Chronograph Surprises

[Sartori42]

I got a MagnetoSpeed V3 chronograph for Christmas. So, I strap it to my Tikka T3X Varmint in .223Rem and start recording velocities, SDs, and ESs. I have so far tested 8 different factory-produced ammunition types in 2 different shooting sessions. I admit that my 10-shot samples are bare minimum for establishing a pattern, but I am still surprised by some of the results.

Bryan Litz says in Applied Ballistics For Long-Range Shooting… “Regarding available ammunition types, a Standard Deviation (SD) of 20 fps is considered relatively poor consistency, and is generally representative of mass produced factory ammo. 15 fps is considered better than average for factory produced ammunition….”

Federal American Eagle 75g. (AE223T75); mean = 2709 fps; SD = 11.8 fps; ES = 33 fps
Federal Gold Medal Match SMK 69g. (GM223M); mean = 2831 fps; SD = 26.1 fps; ES = 88 fps

Fiocchi Shooting Dynamics 55g. (223A); mean = 3169 fps; SD = 14.0 fps; ES = 42 fps
Fiocchi Exacta 77g. (223MKD); mean = 2667 fps; SD = 36.5 fps; ES = 117 fps

I don’t understand how the cheaper ammunition types from these two manufacturers have more consistent velocities. I assume there is something I’m not doing correctly, but I’m not sure what. If anyone has constructive thoughts, it would be appreciated.

Thank you.
Steven

 

[hlee]

Look at the actual data points. Do you have one that is way outside the others?

 

[Steel head]

It’s totally possible to get really good SD’s with factory ammo if it’s tuned to a particular barrel well.

 

[Sartori42]

hlee... The actual measurements for the FGMM were (in order) - 2836, 2884, 2817, 2812, 2809, 2849, 2832, 2856, 2796, 2823.

Steel head - One of the tasks I'm trying to accomplish is to find what ammo works best with this rifle and why. I'm finding that the ammo that groups best isn't necessarily the ammo that measures best. My problem is that I haven't shot farther than 100 yds, and I'm worried that the wide variations I'm seeing are going to result in more POI variations when I stretch the distance later.

 

[Rocketvapor]

I have a second hand Sporter and used it the first time last Sunday @ 100yds mounted to a 28" very heavy barrel 22 Nosler.
I wanted to find a node with a new powder, SB 6.5.

Took some shots a a steel plate with factory 77gr, 100yds, and all ten were the 'normal' 1/2 MOA lower than my ZERO set up for 88ELD and IMR4350. My zero had not shifted.

So, I put on the Chrono and my standard load is hitting a little high and to the left. Not much, but off the dot.
I then proceed with 3 increasing charges of SB6.5 with the 88's and 4 increasing charges with 90SMK's.
ALL are hitting a little high and to the left.

To finish the day and reset my ZERO, I took the MagnetoSpeed off and the groups center right up.
No adjustment needed.
My local range looks like it will be flooded (Honey Island Swamp) so I'm going to my next 600 F-class with 2 different loads, just in case. My old faithful 88IMR load and my best guess 88SB6.5 load.

Until I get a few more sessions with the Sporter I'm not comfortable that not only does it change POI (in an odd way) but changes barrel dynamics enough to alter groups.
I can only imagine what it might do to a lighter barrel.

 

[hlee]

Measure velocity and group size as 2 separate shooting exersizes. Velocity with magneto speed. Group size without it.

If you are concerned that the spreads will open up at longer distance, shoot those longer distances and measure the spread.

 

[Rocketvapor]

Reading about all the plus's about the magnetospeed it just caught me off guard.
Many comments about POI shifts, but it does seem to mess with barrel harmonics.
Had only a good guess for charge weight with the SB6.5 and 88's in a 22N.
Right around 2900 did produce the best groups. 3000 and the groups opened up.

The problem with longer distances is my 600yd trips are meets, for score.
Since both loads are 88's I can adjust my drop for velocity between the two loads but
will have to wait and see how the new one groups.
Starts off bad, at least I'll have my stand by load to finish with.

 

[wpgk58]

I got a MagnetoSpeed V3 chronograph for Christmas. So, I strap it to my Tikka T3X Varmint in .223Rem and start recording velocities, SDs, and ESs. I have so far tested 8 different factory-produced ammunition types in 2 different shooting sessions. I admit that my 10-shot samples are bare minimum for establishing a pattern, but I am still surprised by some of the results.

Bryan Litz says in Applied Ballistics For Long-Range Shooting… “Regarding available ammunition types, a Standard Deviation (SD) of 20 fps is considered relatively poor consistency, and is generally representative of mass produced factory ammo. 15 fps is considered better than average for factory produced ammunition….”

Federal American Eagle 75g. (AE223T75); mean = 2709 fps; SD = 11.8 fps; ES = 33 fps
Federal Gold Medal Match SMK 69g. (GM223M); mean = 2831 fps; SD = 26.1 fps; ES = 88 fps

Fiocchi Shooting Dynamics 55g. (223A); mean = 3169 fps; SD = 14.0 fps; ES = 42 fps
Fiocchi Exacta 77g. (223MKD); mean = 2667 fps; SD = 36.5 fps; ES = 117 fps

I don’t understand how the cheaper ammunition types from these two manufacturers have more consistent velocities. I assume there is something I’m not doing correctly, but I’m not sure what. If anyone has constructive thoughts, it would be appreciated.

Thank you.
Steven

I am surprised by the Federal Gold Medal Match performance. I have shot it with excellent results and much better performance than the above.
Try Hornady Match and see if that is better. Some guns like different ammos.
The, of course, you can jump down the rabbit hole of reloading your own custom tailored round for each gun.

 

[Sartori42]

wpgk58,

When you say you shot the FGMM with good results, are you saying you measured it on your own chronograph, or that you have good precision with the brand? The consistency of bullet velocity doesn't really become a factor until the distances get longer. To date, I haven't shot beyond 100 yds. so it isn't yet an issue for me. My comments here are just that I'm surprised that they measure so inconsistently. As I said originally, I feel like I must have done something wrong because these are brands that have a proven track record with a lot of shooters. I have now measured 14 different types of 223 ammo, and have 2 more to go (Nosler RDF 70g. and Hornady Superformance 73g.) My sample size is minimum (10 rounds), but I feel I can expect the trend to follow my experience so far. So, I remain a bit baffled.

Cheers.

Steven

 

[Sartori42]

Rocketvapor,

From my very limited experience with the MagnetoSpeed, I feel that having it attached to the barrel may slightly alter the POI, but hasn't really affected precision. My groups have been just great with it attached to the barrel. In fact, at my last session, 4 out of 12 groups were at about 33 SOA or better (roughly 1/2 MOA). Granted it was indoors at fairly short distance, but that was enough groups that I don't feel like it was a complete fluke. Since I was shooting different brands of ammo, some of the other, larger groups can be attributed to less precise ammo in my particular rifle. So, I don't think the MagnetoSpeed should be on your rifle when you are shooting for accuracy or to set your zero, but I don't think it particularly hinders precision. Maybe it does at longer distances but, in my opinion, I wouldn't shoot long distance with a chrono attached. You can get the velocity information at any distance.

Cheers.

Steven

 

[wpgk58]

wpgk58,

When you say you shot the FGMM with good results, are you saying you measured it on your own chronograph, or that you have good precision with the brand? The consistency of bullet velocity doesn't really become a factor until the distances get longer. To date, I haven't shot beyond 100 yds. so it isn't yet an issue for me. My comments here are just that I'm surprised that they measure so inconsistently. As I said originally, I feel like I must have done something wrong because these are brands that have a proven track record with a lot of shooters. I have now measured 14 different types of 223 ammo, and have 2 more to go (Nosler RDF 70g. and Hornady Superformance 73g.) My sample size is minimum (10 rounds), but I feel I can expect the trend to follow my experience so far. So, I remain a bit baffled.

Cheers.

Steven

When I shot the FGMM, I chrono'ed it during eval, to determine the MV and consistency. It performed well with close to box MV and SD in low teens. The long distance performance was good. I shot it out to 800 with no issues.
If you are looking for higher quality performance out of factory ammo, then consider testing the Prime line (primeammo.com). I have not shot it personally, but have heard from several sources that it shoots really well.