20 Vartarg with .050 freebore

[michaeljp]

the rifle i have recently rebarreled to 20VT has a freebore of .050 With some of the projectiles im using, 32gn SBK, 39gn sbk, 35 berger 40 berger and some local made 40gn projectiles, with the bullet touching the lands i only have about 2-3mm( .078"-.118") of bearing surface in the case neck. The 39SBK's have a bit more and are close to the neck shoulder junction. The cases are lapua 221 fireball.
Im thinking of getting a new reamer, any suggestions as to the freebore i should get? Im looking at mostly shooting the 35 and 40 bergers in 100-200yds BR comps.
Or if anyone is willing to sell their reamer with less freebore id be interested. Im in Australia by the way.

 

[dedogs]

the rifle i have recently rebarreled to 20VT has a freebore of .050

How does it shoot? My Var-Targ does best with 40g V-Max jumped .030. Haven't tried any lighter bullets but I use this rifle for varmints out to 300yds. dedogs

 

[michaeljp65]

How does it shoot? My Var-Targ does best with 40g V-Max jumped .030. Haven't tried any lighter bullets but I use this rifle for varmints out to 300yds. dedogs

It shots pretty good with 32gn SBK's,thats all I've tried so far, but I'm getting a BR rifle made with a similar freebore and want to shoot the 35 and 40gn bergers, which have less of the bearing surface in the case neck than the 32 SBK's.

 

[rifleman700]

the rifle i have recently rebarreled to 20VT has a freebore of .050 With some of the projectiles im using, 32gn SBK, 39gn sbk, 35 berger 40 berger and some local made 40gn projectiles, with the bullet touching the lands i only have about 2-3mm( .078"-.118") of bearing surface in the case neck. The 39SBK's have a bit more and are close to the neck shoulder junction. The cases are lapua 221 fireball.
Im thinking of getting a new reamer, any suggestions as to the freebore i should get? Im looking at mostly shooting the 35 and 40 bergers in 100-200yds BR comps.
Or if anyone is willing to sell their reamer with less freebore id be interested. Im in Australia by the way.

ZERO FREEBORE

 

[michaeljp65]

ZERO FREEBORE

Thats what i was thinking rifleman700.

 

[Phil]

.020 Free Bore.

 

[NorCalMikie]

ZERO freebore. Start off with the lightest bullets you can get your hands on and go heavier as the throat wears.
I prefer as much bullet to neck contact as I can get.
Nothing worse than having too much freebore and you can't reach the lands with you favorite bullet. If you want more freebore, consider a "throat reamer" and make the freebore whatever you want. You can always go longer but you can't go shorter without it being a major project.
IMHO, "Custom" cut chambers, cut to YOUR specs is the only way to go. And if it isn't exactly what you want, you've got nobody to blame but yourself.

 

['Freak]

Thinkin’ with a throat ID less than .0005” greater than bullet diameter, that having at least some freebore length would help to keep the bullet’s bearing surface better aligned as the ogive enters the rifling.

 

[rifleman700]

Even .020" is considered a long freebore in the 20VT. I have a 243 Win 1-14" twist that has a minimum spec .020' freebore and the bullets used have a lot more bearing surface than the diminutive 20VT. Go to saubier.com and search the forum there for what is common with the 20VT. Those guys know small calibers.

 

[michaeljp65]

Even .020" is considered a long freebore in the 20VT. I have a 243 Win 1-14" twist that has a minimum spec .020' freebore and the bullets used have a lot more bearing surface than the diminutive 20VT. Go to saubier.com and search the forum there for what is common with the 20VT. Those guys know small calibers.

I have looked there rifleman and it seems most blokes use 32gn projectiles and a zero freebore. Today i measured the base to ogive on some projectiles, the 40gn bergers were slightly longer than the 32 SBK's but the 35gn bergers were a bit shorter than the 32's. So I'm thinking either a .010 or .020 i want to use the 40's as i hope they will hold up in the wind better than 32's or 35's.

 

[rifleman700]

32 grains seems to be the best bullet weight for the case capacity in the 20VT is why most go that route. I have a 20VT planned and that's the route I am going. In my 17FB I learned the same thing. I was shooting 30 grain pills for years but was never 100% happy with the performance. Switched to 25 grain pills and problem fixed. Perfect mix of speed and accuracy.

 

[Tiratore]

I just looked up the dimension on the reamer drawing in Todd's book - it's 0.032 from the end of the cylindrical portion of the neck cut to the point where the taper begins on the rifling. The reamer used to cut my chambers is made to this standard. All the bullets I have tried can be seated to touch.

 

[SS427]

When I was doing some 20VT reamer research I was told my Cooper they use a .050 throat reamer made by PTG. Bullets.com carries 20VT reamers and they stock a .050 reamer made by PTG, which according to them is what Todd designed the cartridge around. I got a copy of a PacNor VT reamer and it too is .050. I would say the standard is .050. If you go less throat it means less powder capacity, but understand the desire to have more bullet in the case.

In my single shot Cooper using 32 grain Hornaday Z-max flat base bullets I have about .140 of the bullet inside the case with the bullet slightly into the lands. If I had a repeater I would want more but with a single shot I consider it no big deal. It sure shoots good. I'm having a new barrel chambered for 32 and 35 grain bullets and am going with the .050 throat...but it will go on a single shot rifle.

 

[rifleman700]

.050" freebore reamer built for safety and legal purposes only. Even the 17HH saami spec reamer is .050." There is no practical reason to have one unless you are inexperienced in handloading. Even with a zero freebore there is room to jump because of the length of the ogive with the bearing surface in the case neck. My zero freebore 17 tac load jumps .012." I even had a 7RUM with a .063" freebore reamer built for a 180 VLD with the majority of the bearing surface in the neck and I still jumped it. As NCMikie said above the more bearing surface and neck contact the more concentric your round. Less freebore gives you more room to chase the lands if needed.

The thought that there is less capacity with a zero freebore in a 20 cal is false. Look how short the bullet is. Even if that was true, less capacity = higher pressures = higher velocity for that given charge. Its ideal anyway to match your powder burn rate to your case capacity / cartridge and barrel length anyway so nothing is lost with much to gain in a zero freebore. Take a caliper and open it up to .050" and tell e how much case capacity you would lose if seating at the lands. You count the difference in powder kernels.

 

[SS427]

How much accuracy gain would I achieve if I had .190 of the bullet in the case as opposed to .140? Just curious...the new barrel is not chambered yet.

 

[rifleman700]

Otter, Its about how much bearing surface in the neck.

Also, let me make it clear I am not bashing a .020-.050" freebore its just that the zero freebore is better in the long run. For example, if you were to build a 20VT with a .050" freebore and it shot great jumping bullets what do you do when throat erosion requires you to seat the bullets out longer to get that accuracy back but you can't because you are left with minimal or no bearing surface in the neck? You would then need to either re-barrel or set original barrel back. With a zero freebore once the throat erodes you will still have plenty of bearing surface in the neck of the case to support the bullet when seating depth adjustments are done.

It gets confusing sometimes I know to get so many differing opinions on forums so let me give some advice. Send Greg Tannel at Gre'tan Rifles an email and ask him what freebore he recommends for a 20VT. Greg IMO is one of the best and most knowledgeable gunsmiths in the world. He currently has a 24 month wait time on rifle builds for good reason - he is the best. I am currently on his wait list for a 20VT build in January of 2018. The 17 Tac he built me shoots in the zeros and the 6.5x47L and the 7MM SAUM both shoot in the low 2's.

 

[Jonathan Zimmerman]

Spec'd for the 55 Berger. Haha

 

[ASbobcat]

the rifle i have recently rebarreled to 20VT has a freebore of .050 With some of the projectiles im using, 32gn SBK, 39gn sbk, 35 berger 40 berger and some local made 40gn projectiles, with the bullet touching the lands i only have about 2-3mm( .078"-.118") of bearing surface in the case neck. The 39SBK's have a bit more and are close to the neck shoulder junction. The cases are lapua 221 fireball.
Im thinking of getting a new reamer, any suggestions as to the freebore i should get? Im looking at mostly shooting the 35 and 40 bergers in 100-200yds BR comps.
Or if anyone is willing to sell their reamer with less freebore id be interested. Im in Australia by the way.

I don't know what the FB is on mine, but it's the most accurate gun I own with 32 and 39 SBK's. No difference in accuracy. I originally thought the 39 would be too heavy for the case, but not true. With a full case of H4198 it gives me the best combination of accuracy and long range performance. The only difference between the two is in the boat tail, so the ogive is the same. I keep my seater the same for both. 40gr VMax will shoot in my 12 twist, but not sure about long range stability. The 39grSBK gives the highest BC in the shortest package.