, I run alot of LC brass and it is good brass.
Most 20 Prac reamers have a chamber .232 nk its what mine is and I believe without looking my loaded rounds are .228
If turning necks are an accuracy gain is what your after not sure if that goal is gonna be achieved on a 20 prac but thats something you may have to try yourself I just never found it much of a gain.

 

[232]

I have both 21st century and pma 20cal expander mandrels. Did they quit the 20's cause of the chino virus? Last I knew they both had 17cal expanders also.

 

[B23]

Personally if you use good brass I see no need to turn necks on 20 Prac brass unless your reamer used leaves you no choice.

X2

I neck down Lapua 222 brass for my 20-222 and Lapua 22-250 brass for my 20-250 and I don't turn the necks on either one. With the Lapua brass unless you have a tight neck situation due to the reamer used there is no need to turn necks.