Out of my Marlin 1895 lever (post 72) with microgroove, I have been shooting IMR4198 with 300gr partition.

At 46-47gr, I get a slight bulge above the rim. With new brass (winchester) as a comparison, I get a .0054" bulge using starrett mic's. Woudl that be of concern to those who understand and look for this expansion? It is noticable. Primers look great. I am getting around 2050fps.

I need to go thru my old remington brass to see if I see the same. I did all my original load development with remington brass from 41gr-51gr. Nothing stuck out in my mind as an issue. I was told by Brian Pearce from handloader and rifle mag, that this action (1980's) can easily digest this load up to 51gr. Nosler also told me the same. But lymans and Sierra back off majorly for any leverl, post 72 or not.

I get 1.5MOA accuracy at 100 yards with 46gr, but it starts stringing vertically past that.

This is common in Marlin 1895s. You are just seeing the case conforming to the chamber of the rifle.

I was wondering that jack, because after looking at my old brass, its about the same for 41gr loads as it is for 51gr.

When your using the "case head expansion" methiod, the origional (factory) head size dosn't mean a F'in thing.
Fire a box of factory loads (preferably using the same brand of case), THAN measure those (in several locations around the case head). Take the average of those measurments and consider that to be the maximum case head expansion "in that rifle". Keep your loads at or below that expansion.

Compared to more modern cases the case walls near the head end of a 45/70 case are a little thin. It was never designed for the higher pressures being used by a lot of shooters today. I do not have a 95 but I have a 375 Marlin. The Marlin's chamber is sort of on the large side.
The action may be strong enough for your loads but a large chamber and thin brass will limit what you can do safely and how many safe loads you can get. Weigh your Remington cases. I suspect they were heavier than the Winchesters or harder or both.
I have some .45/70 Winchester brass that have been shot in 6 or 7 different 45/70s over the last 35 years including a Siamese bolt gun, #1 Rugers and 1885 Browning Highwalls. They would all bulge with high pressure loads. All these rifle are much stronger than a Marlin. To keep things safe I keep the pressure down so the bulge is not so pronounced. These 20 hulls have been fired so many times that 4 have cracked and burned a pin hole through about 1 inch above the head.

The case lies against the bottom of the chamber. I can only expand upward. This is common and not a pressure indication.
Good Luck!

quote:

Originally posted by Tailgunner:
When your using the "case head expansion" methiod, the origional (factory) head size dosn't mean a F'in thing.
Fire a box of factory loads (preferably using the same brand of case), THAN measure those (in several locations around the case head). Take the average of those measurments and consider that to be the maximum case head expansion "in that rifle". Keep your loads at or below that expansion.

In the 45-70, most factory ammo has a pressure of around 21,000 PSI. The safe operating pressure of the Marlin 1895 45-70 is approximately 42,730 PSI. Factory 45-70 ammo and case head measurement will never allow one to determine loads for the potential of the Marlin 1895 45-70. If you use Buffalo Bore or Garretts good luck trying to find new brass that is the same as what they use. Additionally, case head expansion and pressure ring measurements are not reliable indicators of relative pressure.

Jack
My main point being "the origional factory diameter" is a useless measurment.
I do tend to make my answers generic, rather than specific, so your point on factory pressure levels vs what that rifle will take is be a valid one, in this case.