Understanding chrono results

[excess]

I have a JP CTR-02 in 223 with a 20" barrel. I shot some Fiocchi 77gr factory loads through it as I have heard good things about the load. Chronoeing it, I am a little surprised at the results I got. This is from a Magnetospeed V3:

1) 2525
2) 2643
3) 2605
4) 2667
5) 2647
6) 2649
7) 2639
8) 2659
9) 2560
10) 2603
11) 2608
12) 2603

This is an average of 2617, with an S-D of 42.2. What I am surprised about is the 2525 fps reading, and maybe the 2560 reading too.

A plot of that looks like this:

Just seems like the 2525 shot is pretty far off from the rest. So - do you think that one was a bad reading from the chrono, or does that seem realistic?

If I drop the 2525 shot the average increases to 2625 fps, and the S-D drops to 32.2.

If I drop the 2560 shot also the average increases to 2632 fps, and the S-D drops to 25.0.

In the end I am trying to figure out what to use in my ballistic calculator, and whether I should look for a different load.

Thanks

 

[hlee]

While I have not chronographed any Fiochi ammunition, I am not surprised by your results. It shot very poorly in my rifle- though this is a sample of 1 rifle and one box of ammunition. I've not read anything abysmal about Fiochi, but nothing stellar either.

 

[TimK]

I'd definitely look for another load. I've had decent results with Prime. IIRC, SD's were in the teens. The 77g load is slow, but accuracy is decent. The 55g is the appropriate speed and quite accurate, but I rarely shoot 55's due to the low BC.

I have a JP Ultralight that I never could get to shoot to my satisfaction with handloads. I ended up running Prime 77 in it for matches.

 

[NighthawkCG]

Thats about the consistency of it that I have found. Ran it through 2 rifles with magnetospeed V3 and had ES up in the 125 - 150 range and high SDs to go with it. Shot ok on steel out to 600 yards in both rifles though for some reason. Not great, but better than I expected. Didn't try it beyond that.

 

[JSTARSZ]

If you are looking for a really good production 77 grain round, look at Norma. I have seen SD's in the 10-15 range and is extremely accurate.

 

[bfoosh006]

I also would suspect the ammo is at fault.

IMHO... most Fiocchi ammo isn't really known for outstanding across the board / multi rifle accuracy... ( not trying to stir the pot ) ... for me, it is actually better known for having off center flash holes.

 

[el_cazador713]

Are you guys seeing better results with Hornady match ammo?

 

[Greg Langelius *]

Padom pointed me toward IMI 77gr., and I have 6 boxes of the new Hornady/Frontier Military Grade 75gr HPBT Match currently inbound for testing.

Greg

 

[Greg Langelius *]

To answer your question more directly, I don't use factory ammunition very much, preferring to handload fresh ammo that's been load developed for my individual rifles. The Frontier testing is an attempt to find a reasonably priced alternative to handloading such loads on a more generic basis, since I do tend to use this type of load in some greater volume.

I have tried Hornady 75gr match ammunition and steel match in small quantities and found them to be pretty good, accurate ammo in my rifles, but prefer to load my own for reasons of cost, and for the accuracy advantages that allow me to customize loads for individual rifles, and to allow some control over load consistency that makes bad accuracy my fault rather than someone else's.

Blaming other entities or the equipment for the miss is no longer a policy of mine. No matter what the cause, it all hinges on my own decisions at some point.

I do believe you will find that Hornady Match and Varmint offerings make you happy enough. I have yet to try the IMI 77 stuff, but do I put faith in Padom's recommendations.

I also hope that you can manage to get into accuracy handloading in the future, as I have personally found it to be very satisfying.

Some may question my preference for the Hornady 75gr HPBT-Match projectile over the A-Max or ELD-Match, the 77, and others like it. I have chosen it because I also use it in 24" rifles with 9" twists as a generic load that I can employ in at least three of my six .223/5.56 rifles. While the 77 may also suit such a need, I have plenty of experience with the Hornady projectile, and have no compelling motivation to change to another. Add to this my living at 4Kft+ altitude, and a declining interest in formal competition, and the need for a more slippery bullet just isn't there for me.

You might also benefit from my own rather extensive use of the chrono for load development for going on three decades. I found that although I could find loads that showed quite satisfyingly low deviations; I also found that those loads really had almost no direct reference to what I was seeing on the target, basically because good (consistent/identical) velocity numbers and barrel harmonic sweet spots are simply not linked. When you find a node, consistent velocities help, but the node is the important thing.

IMHO, the chase for good numbers may have included some disregard for barrel harmonics, in the belief that harmonics don't matter so much, because if they all have the identical barrel time, or same velocity, they will all group together. I haven't found any such correlation. They will group together because they adhere to the individual barrel's harmonic pattern, regardless of the numbers.

Some time over the past decade, I started leaving the Chrony(s) home and concentrated almost solely upon the target. I haven't even picked up the Chrony in years.

I have also determined that hot loads and peak velocities are simply barrel killers that are probably unnecessary. Peak velocity mostly helps terminal performance in my viewpoint, but for target shooting, no matter what the velocity, as long as the bullet arrives at 1300fps or better ontarget, shooting any load will need to conform to the same wind compensation skills as any other.

High velocity advantage is like the proverbial free lunch, there ain't no such thing. When my .223/5.56 rifles can't perform far enough out there, that's what my .260 and .308 are for. It's time to stop incinerating good barrels.

Greg

 

[Birddog6424]

The only decent factory stuff I have found is Hornady Match and Norma.

I buy the Norma to shoot through my 223 Ackley Improved trainer bolt gun. Even the basic 55gr stuff shoots pretty well for barricade training. Then I use the brass for my reloads in 55gr trainer ammo or 80gr get serious about accuracy ammo.

Good stuff

 

[isofahunter]

I have run a fair amount of Black Hill Match 75gr and 77gr have found both to be very good. I have just started shooting a case of IMI 77gr but reserve judgement because the first trip out was very windy and time was spent shooting steel not groups. Function was perfect.

 

[Greg Langelius *]

Black Hills 75gr Match was what we used in Savage 10FP .223's back just after the turn of the century. It was impeccable, and the Black Hills 75gr Remanufactured Match was every bit as good, and cheaper by some as well. I did some extensive load development, and was able to equal, but never exceed the accuracy of that BH stuff. The HDY 75gr HPBT Match bullet was the common denominator, and has been my distance bullet ever since back then.

We tried the 75 A-Max, but it had troubles in the magazine, and we were concerned that it mightn't stabilize in our 1:9" barrels. This was probably stupid since we were single feeding anyway.

Greg

 

[Greg Langelius *]

FYI/FWIW, the frontier 75gr match arrived, and the primers are crimped.

Greg