SSShooter wrote on Dec 25^th, 2015 at 6:54am:


Well, the difference in wall thickness isn't as dramatic as I expected, but I just measured wall thickness on a new, unfired Starline long case at .007" and a fired, unsized W-W at .009-.010". I don't have a ball micrometer, so my numbers should shade a bit high, but give a good idea of relative thickness of my brass with dial calipers.

I use the W-W brass in a High Wall with a .375" groove barrel, the Starline long in my 336 Cowboy with a .381" groove, and Starline short in a Winchester 94 with a .379" groove.

Outside neck turning the W-W cases did work for me and allow me to fire bullets closer to groove diameter. Back in 2003 when I was taking that route with the W-W brass, I didn't have a mold that threw a .381" or .382" bullet but was using a Lyman 375449 that threw a .379" bullet.  I was also paper patching a Lyman 366408 9.3mm bullet and using it in the neck turned brass for good accuracy and no leading. Even though the PP bullet was under groove dia. it shot well.

Have found that the Lee expander die & plugs work well. For my 38cal the 0.379" plug and for the 40cal the 0.410" plug do the trick, regardless of the brass used. Easier than neck turning. For 0.381" you might need a custom plug made up. YMMV.

I have a 38/40 Marlin 1894 use it for Pistol caliber Silhouette. Fine 100 yard Caliber all the years shooting 200 Ram Bash matches our club and up at Fairfax R&G never saw a pistol Calber do well at 200   Same thing NRA lever silhouette pistol calibers are legal in the Rifle Silhoutte match, to 200, they never do well.

My 18 twist 38/55 set up 22 years ago was the norm  do it again  I may go 16, doubt if I would put a 14 twist on a 38/55 but will admit some do well with them, no way would I use a 12.  Spin cast too fast looking for problems.

Plain 38/55 .375 bore .377 bullet chamber length to suit the brass you have has the best chance of turning out well. 18 twist if intending to use bullets under 300 gr 16 if 330's 

Stick with boring let the other guys hot rod, 

Boats

I like to fiddle. Life is too short for boring.
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I think we all like to fiddle a bit, or we'd be shooting AR's

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A   so it would start
Sorry for off-topic reply.

If anyone enjoys talking reamer/chamber design I got a hypothetical for you.

Take Frank’s PTG reamer drawing.   It shows a .100 cylindrical free bore.    Anyone ever see someone take that free bore cylindrical shape and length and make it conical.    I’m not talking about a flat transition from the case mouth diameter to groove diameter.   Most of us have probably seen those from the vintage chambers that have say a 4* or 6* transition from case mouth diameter to groove diameter. I’m talking about something way more subtle than that.

Modern chambers with free bore (or without) usually have a 45* transition that leads to free bore or, if no free bore, then right into groove diameter.  So instead of that, let’s say you still had the 45* transition at the end of chamber length where the case ends.    

Now say you had a .100 free bore but the 45* transition leading to the free bore tapers instead to a dimension at the start of the free bore just .003 larger than the obderated bullet diameter as it leaves a fire formed case mouth, (that would be .014 smaller than the neck diameter of your chamber) and from there tapers to your groove diameter of say .379.   The shape of that portion of the chamber would no longer fit the definition of a free bore obviously but put that aside for sake of discussion.   That would be a subtle swaging as opposed to the old taper that left however much space for the bullet to obdurate -  as your case wall was thick.     In other words, the old vintage chambers with a flat transition from neck to groove left a lot of room for upset, maybe as much as .020 or more with the older thicker brass,  followed by a lot of swaging back to groove diameter.       

The problem I see with that design is for those wanting to seat your bullets out to accommodate more powder.   Driving bands would arrest somewhere along that cone shape and would restrict forward seating.   In return for that limitation you get a very gradual swaging with very slight obduration before swaging into the groove diameter.    Many contend the less changes your bullet is undergoing the better.   And filling the throat, like they say,  would be something you could design a bullet for.   

frnkeore wrote on Dec 24^th, 2015 at 2:44am:


Could be a colossally dumb question here:    Just realized that PTG diagram Frank posted shows no defined neck length.   Appears to be a straight taper all the way to case mouth.    It does indicate a “Resize ND” in the legend of .391.   I'm assuming that neck length is just established during sizing then.    Or could this be a chamber meant strictly for breach seating and there is no need for a defined neck?

Thanks Frank.    I would have had a harder time following all that but I struggled through it recently while drawing up a reamer for a 40-65 Ballard.   First I’d read on it was in some of TexasMac’s observations on the Browning chamber.    That chamber has a defined neck that is .500 long if I remember right.    Read a good thread where he and others were talking about your point, the question being:  If you have a true cylinder inside, then you won’t on the outside… and vise versa.    When deciding on specs for that reamer I called Starline to see what the taper in wall thickness was for their 45-70 (plan on forming that to 40-65) and Hunter I think it was pulled their drawings up just to be sure and told me their 45-70 specs showed taper only up to the case neck, after which the thickness was uniform.   Hope that’s the case or I could be tight where the base of the bullet is seated.   I’m prepared to turn necks there if I confront that.   

In the PTG case I was surprised though.   Most diagrams I see show two diameters… one at the case mouth and another roughly ½” back from there, generally .001 larger at the start of the neck.    

Interesting that the fire formed cases that come out of my Marlin 1895 in 40-65 are also close to not having a defined cylindrical neck.     It does turn into a cylinder in the last quarter inch.    Otherwise, it’s a straight line taper but for the last .250 where you could measure the start of a short defined neck. 

I guess I better check the brass I have for the 38-55.  I know it’s thinner but I don’t know about the thickness taper.   I think in this case I'll build that .001 fudge factor in at the base regardless of what Starline might say or show   

Well, I do like the thought of the 35-40 Maynard now that its been thrown out there.   I've been guilty of jumping on the bandwagon before and not always with good results but with a string of lessons-learned to be sure.   Won't be much backing up from that one though. 

I talked with Sayers at TJ's and with Steve Baldwin.   Verdict is still out but I might be taking another fork in the road if some information comes back favorable.

Btw... SSShooter, I have done a little pp'ing in the 40 caliber.   Never had a chamber set up specific for it.   Ideally I think I'd want a neck diameter that only allowed for a bore size patched bullet.    When I first dove in there, which wasn't a very deep dive, I was wondering why the stock 40 caliber sizing dies pushed that neck all the way down to .422 when most necks were fire-forming out to over .430.   Dawned on me that they were trying to make their sizers a do-all affair.   And turns out .422 is a perfect fit for a patched bullet for bore size in a 40 caliber.   But the serious patchers like Brent are cutting their chamber for a tight fit, so that precludes gg bullets sized to groove diameter.   

And people wonder why the old bores won't chamber groove size bullets.    Logical explanation would be that most shooters back in the day were shooting patch.