.20 Practical question

[nmkid]

Totally lost. I have no idea in this department. So...My new (when I get it back) .20 Prac. will be a no-turn neck with the reamer print showing a measurement of .233 for the neck. To form my cases I went with .223 sizing die for the initial step. Then used my Redding bushing die with .233 and .225 bushings in succession. Necks measured (Lapua cases) .014 +- I then loaded up a dummy round using a 40 gr. VMax. The best neck measurement I could get was .227-.228. So...Would that mean that I would have .005-.006 of clearance? I thought I read that .002-.003 was optimum? Should I be OK?

 

[ratbuster]

Totally lost. I have no idea in this department. So...My new (when I get it back) .20 Prac. will be a no-turn neck with the reamer print showing a measurement of .233 for the neck. To form my cases I went with .223 sizing die for the initial step. Then used my Redding bushing die with .233 and .225 bushings in succession. Necks measured (Lapua cases) .014 +- I then loaded up a dummy round using a 40 gr. VMax. The best neck measurement I could get was .227-.228. So...Would that mean that I would have .005-.006 of clearance? I thought I read that .002-.003 was optimum? Should I be OK?

Are you measuring the Lapua neck walls with a caliper or a tube micrometer? 223 Lapua brass I have is close to .013 wall thickness which puts the loaded rounds at .230. Regardless I would not worry about it. I have a couple of 20P's which have .233 neck chamber diameters and the barrels shoot a variety of brass brands with varying neck thicknesses, all very well.

 

[SmokinJoe]

With Lapua brass you should be getting around .232 on a loaded round, which is a little tight for a field gun IMO. I turn my 20-223AI after FF to get a loaded round dia of .230, which is a little loose by accuracy standards, but foolproof safe. I think you will enjoy your 20Practical.

 

[nmkid]

If your case neck is 14 X2 thats 28 plus 204 bullet dia makes 232?

Well, you certainly got me thinking in a different direction!!! My next door neighbor is a retired engineer. Went and asked if he had a caliper I could borrow. We go into his garage and he pulls out a "Mitutoyo" of some kind. Kinda makes me blush as I think about my HF caliper. He measures the 2 dummy rounds I had with me and...They both measured .232...Twice!! Checked a empty brass and it measured .014. What!? Why would my cheapo measure the neck thickness right and not the dummy round? Oh well, I guess I need a new caliper. Thanks to all...A new day is here!!! Oh. Suggestions on a good , moderately priced caliper.

 

[Mark M.]

What should the case length of the 20 practical be after forming, do I trim the 223 brass to 1.750 before forming ? Need some help here, what are the steps I need to take, thanks

 

[jepp2]

He measures the 2 dummy rounds I had with me and...They both measured .232...Twice!!

My loaded Lapua 20P rounds measure 02305" measured with a B&S micrometer 0.0001" accuracy. I don't turn for my .233" necks, but at .232" you will have to. Did you chamfer after trimming to make sure you were getting an accurate reading on just the neck?

What should the case length of the 20 practical be after forming, do I trim the 223 brass to 1.750 before forming ?

The case length grows during the neck down and needs trimmed before using.

 

[jepp2]

Suggestions on a good , moderately priced caliper.

https://www.amazon.com/gp/product/B00INL0BTS/?tag=accuratescom-20