FPS variances

[Panhandler80]

What's a respectable FPS variance for off the shelf ammo?

Bought a chrono and shot 5 cold barrel shots through it.

3031
3074
3048
3066
3037

Gives me a spread of 43 total and an average of 3051. 43 as a percentage of average is 1.4%. Box says 3100.

????

140 grain out of a 270 wsm. Nosler ammo with 140 accubonds

EDIT: Also learned that muzzle needs to be a few feet back from the chrono. Blast was giving us some crazy readings! Had like a 2800 and a 3144 when I was too close. Once we got a few feet back things settled in and those are the results above.

Only shot two out of 300WM. 3131 and 3128 with 180 grains. Advertised 3130. Pretty impressive. It's their Superperformance line. I would have expected more from Nosler Trophy Grade.

 

[wind gypsy]

Sub 20 SD, sub 60 ES is decent for factory ammo IMO.

 

[WoolyBugger]

Seems pretty normal for factory ammo.

Also two shots isn't a big enough sample size to get a handle on the es of the ammo. For instance take your two closest shots of the nosler and you have a spread of 6

 

[Q_Sertorius]

What's a respectable FPS variance for off the shelf ammo?

Bought a chrono and shot 5 cold barrel shots through it.

3031
3074
3048
3066
3037

Gives me a spread of 43 total and an average of 3051. 43 as a percentage of average is 1.4%. Box says 3100.

????

140 grain out of a 270 wsm. Nosler ammo with 140 accubonds

EDIT: Also learned that muzzle needs to be a few feet back from the chrono. Blast was giving us some crazy readings! Had like a 2800 and a 3144 when I was too close. Once we got a few feet back things settled in and those are the results above.

Only shot two out of 300WM. 3131 and 3128 with 180 grains. Advertised 3130. Pretty impressive. It's their Superperformance line. I would have expected more from Nosler Trophy Grade.

What chrono do you have?

Your sample sizes are too small to really mean anything.

 

[Panhandler80]

What chrono do you have?

Your sample sizes are too small to really mean anything.

I figured 5 would be sufficient. Leupold suggested chrono reading for CDS dial and not going with number of box. I had planned to tell them the average of 5 for that.... 3,051. Maybe I need to shoot some more through it. Grrrrr.

Bought this one. Pretty good reviews online.

Amazon.com

 

[anonymous22]

The box fps is based on a 24 inch barrel test barrel. Unless you have a 24 inch barrel, that is their barrel, in “standard conditions” I wouldn’t care too much about “advertised velocity”

Yes, on an optical chrono you usually want to set it about 10 feet back but you need to account for the distance to correct the MV.

ES is a derivative of SD. It can only get worst the more you shoot.

Know if your chrono does population or sample SD. Most opticals are sample.

If you pay attention to nothing else, pay attention to this: Having a larger sample size is indeed more accurate. However, there’s only 20 rounds in a box, and once the lot numbers change, it’s almost 100% going to be different for the next lot in velocity and SD.

 

[Tobe_B]

You’re standing on the edge of the rabbit hole. Next step is a full on dive in to how to make things better.

I’ve seen a variance of 100fps in one box of Hornady frontier 5.56 ammo, quite appalling really. But that ammo and that rifle max out at about 450 yards. So 100fps at that distance doesn’t affect my groups enough to be out of the vital zone I’m after.

This is what pushes guys in to reloading. You really just have to decide what’s right for you and what you’re doing with the rifle. Is a large spread going to matter at your max distance range? If not, shoot and practice, knowing that your groups are going to spread out as you get out there with no way to really adjust it.

 

[flyfisher117]

That seems about right for factory ammo. The SD is 16.5 which is roughly what I see every time I have shot quality factory ammo over a chronograph.

It’s not a bad thing to shoot as much as you can to get an average but I’d personally have no drama taking that 5 shot average and verifying the data at distance.