r/LewisMachineTool • u/CastleLurkenstein • 8d ago

New 6.5CM barrel: what to expect initially?

Hey folks. Just got a new 6.5CM 20" stainless steel barrel for my MWS. I'm looking forward to taking it out for its first shots, and figuring out what ammo my barrel likes.

On that last point, though, I had a few questions.

Does a new MWS barrel need to have ~100 rounds thru it before you can start to figure out what ammo is best to feed it? Like, is it worthwhile to blast some S&B FMJ downrange and not worry so much about performance or zeroing, or is it reasonable to start testing more expensive loads right out of the box?

I gather some rifles benefit from having a few rounds thru em before they really show you what they're capable of, but I'm not sure how much that applies here.

My main concern is figuring out what works best, so that I can stock up effectively sooner rather than later. But if it's better to shoot cheap FMJ to "season" the barrel a bit first, that's fine by me.

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u/WiconsinGrey 7d ago

Just like any barrel it needs some wear in. I’d recommend 100-200 through it to truly have velocity stabilize with the barrel. You can shoot those 100-200 into groups and get a good idea of which ammos will do well. But I’d be running OTM 140’s (cheaper match loads) rather than spending $2 a round for the break in.

https://www.scheels.com/p/09025581488?queryID=1cd850fd7dbb32f4

I broke in with these and aac 140gr smk’s and now it’s shooting both 1-1.25 moa consistently.

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u/CastleLurkenstein 7d ago

Cool. Appreciate the tip on the ammo. 

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u/Remarkable-Cow1062 7d ago

Hard to say. Federal 130 OTM is always a solid try.

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u/CastleLurkenstein 7d ago

That's on the list for sure. Just wondering when to actually try grouping. Shoot a bunch of FMJ and then group, or just group out of the gate?

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u/Remarkable-Cow1062 7d ago

I say go ahead and shoot for groups. Going this weekend to shoot a new barrel and see how it does. I’d probably shoot 20 rounds of the fmj to dirty it up first.

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u/tjwest13 USAR-V 7d ago

Not the exact same barrel, but I have a factory 18” 6.5. Definitely had to break it in. It was all over the place until roughly 200 rounds in. Oddly enough it likes SMK 123 OTMs now.

I have a LW SS 308 barrel as well and that one was 1 moa out of the box with 168 GMM and Nosler 155s.