rimmed vartarg

[chuckshooter]

Since I like shooting my 20vt so much, I decided to make a rimmed version for one of my martini's. . My goal was to use reamer and dies I already had on hand. I cut the chamber using PTG 20 vartarg reamer. I bought 360 DW brass from starline and formed it using redding 221 fireball dies and all was looking good until the last sizing with the 20 vartarg die. it was trying to size the brass by the base a little too much and left a little ring of brass. I removed the ring with a file and some emery and loaded it up. I went to the range with the first firing and was quite impressed with a nice 1/4" group at 20.8 gns. of 2200. My next step was to duplicate the firing and also to increase the load until I saw signs of pressure. At 21 grains, I lost every piece of brass to case head separation. My conclusion is that in the last step of sizing, I am damaging/ work hardening the brass at the base and that I need to fork out some cash for the right size reamer and dies that fit the 360 DW base. I calculate .004 to .006. more than the std. VT. Has anyone else dealt with this and/or have reamer or die info? I know I could have tried to find 222 rimmed brass, but 360DW was available and cheap. Any help would be appreciated
Thanks

 

[chuckshooter]

[ here's some pics

 

[rifleman700]

Very cool CS.

 

[BoydAllen]

Neat little round. Generally, head separations come from bumping shoulders back too far when sizing, but I do not have much experience with functional rims in bottle necked cartridges. About the only one that I had experience with was a 30-30 chambered 788 Remington. Nevertheless, that would be what I would look at for the source of the problem. How much did the first firing on newly formed brass move the shoulder forward, and how far did you bump it back each time that you sized it? How much did the cases expand near the head when you fired them the first time. Is your problem the chamber and the die, or possibly just the die?

 

[dkhunt14]

I believe Boyd is right. I looked at your pictures and it seems like the last picture before Fireforming and the formed one has a lot of shoulder moved forward. Similar to fireforming a Dasher. Maybe if you neck up and formed a false shoulder to fireform, it wouldn't stretch the brass in the area above the rim. I would also form with bullet in the lands. I am just guessing but it might work. Matt

 

[dedogs]

I calculate .004 to .006. more than the std. VT.

How did you arrive at this calculation? I am not familiar with 360 DW brass. dedogs

 

[Tiratore]

I sort of THOUGHT I knew what I was doing a few years back. I had the same problem with a 6.5. Putting more gap between the shell holder and the die when forming cases helped some. I suspect making cases do what they weren't designed to do is part of the problem, but I'm guessing. I'm interested in what others say.

 

[chuckshooter]

How did you arrive at this calculation? I am not familiar with 360 DW brass. dedogs

vartarg brass from the 223 family is .374 at the .200 mark and 360 DW brass is from the 357 mag family and is .379 at .200 mark.
after speaking with Adam I going to try head spacing at what we call hard to close bolt and see if that works. I checked my previous loaded against my new hard to close rounds measuring to the datum line and I have .003 difference. But I don't know what the first load measured. I also have chucked up the Redding 20 vartarg die and tried to open up the base a little. my measurements say I did nothing. dies are so so hard as I'm sure you all know, the good news is I am not leaving that little ring at the base anymore. I think I am pushing the Martini to it's limits and the answer is going to be head space.

 

[chuckshooter]

here's one of my martini's in 20 Ackly bee. I have a 1000 rounds down the tube and no issues with head spacing

 

[chuckshooter]

Neat little round. Generally, head separations come from bumping shoulders back too far when sizing, but I do not have much experience with functional rims in bottle necked cartridges. About the only one that I had experience with was a 30-30 chambered 788 Remington. Nevertheless, that would be what I would look at for the source of the problem. How much did the first firing on newly formed brass move the shoulder forward, and how far did you bump it back each time that you sized it? How much did the cases expand near the head when you fired them the first time. Is your problem the chamber and the die, or possibly just the die?

Boyd
I have backed off the last sizing .006. measured by feeler gauge between case holder and die and that is getting the hard to close bolt. we'll see
thanks to everybody for bringing me back to my senses, I became overly obsessed with that ring and forgot the basics

 

[dedogs]

here's one of my martini's in 20 Ackly bee.

Nice rifle. What's your prefered load? I have a .17 CCM on a Martini that I really like for close in work. dedogs

 

[NorCalMikie]

PM on the way, Mike.

 

[chuckshooter]

that one shoots 16.7 gr. of aa1680 32 gr zmax . my other 20 Ackley bee shoots 13.4 of Little gun 32gr zmax. I shot 4000 rounds last year at squirrels and these two became my favorite guns. that's why I want this rimmed vartarg to work out. just a little more hp than the bee

 

[dedogs]

that one shoots 16.7 gr. of aa1680 32 gr zmax . my other 20 Ackley bee shoots 13.4 of Little gun 32gr zmax. I shot 4000 rounds last year at squirrels and these two became my favorite guns. that's why I want this rimmed vartarg to work out. just a little more hp than the bee

Thanks for the reply, and please keep us posted on your results. dedogs

 

[NorCalMikie]

I sent Chuck Shooter some 256 Win Mag brass to see if he has any better luck. Some already necked down to 20 so there shouldn't be too much work involved to make it the rimmed VT. We'll know more once he gets his hands on it and has a chance to check it out.

 

[chuckshooter]

I made fifty new pieces of brass and went to the range: 2200 powder from 20.3 to 21.8 behind 32 gr vmax
this is just the first firing on this brass, but looks incredible, so far up to 4000 fps and no obvious signs of pressure. the gun likes 20.8 and I'm ok with 3800 fps

 

[Shaggy357]

So re-adjusting the die stopped the case head separation? Headspacing off the shoulder is optimum for case life and fit. The photo above did look like some excess room for case movement from my vantage point.

The .003" difference in brass diameter can be resolved with a SB sizer die. I recently made a buddy 400 VT brass from .223 once fired brass. I ran them in a 300 Whisper die, then a carbide 270 Ren die, and then a .223 SB die. Came out with the funky shaped brass in the following photo, which sized down to .221 Fireball quite well. I cut, trimmed, deburred, etc so the brass just fit my .221 with firm closing. I sent the cases to my buddy and he took them from there. Sometimes you get there on the first try, sometimes you lose a few lots of brass. Getting there in the end is where the satisfaction lies. You are doing well. I like it.

Steve

 

[chuckshooter]

I just finished the second firing and there is no sign of case head movement. I pretty much duplicated the above targets and can shoot either 20.8 or 21.8 of 2200. I didn't notice any issues with extraction. when I finish the stocks, I will post a couple pics
thanks everyone for your input

 

[ab_bentley]

I just finished the second firing and there is no sign of case head movement. I pretty much duplicated the above targets and can shoot either 20.8 or 21.8 of 2200. I didn't notice any issues with extraction. when I finish the stocks, I will post a couple pics
thanks everyone for your input

Remember, people will tell you 4000fps from a 20vt is impossible. ...

 

[Wirelessguy2005]

Not so much that it's impossible, more so that people with an interest in their own safety and the safety of those around them don't do it.

Remember, people will tell you 4000fps from a 20vt is impossible. ...