357 Mag Loads Flying Slow - Advice Appreciated

M

mactroneng

CGN Ultra frequent flyer
Rating - 100%
29   0   0
Location
SW Ontario
Forward: I am relatively new to the game of reloading and not above admitting to making mistakes, fixing them, and learning from them.

So far, I've pumped out about 600 rounds of 357 magnum, in lots of 300. First lot was really light, this current lot I tried to make a little heavier. Using mixed headstamp brass (though all the test rounds I chronographed were twice-fired Starline brass), 8.0 gr of Longshot (+/- 0.1 gr confirmed from pulled rounds, most at 8.0), CCI small pistol magnum primers, Campro 158 gr bullets seated to OAL of 1.59" as recommended by Campro (+/- 0.003, most at 1.59"). I've been using Campro bullets because of cost and I noticed that their smokeless powder charges are basically copied from Hodgdon so I felt comfortable using Hodgdon Longshot loads with the Campro bullets. None of these have showed any signs of over-pressure (primers flattened a bit but look fine (still a bit round at the edges, no worse than factory ammo), zero difficulty with extraction). Using the Campro OAL with brass trimmed by a Lee hand trimmer puts the entire cannelure above the rim of the brass.

I recently got an old, used chronograph and finally got around to trying it out: 22 LR chrono'd more or less where I expected them, as did my reloaded 9mm, so I think I'm safe to rule out my chronograph as the problem. 357's came it at maybe a little above 1,000 fps, which is significantly slower than even the minimum load from Hodgdon for Longshot in 357 (which is listed at 1,258 fps). Since I'm closer to max, I figure I should be around 1,325-1,350 fps (but pressure - velocity is non-linear so maybe I'm wrong).

So a few things that are different from my load vs the Hodgdon load:

1) I'm shooting from a S&W 686 with a 7" barrel vs the 10" test barrel Hodgdon uses. After doing a little research it looks like you lose maybe +/- 20 fps per inch of barrel length so I figure that knocks off +/- 60 fps (though maybe it's also non-linear and there's more of a reduction than that?)

2) I found measurements of the Hornady bullet used in the Hodgdon data and measured the Campro bullets, and the Campro's are about 0.025" shorter. I also loaded to Campro's OAL which is 0.01" longer than Hodgdon data. With the two combined that's 0.035" more space in the case than accounted for from Hodgdon, which I imagine would drop pressure than therefore velocity, but I have no idea how that would quantify.

(As an FYI - further research showed that Speer's 158 gr JSP (so similar shape to the Campro) gets slightly lower velocities with Longshot as Hodgdon did, but loaded at 1.585" OAL and with a 5.64" test barrel length - but still 200 fps faster than what I'm getting)

Unfortunately I don't have another gun to try them out in (I might be able to meet someone at the range but I'm not sure). I was considering putting the few that I pulled back together with using the Hodgdon OAL of 1.58" instead of the Campro measurement at 1.59" but if this is only wasting my time, let me know. Or maybe even 1.57" given the difference in length between Campro and Hornady bullets, and the fact that nearly the entire cannelure is showing at 1.59"

EDIT: As I continued researching after posting this, it looks like keeping my OAL and increasing powder charge may actually be a safer bet (and be better for accuracy to boot). Thoughts?

Any tips of further things to check or try would be appreciated, as would any additional knowledge you can impart to me.

Thanks!
 
Last edited:
PEW.jpg


You're welcome :)
 
lol, I've been doing more reading on how OAL relates to velocity and came to the same conclusion just now. Don't want to get into pressure issues and it seems that keep my OAL the same and putting in more powder is the safer way to go.
 
I just seat my .38/.357 bullets to the middle of the cannelure. I've never bothered to measure OAL or velocity, so I don't worry about it. lol. Gun doesn't kaboom, bullet leaves barrel, I'm happy.
 
1-OAL: changes of 0.01'' or so won't make a meaningful difference in pressure. I would just make them the right OAL so you can crimp on the cannelure;

2-I have never got the same speed as Hodgdon. Whenever I use an Hodgdon powder, my result is ALWAYS a lower fps than what they get. Sometimes it's meaningful, sometimes I'm just a bit below. I've tried using the same primer/powder/bullet in the same brand of guns, and it's always the same result: lower FPS. Our lab tests (with both a piezo and a strain gauge) shows that pressure is also lower than their published loads. Every time. The amount by which the pressure and FPS they report are below our measurements vary quite a lot (sometimes it's almost nothing, sometimes the difference is quite large). But for every load (as far as I know), the relationship of load volume to pressure/velocity is rather consistent from min to max load.

So I'm not sure which equipment the good people at hogdon used for their tests, but my theory is mostly that some of their load data are as old as Matusalem, and that somehow, the powder they used has changed a bit over time, or their method of testing has changed, and they update their published data only in one direction: when a given load creates more pressure than the published data says it does, they update to the new data. So for a given powder, what you would see is the data they found with the most "aggressive" powder, the one yielding the highest fps per grain of powder. It doesn't have to be the actual powder that changes, it can just be the testing equipment or protocol. That would be the "safest" way to publish load, as that would insure that reloaders who start at the minimum load would actually have a minimum load, no matter which lot of powder they end up with.

Anyway, that's a freaky long explanation just to say: you're not alone in your boat, we also get lower pressure/velocity using top-notch equipment that you get using an inexpensive chrony.

3-Trying to diagnose overpressure by looking at a primer is a crapshoot. Using a chrony is a much better method of (indirectly) measuring pressure. Not that good, but better than looking at a primer.

4-The 20fps/inch of barrel isn't particularly true. The relationship between barrel length and velocity is non-linear, and varies widely per calibre and length of the barrel. I think the 20fps/inch rule of thumb comes from a commercial 223/556 at short barrel length (my memory might be wrong on this one), and is not very helpful in most cases.
 
Thanks for the advice guys!

I'll try reloading the pulled rounds to the cannelure with the same powder amount and chronograph them before I try more powder. Luckily I kept the pulled components organized so it's literally just seat and crimp. If that doesn't bump it too much (and shows no signs of pressure) maybe I'll try pulling a few more and increasing the powder charge by 0.1-0.2. I still have about 250 of my lot and don't really feel like pulling them because at the end of the day the velocity isn't a huge deal, I just wanted to know if there was something I was doing wrong or could improve.

VinnyQC: interesting info about Hodgdon data. I have the Speer app on my phone and find that it is usually a bit more aggressive with powder charges than Hodgdon is, have you looked into it all to see where it stands vs your own testing?
 
The quoted velocity may be from a test fixture. A solid barrel. You gun has a big gap in front of the cylinder where gas blasts out. That drops the velocity.

Get a factory round and chrony it. If it is a 158 gr bullet, it gives you a speed limit for your loading.

I would not use Longshot if I was looking for velocity. 8.0 is plenty. I would expect about 1150-1200 and would call that good.

For velocity, you want 296, 2400 or Universal. I like to use 2400 because it can be loaded down a bit, whereas H110 and 296 have to be loaded full power.

Note: I just checked my logs. I have loaded book MAx in my 6" 357 several times , with 158 gr XTP bullets using powders like 296 and 2400 and Blu Dot. Never got as much as 1100 fps.

I test fired Remington Factory 357, 158 gr jacketed, - 1102 fps.
 
Last edited:
I'm glad some knowledgeable people came in here and countered my nonsense with facts and experience. '####in send it' might not have been the response you were looking for, haha
 
look at trying other powders.

I have used blue dot when I want a screaming hi powered load.

most of my other standard 38s and 357s are loaded with tite Group. I find it a consistent powder with a easy to get in big qtys here in SW Ontario.
 
Thank you for even more advice, and the data points! I don't feel so bad about 1,000 fps now (not that I was gonna pull over 200 rounds anyway, I'll live with it... I may pull a few more to experiment with rather than waiting until I'm onto a new lot though).

I wasn't particularly after high speeds, just a bigger bang than my minimum loads. Longshot is just what I had on hand because I'm using it for two different rounds (other being 500 S&W magnum), it is a good medium power powder. Only thing I was worried about was the discrepancy in velocity, which seems to be adequately explained.

I did pick up a 1 lb container of Lil' Gun to try out at some point.
 
Scotty454 said:
I just seat my .38/.357 bullets to the middle of the cannelure. I've never bothered to measure OAL or velocity, so I don't worry about it. lol. Gun doesn't kaboom, bullet leaves barrel, I'm happy.
Click to expand...

I agree. seat and crimp to the cannelure. Forget over all length.

The Canpro bullets are a good inexpensive plinking bullet. But being plated bullet they can be damaged by over crimping or crimping outside of the cannelure.

If you are looking for a new powder, try Alliant's 2400.
 
redbirddog said:
look at trying other powders.

I have used blue dot when I want a screaming hi powered load.
Click to expand...

I can only speak for 158 grain bullets but Blue Dot was actually slower than Longshot in my testing. Longshot is nice for punching paper. I use full charges of H-110 with a Rem 7.5 for the times I want max performance. I would also say that velocity loss from cylinder gaps is pretty minor with the .357.

I had a gun with a .009" gap that I had tightened, the smith did a little too good of a job and I can't even measure the gap with any feeler gauges I have (it would be less than .001"). The before and after velocities are identical... There is also plenty of data from Ballistics by the Inch that shows negligible loss.

That isn't to say that it is never a factor though, I had a Ruger Toklat tightened from .013" to .006". Velocity jumped 150-200fps after the gap was tightened.
 
I just got a email from my son and he chronograph my handloads vs Speer 125 gr + P factory loads in a GP 100 .357 and S&W 686 .357.

The loads were .38 +P loads from Hodgdon's data, in the GP 100 my loads were 50 fps slower than the factory Speer .38 +P.

In the S&W 686 my same handloads were 30 fps faster than the factory Speer .38 +P ammo.

In the Speer No.9 reloading manual there is a chapter "Why Ballisticians Get Gray" and it has different velocities from .357 firearms. And with firearms of the same barrel length the velocities varied over 250 fps between the same model handguns with the same load.

So just remember some reloading data is from unvented test barrels using the copper crusher or transducer method. And if a specific firearm is listed a strain gauge is glued to the barrel and calibrated with a cartridge of known pressure and velocity.

Bottom line, loading data is "ball park data" and why the manuals tell you to start low and work up looking for signs of excess pressure.

Below is some very good .357 loading data by Skeeter Skelton

My Friend, The .357
by Skeeter Skelton
http://www.darkcanyon.net/MyFriend_The357.htm
 
Scotty454 said:
I just seat my .38/.357 bullets to the middle of the cannelure. I've never bothered to measure OAL or velocity, so I don't worry about it. lol. Gun doesn't kaboom, bullet leaves barrel, I'm happy.
Click to expand...

Most of the time. It's OK, I'll have my squib rod with me Thursday! :d

Auggie D.
 
Do you have feeler gauges? Measure the gap between each cylinder chamber and the barrel. Might prove interesting.

Dan Wesson models have a means of adjusting the gap with their barrel and barrel shroud.
 
You must log in or register to reply here.
Back
Top Bottom