20 practical coal

[JB10]

I was just asked by my gunsmith to bring over some seated bullet rounds to make sure they chamber good. I had him go off go/no go gauges but he still wants some rounds to check. I have no idea what to seat some dummy rounds to just to check. I have some 32 vmax and 40 vmax to try for now untill bergers are arround. What are you guys setting ur coal to for me to make some rounds for him to check? I dont want to seat them too long and him throat it longer if not needed. This is a bolt gun

 

[Bill K]

Seat them to the measurement shown in your loading manual for the bullet used. OAL in other words.

 

[JB10]

There is no loading manual for this round, otherwise i would do that

 

[RegionRat]

If you consider the bullet's boat tail to bearing surface junction, and if you intend to load them in the necks above the case neck-shoulder junction, that is a way to decide.

In so many words, if you plan to always seat above the donut.

 

[Coyotefurharvester]

Mine is a gas gun, tipped(32-40 gr) bullets 2.210-2.215 ish coal. I have heard of the bolt guns 2.230 coal with the 40 gr bt Berger. If I seat that long I'm into the lands, Black Hole Weapons barrel. Never felt or seen a donut in any of my cases,probably since it is a neck down cartridge. Your reamer print should give you a good estimate. The gng have nothing to do with freebore/throat.

 

[jpx2rk]

Could probably use the OAL for the 40g vmax in the 223 data.

 

[Bill K]

On this web page on the

There is no loading manual for this round, otherwise i would do that

left side bar, open up 20 cal. also google 20 practical cartridge and I believe sites like Hornady Load Data all show a OAL for loaded ammo.

 

[JB10]

Hornady shows for a 20 tactical. I was thinking about using that info

 

[RegionRat]

Hornady shows for a 20 tactical. I was thinking about using that info

Going off of memory (risky), I think I recall 2.240" COAL kept the 40 VMax out of the junction on 20P and I was typically using 2.250 anyway just cause they would also fit magazine length. YMMV

This was the print from the AS main web site. Maybe ring Kiff and ask him about which bullets seated and how deep?

 

[RegionRat]

Going off of memory (risky), I think I recall 2.240" COAL kept the 40 VMax out of the junction on 20P and I was typically using 2.250 anyway just cause they would also fit magazine length. YMMV

This was the print from the AS main web site. Maybe ring Kiff and ask him about which bullets seated and how deep?

View attachment 1503719

https://www.6mmbr.com/gunweek061.html
Plus and article on a 20 P project

 

[Coyotefurharvester]

Seems reamers have trended towards little or no freebore with the 20p, your gs should be able to give you a cbto measurement(from the print) than you can make up a couple dummy rds to test fit. Or better, make you a stub gage with a window. Than you have no guess work when changing bullets. Ops asking for coal, non of any of the articles give that info. There is a reason, the 20p isn't SAAMI, the reamer used to cut his chamber is the real coal determining factor, short of the gs customizing the throat. I gave him coal for my rifles chamber, I do not load into the lands for any of my hunting rifles.

 

[JB10]

I ended up taking him one loaded with 32 vmax at 2.200 and the 40gr vmax at 2.240.
I also gave him empty sized brass if needed. I just went off of the 20 tac info i had. I had plans on just having it chambered off of headspace gauges and then making a modified case to check bullet seating depth. I was not prepared to give him a round with a bullet seated. Ill know more tomorrow!

 

[Coyotefurharvester]

Here is one reason coal is unreliable.
32 gr vmax cbto 1.8570 results in a coal 2.227
40 gr nosler bt cbto 1.8575 nets a coal 2.214
With my rifle 1.8575 is about max before cartridge starts making land contact. And that length is in line with reamer prints. I don't have any 40 vmax to measure, can't help there.
I would want the 223 gng gage used for headspace, than you should be fine with any FL 223 sizing die for body/shoulder sizing.

 

[JB10]

I told him that tonight that there was no specs so i hope he goes more off the headspace and ill do my seating depth testing.

 

[RegionRat]

My guess, is your GS is well aware of the headspace issues. I should say this if they are a credentialed GS, some folks are self taught and may or may not have the background.

What he needs to know from you, is what bullet you plan to use and how you plan to seat it.

Some folks go farther and tell the GS how much to allow the bullet to jump from that seating depth, and what ramp angle they want on the transition of the lands. Some specify a specific reamer.

Some reamers have different values for the freebore and diameter details, and some are designed with the intent that the GS uses a throating reamer post chambering to adjust the throat to achieve a prescribed distance to lands with a specific bullet.

Once you go down the rabbit hole, it is good to get a grip on what you want and what works for you so you have control over your outcome.

ETA: this is critical for VLD usage more so than if you plan to use tangent bullets. Your GS can add freebore, but they can't put it back unless they rework the whole chamber. YMMV

 

[1raggedhole]

The 20 practical was intended to be used in 223 mags, therefore keeping 2.25-2.26” oal is most logical.

 

[JB10]

Actually just got a call from my smith, the dummy rounds i made the bullets were too long for it. I bet its got a zero freebore to the reamer. He is going to adjust the seating depth for me to match the reamer.

 

[L.Sherm]

I've never worried about OAL in just about all my 20's. I've got zero to .030 in all my 20's except my 20BRA that I shoot 55's through and it has .050 with that long neck I could easily get by with .030 and stay above the nk shoulder junction.
These days I prefer zero freebore if I'm not shooting anything bigger than a 40gr.

 

[K9TXS]

Actually just got a call from my smith, the dummy rounds i made the bullets were too long for it. I bet its got a zero freebore to the reamer. He is going to adjust the seating depth for me to match the reamer.

If it has zero freebore, why not seat the bullet a little deeper in the case. As the throat eventually erodes, you could then seat the bullet a little further out.

 

[hogpatrol]

In my experience, with a zero freebore reamer, there was never a concern about COAL in a bolt or AR rifle. With any weight bullet, regardless of seating depth, COAL was always shorter than the magazines.