marlin

[Flint]

Don't know about the Ackley, if the overall length is the same, and a Winchester would feed it, it's probably OK.  Ask a gunsmith.  No lever gun with the magazine and barrel bands and stuff hanging off the barrel is going to shoot like a free floated bolt action rifle.

[GooseGestapo]

ARCH;
Like the previous poster related, the marlin 336's can be charge level sensative.  I've had several Marlins all w/microgroove bbl.  The only one that just would not meet my expectations was a 1894 in .44Mag. with cast bullets (non-gas checked)
A .45/70 (w/ballard style rifling) was the consistently most accruate with all loads but wouldn't do much better than 1.25" with best loads. It was just too much gun for my use, and was a little too heavy; I traded it for a Ruger .22 Hornet!!
I presently have a M-336 in .35 Rem. that is my favorite rifle out of all I have. (certainly not the nicest either!) I like Marlins levers as I'm right handed but shoot longguns left handed due to left dominant eye. Handling is best available w/ ambidextrous guns IMO.
It is finicky, but with the loads it likes, is a real tack-driver (3shots<1"@ 100yds!). I also had a 336-A ('75-76 mfg.) in .30/30 w/24"bbl.  Both had similar charactistics:
1.   Be sure that both the fore-end band screws are real snug and lock-tited. (be careful, the metal is soft and screws booger easy)

2.  Use either Federal or Winchester brass , and trim to "exact" length (Impt. as bad crimp can ruin otherwise good ammo) Always check brass every time after sizing and before priming.  Trim to equal lenght of other brass in "batch" if more than .004" longer.  Not as critical if you use Lee Factory crimp die (I recommend you do!), but don't allow cases to exceed Max. spec's.  Brass is usually good for 5 or so loadingsbefore trimming.  Discard after 15x regardless.

3.  Powders aren't that critical as long as approiate to bullet weight/cartridge.  Best accuracy is usually at about 5% below listed max.

4.  Start at 5% below recommended START charges, and work up to max. for gun (this is indicated by extraction becoming "sticky", when encountered- consider 1.0gr below this point to be max. for your rifle)

I'm usually satisfied with 2"-3shot groups @100yds from my lever-marlins, and tend to push velocities till accuracy falls to this point.  However, this is my criteria, as velocity is more important to me for flatter trajectories and bullet performance.
I've had outstanding performance from my .30/30's with the following powder/bullet combinations:
125FNHP Sierra/ 35.0gr H322 @ 2,625fps (24"bbl)
130Speer HP/34.0gr IMR4320 @ 2,500fps (est.-22" bbl Rem788-One hole accuracy!!!) Load single in lever w/tube magazine.
150FN Speer/ 31.0gr IMR3031@ 2,350fps (24"bbl)
150RN Hornady/ 33.0gr H4895@ 2,400fps (24"bbl) very accurate too

Best load with .35 for accuracy is with BL-C2
200RN Rem. Cl or 200RN Hornady w/39.0gr BL-C2 @ 2,100fps 1"or less
"         "                                       w/41.0gr BL-C2 @ 2,200     1.5"
"         "                                       w/40.0 H4895   @2,250 1.5"
180RN Speer                                w/43.0 H335     @2,500  2" 3-shots
This 180 is a big game devastater, performs better than .30/06 to 200yds.

The .30/30 Marlin is rechamberable to Ackley Imp..  OAL remains same; taper, shoulder, and neck change.  Improvement will be 100fps +/-.  
No experience with this, but I'm looking for a "clean" Glenfield 30AS (20"bbl w/half magazine to do one of these conversions).  If 30/30 AI dosen't please, will re-barrel to 7-30 Waters.
Keep trying with the accuracy, it just takes some experimenting to find combination that causes the right "VIBES" in your barrel.

[Enforcer]

What kind of accuracy can you expect out of a Marlin 336 30-30.  I have been getting 3"-4" groups at 100 yards.  I expected 1.5"to2".

Can you rebarrel a 336 to a more potant caliber.  Any body rechamber to a 30-30 Ackley.  Is it worth it.  How much velocity gain would you get with the 170 grain.

Thanks

Of course you can rechamber M336 to many hotter calibers,as it was already chambered in the 307Win,356Win,375Win.All of them at 52,000cup.A rechamber in 7MM STE(necked down 307Win) or 7x30 Waters(necked down 30/30).Also the 307Win which is just a rimmed version of 308Win.Which was made for Marlin,but never produced except for prodo types.But did come in Win M94AE-XTR.Good luck

[Enforcer]

Don't know about the Ackley, if the overall length is the same, and a Winchester would feed it, it's probably OK.  Ask a gunsmith.  No lever gun with the magazine and barrel bands and stuff hanging off the barrel is going to shoot like a free floated bolt action rifle.

That is true.Two piece stocks,lower pressures,short barrels and flat nosed bullets keep the tube fed levers from being generally as accurate as the bolts.But make no mistake about it.My Win M88 in 284Win at 2885fps-2955fpe with 160 gr SPBT,and 1" at 200yds is as accurate as any bolt 270 or 280 out there(and looks better doing it).They are one piece stocks,longer barrels(22in),loaded to high pressures(56,000psi 284 Win).And basically just a bolt action operated by a lever(same with Sako Finnwolf,which I have both 243Win and 308Win).You can't beat a lever!