Мы наткнулись на редкий винил.

Наткнулись is the past tense, plural form of наткнуться.

Breakdown:

• наткнуться = the dictionary form
• наткнул- = past-tense stem
• -ись / -сь = reflexive ending
• plural past tense agrees with мы = we

So:

• я наткнулся / наткнулась = I came across
• мы наткнулись = we came across

In Russian past tense, the verb agrees in gender and number, not person:

• singular masculine: наткнулся
• singular feminine: наткнулась
• singular neuter: наткнулось
• plural: наткнулись

The basic form is наткнуться.

This verb is:

• perfective
• reflexive
• usually used with на + accusative

A very common pattern is:

наткнуться на + something
= to come across / run into / stumble upon something

So in your sentence:

Мы наткнулись на редкий винил.
= We came across a rare vinyl record.

The -сь (or -ся) is the reflexive marker, but here it does not mean a literal English-style reflexive like we found ourselves.

In Russian, many verbs with -ся / -сь are just normal dictionary verbs with their own meanings.
So наткнуться should be learned as a whole verb.

Compare:

• ткнуть = to poke, jab
• наткнуться на что-то = to run into / come across something

So the -сь is part of the verb’s normal form and meaning, not something you should translate word-for-word.

Because this verb normally takes the pattern:

наткнуться на + accusative

This is just the standard construction you learn with the verb.

Examples:

• наткнуться на статью = to come across an article
• наткнуться на старого друга = to run into an old friend
• наткнуться на ошибку = to come across an error

So in your sentence:

• на редкий винил

The preposition на is required by the verb.

Because винил is masculine singular, and here it is in the accusative case.

The adjective must agree with the noun in:

• gender
• number
• case

So:

• nominative masculine singular: редкий винил
• accusative masculine singular inanimate: редкий винил

Since винил is inanimate, the accusative looks the same as the nominative.

That is why you see:

• редкий
• not редкого

Because винил is a masculine inanimate noun, and for masculine inanimate nouns, the accusative singular is usually the same as the nominative singular.

So:

• nominative: редкий винил
• accusative: редкий винил

Compare that with an animate masculine noun:

• nominative: редкий коллекционер = a rare collector
• accusative: редкого коллекционера

That difference happens because animate masculine nouns usually take accusative forms that match the genitive.

Винил literally means vinyl, but in modern usage it often refers to:

• vinyl records
• a vinyl record
• vinyl as a music format

In this sentence, it most naturally means a rare vinyl record or rare vinyl.

Russian often uses винил this way informally, especially when talking about music collecting.

Because наткнуться на has a special nuance: it suggests finding something unexpectedly, by chance, or while looking at something else.

Compare:

• мы нашли редкий винил = we found a rare vinyl record
• мы наткнулись на редкий винил = we happened to come across a rare vinyl record

So наткнулись feels more like:

• stumbled upon
• ran into
• came across unexpectedly

Наткнуться is a perfective verb, so it presents the action as a completed event.

That fits this sentence well because it describes a single finished occurrence:

• at some point, we came across it

If you wanted an imperfective idea, you would usually need a different verb or a different way of expressing repeated/habitual action.

For example, perfective here focuses on the result:

• we did come across it

It is not describing an ongoing process.

Yes.

It can be literal:

• наткнуться на столб = to bump into a pole
• наткнуться на камень = to run into a rock

And it can be figurative:

• наткнуться на статью = to come across an article
• наткнуться на интересную идею = to come across an interesting idea
• наткнуться на редкий винил = to come across a rare vinyl record

In your sentence, it is the figurative/discovery meaning.

Yes, very often it could.

Russian often drops subject pronouns when the verb form already makes the subject clear.

So both are possible:

• Мы наткнулись на редкий винил.
• Наткнулись на редкий винил.

Including мы may:

• make the sentence a bit clearer out of context
• add slight emphasis to we
• sound more natural in some teaching examples

So мы is not required, but it is perfectly normal.

The neutral word order is:

Мы наткнулись на редкий винил.

Russian word order is flexible, so you can move things around for emphasis.

For example:

• На редкий винил мы наткнулись случайно.
• Редкий винил мы нашли не сразу, а просто наткнулись на него.

But in a simple standalone sentence, the given order is the most natural and straightforward.

A natural stress pattern is:

Мы наткну́лись на ре́дкий вини́л.

Main word stresses:

• наткну́лись
• ре́дкий
• вини́л

This can help with pronunciation, especially because Russian stress is not always predictable.