I just purchased my first ever lever action- a Marlin 1895 SBL 45/70. I have noticed that with handloads that have a compressed powder charge I have difficulty fully closing the lever. I can get it closed and it fires fine but obviously need for it to be smooth and easy. Clearly I can just load less powder or switch to a faster burning powder but I would like to figure out what the problem is and why it is occurring.

I do not think I am even using max charges. A little hard to tell for sure as I do not have load data for the particular bullet I am loading which is the 425 grain Leadhead Cast bullet. But extrapolating from load data Brian Pearce has published I think I am safe pressure wise.

For example 55 grains of Benchmark with a 425 grain Leadhead cast bullet causes this problem with difficult lever closure. The Hodgdon website shows 58.5 grains as being max with the 400 grain Speer JFP bullet and 55.0 as the starting load.

I am guessing that the case is swelling/bulging a bit but it measures the same just below the crimp. Maybe I need to measure it a bit lower on the case. Any ideas?

Does a sized empty case chamber?
If it does the problem is most likely up by the bullet when seated?
Next I would chamber a loaded round before crimping.
If still chambering I'd be looking for a bulge caused by cimping.
I love the lee factory crimp die in my 4570.

Is the length of the 425 grain bullet above the crimp the same as the 400 grain bullet? The 425 grain bullet may be engaging the rifling sooner than the 400 grain bullet.

When you seat and crimp heavily in the same step, the case bulges outward near the mouth making the round tight in the chamber. Try seating and crimping in separate steps. To do this, adjust the seater die up a little so it doesn't apply a crimp, and adjust the stem to seat bullets to the proper spot. After all bullets are seated, remove the stem from the seater die and adjust the die to crimp as desired. Yes its more work, but seating and crimping in separate steps always produces superior ammo. In fact it is absolutely necessary to do separate steps with some cartridges because seating and crimping together will buckle the case. 416 Rigby is one example.

Yep, I've had to extend the leade on every Marlin I've had for shooting cast bullets (45/70 and 35 Remington).

They typically have a very shollow leade and you will hit with the cast bullets.

The other way you can handle it is to shorten the brass a little more, but I frigging hate trimming.

Marlins are not the worst for having a short leade. I had a Miroku/Winchester 1886 that wouldn't come close to chambering a 400gr Speer crimped in the groove. Only bullet I could get to work in it at all was the Remmy 405.

I am seating and crimping in separate steps. I have a Redding die set with separate profile crimp die. My handloads with lower powder charges chamber just fine. Loaded cartridge length is 2.52" so I kind of doubt the issue is a short leade but maybe???

I do have some lapping compound so maybe I will firelap the bore and hopefully it will polish the throat/leade a bit and help the problem.

On the flip side, that seems like a bunch of powder for a 425 cast bullet.

I am now pretty sure you guys who mentioned the short leade are correct. This 425 grain Leadhead bullet has a 0.459" diameter band in front of the crimp groove. I filed that down and seated and crimped the bullet over 56 grains of Benchmark (definitely a compressed charge). Loaded length was 2.540" and it chambered easily with lever fully closing easily. So I need to try fire lapping to see if that will cut away some of the rifling.

Any suggestions on powder and charge for fire lapping? I have heard that it is best to load really light for low velocity. Could I use H110? If so what charge weight?

Leade is pretty damn common. Mine were lengthened with a reamer.

Had that happen to me as well....with a Miroku lightweight.

Why try fire lapping to maybe resolve your problem? Either take on the slugs (run through a sizer) or ream the chamber and know that things are rectified.

Overall the load data I have seen for the 45 Colt (which I load for in a Ruger Bisley) and the 45-70 indicate that one can safely use the same powder charge for a heavier cast than compared to a jacketed bullet.

For example the Hodgdon website lists 55.0 grains as max of H4895 as max with the 400 grain Speer while Brian Pearce has a load of 55 grains of H4895 using the 415 grain RCBS cast bullet.

Another example from Pearce's data has the 395 Belt Mtn Punch Solid bullet loaded with 54 grains of VV N133 and the 430 grain Oregon Trail 430 grain cast bullet loaded with same powder and charge weight. Lots of other similar examples. Anyway I am proceeding with caution. No desire to blow up my new gun or myself.

Rufous, If Loads with a lower charge chamber fine, what makes them different from the higher charge loads?
OAL, heavy crimp bulging the case?

Yeah maybe renting a reamer is the way to go but I do see a fair amount of circumferential marks in the bore that I would like to lap out (I assume these tooling marks will collect lead and make bore cleaning more arduous).

Rufous, If Loads with a lower charge chamber fine, what makes them different from the higher charge loads?
OAL, heavy crimp bulging the case?
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This is probably the answer. Measure a case just below the crimp and compare to a round that will chamber.
Take a round that will not chamber and just enter your size die. If the round chambers begin looking at case length an the way you set you seat/crimp die.

I didn't see it mentioned previously, but are you compressing the powder with the bullet while seating? This can distort the nose of a lead bullet and cause chambering difficulties. This comes up frequently in the BPCR circles - the use of a compression plug to compress the powder prior to seating avoids these issues. Granted, this is usually with blackpowder and soft lead bullets, but it's the same concept. If the problem only occurs with lead bullets and compressed charges, I'd be looking there (in addition to some of the other things mentioned)...

Soot smoke or use marker on the whole case and bullet, chamber and see what's scraping. Check the shoulder against a factory case. Hard to believe you may be thinking that the case is swelling because of the amount of powder you're cramming in there and still proceeding with the load.

I highly doubt the cases are swelling, but I have seen compressed loads push bullets back out, making the rounds too long