Marlin Hot Barrel

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MOTO VITA
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Marlin Hot Barrel

Post by MOTO VITA » Tue Nov 27, 2018 7:54 pm

I recently got an early 336A 30-30 to shoot rifle caliber, I've been shooting smallbore for a while. When I'm about 25 rounds into a 40 round match the barrel heats up and shots start going high by 12 to 18" at Turkey distance. At first I thought it must be me, but today I confirmed that it happens when the barrel gets hot, I'm sure it must happen somewhat gradually, but it seems like it happens all at once. I suppose it may have something to do with the connection of the magazine tube to the barrel. I imagine some of you are shooting 60 round matches with similar rifles so there must be a way to deal with it. Anybody have any experience or advice to offer?

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Another Dang 9
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Re: Marlin Hot Barrel

Post by Another Dang 9 » Tue Nov 27, 2018 8:17 pm

Almost all LA rifles do that. It depends mostly on how quickly the match goes. Does the gun have time to cool down between relays? What powder are you using, are they hot/max loads? How are you holding the gun does that change as you shoot? These were never ment to be match target rifles but some guns will do it more than others. I would do more testing to see exactly when it occurs.
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MOTO VITA
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Re: Marlin Hot Barrel

Post by MOTO VITA » Tue Nov 27, 2018 9:04 pm

There are only two relays, so the rifle doesn't cool down completely. My loads are pretty typical, 32 gr. Varget, although I did shoot ten factory loads at the Rams. My hold is also pretty typical and doesn't change.
I'll certainly monitor it more closely in the future, but for it to happen that early in a match I think I'm going have to change something.

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Jason
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Re: Marlin Hot Barrel

Post by Jason » Wed Nov 28, 2018 12:52 am

You need to get the barrel off of the wood of the forend. It's the same principle as floating a bolt action rifle barrel, but you won't be fully floating the lever action rifle's barrel. There are several how-to tutorials out there, with varying guidance on whether to bed the forend wood into the steel forend cap with the same type of materials used to bed bolt action rifle actions or to use high temp RTV sealant between the barrel and forend wood. I chose to remove enough wood to not have it touch the barrel and bed the ends of the wood into the forend cap and receiver. I also needed to relieve a bit of metal on the forend cap so that it didn't put pressure on the barrel when I tightened down the screws into the forend cap. That left my barrel touching only the receiver and barrel tenon that the magazine tube hangs on. There's no need to do that until you try dealing with the wood first, though. That's almost surely where the POI shift is coming from. If that fixes it and it shoots up to your standards, you can skip the modification of the forend cap and having to re-blue it after you're done.

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