Can someone explain this.

[Sticks&Strings]

My dad and I both shot new guns through the chronograph this weekend. His is a 6.5 with a can on the end. He shot a 140 grain bullet 2850 fps avg. I shot a 6.5 x 284 norma with a 130 grain bullet at 2750 fps avg. My box of ammo said 2900 fps is what they would be, and his showed 2700 fps on his box of ammo. How does this happen? I have more powder and lighter lead, he has less powder and heavier lead.

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[kcnatural]

Barrel length possibly

[DirtyDave]

The can adds velocity. Just like a longer barrel. Getting a more complete powder burn

[DirtyDave]

Most of the numbers on the box of rifle ammo are from a 26"+ barrel

[Leverhunter]

Unless you are matching the conditions the manufacturer used when testing velocities you will get a difference.

[El General]

Different brand ammo. Different barrel lengths. Different test barrel lengths. Physics hates you.

[meltingfeather]

Number of factors could contribute--
powder quantity (actual weight)
burn rate
whether either of you is at an accuracy node
barrel length (I've never heard and it doesn't make sense to me that a can would add speed-- I can test that).

[Muygrande]

Sometimes it varies quite a bit from barrel to barrel. I’ve shot two 26” 300 mags with the same ammo and one was consistently 40-50 FPS slower.

[az2tx]

His is a 6.5 what?

[Wayspr]

Sometimes it varies quite a bit from barrel to barrel. I’ve shot two 26” 300 mags with the same ammo and one was consistently 40-50 FPS slower.

Some barrels / chambers / throats are just faster than others

[Texas89]

Like stated above. Barrel length, barrel brand, and suppressors can add a little bit of speed as well.


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[Sticks&Strings]

His is a 6.5 what?

Creedmore.

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[Sticks&Strings]

Number of factors could contribute--
powder quantity (actual weight)
burn rate
whether either of you is at an accuracy node
barrel length (I've never heard and it doesn't make sense to me that a can would add speed-- I can test that).

His definitely increased after he added the can. Here is the set up

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[mpotts]

Twist rate will determine how much pressure you are building up behind the bullet.

[Capt Glenn]

Only one thing can account for this. Manbun magic.