More on Micro Groove rifling

[mdi]

I didn't want to hijack Mr LaRoche's thread so I started this one. I don't own a gun with micro groove rifling (but a Marlin in 45/70 has been tugging at my heart for a while), so this is mainly for my own curiosity. There have been many threads about shooting lead in micro groove bbls and I have an idea about the process, but have other questions. (I really don't like castboolits' search feature). I have been casting for my "standard" rifling guns (9 handguns and rifles) for roughly 22 years but never for a micro groove barreled gun.

What is the percentage of the groove depth of micro groove vs. Ballard? I have a good grasp of the bullet to gun fit necessity, but do the "standards" for Ballard rifling fit micro groove? The same as Ballard rifling? I've read quite a bit of "stuff" about micro groove rifling like "micro groove fill up with lead much sooner than regular rifling", and "micro groove barrels are inherently inaccurate with lead".

So fellers, share your thoughts and experiences with shooting lead in micro groove rifled guns...

Thnx
Mike

I'd welcome any input from Mr. Gibson...:bigsmyl2:

[Harry O]

I have a number of microgroove barrels that I load for in different Marlins. Slug the barrel to find the ACTUAL groove diameter. One or two thousandths over that is fine. I also found that a slightly harder bullet works best, too. Bhn 10-13 works great for me. Do it right, and microgroove will shoot just as well (maybe even better) than conventional rifling.

The microgroove rifling will lead quicker and easier than other types of rifling if the bullet is too soft or too small. When it does start leading, it the grooves fill up quickly. Don't get too small or too soft and you won't have a problem.

[popper]

Interesting about the various types of rifling. Note - Military cannon use 'micro groove' barrels. They work. Don't think the 45/70 is MG. I have a MG 30/30, seems to do OK with soft alloy, for the limited testing I've done. Groups are larger though.
229840 M30/30 ~40 yds 175gr RD GC hard 311 with veggy oil lube. Full load of LeverE, from sitting position. 3x9 scope as I can't see worth a darn.
Yes, those 308MX are dandy even with cast -VERY accurate. about 3x the $ of my 30/30.

[MyFlatline]

Harry is right, slug the barrel. All of my Marlin rifles are micro groove. I cast between 10 and 13 BHN and powder coat. Have never leaded a barrel.
I cast for 30-30/308 mx.,35 rem.,444/44,375 and 357 in Marlin

Best of luck.

[Gohon]

The microgroove rifling will lead quicker and easier than other types of rifling if the bullet is too soft

This is only true if one attempts to shoot soft lead at higher pressure than normal. Black Powder shooters are at 20,000 psi and rimfire shooters are at 24,000 psi, both using very soft lead. These shooters are not experiencing barrel leading problems. As long as the casts are .002-.003 over groove diameter, whether hard or soft, your good to go with microgroove barrels. Actually the over groove diameter is a good rule to follow even with Ballard rifling.

[17nut]

Marlin MG barrels are no diffferent than any other rifled barrel.
+.002" bullet and shoot away.

What "killed" the wibe was that Marlin made them slightly bigger thus gas cutting and leading with commercial ammo/bullets.

Here is a pic of my Marlin 94 in 44MAG that is close to 5k (full house lead) shots since last cleaning.
229856


229854
229855

[rwadley]

The new 45/70s are not microgroove. I don't know what year they changed (1998?), but they were microgroove in the 70s, 80s and most of the 90s. They are "Ballard" rifled now.

[gundownunder]

I've never owned a micro groove rifle, other than my .22 39A. Which will shoot sub-moa groups with most standard velocity ammo, and even does it with a couple of high velocity brands.

Apart from the recommendation to go 2 thou over size, the other wisdom I have heard is not to use quick powders, such as Unique. Apparently they accelerate too quickly and don't allow the bullet to engage the rifling, which causes skidding on the shallow rifling, which causes leading.

I've also heard that the tapered bore rider design of bullet is not a good idea because the bore rider portion of the bullet is a smaller diameter than the microgroove bore. This causes the bullet to flex in the bore under pressure resulting in a loss of accuracy.

[JonB_in_Glencoe]

my guess is that some of the problem (people complaining about microgroove barrels) comes from the 44 mag, since SAAMI specs pistol and Rifle different (.002 different).

So when some reloaders (myself included when I first started loading for a Marlin with commercial cast bullets that measured .429, about 15 years ago) load up some 44 mag for their pistols and their Marlin leverguns with the same .429 or .430 projectiles, not knowing that Marlin (and most other manufacturers) makes them with a .431 groove diameter (typically).

[GregLaROCHE]

I love my Marlin .45-70. We’ve been thtough a lot together and if you ever saw it you would understand why. It made my heart sink when I heard about how they were taken over by Remington. Then later the poor quality control issues they have had. I hope they get them worked out. I thought all recent Marlins were micro groove until they were taken over by Remington.

I have been shooting almost only powder coating with mine since I started casting and am now moving into paper patching. I be never had a leading problem even shooting gas check type boolits only powder coated. I’m getting ready to drill out the mold to turn it into a flat base. I’m shooting with pretty rough iron sights and it does fine for what I want it for.

I noticed they are offering them in all different versions now. What I don’t like is the .45-70 version with the six shot tube. I’ve never shot one,even though my so has one. We just don’t seem to be in the same place at the same time with our guns. This long tube loaded with all those cartridges, has got to have that gun way off balance and front heavy. The four shot tube just feels right.

I know that wasn’t much about the micro groove barrel, but you said you were interested in one.

Last word, if you are going to use it as a brush gun, change the rear sight to a solid peep sight. The standard flat sight is way too fragile and will get ripped off in the least little amount of brush.

[wv109323]

The rifling in standard barrels is usually .004" deep with 2,4,5 or 6 lands. Micro groove has 12 to 16 lands and are about .001 or.002" deep. It is common that Marlin's actual bore size is larger than nominal bore size. Given the larger bore size many times a mold will not cast large enough to be used in a MG barrel. A .357 barrel on a Marlin may be .3585 actual and needs a .360 or .361 boolit. The mold may only cast .359 with your alloy. You will need to beagle your mold or powder coat your boolit to get it to shoot.
Lead hardness can enter into the equation when boolit diameter is less than optimal. Of course smaller boolits will lead the barrel much easier.
I have a Marlin in .44 mag. It will shoot a hard commercial cast bullet at .429 but my softer cast boolit needs to be .431.
Marlin MG barrels will shoot cast as well as Ballard but they do need a little tlc to do so.

[GregLaROCHE]

The rifling in standard barrels is usually .004" deep with 2,4,5 or 6 lands. Micro groove has 12 to 16 lands and are about .001 or.002" deep. It is common that Marlin's actual bore size is larger than nominal bore size. Given the larger bore size many times a mold will not cast large enough to be used in a MG barrel. A .357 barrel on a Marlin may be .3585 actual and needs a .360 or .361 boolit. The mold may only cast .359 with your alloy. You will need to beagle your mold or powder coat your boolit to get it to shoot.
Lead hardness can enter into the equation when boolit diameter is less than optimal. Of course smaller boolits will lead the barrel much easier.
I have a Marlin in .44 mag. It will shoot a hard commercial cast bullet at .429 but my softer cast boolit needs to be .431.
Marlin MG barrels will shoot cast as well as Ballard but they do need a little tlc to do so.

Thanks for sharing this knowledge it’s very interesting and informative.

[Walks]

MARLIN changed to Ballard rifling with the introduction of the 1894CB Rifle in .45 COLT.
At the End of Trail 1996.
Followed by .357MAG, .44MAG, .44WCF. All with 24" bbl's.

I have 3 pre-safety rifles; 1894 - .44Mag, 1894C - .357Mag and an 1895.
All 3 micro-groove guns shoot great with bullets cast of LINOTYPE and sized .001 over groove diameter.

[243winxb]

Marlin 44 mag micro groove = Poor accuracy. Plain base bullet. A GC may help.

[mdi]

Thanks fellers. I cast for 5, 44 Magnums (along with 9mm, 45 ACP, 45 Colt, and 3 rifle calibers) and have loads/bullets that nearly eliminate all leading. I have a Puma in 44. Magnum and yes, SAAMI dimensions for 44 Magnum rifle barrels is .431", but my rifle slugs at a hair over .432", which gave me a bit of trouble at first but now leading is almost nonexistent. Thanks for the facts like .001"-.002" vs .004" I slug the barrels of all my guns just to have the info on hand whether I'll cast for them or not and size bullets appropriately. I've even customized some 44 cal Lee sizer dies to .430". .432" and .434". I'm still thinkin' if I found a Marlin on the used rifle rack, 44 Mag., 45/70, .444 Marlin (?). I'd be sorely tempted, regardless of the riling...

Thanks fellers, keep 'em comin'...

[odfairfaxsub]

My 35 rem is a micro groove. I shoot .360 dia bullets in it and super pleased no issues. My marlin 375 Winchester is also micro grooved I shoot .380 dia bullets and it’s awesome to say the least

The 35 is gas checked and of 50-50 lead variety ww/range scrap The 375 is plain based of the same lead.

[blackthorn]

Has Marlin always used MG rifling? If not, when did Marlin begin to use MG in their firearms?

[Nobade]

Marlin 44 mag micro groove = Poor accuracy. Plain base bullet. A GC may help.Mine works great as long as the bullet is 433". Any smaller and it's terrible. And it does best with paper patched.

[Chihuahua Floyd]

Only clover leaf group I have ever gotten out of my 44 Mag Micro-groove barrel was with cast. 100 yards, three shots, one hole. Do not know what the bullet was as they where commercial reloads, I had requested 240g JHP, but got LSWC instead. shot great, but I started reloading again right after.
Don't push my cast bullets quite so fast.
CF

[Char-Gar]

I was shooting cast bullets through various Marlin MG barrels for many years before Marlin decided to reintroduce the "Ballard" rifling in some models.

Most of negative stuff written about Marlin MG barrels is based on a lack of understanding of these barrels. The groove diamter is over a few thou over normal and/or the land diamter is a few thou over normal. This means that bullets designed for traditonal rifling often do very poorly in the MG barrels. Either the bullet is too small for the grooves or too small for the lands or both. Cast bullets to do well requires both to be right. Find a bullet that fits and the Marlin MG bullets will deliver accuracy as good at any barrel.

I spent couple of years, looking for a 30 cal cast bullet for my 30-30 Marlins made from 1960 -72, all MG of course. The bullets that did well in my Winchesters rolled eye in the Marlins. I knew the problem but the bore specs, but what to do.

It was about the year 2,000 that I looked at the SAECO moulds and discovered that their #305 which they sold as a 31 cal mould, was nothing more than a fat #307 which was their 30-30 mold. This proved to be my salvation, and with the #305 my Marlins would outshoot the Winchesters with cast bullet of similiar design and weight. Life was good.

Since that time Ranch Dog came along with a line of moulds in all Marlin calibers designed to deal with the special nature of the Marlin rifle. Another issue was the lack of a throat, I might add. Chose a mould designed for the MG barrel and they will perform like a show pony in you rifles. Bottom line is we should not shy away from Micro-Groove barrels, but be aware they have special needs when it comes to bullet fit.

[Char-Gar]

Only clover leaf group I have ever gotten out of my 44 Mag Micro-groove barrel was with cast. 100 yards, three shots, one hole. Do not know what the bullet was as they where commercial reloads, I had requested 240g JHP, but got LSWC instead. shot great, but I started reloading again right after.
Don't push my cast bullets quite so fast.
CF

I have a Marlin MG in 44 Mag and found accuracy with cast bullets very easy to acquire. Before I started I noticed that Marlin kept the old slow twist in the barrels designed for the 44-40. I used a 210 grain bullet and a charge of Unique that would duplicate 44-40 ballistics. I used a .432 cast gas check bullet and first trip to the range, started to making one hole groups at 50 yards and 2.5" groups at 100 yards. I sighted the rifle in and I was done with load development. One load and done. The 44-40 round out of a rifle is a thumper on man or critter.

[Char-Gar]

Has Marlin always used MG rifling? If not, when did Marlin begin to use MG in their firearms?

No, Marlin introduced the Micro-groove rifling in 1953 in their 22s and shortly thereafter in their larger calibers. They hyped is as all kinds of better, as it didn't cut into the bullet jacket as deep. It was hype, but none-the-less, they sold lots of rifles. These MG barrels acquired a bad rep for accuracy with cast bullet, simple because folks didn't take the time to understand the barrels.

[dragon813gt]

Marlin 44 mag micro groove = Poor accuracy. Plain base bullet. A GC may help.

A lot more information is needed than “plain base”. I’m betting the bullet was to small if a diameter. 44 mag rifles are .431 so you’re gong to need a bullet a few thousandths over if you wan it to shoot well. Second thing is velocity. You can shoot plain bass bullets w/ accuracy as long as you watch the speed. I haven’t found the need for gas checks w/ an 1894C in 357 mag. 44 mag is a different animal but the same principles apply.

[MyFlatline]

I am of the school that if the mold calls for a check, I check it. If I want plain base, I order a plain base mold. So far I have had no issues with multiple calibers and weights using that method.

As for speed, powder coating brought in a whole new dimension. I have friends pushing 2000 fps. with no leading but accuracy does suffer.

If I can't hit what I am aiming at , all the speed in the world means nothing.

[blackthorn]

The first rifle I bought was a Marlin 30-30 (not a carbine). I got it in a second-hand store in New Westminster BC in 1956. It cost me a whole fifteen dollars! It weighs around nine and a half pounds and has an octogen barrel. Later for less than twenty dollars, I bought a 32-40 that, except for the butt-stock profile is identical to my 30-30. Both were made loooong before 1953. Thanks for the information on Marlin.

[GregLaROCHE]

Great to hear from all you Marlin Micro Groove owners. I was beginning to think I was all alone.

Hi can see now that I need to buy some larger sizing dies from NOE. My Lee molds are ok since I PC my .45-70 boolits. I’ve just been sizing them down too much. They still shoot well. I guess they will shoot even better now.

[robertbank]

This question goes out to Char-Gar. I just acquired a Marlin 1894CS. The rifle has been at the top of my bucket list for years. With a lot of things in life, timing is everything and the stars aligned two weeks ago and I now find myself in possession of a slightly used 1894CS in ,357Mag.

I know you will have experience in loading for this gun. I have several Lyman molds available ranging from 158gr SWC to the 200 gr RN. I intend to start with the 358156 GC bullet water quenched sized .358. I will try in time the 358429 and 358477 bullets sized .358 both PB and GC'd.

Any suggestions you have for me would be appreciated. Your thoughts on powders eg Unique, 296, 4227 would be helpful.

I intend to mate the 1894CS with my Ruger GP-100 and Uberti SAA.

Take Care

Bob



I have not slugged the bore yet but will depending upon your reply.

[PAndy]

My 1959 336 has a 21 groove bore. Not my preference. But it shoots well with cast bullets. Just have to experiment with speed etc. I think the 12 groove barrels would be easier . But even the shallow early microgroove can work

[45-70 Chevroner]

I started to make a comment but I figured that the thread starter "mdi" has figured this out after almost three years.

[robertbank]

I should have started a new thread but some of the answers to my questions were answered here so...knowledge is ageless.

Take Care

Bob

[yeahbub]

Congrats on the signs, portents, stars, planets and sundry falderall making your acquisition possible. I once loaded for one with micro-groove rifling and learned the value of sizing them .002-.003 over groove diameter. Since lever-action chambers have a chamfered end directly into the rifling instead of a true throat like bolt-actions do (check SAAMI chamber drawings), it has become my practice to size the cast boolit as large as will readily chamber from the get-go and let the chamber-to-rifling chamfer do the necessary sizing on launch. After I see what accuracy I'm getting, I can always size them smaller if improvement is needed.

This probably isn't true of your .357's chamber, but for some reason .45 Colt chambers in lever-actions are sometimes HUGE to the point of being able to chamber a .458 diameter boolit. Some folks have taken to casting/loading these fat ones to avoid over-working the brass for longer case life and letting the end-of-chamber chamfer take care of getting it to groove diameter. At pistol pressures this doesn't present any problems.

[robertbank]

Yeahbub mine is a Remlin/ I have looked at the rifling a dozen times and remain unsure whether the rifling is ballard or Micro. Did Remington continue with the micro groove barrels or go with Ballard? You would think I could see the difference but I can't.

The gun is very well put together. Wood to steel is verging on excellent. I first sighted in a Vortex Sparc11 but have decided to pit a 1x5X scope and will be off to the range to sight it in when I am done here. The scope is a knock off of a Leupold. To date it has performed well mounted on a Ruger PCC. We shall see ho it handles .357mag.

Thanks for the info.

Take Care

Bob

[oldblinddog]

I once owned a 1972 1895 .45-70 (tapered 22” barrel and straight grip stock) that had 4 groove Ballard rifling. I loaded and shot the Gould HP sized .458” with great accuracy. I also owned, previous to the one just described, an 80’s vintage 1895 (a much heavier barrel and blocky pistol grip stock) that had 12 groove Micro-groove rifling, but I never cast for the .45-70 then. It was very accurate with the 400 gr. Speer flat point.

[MostlyLeverGuns]

I have loaded for MicroGroove Marlins since about 1964/65. As a 14 year old I got severe leading with a 31141 that threw .309 bullets, I got a 311407 that threw 312, sized to 311 and everything came together with under 2" groups at 100 yards. I still shoot MG 30-30 and 35 Rems a 444, .310 or .311 works in th30-30's, .360 in the 35's and .432 in the 444. Leading not usually a problem unless lead too soft or pushed very fast. Ranch Dog designs were developed for the Marlins and work well. I usually run gas checks, plain base work up to 1100 fps +/-. Under 2 MOA attainable with decent sights/scope.

[Dom]

I have a Marlin 45-70 with the Ballard type rifling. Previously owned one with the Micro Groove style. For me there is a definite difference in obtaing accuracy. Without a doubt , a much harder bullet was required & much more attention to detail for me to get decent accuracy with the MicroGroove 45-70. In my now Ballard rifling Marlin I shoot cast bullets I make from my pile of scrap WW. BHN 10.5 & PC coated. Amazing accuracy. No fiddling with oversize or extra hard bullets. Also have three other Marlins with the Ballard type rifling. 38-55, 25-20 & 32-20. All are deadly accurate with my BHN 10.5 WW bullets.Why create extra problems if you don't have to.

[rbuck351]

I have a like new JM 1894 Marlin micro groove in 44 mag that doesn't shoot cast bullets well at all but then it doesn't shoot jacketed bullets much better. 4" patterns at 50 yds is about the best I have done with jacketed factory 240gr ammo. If I ever get it to shoot jacketed bullets I'll give the cast another try. So far I am underwhelmed with the Marlin.

[yeahbub]

rbuck351, I had a pre-safety Marlin in .44 mag like you describe which had the same accuracy issues. I got about 3" at 50 yards but cast was a waste of time. Then I found out how MG barrels (and barrels in general) are made. They are drilled, reamed and rifled as a cylindrical blank and if they're fired in that form, they'd be excellently accurate. But, then they are lathe-turned for the outer contour, thick at the breech to thin at the muzzle. Not a problem for cut-rifled barrels, but for broached and button-rifled (as MG barrels are), this leaves a lot of unresolved stress in the steel. The industry practice is generally to stress relieve them with a heat soak in a furnace before turning the outer contour, but this is not a perfect answer and some unresolved stress remains. When they are contoured, steel is removed from the outside allowing the stresses to "spring" the barrel, more where it is thinnest. The breech end is affected the least and remains at original dimensions while the thin muzzle is free to expand - resulting in a tapered bore, tight at the breech to loose at the muzzle. The opposite is the ideal condition. The difference is small, on the order of generally .001 or less, but it leads to leakage/leading and lack of guidance at that last 2" of rifling that's most critical. All is not lost, though. Such barrels are excellent candidates for pressure-lapping to get the bore cylindrical or even introduce some proper taper, which is more likely, pressure-lapping being what it is. You might try driving a .440 or so round ball from breach to muzzle to see if it gets looser as you go. Once I got half way, mine presented no resistance at all. Drive one through from muzzle to breech and see if it tightens as you go - and observe whether there's a hard stop at the rear sight dovetail or at the chamber. The dovetails are one of the last things done and a dull tool can depress the bore slightly out-of-round, or a heavy wire edge can be thrown up at the front of the chamber, both of which can cause mediocre accuracy.

The great majority of barrels turn out fine and those on the edges of the bell curve probably won't get noticed since the average shooter shoots jacketed ammo and gilt-edge accuracy isn't generally on their radar anyway.

[robertbank]

I just bought a Marlin 1894. It is a Remlin. Fit and finish is, frankly, excellent and I have no issues at all with the the gun.
So far what I have found is the gun prefers heavy bullets driven fast. H110 and 4227 loaded near maximum as set out in Lyman manuals seem to produce the tightest groups at 25 yards. I am no rifleman and have yet to attempt to test the gu out further to determine accuracy with the gun. I doubt my attempts would not reflect what the gun is capable of. The bullet it seems to like is the Lyman 358429 with 13 to 14.5 gr of either of the powders mentioned loaded in .357mag case using SPMP.

I have an inexpensive knock of of a Leupold scope on the gun. So far I have no complaints. I have the gun sighted in at 25 yards and will take it out today and eset my zero for 50 yards using 14.5 gr of 4227.

One thing I have noted is when i go from the heavy bullet to a lighter 358477 I go from tight groups to patterns. I would think I would see tight groups hitting lower on the target with little no lateral shift. What I get is a drop in hits and off to the left. Thoughts?

So far I love the gun and enjoy shooting it.

Take Care

Bob

[Blood Trail]

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