20 cals projectiles coming apart.

[L-46]

With either hornady 40 vmax or Sierra 39 bks
What velocity do they come apart in either 10 or 11 twist barrels.

 

[L461]

I pushed the 40 gr 20 cal Vmax to 4150 fps and the 32`s to 4400fps accuracy was exceptional

 

[GrocMax]

In my experience for both it isn't velocity alone, but barrel condition, if you've let the corners of the land/groove get some copper buildup or hard carbon in the throat they start coming apart, BK's were much more sensitive for me, they do have thinner jackets.

If after cleaning, patches are still sticky/tight right past the throat, time to break out the JB's or Iosso, that hard carbon buildup ain't coming out with any solvent alone, brush or not.

 

[L-46]

Thanks for the replys.
I will give the throat a polish with JB.
What velocities did you get to when they failed?

 

[GrocMax]

20 Prac the 40's I usually run at 3750. 32-34 4100+. I've had a couple barrels that were MUCH worse than others, and wore out quick.

 

[mshelton]

The 39g BKs hold together fine for me at 4300.

 

[L-46]

The 39g BKs hold together fine for me at 4300.

Have you tried them any higher velocity?
Do you every dust any?

 

[mshelton]

The 39g BKs hold together fine for me at 4300.

Have you tried them any higher velocity?
Do you every dust any?

I got them to 4370 but started to show pressure, never lost one but only shot 6 above 4300.

 

[L-46]

The 39g BKs hold together fine for me at 4300.

Have you tried them any higher velocity?
Do you every dust any?

I got them to 4370 but started to show pressure, never lost one but only shot 6 above 4300.

What twist rate and barrel length do you you have?

I have a 11tw at 28 inches and at 4350 they start coming apart and by 4400 i loose about half of the shots.
4400 would be the next node too!
A couple hit the dirt beside the target and some hit the ground in front, others never made it.

 

[mshelton]

11 twist Kreiger, 27" 20br.

 

[L-46]

Any others have bullets come apart?

 

[Phil]

I've had the 39 gr. B.kings 4550+ in a .20 Dasher with R-15 and moly 'd bullets in a 12 twist.

No blow up's but too hot when the temp warmed up........


Bat action custom rifle 30" barrel.

 

[MrMajestic]

Dang phil, that's smokin'!

 

[pacificman]

When I had my 17 Remington I did have some 25gr. Berger bullets come apart at just over 4400 fps. I ended up with an average velocity of 4165fps. and no more problems. I did push some 25gr. v-max at over 4500 fps. witch all reached their targets. Barrel was 26 inch Pac-nor with 1-10 twist.

 

[Phil]

Dang phil, that's smokin'!

Yeah.....

It was fun, but WAY too much.......

 

[L-46]

I've had the 39 gr. B.kings 4550+ in a .20 Dasher with R-15 and moly 'd bullets in a 12 twist.

No blow up's but too hot when the temp warmed up........


Bat action custom rifle 30" barrel.

Phil that's impressive velocities for sure.
What make of barrel did you have,
i tried a 12 tw and it would not stabilize the 39's even at 4350, had to go to the 40 vmax.
now have an 11tw
im guessing the faster the twist the more likely the blowup.
Just out of interest do you know what you would loose by inch reduction in barrel lenght? i guess it depends on the powder burn rate, but my old 12 twist i was going to cut it inch at a time and measure the drop in velocity back to 24 inches

 

[Phil]

L-46,

This barrel and my .20 BR were both Pac-Nor barrels, both 12 twist, and neither had any problems with the 39`s.

My .20 BR was going 4000-4050 in a 27" tube with moly`d bullets and Benchmark.

I never had the desire to shorten either since i`m a speed demon, so i can`t help you there...

Who`s barrel did you have that wouldn`t stabilize them???


Phil.

 

[L-46]

Phil,
Rather not say who's barrel, it had other issues and was replaced under warranty with no charge.
I now have a Pac Nor 11tw which shoots real nice.
is it possible the current batch of 39's are more fragile?
do you think a good clean 11tw should not rip up the 39's?
I have my replacement barrel just arrive the other day so will chamber that, and see if they stay together
Here's hope-in'

 

[Phil]

EVERYBODY throws a clinker from time to time.........

Good luck with the new tube, I`m glad they took care of you with a replacement.


Phil.

 

[mshelton]

That's odd that the 39s wouldn't stabalize and the 40 Hornadys would, it's normally the other way around, the 40s need a 1-11 though some 1-12s will stabalize them, the 39s though onlt need a 1-12.