big spreads in my 45-70 loads

[k2man]

I loaded five different loads for my new 45-70 1895 Marlin SBL - I shot this rifle once before, about 20 rounds, and cleaned it thoroughly. I rolled them all with 300 gn. hardcast coated bullets from Mo. Bullet Co. All cases were new Starline Brass. I shot them all over my ProChrono, set about 10-15 ft. away. My problem is that the spreads were huge. All strings were 5 shot except 5 was a 10 shot group:

String 1 37 gn. IMR4198 1394 to 1604 fps, ES=210, SD=79
String 2 47 gn. IMR3031 1455 to 1614 fps, ES=159, SD=74
String 3 48 gn. IMR3031 1522 to 1592 fps, ES=70, SD=25
String 4 49 gn. IMR3031 1574 to 1672 fps, ES=98, SD=39
String 5 35 gn. IMR4198 1295 to 1574 fps, ES=279, SD=97

I noticed that the cases were bulged out from the bullet seating. I measured .003" diameter difference just behind the bullet vs the casing over the bullet. Also included photo of the lightest load (string 5 - cases marked with a line) blow by burns. All other cases from other strings looked like these from string 3 (cases marked with a 5) showing no blow by. Any ideas on why I have such wide spreads in velocity?

IMG_4040.JPG

IMG_4037.JPG

IMG_4035.JPG

[Jeffm004]

The cases are a bit dirty. Not hot enough to seal the chamber? The loads are light by Lee, that might add trouble. Finally, I think some cronos don't take the shock wave off that big a bullet well. I throw out the really sketchy data.

I have yet to find a load I like for coated in a 45-70. I'm still looking now and then, but I haven't found one.

[Nathan]

How was your accuracy?

[Mobuck]

Velocity seems way low for a 300 grain bullet. Inconsistent powder burn due to low pressure???????

[Road_Clam]

Were you getting any "err1" or "err2" messages from your Chrony? My alpha gets very inconsistent reading when the sun angle gets low such as late afternoon. Those ES's do seem very wide. My light 45-70 TD loads are usually spread about 50 fps. I'm running about 28 gr of 4198.

[ericuda]

Back your chrony off more, I bet you are getting some muzzle blasts affecting your readings. I usually shoot 45/70 at 20 yards from chronograph.

[k2man]

Never got any "err" with these loads - I've seen that in the past, but no a single one with these loads.

It was not late in the day - about 4pm, bright clear sky, had the white sky things on the chrono.

Accuracy - I was shooting 50 yards, have the Ghost Ring sights on it. My groupings were about 1" horizontally, but 5" vertically. I'm using my stock 61 year old eyeballs, and I was having a hell of a time seeing the front post sight - target was a 10" black glow target - had to keep sighting on the white background to try to find the fuzzy top of the front post.

Those cases that had the black marks, they definitely didn't seal against the chamber before the bullet left - they were my lightest loads, so I won't reload any with that powder down that low again. All others were ok.

I'll try setting the chrono a bit further away, but I never saw it move, so I don't really suspect it was getting significant muzzle blast.

I am concerned that the bullets are bulging out the brass by .003" - is this normal for a 45-70?

[condor bravo]

K2man
If I am reading you correctly, you seem to be saying that the case measurement with bullet is .003 larger than the case immediate below the bullet. My 45-70s with Starline brass and .452 diameter bullets are just the opposite. Case measurement with bullet is .480 and measurement below bullet is .483, a .003 difference but in the opposite direction. Strange there should be that much difference and off hand don't have much of an explanation except perhaps the diameter of the bullets or difference in sizing dies. Maybe your sizing die is reducing the case diameter below the bullet more than it needs to.

But for some reloaded rounds, that would be completely normal. My 30 carbine loads for instance measure .333 at the bullet and .330 below the bullet. But on the other hand, factory Winchester 30 carbine rounds measure .332 at the bullet and .334 below. So what is the answer??

Do you have any factory .45-70 rounds to measure against? I don't.

[Don Fischer]

So how was accuracy? Cast stuff I loaded for my 30-06 varied a bunch but shot fine. I put the chronograph away!

[k2man]

condor bravo, that is correct, the case is larger over the bullet. The case stretched out .003" when the bullet was seated. I don't know if this is because these are new brass? I did use the sizing die on them before loading.

I'm not a "good enough" guy - yes, everything seemed to shoot fine, accuracy was as good as my eyeball, but I don't like a 200 fps variation in my shots.

No signs of over pressure on the brass either.

[random guy]

Looks like you should have a plenty good grip on the bullet. I have never used coated bullets but have loaded for a bunch of .45/70s at different power levels. What I settled on was H322 for loads around what you are shooting and IMR4198 for heavier lever action loads, all with jacketed bullets. I did not get either powder to do well at both levels.

A 5" vertical spread tells me that your eyeball is better than what the gun is currently delivering.

[condor bravo]

K2man:
On a second search I do have a few boxes of Hornady factory .45-70s. Case measurement on the bullet is .478 and measurement just below the bullet is .481, a .003 difference. What is your bullet diameter?

[k2man]

I'm measured three rounds just now at .4794 to .4798" over the bullet. Just below the bullet is .475", so I've got over .004" difference now. My 300 gn. MBC #2 buffalo (small buffalo) cast 15 BHN coated bullets are measuring .45900-.45930".

[condor bravo]

While your cast bullets might be considered just slightly excessive in diameter, shouldn't be enough to increase the other measurements you are getting. I'm also using some cast bullets, moly coated, sized to around .458, not that much difference from yours. So at the moment can't come up with any other good possible solution. Maybe just try a smaller diameter bullet if readily available which might help the accuracy issue as well.

[Unclenick]

Yes, the bulge is reasonable if you resized the case. The factory puts a taper on the case, but a lot of dies make them straighter than that. A long bullet can get far enough down in the taper to show no real bulge, but a short one won't. Figure the brass is sized to make the brass about 0.001–0.002 inches smaller than a jacketed bullet to achieve adequate bullet grip, so jacketed bullets would bulge about 0.001–0.002 inches, and that your cast bullets with coatings are about 0.001-0.002 inches bigger than the jacketed ones are, getting you to 0.003" bulge. Nothing unusual.

The bulge (mirroring of the bullet base location) is actually useful to evaluate how straight you are seating the bullets. If they are straight, the bulge will be pretty even all around. If they are not, the bulge will be sometimes only on one side. They are almost never perfectly even all around because brass case walls are not dead evenly thick all around, except by happy accident. But gross unevenness lets you know you need to flare with a Lyman M style expander die (Redding and, I think, Hornady makes their straight wall case expanders this way).

The velocities and SD's give the impression you are operating at lower pressure than the powder likes. When I put Hodgdon's data for a 300 grain lead flat point bullet either into QuickLOAD with some burn rate adjustment, or into a spreadsheet I have that calculates pressure and velocity from the exponential relationships in the Hodgdon data, your two 4198 loads should be producing about 1610 and 1700 fps if your chamber and barrel were as tight as Hodgdon's test barrel's is. It won't be. But I'd still expect to make 95% of their number even with a loose gun, and and 97-98% or so to be typical of production guns. I see your smaller load made 1574 on one shot, and that's almost 98% and reasonable.

So, then, why aren't the other rounds behaving quite so well? You didn't say how close the chronograph is. When you have loads like these that, even when they fire well, dump about 10-15% of the powder out unburned, it common to get false low reading from them on an optical chronograph. A Magnetospeed or a LabRadar would not. The reason is neither of those two devices can register powder particles while an optical unit can. When the bullet clears the muzzle, the gas accelerates to about 1.4 to 2 times the bullet velocity. That can throw some powder particles out ahead of the bullet for a short distance. They lose velocity very quickly, as they are light and not aerodynamically shaped for low drag, but they can sometimes get to the first chronograph screen and trigger it an inch or so ahead of the bullet, which then passes them a gets to the stop screen first. This makes the time between front and rear screen triggering long and gives a false slow reading, but no error message of any kind. Muzzle blast rattling the diffusers can also cause false triggering.

The cure for both is the same. More distance. We had a board member with a 338 Lapua Magnum who had to get all the way out to 18 feet before the readings became consistent. Usually, 15 feet is enough. But a lot of chronographs have 10 foot cables to a remote display or just get hard to read without binoculars out past that range, so that's as far as some go. For handguns, that's fine, but rifles can cause problems with it.

If we assume the chronograph readings are right, something is going seriously wrong with ignition. That is, some bullets are getting too far down the tube before the powder really gets a good burn going, so its building pressure late and in too much space. Why? Several factors could be contributing. Powder position is one. These loads are low percent case fill. I looked at the bullet photo on line and it looks like its seats less than a caliber into the case when the crimp groove is lined up with the case mouth. About 70% or less case fill. In some cartridges you can get over 100 fps difference in velocity just depending whether the powder is over the flash hole or over the bullet with that kind of case fill. If you didn't position the powder carefully over the primer by tipping the muzzle up between shots, that could be a big piece of the puzzle. A disc of paper over the powder or a tuft of polyester pillow ticking can help. Just be sure you work up from lower down when you add things to the case that affect the amount of air space in it.

With low case fill, going to a magnum primer can help a good deal. Magnum primers make more gas, and that can help reach adequate start pressure with all the extra room in there.

Coated bullets are pretty well lubricated. Lubrication reduces how much resistance there is to build pressure against, and an extra grain or two of powder is commonly needed to make up the velocity loss you otherwise get.

Lubrication also makes a bullet slip in and out of the case more easily, so you need to be extra careful to get a good crimp. I recommend the Redding Profile Crimp die for a roll crimp into the crimp groove. It holds the sides to resist the rolling in of the crimp expanding the brass below it and spoiling the case neck's friction hold on the bullet.

Lots to think about and try.

[Jim Watson]

Unless you are getting muzzle blast on the chronograph, the next suspect would be your light loads. You are down in the Trapdoor load range with an unusually light bullet for the caliber.
If so, I think you will have to run the velocity up to maybe 1800-2000 fps to get a uniform burn.

[k2man]

Thank you so much for the analysis and suggestions Unclenick. Yes, a lot to think about. All very interesting and understandable. I will move the chrono out further to start (was at 10-15 ft. from muzzle), and try tipping the barrel up before a shot vs tipping it down to see what effect that has.

The bulge in the brass from the bullet seating - some cartridges are uniform all the way around, some are not. Interesting. I would think this doesn't significantly affect accuracy - or does it?

10-15% unburned powder? Wow, that sounds like a lot. If I increased the powder charge, will I have even more unburned powder?

[snuffy]

If I am reading you correctly, you seem to be saying that the case measurement with bullet is .003 larger than the case immediate below the bullet. My 45-70s with Starline brass and .452 diameter bullets are just the opposite. Case measurement with bullet is .480 and measurement below bullet is .483, a .003 difference but in the opposite direction

.452?? CB, is that a misprint, ?? 45/70 bore diameters are supposed to be .458. A .452 bullet would not even grip the rifling, rattling down the bore with no sealing of powder gasses.

That Missouri bullet should be plenty big for any 45/70 barrel, BUT you don't really know without slugging the bore.


Vertical stringing usually results in the wrong burn rate of the powder. Also too low a charge does the same thing. How did the rifle sound? It should be speaking with a sharp report, I'd bet it was rather a punky sounding report. I'll bet an examination of the bore after firing would show an excessive amount of unburned powder.

[condor bravo]

Re: snuffy
Yes, definitely a misprint. I had noticed it and thought I had it corrected. Should have been .458.

[Road_Clam]

Any un-burnt powder kernels in the chamber ? This is a sign of inconsistent ignition as Unclenick was suggesting...

While I did not observe poor ignition with my 28gr / 4198 TD loads I have observed some un-burnt kernels in the chamber. Come this spring I am going to start wadding my charges, and switch to mag primers. In the past all's I was doing was dumping the powder and seating the bullet.

[k2man]

I did not notice any unburnt powder kernels. It was the dirtiest rifle I've ever cleaned though. I ran dozens of patches with M-Pro7 on a wire brush down the barrel, and kept coming up up dirty. Never remember having to clean a barrel this much, as I always clean each time I shoot.

Mag primers - I guess I would consider switching to them, but I'll first try loading these hotter, as I can stand the kick ok - more of a shotgun type shove, and I use a big shoulder pad (Couldn't shoot 30 rounds from a bench without it).

Tilting the barrel up or down before firing should tell me if there's any need to add fluff to keep the charge back in place. I'll give that a try and report back.

[849ACSO]

Those numbers sure seem low speed to me for a 300 grain pill. Those look more akin to 405 grain hard cast lead speeds. I'm thinking you're not running hot enough to be consistent.

[Unclenick]

Originally Posted by k2 man

The bulge in the brass from the bullet seating - some cartridges are uniform all the way around, some are not. Interesting. I would think this doesn't significantly affect accuracy - or does it?

10-15% unburned powder? Wow, that sounds like a lot. If I increased the powder charge, will I have even more unburned powder?

Whether or not the non-uniformity of the bulge affects accuracy depends on the degree and the cause. A small amount is probably just that the case walls are a thousandth or two thinner on one side than the other, and the thinner side stretches more easily. A larger amount is probably because the bullet didn't seat squarely into the case. The mismatch in its shape and the shape of the seater ram contribute to this. If you start the bullets in straight, then they tend to stay straight, regardless of exact expander profile. You can make that happen by using a Lyman M type expander die, which creates a little step in the case mouth that you can set your bullet base squarely into, so it has no tilt on its way into the seating die. The Redding expanders have that profile, too.

In a target rifle with jacketed bullets, groups can be opened up on the order of one moa because of bullet tilt. This occurs because a pointed rifle bullet has its center of gravity out in front of the center of the bullet's full groove diameter bearing surface. The tilt is centered around the bearing surface, so that throws the center of gravity to the side of the bore axis, causing it to spiral down the bore on firing. That spiraling CG is like a weight tied to a string and swung around the bore axis, so when the bullet exits the muzzle, it's like letting go of the string, and the bullet moves off tangent to circle it was spinning in. That motion is small, but it constitutes enough drift to move the bullet a half moa off the target by the time it has traveled a couple of hundred yards. With lead bullets it's less easy to tell how much drift you'll get from this. They are softer and will swage into the bore with more tilt than a harder jacketed bullet does (usually around three to five thousandths of tilt at most, depending on the bullet geometry), but the CG isn't as far forward of the center of the bearing surface in most more blunt lead bullet designs. So it could go either way. I don't have numbers for the lead, but my personal experience suggests they can be made to fly further of course by this than a jacketed bullet can.

The unburned powder will decrease some with higher pressure. So will all the soot you are cleaning out. You will still have some, though. The way I handle heavy carbon powder residue is usually with Gunzilla. I use a pump sprayer to get enough flowing down the bore to coat it. Then let it sit overnight and patch it out the next day. At that point there won't be much left. Boretech C4 is another good product for this purpose.

[k2man]

Thanks Unclenick. The bulge in some of the jackets under the bullets are definitely one sided. That is, there is no bulge on one side of the jacket, and 180 degrees opposite is the maximum. I've ordered a Lymann M expander die and will see if that fixes the problem.

Also just ordered some Gunzilla. Always looking for easier cleaning!

[condor bravo]

Die sets for straight wall cases like the .45-70 normally come with a flaring die like an M die. Check to see if you might already have one.