.45-70 leading threshold?

[GeoDudeFlorida]

I know this is a multi-faceted question. I have (bunches) some H4198 and a bunch of MBC 405 grain HCL bullets, I have mostly been loading the bullets for plinking level loads using Trail Boss at 900 to 1,000 FPS and light 1,200 FPS "hunting" loads. These MBC bullets are not gas checked. Using the various data, I see loads for 405 gr HCL bullets with 27 to 31 grains of the H4198. Looks to give about 1,400 FPS at 30 grains. I am shooting a Guide Gun so the actual velocity will probably be less.

The question comes back, am I on the threshold of needing gas checks with 30 grains of H4198, how fast can I send a HCL bullet of good size match to my rifle before I begin to see excessive leading? Any thoughts. I would rather ask now than clean Pb from my barrel later.

Did you read this?
https://www.missouribullet.com/technical.php

 

[3Crows]

Did you read this?
https://www.missouribullet.com/technical.php

Yes sir, I did. The MBC is listed as 18 and the LaserCast at 15. I am trying to build a hunting load that does not finish detaching my retina but which is sufficient to hunt deer/hogs with confidence. I figure that to be around 1400 to 1500 fps. And since I am working with 18 inch barrels I need to account for that.That puts me in the load data Gap between trapdoor loads and Marlin loads where oddly little data exists.

I am getting low on the MBC Large Buff but I have a good stock of LaserCast 405. I probably dig into those and make an order to MBC soon.

If I had known Remington of yore would stop selling the 405 SP to reloaders I would have bought a lifetime supply of them and use nothing but. Unfortunately, I have only a small stash of them.

I loaded up 20 rounds last night with the MBC Large Buff over 32.0 grains of H4198 (not a published load, tops at 31.0 grains). I am hoping that gets me right around 1400 fps. I have worked up from 30.0 grains which was 1230 fps. I do see smears of Pb in the barrel but it does not seem to accumulate beyond that and accuracy is holding pretty good.

I am the odd fellow who owns four Marlin 1895s, two SBLs, a GBL and an older JM Cowboy. The Cowboy has issues in that some CAS yahoo decided to slick up the action, well, it is slick and completely non-functional and a project for the day that parts are available to repair or I find a smith I can trust to add some metal back. My Rem-Mar SBL is dedicated to Pb as is my Ruger-Mar GBL and my Ruger-Mar SBL is dedicated to copper plated ammo.

Speaking of which, whilst rambling, the Ruger SBL really shoots the Hornady LR 325 grain round MOA but I do not like those short cases. So I got ahold of some Hammer Down and Fusion and it shoots those nearly as well so at some point I am going to try and duplicate that Federal Hammer Down/Fusion 300 grain load. Both the Hornady and Federal stuff have some pop to them, recoil is beginning to get to the point that they are not fun to shoot but that is okay because at $2.50 per round I cannot afford to . And my right shoulder was injured and had to have the tendon sewn back to the bone due to a cell phone texting bimbo who ran a stop sign. Even now nearly a year out that shoulder is a little sore after a session of .45-70!

 

[3Crows]

Well, a quick update, got off the couch and put a couple of rounds over the chrono. I got an average of 1420 fps with the 32.0 grains of H4198 and the MBC 405 Large Buff. Starline brass, CCI LRP. I might go to 32.5 or not. I think it stout enough to stomp pigs and it does not stomp my shoulder in return. That is through a Ruger-Marlin GBL with the 19 inch barrel. Should be golden huh?

 

[applefish123]

Lyman 50th has the 1873 Springfield 45-70/ p354
- 405gr(Lym457193 #2 alloy) 2.550 OAL
- 31.5 - 35.0gr / IMR4198 (12,400 - 17,700 CUP Max)
- 1,312 -1,463fps
(Doesn't specify whether 24" or 30: barrel used. From QuickLoad I suspect 24" )
.

Any idea why Lyman is listing loads that are 3 grains heavier than Hodgdon's reloading data center? This is for trapdoor-safe pressures, correct?

Hodgdon is saying max of 32 gr of IMR 4198 gives 1462 fps and 19,000 CUP. OAL length is practically the same too (difference between 2.550" and 2.540" should only create pressure difference of 100-300 psi with that large of case capacity).



Strange my Lyman 48 shows the same IMR load of 35 gr and 405 cast gives 17,700 CUP.

 

[3Crows]

Any idea why Lyman is listing loads that are 3 grains heavier than Hodgdon's reloading data center? This is for trapdoor-safe pressures, correct?

Hodgdon is saying max of 32 gr of IMR 4198 gives 1462 fps and 19,000 CUP. OAL length is practically the same too (difference between 2.550" and 2.540" should only create pressure difference of 100-300 psi with that large of case capacity).

View attachment 1117452

Strange my Lyman 48 shows the same IMR load of 35 gr and 405 cast gives 17,700 CUP.
View attachment 1117453

I have found similar discrepancies in what I am calling the .45-70 Gap. The Gap is the region between where trapdoor loads leave off and Marlin loads begin. And betwixt those two, it is the Wild, Wild West.

 

[GeoDudeFlorida]

Well, a quick update, got off the couch and put a couple of rounds over the chrono. I got an average of 1420 fps with the 32.0 grains of H4198 and the MBC 405 Large Buff. Starline brass, CCI LRP. I might go to 32.5 or not. I think it stout enough to stomp pigs and it does not stomp my shoulder in return. That is through a Ruger-Marlin GBL with the 19 inch barrel. Should be golden huh?

Yup. The thing is it’s pretty easy to kill a pig with a .45Colt 255gr moving 900fps - at close range. Spin up the Ol’ spreadsheet machine and run the numbers to see how far that 405gr LFRN MBC will go before dropping down to under 800fps using a starting velocity of about 1300fps - by using the BHN -> kPSI calculator MBC provides - and it looks to me like, for the sighting radius of your guns you can load as low as 1100/1200fps at 18/22kPSI with H4198 and still be well above pig-rolling velocity. Just be careful to peg piggy behind the shoulder or you’ll roll him without killing him.

 

[GeoDudeFlorida]

I have found similar discrepancies in what I am calling the .45-70 Gap. The Gap is the region between where trapdoor loads leave off and Marlin loads begin. And betwixt those two, it is the Wild, Wild West.

I tend to think of it like the .38LC/.38Spl/.357Mag/.357Max relationship: you can shoot anything weaker in any stronger action as long as you are above stiction velocity.