Marlin 336 accuracy

[Slaymoar]

Good day guys, I have gone to the range a few times with my marlin 30-30 and have found that after I have painted it, accuracy has been more intermittent. Sometimes it shot ragged holes at 100 yards, and as the barrel would warm up it just depended which ammo was in the tube. Some ammo would do well cold, and some would do better on a hot barrel. But what was pretty consistent was the POI shift per group - as barrel got hotter.

I have done some research over at Marlinowners and some other forums, and took her apart yesterday. I found that the paint added thickness to the barrel and the bands were tighter afterwards. I also found that the magazine tube was touching the barrel at the receiver end and had to be bent for the front barrel band to go on. These are two critical pressure points where the barrel definitely can change shift. Adding to this the two barrel bands were added choke points. I opened up the barrel bands until they fit snug without needing a tool, while sanding off the paint at those points. I also sanded down the channel/groove underneath the barrel where it meets with the mag tube at the receiver until they were barely touching with the front band on. That took a while. After a good clean, I reassembled everything and I will take her to the range tomorrow morning hopefully. I will report as soon as I have a chance.

Here is some useful info I have gathered yesterday:

1. Barrel channel putting pressure on one side of the barrel.
2. Fore end band pressing to hard on the barrel. You'll see the bluing worn when you take it off.
3. Forend cap does not have enough cleance for the barrel and makes contact- vey common on newer ones.
4. Mag tube making contact with the barrel inside the forend. Requires filing the barrel to get enough clearance. Not in book. Look at one that's good and match the amount of metal removed.
5. Trigger pull gritty and too heay. Trigger and sear have heavy maching mar s and maybe even burrs on them. Get rid of burrs and follow trigger job instructions here on MO.
6. Barrel band by front sight has been way over tightened. It has narrowed because of this and is pinching way too hard on both tube and barrel. Need to spread it, or get a new one.
7. Tang to stock fit too loose. You can inprove this by having it bedded if you don't want to do the through bolt.

Out of several Marlins I've looked at for friends, every rifle has had at LEAST 2 of these issues w/o including the trigger problem. And these rifles come from all years of production. My 338MX had issue 1 and 3. The old Glenfield I wrote about had issues 1,3,4,5,6.

This is a long overdue update but after some dremel work to get he forend cap to sit nicely, removing high spots where the forearm touched the barrel, and then bedding in silicon to stop play / rattle at the receiver and forend - this gun now shoots 1 ragged hole at 50 yards and about 1.5 inches at 100 (5 shot groups). The groups will still start opening up if I let the barrel get to hot, but I'm not complaining# Thanks for the advice Swany and sorry it took me so long!

Adding to this: At the end of my modifications, everything fits on finger snug, which still ends up making the rifle feel nice and tight.

 

[eberlestock]

good stuff to know