.25cal partitioned nose

[Bill G]

Are GM barrels choaked?

Yes sir.  These slugs go into the chamber at ~.2517 and come out the choke end at .250.  the resistance is extremely low when pushing one through the bore and increases for the last couple of inches.  The TJ barrel liner has a constant resistance once seated and the slugs that I've measured are in the .2499 .2501 range upon exit.  My current .25 cal slugs are made to fit a .243 lans and knurled up to fit a bore up to .2515. 

My Green mountain barrel had a chamber size of .258 and had little to no taper going into the lans.  I have since re-chambered it to better accept slugs.  .258 allowed the slug to yaw as it seated and that is unacceptable.  My new chamber is ~.252 and tappers in at 1.5 degrees included.  Not what is typically used.  My reasoning is to have a taper but allow, perhaps, a more versatile leade in.  An attempt at comprimise for the sake of shooting pellets and slugs of various weight.  By having the throat at .253, I think that the deviation from center axis will be minimal if at all.    There been lots written on this subject and articulated far better than I might. 

Bill

[Bill G]

Bill,

Just save me some for testing on game and some new CLEAR test media i'm dying to try.

Hopefully here soon (friday) my new 25 (.250 cal) will be complete so i can start tuning and shooting her.....ARRRRGH, the wait!

 And you had to come out with these like right now.....lol

Cedric are you using the TJ liner on this .25 build? they fit so good in the TJ liner that I've pushed them through.  What weight are you panning on shooting through this build?

Bill,

Not 100% sold on whether its going to be a Diabolo shooter ONLY or if BOTH slugs and Pellets.  Yes, its a 14" twist TJ 250 liner with no choke.  I heard they shoot pellets pretty well.  So we shall see when its all done.  I also plan on shooting slugs at about the weight your making and lighter as a possibility.  The barrel should in theory perform well with both.

Accuracy and shot count well determine it for me.  Actually, that's a lie, if pellet do extremely well, i'm still going to shoot slugs no matter what.......lol!

HAHAHAHAHA!   Cedric self awareness speaks volumes.. You are an honest man. 

[drewciferpike]

I hope you post some pics, here... this is interesting

[scottyhazzard]

Bill, you might want to send some of your rounds to this DJ guy...
http://www.gatewaytoairguns.org/GTA/index.php?topic=109425.0

He has the cameras and gel.

[Bill G]

Thanks Scott, I will consider that for sure. 

Did some experimenting last night and the evening to see just how light they can be made.  31gr is as short as I can go and maintain sufficient bearing surface.  At that weight, they look like they will just break apart.  Especially if they were launched from one of these hot rods out there.  Estimating the required twist, it looks like 79gr is where the 1:14 twist requirement is.  That leaves a lot of lead as the base.

I managed to get the spot face for the TP cut this afternoon and will assemble for accuracy testing through he GM barrel, hopefully this weekend.  I'm skeptical though.  The GM is a lot looser than the TJ.  I'll keep everyone posted

Bill 

 

[Diesel500]

Very interested in the outcome. CCI makes a partitioned subsonic 22lr and they are brutal

[Bill G]

Ooooh I need to see those CCI's.