diffusers for my chronograph

PaulS · Posted: Sat Jan 04, 2014 12:32 am Post subject: Re: diffusers for my chronograph

Well, after putting up some insulation in the garage this morning we headed out to the range. I wanted to sight my 22 for 80 yards for the upcoming silhouette season so we took the chronograph with us. After sighting the rifle I ran 10 rounds over the chronograph and it didn't miss a single shot. All ten registered and it gave me an average velocity of 1208 fps. That is with the ammo that I have been using so now I can see what the ballistics program predict and compare that the the actual targets I shot at 20,40,and 60 yards.

My brother fired five rounds from his 357 and got... 2340 fps with a 140 grain bullet. That's about 1000 fps faster than it should be so I gave him some of my reloads which clocked at 1340 or so (memory is going) which is about right for the 18 grains of H110 and the same 140 grain bullet. I thought maybe it was a fluke so I asked him to fire five more - same velocity. The shells fell out of the cylinder and the primers showed only minor flattening but no cratering. we are going to pull one down to see how much powder is actually in the case. I wouldn't have thought it was possible to get that kind of velocity out of a 357 magnum without some serious pressure signs.

Ominivision1 · Posted: Sat Jan 04, 2014 4:55 am Post subject: Re: diffusers for my chronograph

Interesting Paul, I also got some erroneous readings from the chrony using different types of bullets, but when I painted the bullets with a black marker the readings came down to normal.

Vince · Posted: Sat Jan 04, 2014 7:12 am Post subject: Re: diffusers for my chronograph

Paul wrote:

...My brother fired five rounds from his 357 and got... 2340 fps with a 140 grain bullet. That's about 1000 fps faster than it should be so I gave him some of my reloads which clocked at 1340 or so (memory is going) which is about right for the 18 grains of H110 and the same 140 grain bullet.

2340fps from a .357 Mag??? What pistol was he using, or was it from a rifle? I used to mix up some pretty stout loads for my 586 S&W Revolver in .357 Mag, but the best I ever managed with 150gn SWC GC was about 1550fps.

Using H110, velocities in the 1500fps range are easily achievable, depending on the pistol. Velocities of 1340fps would most likely not show any pressure signs because the powder charge is most likely below the starting load for 140gr bullets.

Of course the obligatory warning must be said...start low and work up your load checking for pressure signs as you go. ALWAYS use reputable data for your pistol, the calibre, the bullet and the powder. Never guess at a powder charge for any bullet and do not trust a load in your gun that works for someone else...always do your own load development.

Bushmaster · Posted: Sat Jan 04, 2014 9:32 am Post subject: Re: diffusers for my chronograph

Your chronograph is seeing the sound wave??

TRBLSHTR · Posted: Sat Jan 04, 2014 11:14 am Post subject: Re: diffusers for my chronograph

To heck with all of that;I just want the data for that load!I'll build the pistol for that load! Razz

gelandangan · Posted: Sat Jan 04, 2014 3:34 pm Post subject: Re: diffusers for my chronograph

2300+ fps from a .357 Mag?

Bloody awesome!!
What is the recipe?

Bow

PaulS · Posted: Sat Jan 04, 2014 4:37 pm Post subject: Re: diffusers for my chronograph

There is something strange going on here. My loads were 18 grains of H110 powder with a 140 grain bullet. His load (or at least the one we pulled today) was only 17.4 grains of H110.

The bullets are traveling faster than sound so it is not the sound or blast wave that the chronograph is seeing. The bullets that I loaded were fired from his gun too. He did say that the 10 rounds that he fired were from a different batch but he has been using the same load for better than 15 years.

Right now I would like to say it was an aberration but with two five shot groups showing the same velocity and five of mine between them that shows 1300+ it just doesn't seem like an aberration would be that consistent. His loads also generated more recoil than mine did.

I still don't have any answers but we will do more testing as we get the chance.

For those of you with hopes of super-speed 357 rounds here is the recipe:

Remington nickel plated 357 brass trimmed to 1.29"
Speer 140 grain JHP
17.4 grains of H110
CCI 550 primers
o/a length of 1.59"
the listed starting load is 16.0 with a maximum of 19.6 grains of H110

My load was the same except it was 18.0 grains. I loaded them so they wouldn't hurt my back. My normal load is 19.13 grains of H110.

I have never loaded any 357 that was faster than 1700 fps with a 140 grain bullet. Oh, 19.1 grains is fine in my Ruger but I don't think I would use it in lesser guns. It dates back to the old 43000 cup (45000 psi) loads and the current maximums are for 33000 cup.

Bushmaster · Posted: Sat Jan 04, 2014 4:41 pm Post subject: Re: diffusers for my chronograph

Is he sure he has H110 in them cases?

PaulS · Posted: Sat Jan 04, 2014 4:48 pm Post subject: Re: diffusers for my chronograph

We compared the powder with my comparator and it seems to be H110. The only other ball powder he has is H335 and the grains are bigger. remember that the only sign of high pressure was partially flattened primers. They still had a bit of a radius on the outside, no cratering and the shells did not stick in the chambers. That means that pressures were near the limit for his gun but not like a double charge of a faster powder.

gelandangan · Posted: Sat Jan 04, 2014 9:16 pm Post subject: Re: diffusers for my chronograph

PaulS wrote:

His loads also generated more recoil than mine did.

Hmm..
I think it is more like the chrono sensed unburnt powder being spewed around the projectile.
try measuring at least 3 meters (yards?) away from the muzzle.

Vince · Posted: Sat Jan 04, 2014 10:45 pm Post subject: Re: diffusers for my chronograph

I tend to agree...a chrono hiccup there somewhere.

Gelan...H110 is AR2205, which is the powder I used for my .357 Mag loads...a great powder mate.

gelandangan · Posted: Sun Jan 05, 2014 12:47 am Post subject: Re: diffusers for my chronograph

Vince I also use 2205 on my 357 Mag loads for my Rossi Puma .

Often recoils are result of powder still burning after projectile left the barrel, something like a rocket with your muzzle as a nozzle.
At the same time, to burn efficiently powder need pressure, thus when your powder burns outside the barrel, there would be likely left with plenty of unburnt powder inside the barrel.
Thus loads with lots of unburn powder often feel like having higher recoil.

RePete · Posted: Sun Jan 05, 2014 1:32 pm Post subject: Re: diffusers for my chronograph

Muzzle blast will cause that too.

Place a bullseye target over the opening. The target will protect the sensors from the blast.

PACT recommends 10 feet from the muzzle to the first sensor.

I use 16 feet when I shoot my .308 and .338LM without issue. (PACT Professional).

PaulS · Posted: Tue Jan 07, 2014 2:06 am Post subject: Re: diffusers for my chronograph

I always set the chronograph at 3 yards from the muzzle - that way I can correct it for the software. It was the most consistent aberration that I have ever seen - five rounds in a row at over 2300 fps and then my loads at 1340 or so and then five more of his at 2300 fps. If it had been powder it would have left a residue in the box. I don't know what it is but it has me looking for more questions to ask so I can get some believable answers.

Saying it was a chronograph aberration is just not any more believable than 2300 fps from a 357. The flash didn't come close to the box and the bullets were traveling faster than the shock wave or blast wave. Standing there I could feel that there was higher pressures in the blast wave but I just don't think you could get enough H110 into a 357 case to get it anywhere near that fast. There was too much powder to have a "flash-over" where most of the powder is ignited at the same time. That would cause more pressure but I would expect to see a drop in velocity. I don't have enough questions yet.

Vince · Posted: Tue Jan 07, 2014 4:13 am Post subject: Re: diffusers for my chronograph

This is very interesting Paul...and intriguing. Have you spoken with your mate and asked what the load is in his rounds? Might be the easiest way to get to the bottom of the mystery mate. I'm beginning to think he has the weight of the bullet wrong...it may well be a 110gn, 115gn, 124gn or a 125gn.