First shots with my chrono.

[Clamper13]

357_mag_14_5_2400.pdf

I finally got a chrono and tested some of my loads. The spread seems high and I think it is from inconsistent crimping. Some were light. Any feedback is appreciated. Thank you.

158gr ACME coated RNFP
2400
14.6-14.7grs
GFL Brass
Winchester small pistol magnum primers

[TNsailorman]

My experience with 2400, H110, and W296 tells me that they need a good firm roll crimp to get steady burn rates which is what you are looking for. These slower burning powder need to get up to at least a 75% of listed maximum before they start delivering the goods. Some cases have a thicker or thinner wall and that can make a difference also. I am not a fan of GFL brass and I do trim all my cases to the same length. I do not trim them after every firing, just the first time when I get them and then they are usually good to go for several firings. Straight cases such as the .357 do not grow much with repeated firings. my experience anyway, james

[metricmonkeywrench]

Those with far greater experience will chime in but I believe your right on the ball park of where you need to be for a 357 revolver. For the most part at this point you can try to dinker a bit with the powder charge and/or the crimp. Case length is the key to a consistent crimp and having the brass trimmed to a standard length will aid in that along with brass consistency (wall thickness and age hardening if cases are not from the same batch/lot). Plenty of tips and tricks out there but I'm not sure if you will see the ES/SD close much more..

It may not be correct but I have read that anything less than a 30 for SD in a revolver is pretty good.

As I am learning with my chronograph data tells half the story, the chrono data may look good but how accurate are they? Sometimes good chrono consistency doesn't always equal to good accuracy.

If anything it just means more trips to the range to find out.

[Larry Gibson]

Clamper13

A 10 shot test with that load out of a revolver having an SD/ES of 21/65 fps is actually quite good. If accurate with an average of 1253 fps then I'd not change anything.

[Clamper13]

Those with far greater experience will chime in but I believe your right on the ball park of where you need to be for a 357 revolver. For the most part at this point you can try to dinker a bit with the powder charge and/or the crimp. Case length is the key to a consistent crimp and having the brass trimmed to a standard length will aid in that along with brass consistency (wall thickness and age hardening if cases are not from the same batch/lot). Plenty of tips and tricks out there but I'm not sure if you will see the ES/SD close much more..

It may not be correct but I have read that anything less than a 30 for SD in a revolver is pretty good.

As I am learning with my chronograph data tells half the story, the chrono data may look good but how accurate are they? Sometimes good chrono consistency doesn't always equal to good accuracy.

If anything it just means more trips to the range to find out.

Accuracy is another thing. I was shooting offhand at 25yds which I'm normally no good with. I will need to shoot from rest next time. I didn't shoot horrible but I could use some improvement.

[Clamper13]

This is in my SW 686+ 3" by the way.

[country gent]

a lot of things come into play with reducing spreads and standard deviations, Ignition of the powder charge, the right primer for the job. Powder burn rate and running in the right pressure range to burn consistent. Here this can sometimes be seen by unburnt powder in the barrel or on the bench. Bullet tension, crimp, bullet ( weight is one factor bearing length shape ). Another is cases older tired cases may not give as good of numbers as fresh new brass.

Try stating with new brass same maker same lot number. Lightly trim to same overall length and square mouths. lightly chamfer and deburr. Deburr flash holes inside case ( burrs can affect ignition). A consistent powder charge, weigh them +/- .1 grn. Seat bullets and crimp in a separate operation, this gives the most accurate oal and crimp. Start with a moderate crimp. Last thing is to pick one chamber in the cylinder ( preferably the one with tightest barrel cylinder gap if they vary) Mark it with a marker and fire every round thru the chamber, Variations in chambers throats and length will have an effect by using one chamber this is eliminated.

The last is to prove your chrono graph and set up. A good spring cocker pellet gun is usually very accurate in velocity ES and speed. buy 1000 of the pellets it likes and set these back for this purpose. When choreographing the same spring cocker air rifle and these pellets fire 10 rds over the screens to prove set up and accuracy. After a few times this becomes a known velocity when outside the range then something is off.

[Beerd]

Accuracy is another thing. I was shooting offhand at 25yds which I'm normally no good with. I will need to shoot from rest next time. I didn't shoot horrible but I could use some improvement.

You are a lot braver than I am. First time shooting over your new chrony and you do it off hand at 25 yards
..

[tsubaki]

If it were my loads doing that, I’d call that ES “bragging”!
For me anything with an extreme spread of 50 or less is a miracle.
I have yet to correct the problem but found one of my revolvers has a tight and loose chamber in the cylinder. I numbered the chambers and sure nuff one always has low velocities, the other one higher. The other 4 always run about the same.
Thanks for posting your data and results! I’ve been meaning to play with 2400 with 357 for years and your numbers reinterested me!

[GARD72977]

I would say good to go. Try shooting a few factory loads over the chrony

[dhom]

Generally with 2400 I also get what I consider high ES. I was just chronograghing .357 loads with 158 gr Hornady's and 2400 with CCI regular primers. At 14 gr the ES was 30 fps and at 14.5 gr ES was 40 fps. I was elated with that. I am getting over 1300 fps approaching 1350 fps. These results were from a 6" GP100 at 33 degrees. By the way, accuracy was excellent.

[mattw]

I have one load for 357 with H110 data powder and the RCBS 180 GC mould that in new brass and with good loading processes will hold a SD of about 11. Most loads are in the 20 to 30 SD range and shoot fine. Now, if you stretch out the distance the higher SD might bite you. For a revolver load, you are in pretty good shape.

[country gent]

Here's a comparison, Most of my BPCR loads when done with work up have a sectional deviation of 3 - 6. for 10 rd groups. AN extreme spread of 10-12 fps. These are rifles with 30-34" barrels firing heavy for caliber bullets for caliber bullets, 38 - 55 is 360 grn bullet, 45s are 550 gr. Loaded with Black Powder and compressed to where it wants to perform the best.

Uniform your brass, cut primer pockets square flat and to same depth, deburr flash holes, trim to same length in a batch, Annealing does help some also. Do everything needed to make cases identical. I have seen true accuracy nuts set a trimmer up to inside out side chamfer so they get the same on every case. For a side note annealing gives etter neck tension and crimps.

Now when loading these cases weigh each powder charge to +/- .1 grn or better. Drop it in the case with a slow pour thru the funnel. Even better is a 4" drop tube on the funnel. This helps stack the powder more consistently and evenly. ( with the above loads I use a 3' long tube). Seat the bullet into the cases in a separate operation and hold OAL as close as you can then crimp . In the way the bullet isn't moving when the crimp is applied.

I believe that compressed loads may give better numbers do to the better ignition of compressed loads. ( powder is in varying positions in the case)