I set it it on it weakest power 2.5X. It goes up to 10X, it's a pretty big scope. I had thought that maybe the scope had gotten knocked out of alignment on our trip to the Fifth Annual Northeast Bloggershoot not too long ago and wanted to make sure I had it pretty much zeroed in before hunting season. I thought that if it was still zeroed, that would be fine. If not, then that would mandate a trip to the outdoor range to zero it at 50 yards. My 336 shoots .35 Remington caliber. I remembered that it shot about 2-3" low at 25 yards with Winchester-Western ammo. I could not remember how low it shot at 25 yards with Remington Core-Lokt ammo but it also shot low with that ammo at 25 yards when zeroed in at 50 yards.
Somehow, I forgot to bring along a box of the Winchester-Western Ammo. I brought only a box of the Remington Core-Lokt and 3 rounds of the Winchester-Western that I had loose in my bag. So, I loaded it up with 3 rounds of the Remington first. I figured if it was really off the mark, since I suspected it had gotten knocked out of zero at the bloggershoot, I could sight it in good enough with the 20 rounds of that ammo. I fired the first 3 shots of Remington Core-Lokt at 25 yards. That is all I needed to fire with that ammo, it told me all I needed to know once I saw the grouping.
I had the scope set on 2.5x for the first shot. I set it to about 6X for the second shot and back to 2.5X for the last shot. I was standing, leaning over the bench, with my right elbow supported on the bench, left elbow up in the air. No sand bags or anything like that, I wanted this to be somewhat like me maybe leaning on a stump or log out in the woods or as if I was firing from a seated position supporting my arms on my knees. It was about as realistic as I could get at this range. The target was a 12" x 12" sheet with a 3 3/4" x 3 3/4" diamond outline around the center. I aimed the cross hairs dead center, at the smaller orange diamond, which is just about 1/2" by 1/2" across. The small squares in on the target are 1" x 1". My group size, across the widest spread from outside rim of one shot to outside rim of the other, was about 11/16th of an inch across. If you measure from the outside of one the shot on the left, across the center shot, to the inside of the shot on the right, then it was a group size of about 7/16th of an inch or thereabouts - hard to measure because it is a one hole group for all three shots and the inside rim of that shot hole had to be estimated.
As you can figure from the picture, I figured it was still zeroed. Also, as I had thought it would do, it shot a bit low at 25 yards, in fact, if I recall correctly the Core-Lokt would shoot about an inch or two high at 50 yards when the gun had been zeroed in with the Winchester-Western ammo, which is what ammo was used the last time I zeroed in this gun. That means it would not shoot quite as low as the W-W ammo at 25 yards. As you can see, it shot about 1/2 to 3/4 of an inch low at 25 yards. Splendid - I tell you - splendid! I then took the three rounds of the W-W ammo I had on hand and shot it. Well, I shot my Glock 19 and my Ortgies pocket pistol first. Then I shot the Marlin 25MN in 22 WMR, I went through about 50 rounds with that rifle. After that, I decided to shoot up the three rounds of Winchester-Western ammo, that I had with me, through the Marlin 336.
The W-W ammo shot about an inch and a half to two inches low and the group was opened up quite a bit over the Remington Core-Lokt ammo out to 2 1/8th inches at the widest spread, outside rim of one hole to outside rim of the other. Not so good but okay for deer hunting. I know can do better with it, probably as good as I do with the Remington ammo, and am guessing that after the first few shots with the 336, followed by about 100 with the Glock and another 16 with the Ortgies, and then 50 with the 25MN, I was a bit fatigued (Bear in mind that I broke 2 ribs just 2 1/2 weeks before and they are still aching a bit when I do certain things; good excuse for crappy shooting anyway.)
When it comes right down to it, the old Tasco scope I have on the Marlin 336 was not knocked out of zero at all. I will take it to the range again, maybe in a week or two, next time with more ammo, and will shoot it more to make sure it is good for myself. Hopefully Brendan will cone along and shoot it too although if zeroed for me it is usually okay for him too. I have to say, I have surely gotten my money's worth out of that scope. It was very inexpensive, on sale, several years ago. I was advised against getting a low end scope and almost regretted it because within a year or three of me having bought it, Tasco went out of business. They have since reopened under another corporation and no longer honor the warranties on older scopes like mine but mine has taken a beating at the range, in the trunk and while out hunting and has remained in great shape. I have had that scope on the Marlin since about 2006, taken off for cleaning the rifle now and then but that has been the scope for the Marlin since then. I have owned it at least a couple to a few years longer; it sat around in the box that long before it went onto the Marlin. I had bought it with an idea of getting a very different gun on which to mount it but when my eyes started to get a little weak, I put it on the 336 and am happy I did so. Not a bad decision at all, Brendan got his first big game animal, a black bear, with the Marlin 336 with that scope on it - a one shot and immediate kill.
Yep, you can say, I am a pretty darned happy shooter with that Tasco scope sitting on the Marlin 336.
All the best,