Home Forums Hunting & Shooting Hunter's Campfire Marlin microgroove

Ok guys. I need to know how good the marlin microgroove rifling 44 mag is. the rifle I just bought has a very shiney and clean bore , it looks ok to me , but I never owned or shot one . I really like the rifle and am hoping it shoots ok... it was made in 1964 . the bluing is about 95+ percent. wood is about same so I don't think it was shot much... thanks for any help.. Hubert

Bough one and was planning to shoot cast lead in it. The cast bullets key holed at 50 yards.
Never tried jacketed, but presume they would shoot fine.

They're good barrels. Shooting cast through them successfully takes a bit of skullduggery. But other than that,...just shoot it.

What diameter were those cast bullets sized to? I haven't had a Marlin in .44 mag. for a long time now but IIRC, I sized my bullets to something like .431" but don't quote me on that. The only Marlin I still have is a 30-30 and .30" bullets scatter like bird shot but bullets sized .310" runabout " at 100 yards. Also it seems Microgroove barrels seen to like bullets from a slightly harder alloy. That's what worked for me.
Paul B.

They can shoot pretty good. Some suffer from tight spots under the roll markings on the barrel which can be lapped out if desired, and I've found from several examples that if you size cast bullets on the large size they shoot better. Like PJGunner I had a Marlin .44 Mag (back in the 70's) that did best with .431" bullets. My 336 .30-30's (lost count of those but have had several) all did best with .309" up to .311". Had an 1894 .45 Colt that ostensibly used .452" bullets but the accuracy was much better when bullets were sized to .454".

SAAMI has different groove diameter specs for rifle and pistol for .44 magnum (see attached docs.), so cast bullets for rifles do have to be sized to a larger diameter than what you would probably size for a pistol. I've done well with cast bullets in microgroove rifling by following three simple rules: use a hard alloy (wheelweight metal is hard enough), size 1-2 thousandths over groove diameter, and use a gas check.


https://saami.org/wp-content/upload...CFR-Approved-2015-12-14-Posting-Copy.pdf

https://saami.org/wp-content/upload...d-R-Approved-2015-12-14-Posting-Copy.pdf

I do not recall the sizing on my 44 cal bullets. It’s been 10 years, but I saved the targets and my notes on the keyholing.

Hubert just shoot the rifle and enjoy it. It's a good barrel and sounds like the rifle is in fine condition.

Go to walmart and grab the first pretty, colorful box of 240 jacketed ammo.

Post pics if youre able. Sounds like a nice find.

Marlin micro grove rifling was a sales gimmick from way back....not to say it not good as it it...but there is no real magic there...to probe this...how many micro grove Marlins hold rimfire world records....or why isn't this process used on target barrels....micro grove or not it's sure not a deal breaker on that rifle...I wouldn't even think about it...

Microgroove likes em fat.........cast boolits that is

https://www.marlinowners.com/forum/336/69232-ballard-vs-micro-groove.html

If the twist is 1/38, that'll limit your options with the heavier bullets. Cast bullets have to fit snug, 001" or .002" over bore diameter and they'll shoot good. I bet some .432" 250 grain LBT GCs would be dandy in that rifle.

Dardas Bullets.......now gone......

built 200 gr RN FP .433"

Microgroove is much better with jacketed bullets. That's not to say that they won't shoot cast, but they're a lot more finnicky with lead than copper bullets.

Good for shooting local cats!

Well mine is a 78 Model 1894 with Micro groove rifling,it sure shoots a RCBS cast SWC with gaschecks just fine. 1300 fps? MB

Punch out the barrel, copper clean it with Montana extreme .
Fire a fouler and zero it.
Shoot factory jacketed stuff thru it, clean with good ole hoppes#9
Buy 3 or 4 different 240 gr brands
Fire a fouler,then your back to your zero for the rest.
Copper clean every 100 or 120 rounds.

It's a marlin....
It will shoot....
I bet it groups under a inch at 50 yards with open sights with ammo it likes.

I took it to the range today. but my targets and range stuff was at home I had a target that was used with a 22. so I had to use that.. I only fired 2 rounds that were factory 240 gr Remington loads. the bullets made round holes , no keyholing and were 1 inch apart at 50 yds open sights... I will have to try my semiwadcutters that I used in my Ruger pistol to kill deer with...when I find my range bag..LOL… I believe it is a keeper..

I thought I was the only one who went to the range with either no stuff or wrong stuff
I read somewhere that microgroives tend to run big on bore diameter, hence use oversize lead

Nice score Hubert! I had the same rifle and it shot any jacketed bullet well. I never did get to shooting cast in that one but I've had other MG Marlins that I have, 375 win, 45-70, 30-30. As has been said they will shoot cast but it will often take some tinkering. As a rule a tight fit and moderate velocity; 1700 ish seemed to be the ticket.

I had a Micro-Groove .45-70. They'll shoot cast just fine, but many folks give up before doing adequate experimentation. Use the largest diameter bullet that will allow a cartridge to chamber without difficulty. You may have to try a couple of different alloy mixes before you get it right, but a Micro-Groove barrel can do very well with cast bullets.