THE ACCURATERELOADING.COM CAST BULLET FORUM


Moderators: Paul H
Go
New
Find
Notify
Tools
Reply
  
Re: Sizer Die Choice
 Login/Join
 
aladin
one of us
posted
Quote:

Byron,
Good question, thanks for asking.

Actually, conventional wisdom is shifting from "groove diameter" to "throat diameter". If the bullet is a sloppy fit in the throat, it is less likely to be delivered straight into the rifling, and may also experience some gas cutting while it is in the throat.

In a perfect world, the throat diameter is the same as the groove diameter or maybe 0.001" larger.

If the throat is a few thou larger than groove diameter, size to fit the throat, allowing a little clearance for easy chambering.

If the throat is more than a few thou larger than the groove diameter, as many mass produced guns are, I am not sure what is best -- perhaps a new barrel.



mountaingun you did at least address the throating specs which I dumped... methinks seeing the Palma Match chamber in the original posting got my enthusiasm churn'n.

Often Palma chambers are quite tight. I've seen reamer specs with the throat only a half thou over standard groove for the 308 and neck dia's requireing turning of standard brass. If that's case here I dunno... but it'd be best to find out before loading. Impact slug is the next step unless those dimensions are known.

In cast BR shooten most often throat dia's are purposely cut to a taper allowing tight fitting to the design of choice. These vary from 1/2 a degree or less per side to 2 degrees per side. Dia's go from around 2 and up to 4 thou on the check heel. These heel diameters can vary per cutting neck thickness to alter that dimension. Alignment is the idea with the tapered throats but I think one of the major benefits is engraving resistance when the hammer drops. All of the bullet loaded into the bore is being swaged down into the groove dia. I've fired one of these thru slowly for a looksee and my popper load normally used to spit them thru didn't hardly budge that hard slug. That design gave HARD engraving resistance... unforms the boom and makes that one hole accuracy possible IMO.

It's easy to prove larger dia slugs shooten better. Fire some groove dia ww slugs thru and then turn up the speed dia. Groups start to open at some pt. Now heat treat them and refire. Given some semblence of decent load groups will stay tighter longer. Now increase bullet dia gradually and speed up the loading. In a good bore it helps up to a point and normally makes the biggest difference in poorer bores given a decent lube.

In match bores with runout in the 1-2 TEN thousandths category, I've found something 1/2 thou over groove shooten's good. Never could pin it down cause I don't think dia was the big issue. So many other variables to try to grip...
 
Posts: 1529 | Location: Central Wisconsin | Registered: 01 March 2001Reply With Quote
sundog
one of us
posted Hide Post
Aladin, I'm of the same opinion about the size not as important as other things such as proper alignment, concentricity - and maybe bolt face and a few other things. The throat and bbl are a swaging tool. If they are right, then you gotta get the boolit lined up. One or 1.5 or 3 over has alot less affect than getting it going on its way straight and true. The straighter and truer, the harder you can push it, too. sundog
 
Posts: 287 | Location: Koweta Mission, OK | Registered: 28 August 2001Reply With Quote
Byron
one of us
posted Hide Post
Good to see things back and working again.

I attempted to post a picture of the bullet but didn't have any luck. If anyone would like a pic my e-mail address is listed if you click on my name.

The throat dia. according to the reamer (Pacific Tool - .308 Bisley) blueprint is .3085" with what looks like 1 degree (small circle to right and above the 1) -30. The barrel itself is a Mike Rock 5R 1:11.25 twist. It is actually a tactical rifle and the best in my safe so I figured the cast bullets aren't going to hurt it and it might give me the best results. If not I pull another one out of the safe and try with it .
 
Posts: 78 | Location: CA | Registered: 02 March 2002Reply With Quote
aladin
one of us
posted Hide Post
Quote:

Good to see things back and working again.

I attempted to post a picture of the bullet but didn't have any luck. If anyone would like a pic my e-mail address is listed if you click on my name.

The throat dia. according to the reamer (Pacific Tool - .308 Bisley) blueprint is .3085" with what looks like 1 degree (small circle to right and above the 1) -30. The barrel itself is a Mike Rock 5R 1:11.25 twist. It is actually a tactical rifle and the best in my safe so I figured the cast bullets aren't going to hurt it and it might give me the best results. If not I pull another one out of the safe and try with it .



Byron I've very sure that Mike Rock tube won't shooten cast worth a darn. 'Specially the 5R stuff... not worth a hoot for cast shooten. Best to send it down to me for an extended visit. Ya right.......

Your first move IMO is getting a Lee 3080 push thru die. You'll be able to talor a 3085 dia otta it. Slide that wide driver in there snug and see what gives. I even taper size with these Lee's. Lube dia oversized to not mess with that slug.

2500 I doubt w/ 311413 but you never know. What'd be almost ideal is one of these HBC-A's were going to cut Jan or Feb of '04. I'm about sure one of them would be a 3085 front driver [ordering 3090]. We're gonna have full DE-tales up SOON...

If that gun won't shooten cast well it don't rain in Ka anymore.
 
Posts: 1529 | Location: Central Wisconsin | Registered: 01 March 2001Reply With Quote
  Powered by Social Strata  
 


Copyright December 1997-2023 Accuratereloading.com


Visit our on-line store for AR Memorabilia