20 Vartarg .150 Short

[ricco1949]

My K-Hornet is the split bolt 77/22

I don't know what PSI the carbine brass 20s generate but I doubt the split bolt 77/22 was made to take up to the 60K PSI that a Vartarg can generate.

I didn't know the Hornet and Carbine case heads were the same.

That'd be a nice re-chamber if the 77/22 could take the pressure.

 

[ricco1949]

Made some brass today.

Photo is 20 VT vs .100 Shorty. Brass on right is cut off at the exact neck/shoulder junction.

I filled the RH brass with CFE BLK.

Capacities of CFE BLK:

20 VT 20.5g
.100 Shorty 18.5g

I now shoot 18.0g of CFE BLK with 40 VMax in 20 VT @3400

20 VT =18.0/20.5 = 87.8% capacity

Shorty Targeted max load with 32 VMax, 15g. @3400-3500.

15.0/18.5 = 81.1% capacity

Looks like I can go to my original plan of .150 Shorty.

 

[ricco1949]

Wow that was really an easy conversion from 17 FIreball to 20 VT .100 Shorty.

1. Heat die to ruby red with Mapp gas in center only neck section
2. Air cool
3. Ream neck
4. Cut off die .100 and chamfer.

I plan to try Shorty first as a no turn .238 chamber.

Die reamed and cut easily. I was concerned about reaming but it went without a hitch after annealing neck section.

 

[ricco1949]

Well learned that this case is definitely NOT a no turn @ .238 chamber neck.

Brass is .015-.016+ neck thickness. I will try a clean up turn @ .015.

 

[ricco1949]

FL 20 VT & 40 VM vs .100 Shorty 20 VT & 32 VM

Getting close to chambering...just need to make decision on going to .150 Shorty or trying .100 Shorty first.

 

[20 TAC]

Very interesting cartridge idea. Thanks for sharing! Here is a little project a friend and I have been working on for the last couple of years. We have both played with wildcats before. Without a doubt, this one has posed the most difficult challenge due to the length of the case, or rather the lack thereof. Based off the TCM case so it's much shorter than what you're building. Beginning stages of load development show promise, but much work left to do. Please keep us posted on your updates. I would sure think your velocity targets will be attainable?

 

[ricco1949]

Very interesting cartridge idea. Thanks for sharing! Here is a little project a friend and I have been working on for the last couple of years. We have both played with wildcats before. Without a doubt, this one has posed the most difficult challenge due to the length of the case, or rather the lack thereof. Based off the TCM case so it's much shorter than what you're building. Beginning stages of load development show promise, but much work left to do. Please keep us posted on your updates. I would sure think your velocity targets will be attainable?

Thanks for your comments and interest.

I considered the TCM and the 4.6 x 30 cases but one previous experimenter on the TCM wrote that it was 'very touchy and got ugly fast'.

I plan to keep posting through chambering and load development.

 

[ricco1949]

@20 TAC

In your photos the lineup appears to be:

20 Banshee, 20 VT, 20-222, 20 Tac?

What powder and bullet did u use to achieve 3278?

 

[20 TAC]

@20 TAC

In your photos the lineup appears to be:

20 Banshee, 20 VT, 20-222, 20 Tac?

What powder and bullet did u use to achieve 3278?

Yes you are correct on the line up but I think the far right is a 204 if I recall correctly. My friend has tried a little Accurate 1680 but he achieved this velocity with Alliant 300-MP. Going to step up charge of this powder a little more to try to find a nice accuracy and velocity node then possibly try some N110 as well. Bullet is a moly coated 32 V-Max.

 

[Evan]

FL 20 VT & 40 VM vs .100 Shorty 20 VT & 32 VM

Getting close to chambering...just need to make decision on going to .150 Shorty or trying .100 Shorty first.
View attachment 1599823

Love it! Go big…err…. I mean short! I’d go for the -150. My gut says it’s going to match up better with the slow pistol powders. I will try it out in GRT and report back.

 

[Evan]

Ok, I took a 20VT and shortened it 150. The body length is now 0.916, case is 1.25. All other dimensions the same. GRT thinks it has a capacity of 20gn H2O. OAL is 1.6" and with a 40 VMax, it predicts:

• 14gns of IMR-4227 gives 3250fps in a 24" barrel at 55ksi.
• 12.7gns of N-110 gives 3175fps at 56ksi.
• 10.8gns Accurate No7 gives 3100fps at 56ksi.
• 7.4gns of Unique gives 2620fps at 55ksi.

Generally I have been able to hit predicted speeds in GRT, but usually need more powder than GRT predicts out-of-the-box to do so. The bulkiest load, IMR-4227, is still only 93% full. It looks like you could comfortably fit 15+gns of 4227 in that case before running out of room.

EDIT: A quick re-read and I see you're thinking 32gn VMAX, so new numbers with an OAL of 1.5" using the 32 VMAX:

• 14.7gn IMR-4227 for 3570fps at 56ksi at 98% fill
• 13.3gn N-110 for 3530fps at 56ksi at only a 94% fill

 

[ricco1949]

Love it! Go big…err…. I mean short! I’d go for the -150. My gut says it’s going to match up better with the slow pistol powders. I will try it out in GRT and report back.

10-4. Yes just the basic comparison to VT usable and capacity usage also seems to tell that .150 Shorty is the better option. However if I cut the die off another .050 and it's too short I'll need a another die to go back and start over...that's the dilemma.

That would be great if you can run it on GRT. I'll wait to hear from you.

I have tried to download GRT but have not been successful. I just gotta spend more time on it.

 

[Evan]

10-4. Yes just the basic comparison to VT usable and capacity usage also seems to tell that .150 Shorty is the better option. However if I cut the die off another .050 and it's too short I'll need a another die to go back and start over...that's the dilemma.

That would be great if you can run it on GRT. I'll wait to hear from you.

I have tried to download GRT but have not been successful. I just gotta spend more time on it.

See above. I am happy to run more scenarios for you - it is quick and easy. I can also model -100 if you’d like.

 

[ricco1949]

Ok, I took a 20VT and shortened it 150. The body length is now 0.916, case is 1.25. All other dimensions the same. GRT thinks it has a capacity of 20gn H2O. OAL is 1.6" and with a 40 VMax, it predicts:

• 14gns of IMR-4227 gives 3250fps in a 24" barrel at 55ksi.
• 12.7gns of N-110 gives 3175fps at 56ksi.
• 10.8gns Accurate No7 gives 3100fps at 56ksi.
• 7.4gns of Unique gives 2620fps at 55ksi.

Generally I have been able to hit predicted speeds in GRT, but usually need more powder than GRT predicts out-of-the-box to do so. The bulkiest load, IMR-4227, is still only 93% full. It looks like you could comfortably fit 15+gns of 4227 in that case before running out of room.

EDIT: A quick re-read and I see you're thinking 32gn VMAX, so new numbers with an OAL of 1.5" using the 32 VMAX:

• 14.7gn IMR-4227 for 3570fps at 56ksi at 98% fill
• 13.3gn N-110 for 3530fps at 56ksi at only a 94% fill

Evan...your 2nd post came through when I was typing.

Thank you very much.... A big help. I was flying by the seat of my pants. GRT pretty much confirms that 3500 should be attainable with the .150 Shorty and 32 VM.

I'm gonna go for .150 Shorty.

I have another Wildcat friend who uses N110 in a .150 Shorty 221 FB type case.

Does GRT allow you to pick powders. Wondering if can it can give stats for CFE BLK, the VT powder I'm familiar with and currently using?

 

[ricco1949]

See above. I am happy to run more scenarios for you - it is quick and easy. I can also model -100 if you’d like.

Seems I'm again typing as you are.

Yes any other powders would be especially valuable to me. I have CFE BLK, Lil Gun, 2200, 2520, 1680, H110, if that's possible.

Wow I have to get GRT running. Sounds like it's an invaluable wildcat data source.

You have made my day....thank you.

 

[Evan]

Seems I'm again typing as you are.

Yes any other powders would be especially valuable to me. I have CFE BLK, Lil Gun, 2200, 2520, 1680, H110, if that's possible.

Wow I have to get GRT running. Sounds like it's an invaluable wildcat data source.

You have made my day....thank you.

32gn Vmax, 1.5" OAL again:

• H110, 14.7gn, 56ksi, 3610fps
• Lil Gun, 14.0gn, 56ksi, 3725fps
• 2520 - too slow, dangerous
• 2200 - don't have in the database
• 1680, 16.2gn, 55ksi, 3480fps
• CFE-BLK, 17.4gn, 55ksi, 3530fps

Only H110 and 1680 have "good" calibration in this set - meaning a large set of data backing up the powder simulation as defined by the GRT team. I've found low calibration to be hit or miss - for example it way under-predicts speed and over estimates pressure with H-4198 in my 20VT. I don't know if Lil Gun would actually give the colossal increase in speed that is predicted. That said, we're seeing a good trend here with a broad set of powders. I've found GRT to be very helpful in finding relative changes. A great example is when I was looking at shooting the 90gn SMK. GRT told me that a 22 PPC could max out at 2950fps, a 222 could max out at ~2750fps, but the 221 would max out at 2600fps because it falls into a dead zone in powders. I had to move to faster-than-optimal powders and the loss in speed was disproportionate to the loss in capacity taking that next step down - pretty cool! I really wanted to go smaller than the 222, but GRT raised the red flag that I was giving up more than I expected. My 22 PPC barrel and 222 barrel backed up those numbers, even though in both cases I ended up needing more powder than predicted to get the estimated speed at max pressure - it was still a useful simulation of the relative performance between the cases.

 

[L.Sherm]

One thing to keep in mind is case fill with the faster powders, I learned a valuable lesson when I started first playing around with my 17 Badger. In the beginning I used AA1680 but things were just a little erratic so I tried AA2200 and big difference with more case fill.
I'm really looking forward to your results with this project.

 

[ricco1949]

32gn Vmax, 1.5" OAL again:

• H110, 14.7gn, 56ksi, 3610fps
• Lil Gun, 14.0gn, 56ksi, 3725fps
• 2520 - too slow, dangerous
• 2200 - don't have in the database
• 1680, 16.2gn, 55ksi, 3480fps
• CFE-BLK, 17.4gn, 55ksi, 3530fps

Only H110 and 1680 have "good" calibration in this set - meaning a large set of data backing up the powder simulation as defined by the GRT team. I've found low calibration to be hit or miss - for example it way under-predicts speed and over estimates pressure with H-4198 in my 20VT. I don't know if Lil Gun would actually give the colossal increase in speed that is predicted. That said, we're seeing a good trend here with a broad set of powders. I've found GRT to be very helpful in finding relative changes. A great example is when I was looking at shooting the 90gn SMK. GRT told me that a 22 PPC could max out at 2950fps, a 222 could max out at ~2750fps, but the 221 would max out at 2600fps because it falls into a dead zone in powders. I had to move to faster-than-optimal powders and the loss in speed was disproportionate to the loss in capacity taking that next step down - pretty cool! I really wanted to go smaller than the 222, but GRT raised the red flag that I was giving up more than I expected. My 22 PPC barrel and 222 barrel backed up those numbers, even though in both cases I ended up needing more powder than predicted to get the estimated speed at max pressure - it was still a useful simulation of the relative performance between the cases.

Thanks again Evan...it's so valuable to me. You musta been burning midnite oil based on your post time! I am forever grateful.

I made about 30 test brass of .100 Shorty's last nite but I'm gonna cut the die another .050 and re-make 'em into .150 Shorty's based on your data.

 

[ricco1949]

Went out and checked my barrel drawer and found 2 fresh X-Caliber .204s, a LV and a straight 1.250, so I'm fixed there.

Only problem is I don't have an existing rifle they will fit in. All my PD rifles have Rem Sendaro tapers. I'll check if my .223 forearm has enough room to open for the LV.... I rarely use it anymore since I built a .222. If not it looks like this will be a 100% new build.

 

[ASbobcat]

Well learned that this case is definitely NOT a no turn @ .238 chamber neck.

Brass is .015-.016+ neck thickness. I will try a clean up turn @ .015.

Three decades ago I experimented with a No-Turn neck making 20VT from 223 brass. First trip to the range I blew my extractor into the next county. I forgot to figure the HUGE increase in neck tension form the extra mass of brass in the neck. The brass also becomes HARDER as you get closer to the head. Annealing can relieve some of that. but you have to be careful because you don't want to soften the head. Very tricky on such a short cartridge. That was the end of that project. Cut the barrel back and rechambered standard VT.

After experience with dozens of cartridges over decades of trial and error, I have found the optimum neck thickness for ALL bottleneck rifle cartridges to be between .011-.012in for most consistent neck tension (the secret to accuracy) and ease of bullet seating (less chance for bullet deformation).