Need Advice for 20 Practical Free Bore for 40 and 55 Grain Berger BT Varmint Bullets

[lgwatson]

Having a 20 Practical built. 26" Lothar Walther 9 twist barrel, Stiller Predator Action. Would appreciate input for free bore/ leade.

 

[L.Sherm]

Having a 20 Practical built. 26" Lothar Walther 9 twist barrel, Stiller Predator Action. Would appreciate input for free bore/ leade.

Send a dummy with the 55 to JGS or Manson. I would rather have the 40 up in the neck than the 55 bearing surface seated below the neck shoulder junction.
Freebore is not gonna be ideal for both.

 

[pintopete]

Check out the article in the bulletins by WarrenB. He used to be on the forums years ago. He was a big proponent of a FB close to zero.

 

[pintopete]

Something like this…although this is a 20-222, you get the idea.

 

[pintopete]

Warren's 4200 FPS "20 Practical"

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[L.Sherm]

The 222 has alot longer neck than the 223 case, optimal freebore for the 55 will be different between the two.
I'm a big proponent for zero freebore using 32-40 grain bullets but the 55 is a whole different animal.

 

[urbanrifleman]

Having a 20 Practical built. 26" Lothar Walther 9 twist barrel, Stiller Predator Action. Would appreciate input for free bore/ leade.

55s need about 60 fb in a long neck case like a 20 br. So, in 223 is probably more like .100" or a bit more maybe even .120" .

That's just a guess.

 

[L.Sherm]

A 6 BR case for a 20BR doesn't need as much freebore as you think, I have .050 in my 20BRA and the 55 is way up the neck, .015 is about right.

 

[urbanrifleman]

A 6 BR case for a 20BR doesn't need as much freebore as you think, I have .050 in my 20BRA and the 55 is way up the neck, .015 is about right.

I would like to see a picture of a split neck case with that.

Of course, the difference between 15 and 50 is 35 thou, which is a a little over 1/32 of an inch.

With a 300 thou long neck that would be a teeny little bit.



Conversely, a 223 is about a 200 thou long neck.

From my experience, you really want to be at least a 1/16" above the shoulder junction to avoid donuts. The donut is a gradual narrowing that is more like a funnel.

 

[L.Sherm]

I would like to see a picture of a split neck case with that.

???

 

[L.Sherm]

I'm not home right know or I would prove what I'm saying about the 20BRA freebore.
My 20PPCAI has about a .275 neck length and its zero freebore. Go over to the 20PPCAI thread and you will see were I posted were a 55 is in that case, right at the neck shoulder junction at the lands

 

[urbanrifleman]

???

What I mean is something like this.

 

[urbanrifleman]

I'm not home right know or I would prove what I'm saying about the 20BRA freebore.
My 20PPCAI has about a .275 neck length and its zero freebore. Go over to the 20PPCAI thread and you will see were I posted were a 55 is in that case, right at the neck shoulder junction at the lands

Keep in mind, I'm not arguing with your fundings. I'm going off of customers and their fundings.

I'm actually very curious myself.

 

[L.Sherm]

I've been playing with the 20BRA for 8-9 years messing with all kinds of scenarios.
Keep in mind also the 20BRA has pretty good throat wear and these 55's really like to be in the lands or close

 

[L.Sherm]

I'm actually very curious myself.

The easy part is send a dummy to JGS, takes all the guess work out of it

 

[L.Sherm]

Here's is my 20PPCA with the 55 on the lands with zero freebore, its not dead nuts but its damn close

 

[Gabe22BR]

Here’s.55gr - seated to lands …015” fb in 20BRAITHAT’ll be $ .50 for the look & my time…..


You don’t want doughnuts, taper the neck.002” or turn into the shoulder…..

 

[urbanrifleman]

Here’s.55gr - seated to lands …015” fb in 20BRAIView attachment 1631793THAT’ll be $ .50 for the look & my time…..


You don’t want doughnuts, taper the neck.002” or turn into the shoulder…..

Very educational. Thank you.

 

[NorCalMikie]

ZERO with the lightest bullet you can get your hands on.
The throat WILL wear the more you shoot, then you just go to a heavier bullet.
Rather have a shot throat chamber, (you can always ream it a little longer) then way too long and not enough bullet in the neck when you try to reach or get close to the lands. Me? As much bullet in the neck as I can get. And what works for me may not work for you. Never know till you try.

 

[Coyotefurharvester]

I would think the 20p is pretty easy on throats. I have a 20p AR, 200+ rds haven't needed to adjust seating depth yet. Shooting mostly 35-40 gr Bergers. Some Nosler BT. Exterminator is normal powder used.