Revisiting the Marlin 357

[mtngun]

When I last left off with the Marlin 357, it was shooting a 190 grain bullet at 1725 fps and averaging 3" - 4" groups at 100 yards (from memory). I had originally wanted a 180 grain bullet at 1800 fps, but was forced to switch to 190 grains to get acceptable accuracy.

Even so, the accuracy was nothing to crow about, though plenty good enough for 100 yard shots on deer, which is as far as I would shoot, anyway. The terminal ballistics were excellent.

I've learned a few things since then and was wondering if I could give the 180 grain / 1800 fps combo another try ?

So ..... here's the 180 grain "Lover-rider," a blend of Loverin and bore riding features. It has only 1 full diameter band, the rest of the bands are bore riding diameter. Meplat is 75%, same as the 190 grainer. OAL and COL are also identical at 0.745" and 1.600" -- I figured that since the bearing length and meplat are the same as the 190 grainer, then accuracy should be similar, too.

(the close-up photo distorts the ogives and makes them look cockeyed, but that's just the camera, not the bullets )


I started out with the same 15.3 gr. charge of Lil Gun that is used with the 190 grainer, however, velocities were much lower than the 190 grainer. Perhaps the "lover-rider" has less engraving resistance, or perhaps the lighter bullet doesn't burn the powder as efficiently. Either way, it looks like quite a bit more Lil Gun is required to hit 1800 fps.


Pressure:
The strain gage had been covered up with wraps of tape to protect it, however, when I removed the tape, the gage came off with the tape ! I'm not going to put another gage on this gun since I tote this gun a lot and the gage just gets in the way.

Accuracy:
5-shot groups with 15.3 grains Lil Gun: 6.1", 4", 3"

3-shot groups while walking up powder charge: 3.6", 5.1", 4"

In other words, about the same accuracy as the 190 grainer. Mind you, that's with a peep sight and my terrible vision, and I don't have shooting glasses that can focus on the front bead. Sometimes it acted like it wanted to shoot, and no doubt it would group better with a scope, but I'm not going to go there.


Things To Try Next Time:
-- use H110 or WC297 instead of Lil Gun. Lil Gun doesn't seem to burn well with this bullet.

-- change one of the bore riding bands (the one just above the crimp) to 0.359". I suspect it won't matter one way or the other, but I'd like to see what happens.

Otherwise I am about out of ideas since I am hemmed in by COL and powder space. I can't make the base longer because I'm out of powder space. I can't make the nose longer because I'm out of COL. All I can do is try to optimize the band and groove configuration.

[mtngun]

I found a couple of bullets downrange. Let's see what we can learn from them.


It's common for the gas check to get knocked off when the bullet hits the target backstop, so I was lucky to find this one intact. Before shooting, the gas check had been very loose, you could easily spin it and wobble it by hand, though it wouldn't actually fall off thanks to the step shank. Now the check is on there rock solid, you can't budge it.

The bottom half of the bullet obturated about 0.005". The top half of the bullet obturated about 0.001". Mind you, this bullet is heat treated wheelweight (plus maybe 1% tin), so was probably 20+ BHN (I didn't let it age long enough to reach peak hardness).

The check and the driving band have been swaged down to 0.3575". I'm wondering if I still have a tight spot in the barrel ? It's been lapped extensively, so you'd think any tight spots would have been ironed out by now. I'll have to investigate that further.

You can't tell from the photo, but careful examination with a magnifying glass revealed no evidence of the bullet "skidding" in the rifling. I wouldn't expect it to skid since the nose kisses the rifling when it chambers.

IMHO the "lover-rider" experiments have proven that even a single itty bitty driving band is plenty to spin the bullet without "skidding." That even heat treated alloy will obturate at magnum pressures. That even a loose fitting gas check will work fine because the shank obturates when the cartridge is fired (and furthermore, the rifling engraves the check which in turn engraves the shank).

[mtngun]

The base of the bullet has become concave. This seems to be common with cast bullets and there are various theories as to the cause.


The check shank has been engraved by the rifling. The rifling engraves the check which in turn engraves the shank.


The "check spinning on the shank" claim can be debunked in a number of ways:
-- the shank obturates to form a tight fit, as these pictures have proven
-- the riflling engraves the check into the shank
-- there is no evidence of the bullet "skidding" in the rifling. Skidding is a non-issue. Get over it.

Here's the real reason that the "check spinning" claim is bunk:
-- Say for the sake of argument that you had a magic way to WELD the check to the shank. Then the maximum torque that could be transmitted by the check would be limited by the SHEAR STRENGTH OF THE LEAD. In other words, if you applied enough torque to the check, eventually the lead would shear near the check/shank junction.

-- the shear strength of the lead shank is the same as the shear strength of a plain base bullet. So a gas checked base can't handle one iota more torque than a plain base bullet, not even if the check is MAGICALLY WELDED onto the shank.

[mtngun]

Lil Gun didn't seem happy with the 180 gr. Love-rider bullet so I switched to WC297. I also walked up powder charges for WW296 so I'd have something to compare the WC297 to.

I settled on 16.8 grains with a Winchester magnum primer to average the desired 1800 fps. I have no pressure trace setup for this cartridge at the moment so I can only say that the load appeared safe in my gun. Your mileage may vary.


The 180 grain Love-rider mold was recut to have a full diameter front band where previously it had a bore riding band. Also, the top bore riding band was fattened up from 0.349" to 0.350". It was only barely kissing the rifling at 0.349" but engraves firmly at 0.350". As long as you work the lever briskly, it's not a problem engraving the nose, but it you work the lever slowly you can feel significant resistance as it chambers.


I decided to mount a scope, after all. The peep base does not have to be removed so it's no big deal to install a scope. A $30 Tasco 4x was borrowed from a 22. It's not a great scope, but far better than iron sights with my aging eyes.


Load data was 16.8 WC297, Winchester magnum primer, 180 gr. HTWW, Rooster HVR, and 1.600" COL.

5 shot groups at 100 yards.

Most of the groups had horizontal stringing. Since the scope was not yet sighted in, I was making scope adjustments in between groups. Like many scopes, this Tasco seems to need at least one shot to "settle in" after making an adjustment, so I started shooting a fouling shot after each scope adjustment, and that seemed to help.


Tossing out 2 groups with bad horizontal stringing due to scope adjustment, I was left with 3.3", 4.3", 2.9", 2.5", 4.4", and 7.7" for an average of 4.2". The majority of variation was still horizontal. The most frustrating thing was the point of impact kept changing. In fact, I never did get the Tasco satisfactorily sighted in because the POI seemed to keep moving and the horizontal scope adjustment didn't necessarily even move the POI in the right direction, let alone the right amount.

Velocity averaged 1801 fps. Standard deviation for the 38 recorded shots was 13.1 fps, or 0.73%.

The best group of the day. If I could do this every single time, I'd be happy, because realistically I can't shoot better than that in the field with the iron sights that this gun normally wears.


Conclusions :
-- the good news is that I accomplished my goal of 180 grains at 1800 fps.
-- adding the front band did not seem to make a difference one way or the other.
-- I'm pleased with the WC297 velocity and standard deviation.
-- it acts like it wants to shoot, but the POI keeps wandering horizontally.

Next Time:
-- test at 50 yards as well as 100 yards and see if MOA is consistent. If MOA is increasing at 100 yards then the bullet may be marginally unstable.
-- try a different scope to see if it cures the wandering horizontal POI
-- give the gun a good inspection looking for bedding issues that might cause the wandering horizontal POI

Otherwise, I'm about out of options on the bullet design, hemmed in by the gun's limitations. No doubt a heavier, slower bullet would be more accurate, but I don't want a heavier, slower bullet !!!

[mtngun]

SInce last time, I swapped the questionable $30 Tasco for a $400 6x42 Leupold. The Leupold has mushy adjustments that sometimes require several shots to "settle in," but is otherwise trustworthy.

Load was the 180 grain Loverider (pronounced "low-ver-rider"), WSRM primer, 16.8 gr. WC297, heat treated wheelweight, HVR lube, 1.605" COL. 5 shot groups at 100 yards.

2.7", 7" (4 in 2"), and 3.4". So ignoring the one flyer that followed a scope adjustment, the load averaged 3", no better or worse than what the Marlin did with the old 190 grain bullet.

Velocity averaged 1782 fps with 0.54% standard deviation for 15 shots. I might need to up the charge to 16.9 grains to get 1800 fps, though it seems to vary a little from day to day so maybe I won't worry about it.

There was no horizontal stringing like with the Tasco, so apparently the Tasco was causing the horizontal stringing last time.

The same load was also used for a lube test. I rolled the lubed bullets in fine brass chips, then let the case scrape off the excess when the bullet was loaded. I prolly should have run the bullets through push-through sizer to embed the chips in the lube, but I was pressed for time.

My thinking is that if a gas check acts as a scraper, as some people believe, then the coating of brass chips should act like a "chore boy" scrubber.


Velocity with the "chore boy" bullet averaged 1777 fps with 0.76% standard deviation, for 16 shots. There was definitely more velocity variation with the brass chips.

Accuracy with the chore boy was 5", 3.8", 2.7", and 4.0" (4 in 1.5"), for 3.9" average, so a little more variation in accuracy. But even the worst groups usually had 4 shots in 2" or less, so it's better than it sounds, by lever action standards.

A 2.7" MOA group shot with the "chore boy" bullet.


I don't have a bore scope, but when the shooting was over I visually inspected the bore in good light. Normally it has a grey "wash" in the bore near the muzzle, but after shooting the chore boy loads, the bore appeared black, not grey. To my eye, it was cleaner than normal.

Lessons Learned and Plans for Next Time:
-- the 180 grain Loverider accomplished my goal of 1800 fps while maintaining about the same 3 MOA accuracy as the 190 grainer. Yea !!!

-- It looks like I'll have to live with 3 MOA unless I want to rebarrel to get rid of the sloppy SAAMI forcing cone. Considering that the Marlin normally wears a ghost ring sight and normally is only used for close range woods hunting, it's probably not worth the effort unless I win the lottery.

-- the only thing left to do is put the ghost ring back on and sight it in.

[mtngun]

Today I planned to put the iron sights back on, sight in the Marlin for the 180 grain load, and shoot 357's happily ever after. But Mr. Murphy had other ideas.

I had planned to install a taller front sight blade, but when I went to tap the old blade out, the entire front ramp fell off the barrel. Long story there dating back to when I first got the Marlin -- the factory sight ramp was crooked, so I had replaced it with a Marble ramp, installed with a new single 6-48 screw plus silver solder for insurance. It was the first time I'd ever silver soldered a ramp and I had a difficult time with it. Nonetheless, the ramp had held up for 10 or so years .... until today.

The 6-48 threads had corroded and stripped out, so I had to D&T the hole to 8-40. I'm not going to try silver soldering the ramp again, instead I'll use JB weld and the single screw. But I have to order the 8-40 screw. While I'm waiting, I installed yet another scope, this time a Mueller 4.5-14. The Mueller was intended for a TC carbine build, but I'm still waiting on parts for the TC.

Today I was playing with yet another variation on the 180 grain Loverider, not that there was anything wrong with the last version. I also shot up some old loads that I had laying around.

The latest Loverider compared to the "old" 190 grain bullet.


5-shot groups at 100 yards:
180 Loverider, 16.8 WC297, WSRM, HVR, heat treated WW, average 1794 fps, 1.04% standard deviation
7.3", 2.9", 3.35", 4.15", 5.5", 4.4", 3.6", 3.9', AVERAGE 4.26"

190 gr. 80% meplat, 15.3 Lil Gun, about 1700 fps, 1.52% standard deviation
6.05", 2.5", 1.8", 2.8", 4.7", 3.505", 2.4", AVERAGE 3.39"

190 gr. 75% meplat, 15.3 Lil Gun, about 1680 fps
3.6"

160 gr. GC, 80% meplat, 6.8 gr. Unique, about 1300 fps
3.1"

180 gr. Speer FMJ, 12.5 gr. 2400, about 1430 fps
4.5", 6.3", AVERAGE 5.4"

The funny thing is that I had abandoned the 80% meplat years ago because I couldn't get good accuracy out of it, yet today it shot some decent groups.


Conclusions:
I take some consolation from my cast bullets outshooting the jacketed bullet.

Even though the 190 gr. 80% meplat outshot the 180 gr. today, the difference was not statistically significant according to a t-test. http://www.graphpad.com/quickcalcs/ttest1.cfm

I was reminded that the Marlin is not an easy gun to shoot from a benchrest -- it literally 'jumps," and sometimes twists, when fired from a rest. I could usually predict whether a shot would open up the group just by the way the gun recoiled. If it jumped and twisted, accuracy tended to be poor. If it recoiled straight back, accuracy tended to be better. I had best luck pulling the gun tight against my shoulder instead of letting it slide on the bags. But it was challenging to pull it tight exactly the same way every time.

I haven't decided whether I will try yet another bullet design. SInce the 80% meplat seems to shoot as well as anything, it's tempting to switch back to an 80% meplat. Perhaps I'll split the weight difference and go with 185 grains at 1750 fps ?

If I ever win the lottery, a new barrel with a better chamber is on my wish list. In the meantime, I'm working on building a custom TC carbine barrel chambered for 357 with a proper throat. I'm curious to see what my 357 cast bullets will do when launched from a good throat.

[6pt-sika]

At first I read the part about the 6x Leupold and was thinking man the groups could be better with more glass !

Then after I made my original post I saw where you were using a 14x .

Glad you got more glass !

From the bags magnification is a wonderfull thing . Just ask any bench rest competitive shooter !

[mtngun]

I have shot many sub-MOA groups with a 2.5X Leopold, providing the target is designed to work with the magnification. I don't feel that the glass holds me back, as long as it is reliable, which is a big "if."

If I remember correctly, sniper Carlos Hathcock used a Redfield 3x9 scope ?

When my eyes were younger, I would have been perfectly content with iron sights, but my eyes are no longer up to iron sights.

What the 14X did do was improve the confidence in my hold -- I could be sure the crosshairs were where they were supposed to be when the gun fired. It was obvious the POI was getting bounced around by the recoil, similar to a handgun.

I have not seen anyone post much better accuracy with full house loads in the 357 lever guns. Either they are shooting at 50 yards, or shooting low velocity loads, or only posting "lucky" groups rather than the average of all groups. Mostly they don't post data, just vague claims, which I take with a grain of salt.

[mtngun]

While I was re-installing the front sight ramp today, I checked the stock bedding and magazine attachment very carefully to see if there was anything amiss that might influence accuracy. I found this - the screw for the magazine cap, which is supposed to fit into a slot in the bottom of the barrel, was instead missing the slot and pushing hard against the barrel.

The screw is definitely supposed to fit inside the barrel slot. Perhaps it is also supposed to push upward against the slot, too, I don't know. But because the factory "clocked" my barrel incorrectly -- the original front sight pointed at 11 o'clock instead of at 12 o'clock -- the slot does not line up with the screw. As I tightened the screw, I could feel it push the magazine tube away from the barrel.


At first I tried to grind a point on the screw, hoping the point would guide the screw into the slot. But that didn't work because the slot is too far out of alignment. So I ended up shorting the screw quite a bit so that it can no longer touch the barrel.


Now it doesn't touch the barrel at all.


I doubt if it will effect accuracy ...... but we'll find out eventually.

Does anyone know if the screw is SUPPOSED to push against the barrel, assuming it fits into the slot correctly ? I'm trying to understand why Marlin designed it that way, and why they bothered to slot the barrel ???

[mtngun]

I shot some more groups with the scoped Marlin today, mainly to see if the magazine screw mod changed anything.

75% meplat, 180 grain loverider, 16.8 gr. WC297, 1.610" COL, 1800 fps, shot from sandbags
8" (mainly due to flyer on 1st shot), 5.25"

Certainly no improvement there. I then switched to a "lead sled" rest. I think it is an Outers brand, but don't remember for sure.
2.4", 3.2", 2.7" as shown in photo.


Then I switched to some old 75% meplat 190 grain loads, with 15.3 grains Lil Gun at about 1680 fps.
2.5", 4.4"

Conclusions and Stuff to Try Next Time:
-- the magazine screw didn't seem to make any difference

-- the lead sled did seem to improve groups compared to sandbags.

-- I've said all along that this gun "jumps" and twists when shot from a bench, so I gotta think about ways to improve my benchrest technique with the Marlin

-- when I do my part, the 180 grain loverider seems to shoot as well as the 190 grain, so I consider that a victory. I like the added velocity, and a 180 grain hard cast is enough for deer or even elk.

-- since I single load from the bench, I'm thinking of removing the magazine spring and completely filling the tube with cast bullets, to add weight and reduce "jump".

-- I still plan to try an 80% meplat 180 grainer.

-- I'm still scheming to increase the COL