.20 cal barrel recommendations

[big7fan]

I need to purchase a .20 cal barrel for dog towns. Going with a 20 practical on a contour at least rem varmint. If I could ever find any, I would like to shoot the 39 gr blzkgs, so I'm thinking about an 11 twist. I have lots of 205M as well as N133, benchmark and some blc2

What are your thoughts on number of groves and barrel length.
Thanks
Kim

 

[Mark M.]

I used a 24" 11 T Bartlein with a Tikka action on my build, the group below is 5 shot @100yrds first-time at the range, 39 blitzing and N133 205M was a real winner for me, ive never shot that well, I believe the attention to case prep had a lot to do with it. Pac-Nor or Krieger would also be a great choice

 

[Coyote Shadow Tracker]

I need to purchase a .20 cal barrel for dog towns. Going with a 20 practical on a contour at least rem varmint. If I could ever find any, I would like to shoot the 39 gr blzkgs, so I'm thinking about an 11 twist. I have lots of 205M as well as N133, benchmark and some blc2

What are your thoughts on number of groves and barrel length.
Thanks
Kim

The SBK 39gr are very good for .20 cal. Get a 26" with 1:10
Just remember that it is not what you want to shoot, the barrel decides what it likes.
Also H-4895 is a good combo with 39 gr SBK.
Say 3,800 fps and getting 273,600 rpm. Good stability and bullet should stay together.

 

[L.Sherm]

Get a Pac Nor 3G 11tw. You really don't need anything longer than 24" unless you want longer. The Rem/ Varment conture is my favorite for barrel heat.
You can also send your action to them to fit up a barrel. If you can I would go zero freebore or very minimal atleast.

 

[Hugnot]

I have a .20P, 4 land-groove, 11 twist, McGowen, # 3 contour, 24-inch. I shoot 40 grain VMax's with CCI 41's, & IMR 8208 or H CFE223. Easy to tote around on exciting rodent hunts. A 10 twist will probably replace it.

 

[big7fan]

Thanks for all your input.
Hadn't really considered a 10 twist, but will have consider it as Len recommended 10 and a different member in another thread stated that his next .20 would be 10T and not the 11 he has now.

 

[Hugnot]

Miller Stability Estimates for .204 bullets, 40 H VMax, 39 Sierra Blitz King, & 40 Berger HpBt:

The Miller Twist Calculator, an estimator, is used by JBM & Berger for determining twist rates needed for adequate stability - Sg. The math is involved but not rocket science. An adequate Sg value should not be less than 1.4. Environmental factors affecting bullet stability are temperature and barometric pressure. Barometric pressure will vary with altitude - higher is lower. Humidity affects barometric pressure as the hydrogen molecules in water vapor are lighter than nitrogen molecules - humid is lower pressure.

My 11 twist works real good on warm days at 3000 plus feet on pop can size rodents but what if some other bullet like the 40 Berger was needed for shots on bigger targets on cold days - 11 twist Sg 1.26, 10 twist Sg 1.53.

 

[L.Sherm]

There is literally 100's of 11 twists out there that shoot 39-40 grain bullets just fantastic. HELL even alot of 12 twists shoot 39 BK's just fine.
If you go to the calculators my 9 tw with the 55's should " marginally stabile" them. I know guys who have tested the 8 vrs 9 at 600 and 1,000 and all pick the 9.
Numbers are numbers thats it just like E.S and S.D.proof is on target.

 

[L.Sherm]

You must be putting in sea level for elevation, I dont know of a sage rat that even lives at sea level this is from Bergers own website.
Hell I have 4 or 5 12 twists I shoot 34 v- nitemares in fantastic

 

[Hugnot]

What, marginally stable! ^^^

Running my quicky Sg calculator for a 2000 ft elevation with a standard pressure of 27.82

I comes up with a Sg of 1.36 the same as the Berger Sg that uses a standard Altitude - Pressure conversion vs. common sense barometer reading.

I live at 3500 feet above sea level and my barometer as I read it at this moment reads 29.57 in Hg, our friendly weather lady at local TV weather has the pressure at 29.75 (TV weather obs. downhill). The Berger Sg estimator is flawed as it uses standard pressures at specified altitudes like:

My guess is that the Berger guy who did the Sg estimator thought shooters could not read barometers or look at local weather reports. Don't mess with the Berger Sg calculator - its probably designed to sell Berger bullets.

A thunderstorm in Death Valley would improve the Sg values of Berger bullets.

 

[L.Sherm]

Play with numbers if you want an 11 twist will stabilize any 39-40 grain bullet out there just fine, to many out there doing it to prove it.

 

[Hugnot]

Everybody "plays" with numbers including Berger & the badly flawed Berger Sg calculator that shooters use to select bullets that cost up to & over $75 per box or. $0.75 each. Sg or ballistic estimators are used to establish standards for bullet design & selection including our DOD for ammo & weapon design & acquisition (standards). I believe the DOD specifies a Sg of 1.5 but need to verify.

The Miller stuff seems valid - I have shot bullets that have printed sideways bullet holes when the Miller stuff came up with a Sg of less than 1.0.
I don't want to load up a big batch of ammo that has "marginal stability" that might be "just fine" for others. I might need to shoot near sea level on a cold sunny day (cold/high pressure).

Each to their own - I expect stuff to work good every time & place.

 

[L.Sherm]

I own 9- 20 cals with 9, 11 and 12 twists that have shot 32, 34, 35,39, 40, 46, 50 and 55 grain bullets and have been around or shot another 8-10 20 cals, I know what works and what doesnt.

 

[Hugnot]

Ever see this - "Your bullet stability is marginal. You may shoot good groups under these conditions, but the BC of the bullet will not be optimized." - from Berger Bullet wizards

No problem - buy a few more 20's and buckets of bullets & continue to meet expectations.