Accuracy Question. Help!!

C

ckpj99

New member
Ok, so I'm having some issues. I recently bought a Marlin 336. When I bought it, I ran a bore snake through it, checked the bore and went to the range with a variety of ammo.

The sights were primitive, but I was shooting 1.5" groups at 50 yards with Hornady 150gr soft points (marketed as whitetail rounds). With any 170gr round, the groups opened up to 3-4". I also opened up to 2-3" with Hornady Lever Evolution rounds.

I was wondering why the heck the 170gr were so erratic and someone suggested there might be copper fouling in the barrel. I took a brush and gave the barrel a good scrubbing. It was filthy. I'm not sure if it was the 50 or so rounds I put through it or just the fact that the shop didn't clean it, but it was pretty bad.

Since I've cleaned it, I really haven't seen any tighter accuracy, in fact it's mostly been looser, even with the 150gr Hornady rounds it seem to like before.

Since my first couple range visits, I've also changed the sights, so I've sort been blaming it on that and thinking I should just change back to the original sights, however, I thought of something today.

Did that first intense scrubbing ruin some of "seasoning" of the barrel? Since that first cleaning, I've been cleaning it with a brush after every range session (which usually only consists of 20-30 rounds or so.)

So what's the deal? Should I stop cleaning my barrel as often? I'm just not sure what's going on here. I have some lead reloads that I'm working out, and I'm really not see too much accuracy out of those either.

Please help!
 
I can't really answer your question, but I had a 336 in 35 Remington for years and my Dad and brother hunted with the 30/30 versions. None were what we might call tackdrivers, but they shot pretty good. I never really shot for groups back then, at least not with the intent of measuring the groups. I will say that once I put a 4 power scope on the rifle, I started doing MUCH better at deer hunting and my random target shooting tightened up. So that's what I'd recommend. Put a 4 power on it and then see how it shoots. Those iron sights that come with the gun aren't that great. I see the scope as a must-have for that rifle.

We shot our rifles year after year and I was the only one that ever cleaned my rifle bore and it kept on shooting pretty well, but so did Dad's dirty bore. I don't think that cleaning the bore would ruin the accuracy of the rifle. The barrel of mine had the Micro-Groove barrel, and it has shallow grooves. If the previous owner shot a lot of cast bullets, that could have leaded the barrel up and be causing accuracy issues. You should be able to look down the bore and tell if that's the case.

And since you don't reload, just shoot various ammo until you find something that works well, and then see if you can get a couple boxes of the same ammo, and even better if they have the same lot number.
 
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Don't make the mistake of thinking that a lever-action rifle designed for hunting would be as accurate as a bolt-action target-grade rifle. (Or, an internet ,under-MOA, super wand ;) )

1-1/2" @ 50yds translates to 3" @ 100yds - plenty enough accurate to hit/take most game larger than a small dog.

I happen to get a little bit (VERY little) more accuracy with a receiver peep sight, but YMMV, certainly.


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I went out and conducted a bunch of testing in my 30-30 M336. I was able to get one ten shot 2.0" group at 100 yards, and that was exceptional for this rifle. I am very happy with 3" inch groups, 4" is fine. Some load combinations with the 170's were eight MOA. Marlin 30-30 rifles are not target rifles and anyone who claims MOA accuracy needs to show a 20 shot group before I will take their claim seriously.


This is my best load in this rifle:


This is my second best:



This is actually good for the rifle:

 
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Some factory barrels have a rough enough fininsh in the bore that it needs a bunch of copper fouling from bullet jackets to fill the micro pits full of copper. Then no more copper's washed off bullet jackets and accuracy is decent.
 
There are a lot of variables at work.Its pretty hard to figure out whats going on if multiple things are changed.Try working toward the old "isolate one variable" trick.
You mentioned you changed the sights.I can't say if they are better or worse,maybe you can verify that.

Are you shooting on a bench,on sandbags?Bolt rifles are easier on a bench...lever guns are sort of crooked with the drop,etc,and are just less friendly to getting a consistent "bounce" under recoil,Not saying it can't be done,but trying to stack range bags,things sliding around,etc can show up on target.

Neither the sights or the bag technique are about the accuracy potential of the barrel.

I don't know how much it would show up on your deer rifle,but even shooting ball powder then switching to an extruded powder and back can open groups a little because the powderfouling is different and it takes a few rounds to settle in.

Some Marlins have micro-groove rifling,there may be something to learn about what fouling that likes.
Take notes,change one thing at a time.Its probably a good deer rifle.Good luck!
 
Rifles like yours with attached magazine tubes tend to string groups due to barrel heating. The magazine tube restricts barrel lengthening and causes warmer barrel shots to go lower and sometimes on a slight diagonal.

That pattern is very evident in your groups. Try shooting cold-barrel groups, letting the barrel cool to the same as the first shot and you may find that it shoots very well.

The rifle isn't a target rifle, but scoped and from a rest, should put the first three shots into about an inch at 50 yards.

Also, when shooting such rifles, I typically, shoot from a softer front sandbag, or place my left hand under the forend to simulate a field position. Oh yeah, don't try putting a bipod on one, as it probably will cause vertical stringing.
 
Like Bake suggested, it could just be the ammo difference.
It's not uncommon for various weight or length bullets to have very different results.
 
Rifles like yours with attached magazine tubes tend to string groups due to barrel heating. The magazine tube restricts barrel lengthening and causes warmer barrel shots to go lower and sometimes on a slight diagonal.
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A 20" long barrel in a lever action tube magazine rifle lengthens about .0003". Having shot a few Marlin and Winchester lever action carbines single loading them one shot at a time with an empty magazine, none had any significant bullet impact change going from ambient to very hot temperatures. Doing the same thing with a full magazine then loading one round from it at a time so each shot was fired with one less round in the magazine, that caused point of impact change. The weight of the combined barrel and magazine changed with each shot; it whipped and vibrated differently depending on round count in the magazine.
 
My 2 cents worth: accuracy is a vague term, and one that is abused a little when it comes to lever action rifles. 3" at 100 yds is probably about average for most lever action rifles. Over the years, I have fired quite a few, and it is not uncommon for many rifles to shoot 150 grainers well and the 170 grainers to wander a bit. So just shoot the 150 grainers!

You described the sights as "primitive", and while that is true it is good enough to put one in the boiler room on a deer at 100 yds.

Your Marlin may also have Micro-Groove rifling, which can be kind of choosy about the bullets it likes. Mine liked Sierra and Hornady bullets but not Speer. Figure out what it likes and carry on.
 
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