Observation: 45-70 with Blue Dot

[unique]

I would like to solicit your thoughts on my observation of leading with Blue Dot (BD) in 45-70. I am using Buffalo Classic with barrel cut to 27". The groove is .455".
The bullet WW cast RCBS 45-325-FN-U which is plain base that actually weighs 340gr and is sized to .458.

As background, when I test a powder I always look at position sensitivity of the load by pointing muzzle up or down before firing (I do not use fillers).

What I observed consistently, meaning over many rounds, is:

BD = 18gr tilt up = 1430 fps lots of leading
BD = 18gr tilt down = 1350 fps no leading

BD=20gr tilt up = 1568 fps and lots of leading
BD=20gr tilt down = 1518 fps no leading

So when tilting down there is no leading even though the velocity is higher at 20gr.

My thoughts are:

When the powder is against primer (tilt up) the powder burns faster which produces pressure spike which causes leading

Or

When the powder is against bullet (tilt down) the the powder protects the base which prevents leading.

Or

Combination of both.

Your thoughts please.

[Scrounger]

I would try sizing .459 and/or .460 before I worried too much about your hypothesis...

[Larry Gibson]

unique

First off I would have to ask why BD in a "Unique" application? The pun was intended, no answer necessary. However i think you've got it backwards; when you tilt the barrel down the velocity is LOWER. I'd venture the time/pressure curve is fast with the barrel tilted up and the bullet has not obturated sufficiently giving you some blowby (probablby before the bullet is all the way into the barrel) of the bullet causing the leading. With the barrel tilted down the time/pressure curve is slower and the bullet is into barrel and there is no blowby.

Larry Gibson

[quasi]

size .460 or bigger and try it again. Why are you tilting the rifle? If a load needs contortions like that, I would find another load.

[jtaylor1960]

I agree with one of the other replies that if you need to tilt the gun to make it work change loads.I would like to know how you make out with that bullet as I have that mold and have a hundred or so ready to be sized.

[Scrounger]

Just kick up the powder charge one grain...

[Newtire]

My thoughts are that the leading is caused by something else other than BlueDot. I use that stuff in my .444 Marlin and get no leading ever. Just my own experience. I also have used Unique but am not that experienced in the use of Unique in this rifle other than a 12 grain load using a 200 gr. cowboy type Lee boolit.

[Trailrider SASS #896]

size .460 or bigger and try it again. Why are you tilting the rifle? If a load needs contortions like that, I would find another load.

I believe he is doing this just for technical comparison. I will sometime do this IF I am looking for particular position sensitivity with a given powder. When running pressure/velocity tests with a .45 Long Colt revolver I would tip the cartridge case nose down for the FIRST round and tape the other rounds to the outside of the gun (only one chamber instrumented), loading each subsequent round into the chamber to see the effect of recoil.

Frankly, I don't use smokeless powders with this fast a burning rate in .45-70. The only powder with which I have used a filler in .45-70, is IMR 4198, where the charges are fairly light (28 gr.) and the bullets are in the 405 gr. cast type. Then I have successfully used a 1/4 sheet of single-ply toilet tissue, poked LOOSELY over the powder, with the bullet doing any final compression.

Hope this is of interest.

[unique]

Thank you all for your replies.

The way I test a powder for position sensitivity is by testing extremes which happens to be powder against the primer or powder against the bullet. For instance I tried 25gr 2400 with same bulltet and I was getting close to 300 fps difference tilted up or tilted down. For me 2400 is too position sensitive in 45-70. In other calibers 2400 isn't nealry as position sensitive.

As an aside I believe a lot of flyers can be explained by powder position sensitivity in cases that are less than full, especially with faster powders.

I do not understand the suggestion to size at .460? As I stated in first post, my groove diameter is .455 so my thinking is .458 should be fine. Besides the bullets are .4585"as cast.

I tried lots of different powder which did not lead with H4895 being the best overall. Second best is HIVel2 (oldie but goodie).

I tried BD at 21gr and got the same thing.

The reason I am trying to utilize Blue Dot is that I have lots of the stuff. Since many claim Unique works fine in 45-70 I thought a slower burning flake powder was the way to go.

[Scrounger]

Perhaps sizing the bullet larger (for the moment ignoring the size it drops from the mould) would increase chamber pressure and cause a more complete burn and negate the position sensitivity factor. By the way, if I had known this was a test project and not an actual problem you were looking for help to solve, I would not have suggested anything. Do you know joeb33050?

[jh45gun]

2400 IS NOT position sensitive that is why I use it.

[unique]

2400 IS NOT position sensitive that is why I use it.

If you are implying that 2400 powder is never position sensitive in any caliber, in any rifle, and under any condition then you are certainly mistaken.

[felix]

ALL powders are position sensitive. It's must a matter of degree. ... felix

[unique]

Perhaps sizing the bullet larger (for the moment ignoring the size it drops from the mould) would increase chamber pressure and cause a more complete burn and negate the position sensitivity factor. By the way, if I had known this was a test project and not an actual problem you were looking for help to solve, I would not have suggested anything. Do you know joeb33050?

joebxxx? I would say most time cast bullets shooting is a test project. I am trying to understand the how's and why's to a leading problem.

If you don't really know what is causing my problem than that's ok. Really.

[joeb33050]

joebxxx? I would say most time cast bullets shooting is a test project. I am trying to understand the how's and why's to a leading problem.

If you don't really know what is causing my problem than that's ok. Really.

I've got some Blue Dot, and will experiment with it.
I load ~14/Unique and any bullet in 45/70 with a wad, Dacron or TP, and it shoots in any gun.
I suppose that the wad keeps the powder in 1 place so reduces velocity variation increases accuracy. That's why we use wads.
I'm very surprised at a 300 fps variation with 2400 or any powder, caused by position change.
I have no idea why a rifle would lead/not lead as the post explains, leading is caused by bullets too small if MV is reasonable, 99% of the time. And it ain't MV cause the 20 gr load doesn't lead.
Maybe it is the MV, these are fast 45/70 loads. Fast for me anyhow.
I've given up on 2400 for 30 cal and up years ago, just me. But BD looks like it should work. Almost loaded it in a test today, but went to AA5744.
This whole thread has me at a loss, I never imagined that 300 fps.
Experiments to come, please keep us informed.
joe b.

[jh45gun]

To each their own but I figure C. E. Harris is pretty smart when it comes to this cast bullet stuff and he claims that 2400 is not position sensitive. If it is it is the least sensitive of the powders then because I use it for every thing with great results 30 cal up to 45. Now I know you got to take most gun writers with a grain of salt but Harris seems to have a good following when it comes to cast bullet load matters. I quote from his article in the 1994 Gun Loaders Digest: " I say this because 2400 is not position sensitive, requires no fiber fillers to insure uniform ignition, and actually groups better when you just stripper clip load the rifle and bang them off, rather than to tip the rifle to position the charge" Later he also states about tipping the barrel with other powders: " Hercules 2400 does not need this precaution Don't ask me why. I only know its true because my expirience has been repeated and confirmed I know and trust who have done so in at least a dozen rifles."

Since a lot of folks here my self included seem to like Harris's loads using 2400 and red dot he must have some creditabilty. Now I know I am no expert and I think a lot of you guys here know your stuff I will not dispute you on that but if I read this in print and then try it and my expiriences mirror Harris's then I figure he has to be telling the truth on the matter.

[BruceB]

I'm quite willing to concede that 2400 (and some others) are not AS position-sensitive as many powders, and that many people are content with its performance when loaded loosely in the case. Felix is correct, in saying that all powders are position sensitive to some degree, and this most certainly includes types that have a reputation of being "INsensitive" to their position inside the case.

I have proven to MY satisfaction, through extensive direct-comparison testing of loads with and without dacron, identical in EVERY way except the presence of the fluff, that 2400 gives me more-uniform performance in most loads when dacron fill is used. In the majority of my tests, velocity is more uniform and extreme spreads are lower. Accuracy is not always improved, but there certainly are general indications of better shooting.

The testing I've done spans case sizes from 6.5x54 MS to the .50-2.5" Sharps. I know that I can load 2400 and 5744 without the dacron and get reasonable results. I prefer to use the fluff, because I like the improved uniformity. Do I need it? That's a personal choice, and most of my fast-burner loads do use the filler. It's another step in the loading process, but that doesn't worry me at all.

[jh45gun]

If filler works for you fine but I prefer not to use it due to some of the horror stories out there now I know some have pooh poohed that and some say its possible. Since I have had good results with out fillers I will prefer not to use them.

[unique]

UPDATE:

So I decided to try something else. I sized and lubed the bullets the same as before. I kept powder charge at 18gr Blue Dot. In other words did not change any variables.

I then painted the base of each bullet with liquid alox theorizing the powder against the base protects the base and liquid alox would do the same. I only painted the bottom of the bullet, not the bearing surface. The results are no leading under any conditions.

So my conclusion is powder against base of bullet protects the base from initial pressure spike and alox does the same thing.

[Scrounger]

UPDATE:

So I decided to try something else. I sized and lubed the bullets the same as before. I kept powder charge at 18gr Blue Dot. In other words did not change any variables.

I then painted the base of each bullet with liquid alox theorizing the powder against the base protects the base and liquid alox would do the same. I only painted the bottom of the bullet, not the bearing surface. The results are no leading under any conditions.

So my conclusion is powder against base of bullet protects the base from initial pressure spike and alox does the same

thing.

As do gas checks and filler material...

[Bret4207]

Interesting experiment. I think it showed me that the pressure curve can play a bigger part in leading than many believe. Thanks for posting it.

[Ricochet]

I believe the flame temperature plays a part, too. I've pushed soft plain base bullets (swaged and cast) to maximum velocity over 1550 FPS in my Super Blackhawk with W296 and WC820 with tolerable mild leading, whereas hot double base flake powders like Unique and 2400 would lead badly if the velocity went much over 1000 FPS.

Tumble and dip lubing techniques leave bullet bases coated with lube as you did with painting with Alox. May be helpful, and may partly explain why I've had good success with fairly high velocities in my rifles.

[unique]

Ricochet, I agree as the flame temperature is a major factor in gas cutting.

I think what may be happening is the alox is flowing due to the pressure spike and acting as an hydraulic seal between the bullet and bore. I painted the stuff on fairly thick with this thought in mind.

Thanks everyone for thoughts and Happy Thanksgiving.

[35remington]

With harder waxes and lower pressure loads, the wax thing on the base of the bullet doesn't necessarily work, as I was trying various experiments to lower the amount of gascutting I observed on the bases of some of my lower velocity loads in various calibers. It does have to be a softer consistency like your use of Alox is suggesting.

As always, experimentation will show the way. I can tell you straight bee's wax don't get it done; a softer wax is needed. And that a thin coat of alox won't work in most situations I've tried in my own guns, but it will do it occasionally, perhaps due to the particular demands of my own firearms. Wax preventing gas cutting has been variable enough for me that when I want to positively protect the base of a plainbase boolit I grab the bull (et) by the horns and use a wad or filler, if appropriate. I suppose if it works that painting on a thick coat of Alox is about the same, timewise, as adding a dacron filler. Or, I can johnny up my own wax wads for my loads

Or, I just live with gascutting if it isn't presenting a problem.

Sounds like it's working for you. Obviously you're following the right path for the load.