Marlin 1894 - Sudden Loss of Accuracy/Tumbling Bullets

[Jonny]

Looking for some help guys. I'm in the UK and we use pistol calibre lever actions in competition. I'm shooting 240grn RNFP lead bullets with 6.0grns of Unique, a proven load that I've used for years.

My Rifle was shooting perfectly well then all of a sudden my groups were massive (6-8" at 25m) and some of the bullets were tumbling. I tried 2 other shooters loads in my rifle with the same results.

Due to the bullets tumbling I've ruled out any issues with sights etc. and I think using others' ammo rules out any issues with mine.

I'm hoping the issue is just that it's leaded up. Has anyone else seen this happen so quickly/dramatically?

 

[357Mag]

Jonny -

Howdy !

A great place to ask this question, would be " castboolits " ( not castboolits.com ).

They talk lead, lever guns, casting, paper patching etc on their site.

Lots of " Cowboy Action " shooters, there... so you should get plenty of input.


With regards,
357Mag

 

[Alex Wheeler]

First thing to do is check the bore for leading, if than is good, measure the diameter of the bullet. Should be .001-.002'' lager than bore diameter. Has this load performed well in the past? I shoot homecast in a couple marlins and they are very accurate when you get them figured out, let me know what you find.

 

[Jonny]

Thanks 357Mag, I'll have a look across there.

zfastmalibu. I'll check for leading. The bullets are measuring bang on their stated .429 and they're the same brand I've been using for years so I've kind of ruled this out.

I'll be having a look at it when I get in from work so I'll report back!

 

[jonbearman]

I had the same thing happen with a 44 mag model 96 ruger.It had so much lead in it I bought a lewis lead remover and modified it to work in a rifle and you wouldnt believe the amount of lead shavings I got out that barrel.It cured it and I clean more often.What happens is when the gun gets hotter from shooting it can cause the bullets to smear and strip through the rifling.Do you have ballard rifling or micro groove?

 

[Alex Wheeler]

That is your problem. I bet that barrel is full of lead. Marlin bores are on the big side. The groove diameter is probably .430''. I size my bullets to .432'' If you cant find bigger bullets try a gas checked bullet.

 

[KevinThomas]

Jonny,

I suspect that Jon has nailed this one. If it does have micro groove rifling, they don't handle cast bullets well, as a general rule. I bought my wife an M94 in 357 Mag many years ago. The thing was a real shooter with jacketed bullets, really a nice little rifle. When I switched to cast, it shot just like what you're describing here; shotgun patterns . . . with an open choke. I played with that one for months before finally finding a single load that shot well with a cast bullet. That used a 200 grain FN intended for a 35 Rem, and loaded to a very low velocity. Kick the velocity up, or go to a lighter bullet (shorter bearing surface) and it went right back to shotgun patterns. Take a look and verify the rifling type, and this may just answer the question.

 

[FroggyOne2]

I had the same problem with a 444 that had the micro grooves, just would not shoot worth a hill of beans!

 

[Jonny]

Thanks for the comments everyone. Went at the rifle tonight with some lead solvent and a very aggressive brush and accuracy was restored. Tested it with my usual load, the same one from Saturday, and groups were around 1" at 25m, from a makeshift rest on a fencepost. Not very scientific but enough to show that the bullets weren't tumbling.

I'll need to go out and do some proper testing but it appears that a buildup of lead finally became too much for it. From what you're all saying about microgroove I think it's fair to presume that the buildup, combine with the shallow rifling, was the cause.

The surprise in all this is just how quickly the accuracy failed. It went from normal to shotgun/tumbling bullets in about 60 rounds.

 

[jonbearman]

You have to drive them fast to avoid the unreal leading.I did it once with h4198 and a 240 grain bullet and pushed it fast but the damn leading creeps up on you really fast.I use only jacketed now till I can buy one with ballard rifling.

 

[MrMajestic]

"Old Timers" filled the bore with Mercury to remove the lead, not very health friendly or advisable now!
"Chore Boy" http://choreboyscrubbers.com/Products/Ultimate%20Scrubbers%20Pure%20Copper.aspx Copper wool wrapped around a brush strips it right out with no damage to the bore. You could try an inverted correct size gas check over the powder to reduce the leading from un-checked boolits. Has worked for some although I have never tried it. Good luck.

 

[firearmdoc1]

I would try using a harder bullet. Look into Oregon Trail Bullet Company, I have used their bullets before with good success. Don't know if you can get them in the UK though.

 

[Alex Wheeler]

I wish people would stop spreading the fallacy that micro groove barrels don't shoot lead well. The very basics of cast bullet shooting is sizing the bullet to the bore. Micro groove barrels run a little bigger than the ballard type and require a bullet sized to fit. If you slug your bore and size the bullet .001-.002'' larger your micro groove (or non microgroove) will shoot great with no leading at all. If your barrel is leading at the throat and all the way out, the bullets too small, if it is only leading at the muzzle end you may be driving it too fast or the lube mat not be doing its job. By the way, aren't marlin .22 rimfires all micro groove?

 

[xpilot]

"By the way, aren't marlin .22 rimfires all micro groove?" I believe the Model 39 (prior to 39A) was not a Microgroove. Model 94 same

 

[Alex Wheeler]

"By the way, aren't marlin .22 rimfires all micro groove?" I believe the Model 39 (prior to 39A) was not a Microgroove. Model 94 same

Your right, I was kind of implying rimfires made after micro groove barrels were actually invented. Haha, Anyway heres a good read for any one interested.
http://www.leverguns.com/articles/fryxell/microgrove-barrels.htm