horrible vertical stringing with 45-70 with RCBS 45-300-fn

[jhunter77]

My go to load is a jacketed hollow point with 46.2 grains of IMR 4198. I wanted to load up some of the cast 325gr I was given. I normally get sub 2" loads from jacketed with a 2x scope at 100 yards off shooting sticks. I have spent the day loading 5 to 10 rounds then going out back and shooting them looking at groups and trying again. I have gone from 34 to 43 grains of IMR 4198 and adjusted my seating up and down but keeping it in the crimp grove. For some reason all my cast groups will create anywhere from a 6" to 12" vertical string. They group horizontally between 2" and 5". Its obvious vertical stringing which I have not had issue with before with jacketed. I pull some of my old jacketed ammo out and proceeded to shoot a very nice 3 shot group that went into 1.5". I have tried regular Winchester primers and also magnum CCI. The rifle is a ballard cut marlin cb. The bullets are Clip on WW and fairly hard, gas checked, and lubed with Red Rooster lube. Suzed .458 or .459. I need to get a micrometer and verify it this weekend.

I have not slugged my barrel but will this weekend when I can borrow a micrometer.


What Could be causing this?

[Yodogsandman]

I'd start load development again and this time would use a tuft Dacron filler large enough to completely fill the space between the powder charges and the boolit base. Please read the sticky on "the proper use of fillers" first, just to be safe.

http://castboolits.gunloads.com/show...use-of-fillers

[jhunter77]

I could see the lower charges maybe needing the Dacron but the upper loads had the most vertical and the case was pretty full.

[chill45100]

How was the rifle rested? Have you found the sweet spot and marked that on the barrel? It sounds not unlike a problem I had on my .45-70. with resting the barrel on a spot that caused erratic vertical stringing. Found the sweet spot and marked that with blue painters tape for a consistent rest point. Use something like a plastic hammer and tap on the barrel every half inch or so until there is a noticeable change in the sound. When the pitch changes to a dull thunk that is the point that will be stationary when the barrel whips during recoil. Rather like whipping a fishing rod back and forth. There are placed that do not seem to move from the original position in space. Try this first and there is an improvement by all means see if Dacron will help even more. Could be a combination of barrel harmonics and velocity differences caused by the powder.
Just a random thought.
Chill4100

[Yodogsandman]

You were on the right track to try different primers. A wise member here told me that both vertical and horizontal stringing was due to ignition. It effects the barrel harmonics causing the stringing. Better ignition will tighten up the nodes of barrel vibration. Dacron will reduce the ignition variation caused by powder position in the case.

[chill45100]

Interesting information which I will remember. Had not thought of ignition variables too.
Chill45100

[Geezer in NH]

I would also try a bench and not a stick. Speed diff off the sticks may not be helping. And yes I shoot of sticks in NMLRA competition but the same light bench/buffalo rifle shoots better groups off the bench.

Get rid of the human factor first and try again. IMHO

[Larry Gibson]

To light a weight cast bullet for lower level 4198 loads. Even a dacron filler most often doesn't work. By the time you get the 4198 to ignite and burn efficiently the velocity will be to high for accuracy. I long ago switched to faster powders. I found Unique and Bullseye to be excellent choices for my own RCBS 300 gr and Rapine 460250 in my own 45-70s.

Larry Gibson

[jhunter77]

Thanks for the help, I will post back when I have tried a few of these and see what works best. barrel was rested on the wood stock and also held. Thanks

[MT Chambers]

For me that 300 gr. RCBS was/is too small for my marlin '95, and accuracy is mediocre at best, they passed a little bit too easily through my .459" sizer.

[knifemaker]

I have a Marlin 1895 LTD-V that will put 3 shots at 100 yards into 1 inch day in and day out. It will do this both with Hornady 350 gr. RNFP jacket and with a cast Ranch Dog 350 gr. gas check boolit. Because you are getting good groups with the jacket bullets, and not your cast tells me there is something wrong with your cast boolits.
The load I use for both 350 gr. cast and jacket is 43 gr. IMR-4198. Going up to 44 gr. started to open the group up. The big difference between my cast boolits and yours, beside the weight difference of 50 grains is that I size my cast at .460. If I size smaller, the groups open up. Most 1895 Marlins I have seen prefer .460 dia. for better accuracy over .458 or .459.

[MBTcustom]

I have a Marlin 1895 LTD-V that will put 3 shots at 100 yards into 1 inch day in and day out. It will do this both with Hornady 350 gr. RNFP jacket and with a cast Ranch Dog 350 gr. gas check boolit. Because you are getting good groups with the jacket bullets, and not your cast tells me there is something wrong with your cast boolits.
The load I use for both 350 gr. cast and jacket is 43 gr. IMR-4198. Going up to 44 gr. started to open the group up. The big difference between my cast boolits and yours, beside the weight difference of 50 grains is that I size my cast at .460. If I size smaller, the groups open up. Most 1895 Marlins I have seen prefer .460 dia. for better accuracy over .458 or .459.

I agree with this. Bullets need to be sized .460. Also, I am not familiar with your lube, but have heard that Rooster Red does not store for long periods of time.

You're problem could be ignition related, but I would lay money on bullet friction differences. The only way to modify bullet friction is with alloy, size, and lube. Reading your description, it appears your alloy is the same, but you say your sizes run from .458-.459. That's not a whole lot of difference in size, but it can cause you untold misery in accuracy.

[44man]

Change powder to see what happens. I had pressure and velocity excursions all over the map with 4198, acts like 4227.
Try 3031.
I also agree with .460".

[cajun shooter]

I would try several things to improve your results but only one at a time or you are back to square one.
On primers, I would try CCI Bench Rest
On crimping, I would try using the lyman taper crimp die
I would try an alloy that is 12-15 BHN
I would try making sure that the barrel is rested on the same spot each time as another member suggested. ( It's very important to have this or bbl harmonics will play havoc with results)
Have you checked the stock clearance for the length of the barrel?
Have you checked the torque of the screw at the attachment point?
I would try another bullet lube as this can change your poi
I know that some of my suggestions are very basic but that is how you find problems.
If using a light powder charge, make sure that you use a Dacron like material to fill your case. Position sensitive powder needs to be at the primer for results. Good Luck David

[jhunter77]

well I finally got cast to shoot good but it is a very low velocity load. 14grains of unique was the ticket. 13 grains of red dot was also not bad but was even a slower load. I am sure 1200fps kills just fine but I am looking for a little more umph for hogs. I normally shoot 3 shots fairly quickly with jackets and cast. Hog hunting I have snuck a group and been able to get 3 hogs on the ground a few times now so that is the reasoning in three shots from a cold barrel. That results in a sub 2" group almost always with jackets. I was able to do the same thing with unique today.

With that said, there are now two possible issues. I believe its the first, or a combo of both.

1) Undersized bullet for that barrel
2) Too light of a bullet for 4198 thus causing erratic burn, then when you step up to enough pressure for a good burn, you are too fast

I will slug it this weekend and see what it shows and then will order a mold and sizer. Any advice on a mold? I would like a very flat meplant and figure I will keep them around 300 grains if possible for the recoil and flat shooting. I am thinking 1700 to 1900 fps. This most likely will take a gas check correct?

[jhunter77]

sorry about the font.

[MtGun44]

Good old Unique. I usually recommend starting at 10 gr and working up to about 15 gr,
stop when you like the results. You fit the pattern. Glad to hear another good result
with a very unique powder.

Bill

[jhunter77]

too bad its hard to find.

[jhunter77]

I slugged the barrel..45765My bullets measure.45870.Not sure if a .459 bullet wouldhelp.At this point it appears to be thewrong powder for the job.I am surprisedthat so many cast loads praise 4198.Mayhave to try another powder to see if I can get to the 1700 fps range. I do plan to try some larger bullets and see if I can get the velocity up some.

[Airman Basic]

Reloader 7 if you can find it.