Marlin FTF

C

CPE 68

Inactive
I have a marlin 30AW (similar to a 336) 30-30.

I fired a box of federal 170gr with no problems. I then switched to Remington corelokt 150gr ammo and had four FTF in a row. The four rounds showed no real impression of the firing pin on the primer, just a faint mark.

I switched with no other changes to Winchester 150gr and federal 150gr and fired a dozen rounds with no problem and normal primer indentation. I tried the Remington again and had the same FTF occur. Switched ammo again and no problem.

I'm stumped why this occurs. This is all new ammo not handloads
 
If rim thickness and primer seating depth are approximately the same, I would suggest checking (or having a gunsmith check) headspace.

30AWs, like many 336Ws, didn't always get as much care given to fitting parts properly. So, in my experience, they are more likely to have improperly-fitted locking bolts; or locking bolts that were very rough when installed, and have now worn to allow excessive headspace.

The 336 design includes an unintentional 'bandaid' that hides bad headspace through standard operation: By having the hammer drive the bolt forward and close the gap upon firing.
 
As far as I recall, as I didn't specifically note it, the lever closes all the way on the Remington. I tried firing 4 rounds from the magazine, then after firing other rounds, 2 from the magazine then one fed directly to the chamber.

I just checked the rim thicknesses on two successful brands including spent casings and also on the Remington. They all have about 2k variation in rim thickness and all fall in the same range within 3k total variation.

Rim diameter I checked for a stupid check even though that shouldn't matter and with a 3k variation they are the same.

Primer seating depth I could not specifically verify as I don't have a depth micrometer but with a straight edge across the rim looking at a light they all appear visually to be the same.

Fired primers are proud of the rim approximately 25k on cases that worked.

I just saw another thread talking about headspace issues on the 336. I'm going to do the basic checks and see what it shows. I'll also thoroughly clean the bolt and pins then head back to the range.

I was also getting very strange groupings with a wide variation of about 4" at 50 yards. I would typically see two holes less than an inch then a three to four inch spread and another pair. I thought the scope mount was loose but it's tight. Not sure if this is related.
 
I had the same problem with a 336. The primers would back out after firing. Too much headspace in my mind. After looking for obvious issues and finding none I felt the "locking bolt" was most likely the problem. It appeared to have been hand ground or perhaps "fitted". I compared mine with some I saw at a gun show and the gunshow one was slightly thicker. I put the new one in and it remedied the headspace problem. No more backed out primers. I was prepared to fit it if I had to but did not.
 
If primers are 0.025" proud of the case head after firing, you have excessive headspace. (The 336 headspace 'bandaid' strikes again.)

More than likely, a new locking bolt needs to be fitted.



(I am not a gunsmith. I am simply a big fan of the 336 action.)
 
In my experience, sloppy headspace is the major (nearly the only) problem with those Marlins, especially in .35 Remington. I always recommend that the purchaser of a Marlin lever action try several brands of ammo and stick to the one that proves most reliable,

Jim
 
Thanks for the help. I'm not sure why this issue only seems to affect the Remington ammo but I'm going to work on the headspace issue.
 
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