.35 Remington handloads are keyholing

[Swift]

I bought a Marlin 336 .35 Remington a couple of years ago to "match" my Marlin 39A and 39M that are family heirlooms. Iowa has recently allowed the .35 to be used for deer (we were slugs only), so I'm looking for a load. It shot pistol bullets reasonably well, but I finally stumbled upon some Hornady 200 grain round nosed Interlocks and they seem to keyhole. I started using H335 at 38.3 grains. That keyholed badly. I disassembled the rifle and gave it a thorough cleaning. It still keyholed. I the tried IMR 4064 at 38.1 gr and 39.9 grains. I also tried Varget at 36.0 & 38.3. I'm shooting offhand with a sling supported from 45 yards. It is still keyholing pretty dramatically. Any suggestions?

 

[AJC1]

It's obviously not stabilizing. Use a lighter shorter bullet or try a bigger diameter.

 

[Swift]

The Interlocks are a jacketed bullet that measure 0.358. I checked them and they are correct. I haven't run any through the chrony, but wonder if pushing them faster will stabilize them? The .35 is a low pressure cartridge, but the Marlin 336 is in good shape, and should be able to withstand a little higher pressures I assume?

 

[AJC1]

The Interlocks are a jacketed bullet that measure 0.358. I checked them and they are correct. I haven't run any through the chrony, but wonder if pushing them faster will stabilize them? The .35 is a low pressure cartridge, but the Marlin 336 is in good shape, and should be able to withstand a little higher pressures I assume?

If you use a stability calculator you will notice that it takes a lot of speed to change the outcome a little. Twist rate and bullet length changes the outcome fast.... play with one and see what happens...

 

[GeoDudeFlorida]

Check the crown. Microgroove is very shallow. It could easily be damaged or copper clogged right around the crown. It’s worth a look.

 

[amflyer]

Your loads seem consistent with the Hodgdon data, and you cleaned the barrel. Good starting places. Did your cleaning include a good de-coppering? Otherwise, you might have to start looking at the crown or the rifling.

 

[amflyer]

GeoDude beat me to it, but good advice.

 

[Palladan44]

At 100 yds, I would get a random complete and total miss of paper with my 35 Remington (M336) This was maybe one in every 5 rounds or so. Using factory loaded Remington core lokt 200gr soft points. Moved to a 25 yd target, to find the one in 5 or so wasn't getting stabilized and was tumbling and keyholing. Switched up ammunition to a new box (call it 30 years newer ) of the same brand ammunition. No problems.

Now, the copper fouling near the crown is another high possibility to cause all of them to Keyhole. Geodude said it.

 

[Charlie98]

You could always pick up a box of cast bullets, .001" larger, with gas checks. Those would probably fill the bore better...

Montana offers 200grn FN bullets up to .360" with gas checks. That same bullet, but in .349", shoots very well in my Browning 71.

 

[Swift]

It appears there may be some copper at the crown. I've never even thought to look for this before. Any suggestions of products to use to de copper it?

 

[GeoDudeFlorida]

It appears there may be some copper at the crown. I've never even thought to look for this before. Any suggestions of products to use to de copper it?

Sweet’s, Shooter’s Choice, Hoppe’s. I like Sweet’s 7.62 the best but it stinks like cat piss. Shooter’s Choice doesn’t stink but you have to soak the bore then do some scrubbing with a nylon brush. Hoppe’s is a good long soak, scrub, soak, scrub routine but it smells nice and won’t cause liver damage.

 

[Charlie98]

Sweet’s

Be aware, Sweets is ammonia-based, which is why it stinks like cat urine. Ammonia breaks down the copper. It can also etch your barrel... read and HEED the directions. Used as directed, it works very, very well.

 

[GeoDudeFlorida]

Be aware, Sweets is ammonia-based, which is why it stinks like cat urine. Ammonia breaks down the copper. It can also etch your barrel... read and HEED the directions. Used as directed, it works very, very well.

Yup. And don’t let it sit on your skin. Wash your hands and wear nitrile gloves.

 

[AJC1]

Eliminator is not toxic.... I use it but never dealt with severe fowling.

 

[Chuck R.]

When I have something that's badly copper fouled out:

Sweets 7.62 is first up. I use it with a timer set to 7 minutes per cycle.

IF Sweets can't do it in a few cycles, then I move to JB Bore Paste mixed with Kroil, like so:

Improve Firearm Accuracy for Under $20!

It's true. For a little pocket scratch, you can improve your rifle's accuracy potential in no time flat, thanks to a little-known technique from the benchres...

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It isn't an every time cleaning thing, but it does help with a really fouled bore.

 

[CWTISME]

You are at Max load for Varget using Hornadys 200 gn RN Close to Max with H335 and my Hornady #11 gives 4064 at Max at 36.9 granted Hornady is conservative but have you tried starting low and working your way up ? 36 gns of Varget lists a speed of 1966 fps while the max load of 39.5 is listed as 2139 fps I used both my Hornady #11 and Hodgdon website for data.

 

[GeoDudeFlorida]

It appears there may be some copper at the crown. I've never even thought to look for this before. Any suggestions of products to use to de copper it?

Did it work?

 

[Nature Boy]

If the rifle hasn’t been cleaned well over the course of its life there’s a likelihood that alternating layers of copper over hard carbon have formed. It might take a bit of effort to get it all out.

ETA: I had the exact thing happen to me. A very accurate rifle started shooting shotgun patterns. I took it to the gunsmith, he looked at it with a borescope and gave me the bad news; my barrel was dirty and my cleaning regiment wasn’t effective. I purchased a borescope and set about changing my cleaning methods. It took me several hours of labor but I was able to get the copper/carbon/copper/carbon layers out of my barrel, verified by the borescope, and getting it back to bare steel.

Accuracy returned to expectations

 

[GeoDudeFlorida]

If the rifle hasn’t been cleaned well over the course of its life there’s a likelihood that alternating layers of copper over hard carbon have formed. It might take a bit of effort to get it all out.

ETA: I had the exact thing happen to me. A very accurate rifle started shooting shotgun patterns. I took it to the gunsmith, he looked at it with a borescope and gave me the bad news; my barrel was dirty and my cleaning regiment wasn’t effective. I purchased a borescope and set about changing my cleaning methods. It took me several hours of labor but I was able to get the copper/carbon/copper/carbon layers out of my barrel, verified by the borescope, and getting it back to bare steel.

Accuracy returned to expectations

That kind of deep cleaning is a labor of love.

 

[sugarmaker]

If it’s winter, shoot into a plowed / stomped on and compacted snow bank and dig the bullets out and examine them. They likely won’t go more than 4 feet. See if they are engraved and if they show signs of stripping in the bore. Then there is the last resort factory ammo test…

 

[Catpop]

Just fired some fresh reloads through my 1960 -+/- Marlin 336 RC. I used 26.1 grains IMR 3031

 

[GeoDudeFlorida]

I suspect it worked based on the absence of the OP.

 

[Riomouse911]

I suspect it worked based on the absence of the OP.

Or he is still scrubbing!

Hopefully he’s found the cure.

Stay safe.

 

[Nature Boy]

I wonder if the micro groove rifling in this rifle would be more susceptible to fouling to the point of becoming effectively a smooth bore resulting in the keyholing the OP is experiencing.

 

[AJC1]

I wonder if the micro groove rifling in this rifle would be more susceptible to fouling to the point of becoming effectively a smooth bore resulting in the keyholing the OP is experiencing.

Definitely take a lot less time to transition than Ballard. My Marlin 357 carbine is a MG and I scrub the crap out of it every trip just to alleviate those concerns.