20 Dasher caseforming pics.??????

[AlbertaAl]

Phil> I can't answer your question, I dont understand false shoulders and how to create them.

[ab_bentley]

Phil, there could be but really there's no need to. The neck doesn't shrink that much so there's no real need for the false shoulder. To create the false shoulder you don't fully size the neck leaving a portion of the original neck. That creates a pressure bulge for the crush fit.

[philip]

I thought the Dasher shoulder moved forward(during fire forming) making a false shoulder necessary???????

[Spook]

Thanks Al

[DAA]

Okay... I wasn't going to say anything, but I just have to know...

Is it just me, or in this picture:



Does the case on the right, labeled "Dasher", look like a Dasher to anyone else??? Maybe it's just the way I'm seeing the picture. But it looks to me like the neck/shoulder junction has not been moved. The neck looks BR length and it doesn't look like the shoulder has been moved nearly as far as the Dasher. It really looks like a BR Improved 40* to me? Maybe it's just the picture or the way I'm seeing it.

Regardless that... Phil, it's possible to fireform Dasher cases without a false shoulder, just relying on a bullet jammed into the lands to hold head space. But, there is absolutely NO reason to try and do it that way with a .20 Dasher. A lot of guys do fireform their 6 Dashers that way, because creating a false shoulder on the 6mm variety requires necking up (expanding) the neck, then necking it back down. Kind of a PITA, especially when needing to neck turn before fireforming with a bullet. With a .22 or .20 Dasher though, you don't need to do the expanding step, simply take a little time with initial die adjustment to place the false shoulder to hold head space during fireforming. I personally have not had a lot of luck using bullet tension for this purpose. Firing pin strike has often as not overcome neck tension and seated the bullet deeper before full ignition, creating excess headspace during fireforming, causing case stretch near the head, beginning the process of eventual head separation. That has just been "my" experience though. Like I said, a lot of guys that use the 6 Dasher in competition have dedicated ugly barrels just for fireforming and are succesful fireforming with just bullet jam to hold head space.

- DAA

[philip]

Search.."tell me about the 20 dasher"

2nd page into the search, posted by "Fred in NE Ohio".

The 3rd post shows a 20 dasher next to a 20BR case..

I believe that MontDoug posted these pics.

Phil.

[DAA]

I just did the search and found MontDoug's picture. Here it is, along with Al's picture. The two cases on the right, in both, are .20BR next to .20 Dasher(?!):




Am I crazy, or is it just an optical illusion of the pictures, or some other logical explanation, or... Is one of these things not like the other??

- DAA

[Mntngoat]

dougs pic looks like my 20 Dasher. and I used a false shoulder to fireform..

ML

[Bayou City Boy]

Like DAA, I've never had any faith in bullet jamming as a way to set head space on cartridges being fire formed. Even with AI cartridges, the chamber, if it's cut properly, should create a crush fit on normal brass and bullet jamming is useless and not needed. Yet you see many folks advocating bullet jamming for AI cartridges.

If you're moving shoulders back to start with before fire forming, you need to leave the case with some way to establish proper head space when fired. The best way to do that is to again leave a slight crush fit on the case neck/shoulder junction using the dies settings to do it.

If you're moving a shoulder forward, a false neck works great - again with a slight crush fit on the brass. As an example, I had a 204 Ruger rifle before brass was available. I neck sized 222 Rem Mag brass down to 20 caliber and I left enough of the neck at 22 caliber to create a crush fit on the brass when the cartridge was chambered. When the cartridges were fired, the case shoulder moved forward but there was no web stretching of the case.

That 222 Rem Mag brass is still some of the best 204 Ruger brass that I have.

JME - BCB

[AlbertaAl]

NEW discovery...for me

With all the head scratching going on here...I checked my reamer which is engraved 20BR 40 degree improved

Sooooo....I phoned Pacific Tool for an explanation.
Dave Kiff, as usual very friendly and takes the time to chat...
told me that I have a 20BR 40 degree improved NOT a 20DASHER...he doesn't recommend the DASHER in a twenty calibre.
The DASHER gets better in .224 calibre designs and very best in 6mm calibres.

The reason he doesnt recommend the 20DASHER build is that there's excessive case stretching required to achieve the 20 calibre sizing hence the shorter case life and higher degree of throat erosion with the shorter neck.

Regardless, of the pros & cons, I was taken a-back by the fact that I dont have what I thought I had. It took me 5 minutes to get over it...
Life goes on !

Dave said the 20BR improved is 5% extra capacity over the standard 20BR and not to trim the necks ...keep them as long as possible.

I don't know where the wheels fell off in this gun project but seems that it's all worked out at the end and I'm still very pleased with what I have.

Thanks to the observance of the Saubier crowd for picking up on my errors !