I may give up EDIT but as of 6/10 I wont

[trevort]

on the JAB 20. Seems a bad design. Chronied the loads at 22gns re 10 ar 3300fps, the case has a slight capacity edge on the TAC20 so this load and velocity very mild though extraction not perfectly smooth.
22.3gns, first round, again extraction by cleaning rod. As were all the loads up to TAC 20 levelsI have checked in the past.

I believe its a design flaw (Whoa, hold on a second, scientific, engineering guru extraordinaire me and "flaw" in the same sentence!). As the case is 30 thou shorter than a 223 and the chamber is formed by a short run 204 reamer I believe that the wider end of the reamer (allowing for case taper) isnt getting into the chamber enough and so the base of the case is too tight a fit.

SO, what to do

I have the 223 dies converted. They could easily be 20 practical dies too. 20 practical? run the reamer in for another 204? send cases off to PTG for a reamer made specifically for my case? See if running the 20 prac reamer in gives enough taper in the chamber for the cases to fit?

I suppose if I have the reamer run in to 204 it would be easier to sell and try something completely different . Wonder what a shilen barreled CZ 527 might be worth?

Hmmm I think I'll ponder until I see Shane at the weekend!

choices choices

[wifecallsmegrumpy]

30thou is not a lot Trev. What happens when you load and extract a round without firing it, does it extract smoothly ? I guess what I am getting at is your sure it's not the extractor ?

[Mudgegonga]

Lets us know what Shane thinks. I am having some extraction issues with his 20TAC version. Brass is gripping at the web or just in front. Brass to chamber tolerances seem tight.

[sbn]

G'day trevort,
I have 2 20 "Pracs", both made with a 204 R reamer run 90 thou short.Brass forming with similarly shortened 204 dies is easy.They love a mild load using
2206 and 40g V-Maxes at 3800fps.
Mudgegonga,did you get my PM on Saubier?
Cheers Dugald

[ogre6br]

What about making it into a 20 V V T or a 20 VT if the Jab doesn't work out.

I hope with a little work from SC the JAB can be made to work as it's a great idea

I wish I had the $$ to make you an offer on it as it would be a perfect basis for a 20 VT or 20 VVT or a 20-222 which would be a great option instead of a 17 mkV or fireball
which
I'm having trouble getting the bits together to have a 17 mkV or Fireball made up- using your has really sold me on the idea of a small case vermin getter rather than buying a 17 hmr.

P

[trevort]

$2500 and its all yours!

[trevort]

its back with Shane, dies brass et al. he will make it work as is or run another reamer in. Yes Mudge, we are having the same issue

[Mudgegonga]

SBN
Todd Kindler 24.9gn 10x, 40gn Vmax, 3804. At 25gn I get 3950 plus.
Todd Kindler 26.4 Benchmark, 40 gn Berger, 3783. At 26.5 with the Vmax I get 3880. Todd took the 40gn Vmax up to 4000!

My barrel is 26.5"

He used IMI brass. I am using lapua. The unfired lapua is .3755 at the web. The chamber is .376

The primers dont look like there is excessive pressure. But I am backing off to see if I can avoid the sticky extraction.

[sbn]

Thanks Mudgegonga,
my query more related to 50 grainers and no data I've seen comes close to your vels until you get up to BR type capacity cases.
Cheers Dugald

[Mudgegonga]

Ok. With the 50gn Berger Todd gets around 3800 in the BR. I tried 27gn of 748, 3700. 27.5 gave me 3750. As noted above at about the 3rd reload I started getting sticky extraction.

I have tried 25 gn of 2208 (varget) and got 3450. Todd used 29.6 in the BR to get 3374.

I have not confirmed it yet but I expect that the 40s at 3900+ and the 50s at 3600+ will be Ok. I am currently using the 40s with 24gn 10x at 3900. Bullets are touching the lands. Not jammed.

[Brad Y]

Trev

If you want a proper spec (Warren B) PT&G 20 practical reamer your more than welcome to borrow mine. But you do have a 204 and your probably not going to see anything different in performance. I guess the use of lapua brass and thats it.

My gun is starting to shot pressure signs at 24gr of R10x but not consistently. Sweet spot seems to be around 23.6-23.8gr so far and that should be around the 3800fps or so mark. Again thats in the 204 range so not really much different in performance, just up to you I guess.

[trevort]

got it already Brad, gotta make it work! Shane is going to measure brass and chamber, if I can keep my long neck by opening the base of the chamber a little by running in his prac reamer then its a JAB20, if not the reamer will go all the way in and it will be a 20 Prac

I have 400 IMI 223 cases kindly given to me by Ogre so keen to get it going in some shape or form!

[Brad Y]

No worries. I will keep posting up my success then to keep you motivated. Its such a neat little cartridge, though the original instruction to get a 225 bushing was slightly off. My neck tension was a bit much and leaving rings on the bullets when i seated them so ive ordered a 226 to get it 'perfect'. This is with remington cases. I was going to invest in a box of lapua, but when i prep the remingtons up they do really well.

[trevort]

sat in front of the TV and chamfered and deburred flash holes on 150 rem 243 cases last night. Yes they work well when prepped but I'd almost forgotten those steps using better brass for a while!

[Plowboy]

OK dumb question to the wise but what does JAB stand for??? (retreating to fetal position for the coming attack! )