Marlin 357

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mtngun
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Marlin 357

Post by mtngun » Sun Feb 10, 2008 6:30 pm

from the old forum:

A Marlin 1894 357 followed me home.
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I stripped the original finish and gave it several coats of danish oil. The wood isn't anything to brag about, but at least now it looks like real wood, instead of brown plastic.

First, I tried pouring a cerrosafe casting of the chamber, but it stuck. Usually when that happens, it means there is a bulge or a reverse taper or a lot of chatter in the throat. To melt it out, I had to dunk the receiver in a big pot of boiling water.

So then I made an upset slug. I poured a case nearly full of lead, seated a pure lead bullet, and chambered it. Then I stuck a brass rod down the barrel and gave the rod several whacks with a hammer to upset the pure lead bullet. I also used a tri-mike to measure the grooves near the muzzle, and an expanding ball gage to measure the bore.
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The rifling is indeed deep cut. This type of throat has sometimes been called a "toilet bowl" throat, and I don't like the looks of it, but these rifles are reputed to have decent accuracy nonetheless, especially with gas check bullets.

You can't see it in the picture, but the leade cone has a lot of chatter.

I haven't shot it yet. Eventually I'll probably end up making a 180 - 200 gr. gas check bullet for this rifle, but I'll start out with the 160 PB load that I shoot in the wheelgun. I think I can fit a strain gage on the bottom of the barrel, and run the wires out at the end of the forearm.

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Re: Marlin 357

Post by mtngun » Sun Feb 10, 2008 6:32 pm

Still haven't shot the rifle yet, but have been tinkering with it.

A strain gage was mounted, hidden under the forearm. The wiring was routed out through the front of the forearm. In the unlikely event that I ever get tired of doing pressure trace experiments on this gun, the wiring could be tucked back into the forearm, completely out of sight. It was a lot of work, requiring some inletting on the wood, but it turned out quite well.

Feeding was not good. An 80% meplat entered the chamber easily, but the cartridge would hang up at or near the case mouth. The edge of the chamber had a very sharp edge that was grabbing the case. I used a carbide burr to barely break the sharp edge. Now it feeds all cartridges, though resistance is still felt as the case mouth passes the chamber entrance. The entrance may need to be polished a little more, but I'm leary of removing too much metal.

Max COL is 1.59" - 1.60". The word is that the carrier can be modified to feed longer cartridges, but I'll hold off on that for a while.

Trigger feels like 5 - 6 pounds, but I want to shoot it before I attempt a trigger job.

So far I really like the gun, but there was something about the front sight that didn't look right. Finally I figured it out -- both the front and rear sights are canted 3° - 5° to the left. Apparently, the barrel was screwed in a little too far. Geeeeezzzzz :cry:

Marlin has a good reputation for taking care of warranty issues, but it may be easier and faster to fix it myself. I only need the front sight, for use with a peep, so it could either be soldered in the correct position, or slid forward enough to drill and tap new screw holes. The old holes would be covered up by the ramp. Only problem is, I've never done either of those things, so I'm worried about making a boo-boo.

Darn. :x And we wonder why American manufacturing can't compete?

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Re: Marlin 357

Post by mtngun » Sun Feb 10, 2008 6:33 pm

Hello Dan,

And congrats for the new rifle. Unfortunately I must say that Your rifle is not unique in the way the barrel was installed. My own 1895G was "screwed" up pretty good and assembler needed to use a shim between the barrel and the receiver. I once turned my rifle belly up disassembling it in to pieces and found the shim; it was full .005" thick and barrel was unbelievable tight with it. I had really hard time with my hardwood block disassembly system. Anyway, without the shim I was able to hand tighten the barrel right up to my index mark so it was not very good. I lapped the receiver face and barrel mating surfaces and it went even sloppier of course. Finally I used very thin aluminum sheet shim to put some tension on it and used epoxy (!) to make it solid. Working good now and as a positive bonus the headspace got tighter than original which is not bad at all. You may want to check head spacing on Yours and maybe it's possible to turn the barrel backwards some still keeping appropriate tension and acceptable head space. It could be also possible to grind the holes in the front sight so that it can be canted straight with original screw positioning. Good luck.

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Re: Marlin 357

Post by mtngun » Sun Feb 10, 2008 6:34 pm

Thanks for sharing that, Finn45. I thought I was the only one who had these problems, and the only one who uses epoxy to fix guns !

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Re: Marlin 357

Post by mtngun » Wed Feb 13, 2008 9:04 pm

I finally made a proper 180 gr. bullet for the Marlin. 180 grains seems ideal for the 357 rifle because anything heavier gives up quite a bit of velocity while anything lighter gains very little velocity.
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Since last time, I took the action apart and gave it sweet action job. The trigger is now 1.5 - 2 pounds. I wish all my triggers were that nice. I reground the carrier so that it can accept longer cartridges, however, if the COL is much more than 1.600", the bolt slams the bullet nose into the edge of the chamber before the carrier gets all the way up, so for now I resigned myself to a 1.600" COL. Maybe someday I will feel ambitious enough to attempt to change the carrier timing.
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Here's what the WW296 traces look like. I expanded the time frame on the X-axis to show you the noise problems. The gage on this gun has unshielded wires running all the way down the forearm, plus the PT cable runs pretty close to the muzzle. Next time I will reglue the connecting plug to face backwards so the connecting cable can run back toward the breech instead of close to the muzzle.
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Here's the Lil Gun traces.
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Here's the 160 gr. PB that I shoot in my Ruger Speed Six. It's not accurate in the rifle but I just wanted to see what the pressure was like. Again, I expanded the time scale to show the noise. The choppiness is probably due to the unshielded wires, and the noise after the bullet has left the barrel is probably due to the cable getting bumped by muzzle blast and recoil (there are a lot of things sitting on the shooting bench that tend to get tangled up with the cable).
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I think this gage's calibration is still a little low, because Quickload says that these loads are doing 35 ksi -- the SAAMI max -- while the PT says 33 ksi. To be safe, I will increase the calibration offset another 2000 psi so that today's 33 ksi loads will read 35 ksi.

Getting a little off the subject, the PT software adjusts the calibration by adding a flat amount of PSI to all pressures. All the traces on this page have 6000 psi added to them, which makes the pressure curve look like it is standing on stilts. I asked RSI to consider changing the software calibration so that the software multiplies the pressures by a calibration factor. Using a multiplier would get rid of the stilt look.

Then I shot three five shot groups with WW296 and three 5-shot groups with Lil Gun, at 50 yards, using my homemade peep sight.

16.5 gr. Lil Gun, CCI #500 -- 1797 fps, 81 ES, 2.4"

16.9 gr. WW296, Fed #210 --1804 fps, 42 ES, 2.5"

Most of the groups had three or four shots in a cluster, so I'm sure the gun could do better if the shooter would do his part. I happen to have a scope mount for the Marlin, and it is tempting to use a scope for load development, however, if I am going to use a peep for hunting I figure I better do all my practicing with a peep, too.

I've got a keg of Lil Gun that my revolver doesn't like, so I'll concentrate on tuning a Lil Gun load for this rifle. Next time I'll see what I can do to improve the ES and tighten up the groups -- different primers, minor tweaks to the powder charge, and maybe bump the nose to engrave a little more.

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Re: Marlin 357

Post by mtngun » Thu Feb 14, 2008 6:10 pm

Last time, Lil Gun gave great velocities but the variation was too high. Today I tried some minor tweaking to the Lil Gun load.

Same 180 gr. TCGC bullet with the short bore riding section, HTWW, sized 0.358", felix lube.

The Mark II homemade peep site was used, but the elevation was way off. If I ever get the sight dialed in, then I'll move the target out to 100 yards.

Standard deviation for 15 shots, ranked best to worst
1) 16.7 gr. Lil Gun, Fed #200, 0.72% or 13.4 fps
2) 16.2 gr. Lil Gun, CCI #500, 0.82% or 14.9 fps
3) 16.7 gr. Lil Gun, CCI #500, 1.39% or 25.7 fps

All loads gave acceptable standard deviation. I don't know what was different compared to last time.

Velocity, ranked highest to lowest
1)16.7 gr. Lil Gun, Fed #200, 1863 fps
2)16.7 gr. Lil Gun, CCI #500, 1848 fps
3)16.2 gr. Lil Gun, CCI #500, 1804 fps

The magnum Fed #200 gave higher velocities than the standard CCI #500.

Peak Pressure
1) 16.7 gr. Lil Gun, Fed #200, 35.5 ksi
2) 16.7 gr. Lil Gun, CCI #500, 34.4 ksi
3) 16.2 gr. Lil Gun, CCI #500, 32.0 ksi

The magnum primer also generated more pressure, but it may not be statistically significant.

Accuracy for three 5-shot groups at 50 yards
1) 16.2 gr. Lil Gun, CCI #500, 1.73"
2) 16.7 gr. Lil Gun, CCI #500, 2.17"
3) 16.7 gr. Lil Gun, Fed #200, 3.37"

The accuracy results are misleading because the limiting factor is yours truly. I started out using the Steady Point rest -- 5" group. Then I chucked the Steady Point and just rested the gun on an old coat, and consistently got 2" groups, with the groups shrinking as more shots were fired just because I was refining my technique.

Since last time, I remounted the strain gage connector so that the cable no longer runs close to the muzzle. However, every string had at least one bogus trace no matter how I routed the cable.

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Velocities are great, so I think I need to stop worrying about load development and focus instead on getting the sight dialed in and refining my shooting technique.

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Re: Marlin 357

Post by mtngun » Thu Feb 14, 2008 8:15 pm

357 rifle diameter experiment

The usual load -- 180 gr. BTC, felix lube, 16.2 gr. Lil Gun, Fed #200 --except for changes to bullet diameter.

I recut the mold to be about 0.001" bigger, including the short bore riding nose. Now the nose is supposed to be 0.348", which engraves quite nicely when the cartridge chambers. I say "supposed to be" because there is variation from one pour to the next so some noses drop out at 0.347", which does not engrave in the 0.347" bore (bore riding noses are an infernal aggravation but I reluctantly use a bore rider in this gun to help align the nose in the ridiculous 0.381" throat). The modifications increased the weight to 182 grains.

Also, I put a 2.5X Leupold scope on because it looks like a custom front sight will be required to get the elevation dialed in, and it's going to take me a while to make the sight. The scope is pretty handy for load testing, anyway.

With the scope, there was no excuse not to set the target at 100 yards.

When sized 0.358", the results were 5.4" groups, 1789 fps, 1.51% standard deviation, and 29.9 ksi, if you have faith in my strain gage calibration.

When sized 0.359", the results were 4.0" groups, 1801 fps, 1.01% standard deviation, and 32.8 ksi.

The best group of the day was 2.5" with the 0.359" bullet. Dispersion was primarily horizontal, and the stiff breeze didnt help.

As with my oversize 30-06 bullets, I am not sure that the fatter 0.359" bullet is better, but I am sure it is not worse. For now, I will stick with 0.359".

The catch is that the fatter bullet makes the case mouth OD a tight fit in the chamber. All of today's cartridges chambered OK, but there may be intermittent clearance problems with some brands of brass.

Realistically, 4 MOA is acceptable for woods hunting, but I'll keep chipping away at the group size just to see what I can learn.

It may be that a heavier bullet and a smaller meplat will be the only way to get better accuracy. I don't want a heavier bullet, but the rifle may.

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Re: Marlin 357

Post by mtngun » Fri Feb 15, 2008 5:04 pm

Are you talking about a Marlin 1894 rifle? I belong to several Marlin forums where members talk about the microgroove vs Ballard rifling and bore restrictions. Most all Marlins have bore restrictions at the front sight and barrel band dovetails as well as under the stamped lettering. I imagine this is the case with Winny's too. Anyway, I guess the microgroove is the hardest to make shoot cast bullets. Most either shoot a ton of jacketed or lap to remove the tight spots. Once lapped most all guns have shown a vast improvement with cast. Beartooth's website has some good articles on this written by Glen Fryxell and his .444. He also has a new article on leverguns.com

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Re: Marlin 357

Post by mtngun » Fri Feb 15, 2008 5:07 pm

Yes, it is an 1894 with deep cut rifling. I haven't pushed a slug all the way through the barrel yet. Maybe I'll do that today.

I am loathe to firelap this barrel since the throat is already grossly oversize. If I find a restriction, I might lap it out the old fashioned way.

People are quick to blame the barrels for cast bullet problems but the throat is a huge problem with most rifles chambered for pistol cartridges. The throat is SAAMI spec but the SAAMI spec sucks. The SAAMI spec is not even appropriate for wheelguns, IMHO.

The oversize section in front of the case mouth leaves the bullet vulnerable to gas cutting and misalignment. The rough tooling marks and the 17° included angle will tend to shave lead. The bullet is likely to be damaged before it even enters the rifling.

Image

One of these decades I will rebarrel it and cut a proper throat, with a step down to 0.359" just ahead of the case mouth, and a gentle (1.5° - 3°) angle into the rifle.

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Re: Marlin 357

Post by mtngun » Fri Feb 15, 2008 5:29 pm

OK, I just now pushed a pure lead slug all the way through the barrel, starting at the breech. In fact, I did it several times, because measurements were not consistent.

Sometimes the slug would come out way small, like 0.354". More often than not, they were 0.3563" with some plus or minus. I could not feel any tight spots except for the first two inches near the breech, and that may have been just the normal engraving resistance.

When the slug was started at the muzzle and pushed out the breech, no tight spots were felt near the breech or anywhere else, and the resulting slug measured 0.3565", with some plus or minus.

In other words, the results were not consistent, and I was confused. The undersize measurements could be due to a tight spot, or they could be due to the slug being abraded. It is also possible that the pure lead slug was being squeezed down by tight spots and then being obturated by the rod.

Just to be safe, I hand lapped the barrel for about five minutes.

Then I slugged the barrel again, and again the measurements were inconsistent.

So just to be even safer, I hand lapped the barrel for another five minutes.

Then I slugged the barrel again, pushing from breech to muzzle. The slug would measure at most 0.3563", but some slugs and some grooves were smaller. I repeated this several times and never did get consistent measurements.

Then I tried pushing from muzzle to breech, and the slug would usually measure 0.3565", with some grooves and some slugs measuring smaller, and I never did get consistent results.

Then I put a dummy round in the chamber, pushed a pure lead slug against the dummy round, and whacked the pure lead slug several times with the brass rod to upset it. The resulting slug measured from 0.3569" to 0.3572" providing I put the mic in exactly the right place. If I didn't position the mic just so, measurements would be smaller.

A calibrated tri-mic at the muzzle recorded 0.3572" - 0.3574" pretty consistently. Before the gun had ever been fired or messed with, the muzzle tri-miked 0.3570", so lapping may have increased the diameter a bit. I trust the tri-mic far more than I trust the lead slug. As for the tight spots, I can only say that I don't feel any tight spots as a slug is pushed through the barrel. I'm not sure that it ever had a tight spot to begin with, but now it doesn't. :lol:

The only thing I am sure of is that it is hard to get consistent measurements by pushing a soft lead slug through the barrel, so if you get funny measurements when you slug your barrel, don't jump to conclusions.

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