Acceptable FPS spread

[muzhunter]

Just got a new Chrony! Went and check the velocity on my 300 WBY. What would be considered ok FPS spread? Mine came in at 60 FPS this was a 10 shot group. All brass was processed normally. No sorting by head stamp or weight just resize trim to length and go.

Thanks in advance Muzhunter

 

[J E Custom]

Just got a new Chrony! Went and check the velocity on my 300 WBY. What would be considered ok FPS spread? Mine came in at 60 FPS this was a 10 shot group. All brass was processed normally. No sorting by head stamp or weight just resize trim to length and go.

Thanks in advance Muzhunter

I like to get less than 20 to 30 ft/sec Extreme spread and Standard deviations of under 10.
10 to 15 is good for SDs.

These are not easy to get but are possible.

For 100 to 200 yards 60ft/sec will work but when you extend the range you will need to
improve it to prevent vertical stringing.

If you shoot 10 rounds in a row (Without Cooling between shots) make sure that the round
doesent stay in the chamber long (Cooking) before shooting it.

J E CUSTOM

 

[JUDD]

I agree with the above...We shoot for single digits on our LR rifles.

 

[RockZ]

I look for an ES of 10 or less.
At long range a big spread will show lots of vertical.

 

[Trickymissfit]

the big Weatherby case likes heavy dense loads, and that may be part of your problem. Also you didn't say how you had the chronograph setup. The muzzel blast from a .300 WBY. is fierce! If the screens are moving from the blast you may well be getting a variation from that alone. A good test would be to move the chrongraph down range another ten feet. If you see the same variation then you know it's in the actually rounds themselves. What is you load data?
gary

 

[JARHEAD1371]

Don't get too wrapped up in what your chrony spits out at you. I was solely looking at the numbers when I was load developing my 7 SAUM. I ended up wasting time and components. If a load shoots good groups at 800+ yds then your fps spread is going to be low. IMO use your Chrony to get an estimate on your velocity, and your groups to choose a load. Good luck.

 

[muzhunter]

My load is 180gr hornady interbond, 85 gr IMR7828 SSC. I did not notice the chrony moving after the shot. I would shot 3 then let cool for awhile then repeat.

I always get groups under an inch at 100yd. Here is a copy of the data.
If I could attribute the one flyer to a special cause it would shrink the STDEV to 11.0.
I don't feel good throwing it out

180gr / 85.0 IMR7828

3348
3343
3352
3351
3377
3352
3347
3335
3356
3397

AVG 3355.8
STDEV 18.05424
MAX 3397
MIN 3335

 

[Trickymissfit]

My load is 180gr hornady interbond, 85 gr IMR7828 SSC. I did not notice the chrony moving after the shot. I would shot 3 then let cool for awhile then repeat.

I always get groups under an inch at 100yd. Here is a copy of the data.
If I could attribute the one flyer to a special cause it would shrink the STDEV to 11.0.
I don't feel good throwing it out

180gr / 85.0 IMR7828

3348
3343
3352
3351
3377
3352
3347
3335
3356
3397

AVG 3355.8
STDEV 18.05424
MAX 3397
MIN 3335

you have three loads that come into question. The 3377fps and the 3397fps loads along with the 3335fps. How are you measuring the powder in your loads? Also what is the variation in the seating depth?
gary

 

[Reloader222]

Getting SD below 10fps is always extremely good. However, below 20fps SD could still be regarded as OK. Low SD does not necessarily implies a good grouping. It all depends on the rifles "sweet spot". Low SD is therefor a helpful guide, but not the overriding factor.

 

[muzhunter]

The seating depth is per the listed COL in the manual. WBY needs free bore. So all loads are to that length. Each load is trickled to target.

Another thing concerning to me is the FPS which is way high for a 300 WBY 3355! Fasted list in the manual is about 3200 FPS for a 84.5 load. I could have a fast barrel it is a Pacnor select match grade 26 inch, if that is what they are called. It was their best barrel available.

I think I will drop it back down in half grain increments and see if it will tighten up some. I guess i have more work to do.

Thanks for all the info!

Muzhunter

 

[Trickymissfit]

The seating depth is per the listed COL in the manual. WBY needs free bore. So all loads are to that length. Each load is trickled to target.

Another thing concerning to me is the FPS which is way high for a 300 WBY 3355! Fasted list in the manual is about 3200 FPS for a 84.5 load. I could have a fast barrel it is a Pacnor select match grade 26 inch, if that is what they are called. It was their best barrel available.

I think I will drop it back down in half grain increments and see if it will tighten up some. I guess i have more work to do.

Thanks for all the info!

Muzhunter

pay very close attention to the starting loads in the manual! These are the absolute minimum for a big case like this! Those cases want to be loaded kinda hot. What I would do is to shorten the loaded length about .025" (check with a gauge at the ogive). As for the velocity, I think you need to find another chronograph to shoot thru. Then see if there are any differences
gary