MBC 357 grooveless unexpected velocities

[303 hunter]

I load a lot of 357 magnum, and velocities have never matched load data velocities. My hunting load is:
-Winchester case
-16.5gr H110/W296
-158gr Hornady XTP
-CCI 450 SRM (yes, it’s a rifle primer, but the load was worked up with it)

It gives me 1300 fps from my 6” GP100, which is far below the 1591fps in Hodgdons data for 16.7gr.

I wish powder manufacturers would give “real world “ velocities in their data, so reloaders wouldn’t expect to achieve the test barrel velocities.

 

[Buck13]

I wish powder manufacturers would give “real world “ velocities in their data, so reloaders wouldn’t expect to achieve the test barrel velocities.

That would be good. The company that did that would risk selling less powder, I'm afraid. Even if they provided both pressure barrel data and "real world guns" data, they'd fear that people would compare the latter to the pressure barrel data from Company B and think that Company A's powder was weak.

I'm impressed that Buffalo Bore puts real world gun velocities on their site. With all the chronos and YouTubers, BS would be exposed quickly.

 

[Buck13]

It varies off both ends, but these guys found that cylinder gap was good for a loss of 50 to 100 FPS in most cases.

http://www.ballisticsbytheinch.com/gaptests.html

 

[quaid]

first handloads
16 grn 10 shots, 1212 fps average, 70 extreme spread, 22 standard deviation, 1.8% coefficient of variation
16.4 grn 10 shots, 1238 fps average, 99 extreme spread, 28.8 standard deviation, 2.3% coefficient of variation

I remade the rounds, using a heavier crimp, but the weather has changed. The above quoted shots were taken with temperatures around 63 F with a ten shot sample size. The new data below were shot with temperatures around 48 Fahrenheit and a 5 shot sample size.

handloads with heavier crimp
16 grn 5 shots, 1170 fps average, 49 extreme spread, 17.7 standard deviation, 1.5% coefficient of variation
16.5 grn 5 shots, 1224 fps average, 44 extreme spread, 16.4 standard deviation, 1.3% coefficient of variation

factory sample, Independence 357 mag 158 grain jacketed soft point
5 shots, 1241 fps average, 41 extreme spread, 16.5 standard deviation, 1.3% coefficient of variation

The heavier crimp definitely tightened up the numbers, especially in the heavier powder charge. But they were just numbers. The heavier powder charge resulted in a larger group, 10 shot 5" group at 10 paces. I was able to shoot a 6" 5 shot group with the lighter powder charge at 25 paces.

They're both probably good to go at this point. Today's cold weather test resulted in 480 ft lbs of energy, and 525 ft lbs of energy; the factory ammo was 540 foot pounds of energy. It's a lot less energy then the 1000'ish ft lb 44 mag I have previously hunted with (velocity bonus in a 20" barrel). I'll have to keep it in mind and the shots close.

 

[GRIZ22]

100 fps variation between guns is nothing with magnum cartridges. This is due to a lot of reasons, most of which have been discussed.

My Rugers tend to give higher velocities than my S&Ws. A load I chronoed in my Speed Six 2 3/4" was nearly 150 fps shot from a Model 66 2 1/2". 1/4" of barrel won't lose that velocity. There are other things going on and that's just the way it is.

 

[RealGun]

I wouldn't use a bullet with no crimp groove on any but minimum loads.

 

[quaid]

100 fps variation between guns is nothing with magnum cartridges. This is due to a lot of reasons, most of which have been discussed.

My Rugers tend to give higher velocities than my S&Ws. A load I chronoed in my Speed Six 2 3/4" was nearly 150 fps shot from a Model 66 2 1/2". 1/4" of barrel won't lose that velocity. There are other things going on and that's just the way it is.

Add temperature change to that. Despite increased crimp I experienced moderately reduced velocities, I assume from the lower temperatures.

I wouldn't use a bullet with no crimp groove on any but minimum loads.

Have you seen these bullets? No lube groove, just a crimp groove. http://missouribullet.com/details.php?prodId=416&category=24&secondary=10

 

[RealGun]

Add temperature change to that. Despite increased crimp I experienced moderately reduced velocities, I assume from the lower temperatures.



Have you seen these bullets? No lube groove, just a crimp groove. http://missouribullet.com/details.php?prodId=416&category=24&secondary=10

Seems like there would be more friction surface on the bore than any conventional bullet referenced in data. I would expect that to reduce velocity to some degree. MO's Hi-Tek coating is not magic. Sometimes I am cleaning coating out of the barrel instead of lead.