Having my new Garmin chronograph, I'm starting to test my chosen factory ammo in the gun(s) I intend them for. In this test, I wanted to see how the Remington .357 Mag 180gr SJHP ammo performed out of my Marlin Cowboy rifle. The Marlin Cowboy has a 24" barrel. My hope was that I would be getting some great performance and screaming velocity. My only knowledge up until now with this video, where the guy tested this ammo in a 16" Rossi rifle. He got 1,563 fps from a single shot, so I was hoping I was going to see higher velocity from the 24" barrel. Of course, that might not be true if the powder completely burned inside the barrel.

Here are the results from five shots:

• 1,498.8 fps
• 1,548.3 fps
• 1,549.1 fps
• 1,512.4 fps
• 1,523.1 fps
• 1,525 fps average, with an energy of 930 foot pounds

While these results are great, it does tell me that my concerns were realized about the powder completely burning in the barrel. None of my shots got to the number the guy in the video got out of his 16" barrel. I realize there are some caveats, such as different chronos, different conditions (I was indoors), and different guns. However, I think it's pretty clear that the powder has burned completely inside the barrel before the bullet has exited, so the bullet is actually slowing down because of friction. I need to develop a handload with a slower powder so I can take advantage of the longer barrel.

Check out the data on Ballistics by the inch..

On the .357 they max out at 18" and 158 gr.; but you do see declining FPS numbers between the 16" and 18" barrel lengths.

Cleaned and oiled barrel will result in the first couple shots from a barrel being faster than dry swabbed barrels. If you look at the video, you see one shot equaling 1563fps and compared with 1549fps, there is no practical difference. It also looks like the muzzle is very close to the chrono, which will give inaccurate numbers. 10 feet should be minimum distance, but with big bore rifles, I do 15 feet.

Aliso, I find lead bullets act differently than copper-clad Lead tends to be self-lubricating giving higher velocities out of longer barrels, while copper-clad bullets tend to not show much difference in longer barrels than short.

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Gary
SWCA 2515

IIRC past threads have "concluded" that a 16-18" barrel is the ideal for .357. Thou I don't recall any discussions of the 180gr bullet.

Try some power pro 300-mp. Brian Pearce had an article in handloader on .357mag in rifles. He got low 1800's with 180gr wnfp bullets, but cast and the 18 ish inch barrel.
That powder gave a little more velocity than LIL Gun with 180gr bullets. Not sure if it will do better in a 24" barrel though. Still might be completely burned up before it runs out of barrel.

Thanks, I'll look for that article. I've got an almost full 8-pound can of 296 that I thought might be good for this use.

April / May 2021. just looked

I just skimmed the article again. It was a 20" marlin CB used for his data. He did list 180gr xtp with AA #9, 2400, and H110 - 296, but 1450 fps was about all he got.
I'm not sure why he didn't try LIL Gun, or 300-mp with that bullet other than it's not practical to test every bullet with every powder and he gave a good selection of bullet and powder combos. Maybe that rifle didn't like that powder bullet combo.
Anyway it's a great article and worth the read.

Thanks, I just ordered a back issue of it.

It'll be interesting to see what a similar load will do in a 24" barrel.

No problem. .

Marlin 1894 (16 in), Win brass trimmed to 1.270, Fed 200 primer, Rem 180 sjhp seated to 1.590.

13.5 gn Lil Gun= 1620 fps, very accurate
14.5 gn Lil gun= 1715 fps, decent accuracy
15.0 gn Lil Gun= 1726 fp decent accuracy

Appreciate the pic of the factory round, they deep seated the bullet. I trimmed the brass to crimp in the cannelure, while maintaining max col. Real pita, and can't say if it was necessary.

Have some more accurate loads, but noticeable slower velocity and very accurate in pistol. Have not seen any Rem 180's (just the bullet) for sale in awhile, but stopped looking. Was waiting for Speer to bring back the 170 gdsp, but doesn't look likely. Shame as it was perfect for higher velocity's. The In my limited experience, the 180 xtp doesn't have the same velocity or accuracy capability. But likely much tougher than the Rem 180 sjhp.

I assume specs for these are out of an unspecified rifle. Looks pretty "high performance" for factory ammo. Joe
Federal Premium Hammer Down 357 Magnum Ammo 170 Gr Bonded HP - Ammo Deals

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Wisdom chases me; I'm faster

From the Federal website:

No mention of barrel length for stated velocities.

Now I just HAVE to try my 357s over a chronograph. My 94 Winchester is 24 inch... I was loading 4227 with a 180 gr TC jacketed bullet. pretty accurate....but I have all the usual suspects of slow powder to try...I even found a can of MP-300 today...and some surplus WC 820 I think I would like to get more velocity than my 14 in Contender in 357 MAX

Thanks for the intel on the loads.

Remington discontinued the 180gr SJHP load. I managed to pick up 500 rounds before that happened. I'll keep a lookout for the bullets.

The 170gr Gold Dot would be a great bullet to use.

It's always interesting to see someone's results with a given load and gun, but my experience over the years has demonstrated that no site is going to give you "the answer" for your gun - you need to do the experimental work. That said: I'm with zeke: Lil' Gun is a sweetie in my 20" .357 Navy/Rossi 1892 short rifle. With that particular (180-gr) weight I only run Tennessee Valley Bullets hardcasts, though.

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Now go make God proud...

you're welcome

Curious as to what kind of velocity are you looking for with a 180 gr. jacketed bullet using the .357 mag. case in a 24" barrel?

I think it's reasonable to expect 1,700 out of it.

I believe the question is really about the powder. That length of barrel needs the burn rate to use the full 24". It seems to me that this factory loading has fully burned long before the 24" is reached, so there's no additive pressure on the bullet to speed it up. The factory load is probably max'ed out by 18"-20".

As Paul Harrell is so fond of saying, cronos vary widely and are affected by environmental conditions. No two will ever produce the same result.