Compression on 45-70 Black Powder

[Lead pot]

I have had problems shooting a less then full case of black in a .43 Spanish when I was a kid. It bulged the chamber enough that I had to drive the case out. But this was a Military rifle with a lighter barrel then what I use now. I rung a chamber with a .45-120 3-1/4" case full of compressed powder. I put the blame of a hang fire when that happen. I was at a muzzle loader match and a guy put a large walnut in his barrel when he shot a short seated ball. It can happen.
I breach seat my bullet past the lead in the throat but I do not use a wad in the case mouth. My load is compressed enough so the powder holds when I remove a .012" card that is flush with the case mouth that holds the powder when I'm on the road so it don't spill out. I have left that .012 card flush in the case mouth that would have about a 1/8" gap under the bullet base and sofar I have not had a problem doing this but I do carry a stick pin so I can remove that thin card.
In a straight wall case like the .45-70 and you put a heavy compression on the powder and the bullet breach seated ahead of the bullet by more then 1/8" I would think that heavy compressed powder is a solid mass like a wad. That might cause a problem when the air gets compressed between the hard powder and the bullet base. Cant say for sure that it could happen or not because I have never done it.
A short volume of compressed air between two solid objects will do a lot of damage.

[Toymaker]

Constantly, repeatedly, and forever we hear and read DON'T LEAVE AN AIR SPACE BETWEEN THE BULLET AND THE POWDER. Yet people do it and have done it for years and we hear about that too - - usually when they blow up a rifle or walnut a barrel.
In person I've only seen it happen once. And I was one of five range officers that investigated the incident. The ammunition left on the table had bullets where the bullet base was 0.25 inch above the powder. The American made modern rolling block was destroyed from the hammer to approximately 6 inches up the bore. The shooter was dead before he hit the ground. The man to his right took a chunk of steel in the back of the head and has a plate as a result. The man to the left took pieces in the side of his face - thankfully he was wearing eye protection.
BTW - breech loading, done properly, is a different animal.
Email the NMLRA or Single Shot Rifle Association or other organization charged with running competitions and disseminating information and see what they have to say.

[BrentD]

Constantly, repeatedly, and forever we hear and read DON'T LEAVE AN AIR SPACE BETWEEN THE BULLET AND THE POWDER. Yet people do it and have done it for years and we hear about that too - - usually when they blow up a rifle or walnut a barrel.

Never heard of it happening with black powder.

BTW - breech loading, done properly, is a different animal.

Why?

[Lead pot]

This airspace subject comes up quite often. Why does airspace cause problems???????I stated above that I have problems with straight black powder and I have first hand seen rung chambers at the range when a shooter came over to me asking if I had a cleaning rod with me. He said I have a stuck case I cant extract. This happen twice in around a 15 year time span. I asked how did you load your rounds. One said I had light loads to cut down on recoil and I used a cotton ball to hold the powder down. The other guy said I used a filler. Both claimed that it was just a black powder load.
I think creating a airspace between the powder and the bullet base is enough when the charge is lite the pressure moves the air forward behind the still stationary bullet especially if a crimp is applied to the bullet is enough to force the case wall out sort of like pushing a balloon between two hands.
Below is what compressed powder in a case looks like from .100" to .600" from L to R. When you get to .200" you will see that the powder starts to make a solid mass in front. At .300" compression you have a very hard flat surface. I feel that that hard flat face is enough to build up enough air in front of that compressed powder to increase the air pressure between the bullet base and powder and more if there is a wad with air between it and the bullet base.
What I think is going on with breach seating where you can get by with a slight airspace is the bullet is already pushed fully into the bore which reduces the pressure behind the bullet. When it is in the case and the pressure builds up and expands that bullet in the wide chamber filling it then it gets swaged back down when it enters the throat. This increases the chamber pressure where a breach seated bullet does not do this. It takes less pressure to get it moving.
Just my thought on this.
By the way. I also used some swiss powder and compressed it like the Goex in the photo's and for some reason it makes a more solid compact for some reason. I do not have those photo's any more, they got lost.

[rfd]

while i'm absolutely SURE there are bp loaders/shooters who routinely build cartridges with loose or somewhat air spaced black powder under bullet/wad/whatever, or even puff wadded cartridges, and have never ever had a problem, i'm simply not gonna tempt fate, i'm too chicken scared for that and i have no problem admitting it. even after a 30" drop tube and vibrated case load of bp, i'll still stick in a thin wad and slightly compress at the least, then push the bullet tight to the wad.

[martinibelgian]

ctually, no reason for conjecture, the reason is fully explained as discovered by the French chemist Vieille - you know, the inventor of smokeless powder. We just forgot it... Nothing to do with compressing air, it is a shockwave thing. Read Vieille, read C. Dell, and find out. And BTW - some people do confuse the substitutes with black....
Try this:

[BRUCE MOULDS]

urban myths abound regarding this issue.
however one thing is plain.
breech seating with black powder cartridges has been used since the beginning when the priority is accuracy, and done safely.
major hinman stated unequivocally that at the and of the long range black powder era most shooters were breech seating with an airgap.
there exist photos of original creedmoor loading kits which include breech seaters.
ned Roberts in his book recommends different airgaps for different calibres.
in fact adjusting the airgap is the way the load is tuned, and when the correct gap is found, the results are pretty obvious.
to this day scheutzen shooters are tuning with airgaps and black powder.
these gaps might be between 1/16" and 1/8", but can be a little more or a little less.
loose powder is also known as a technique to find a good load with fixed ammo.
urban myth and inert brain syndrome seem to feed on each other.
keep safe,
bruce.

[SSGOldfart]

Sir I think most of us loading BP cartridges leave a small air gap between wad and bullet even if we didn't do it on purpose anyways unless the bullet is seated on the powder it's most likely there

[bigted]

so back to the subject asked in the first place ... i really do not believe that there can be enough REAL blackpowder [of the correct F size] stuffed into or compressed in a 45-70 case {45 - 2.96 inch} to be in the least dangerous to the shooter, rifle or bystanders.

another thing is the drop tube ... this is a venue used in the utmost ringing of accuracy out of a firearm. in general plinking {as most shooters have no skill to shoot long range with any accuracy in the first place} there need be no drop tube used as just compressing does the trick almost all of the time [world according to Ted]

as for the question of how much compression ... depends on the powder used, boolit used, velocity desired as well as what kind of shooting is to be used and what general real world accuracy is the object to be sought after.

many answers to a single question. best is to go out and speriment

[mazo kid]

Ted, I resemble the statement about long range shooting. So far, I have only shot to 400 yards with decent accuracy. I think another factor in compression, to a lesser degree, is the brand of brass used. Winchester, having thinner case walls, will hold a few more grains of black. I just built a Trapdoor Sporter/target rifle using the original barreled action, and will be working on loads next.

[matheu]

ok just going to say I compress my power because it (at least in my rifles) seems to stop the fouling problem. I have used as much as 85 grains of 2f (compression die) and as little as 27 grains 2f (filler and compression die) with great success .I can shoot all-day with out havin to brush the barrel .As for the question about air space well lets use the chassepot rifle with its paper wrapped cartridge it has lots of air space. You build the cartridge 12mm in dia. but the space in the gun is 14mm and its 73mm to 70mm long that a ton of air space!!! and works just fine.

[Lead pot]

The air in a paper cartridge used in the Chassepot of the 63 Sharps compared to a cartridge rifle is different. There are no wads under that bullet and it is loose powder. Loose powder below the bullet in a cartridge in very small amounts is less likely to do damage then a cartridge with loose powder and a wad on top of that loose powder and a gap between it and below the bullet will do damage. A heavy compressed powder with out a wad compressed below a bullet with a gap may act just like a wad pushing a shock wave like Martinibelgian said, but isn't a shock wave caused by an explosion actually compressed air getting pushed at high velocity ahead of the vacuume caused by the explosion?

I have seen bulged muzzle loader barrels with bulges caused by short seated balls.

[matheu]

"I have seen bulged muzzle loader barrels with bulges caused by short seated balls"(lead pot)

I have also have seen this and one that exploded the ball was seat short because it got stuck on fouling was not rammed through or removed but fired. The projectile must move as the charge (ie air space ,wads, power ,filler and anything else)expands .Air space gets blamed cause folks don't know what happen so they say AIR SPACE! cause I will tell you from working on a farm pipe bombs made to take stumps work much better compressed than with air space.

[RPRNY]

Shall we leave it at this: It is good advice to those relatively new to black powder loading to avoid a gap between powder and boolit. By the time they have been down the rabbit hole and get to breach seating and long range shooting, they will have learned that there is room for interpretation in this otherwise very solid guidance.

Back to the beginning. The advice offered early on that you have to find out how much compression works best for you with your particular load in your particular rifle is spot on, as is the view that short of bulging the brass to the point of feed problems, one cannot fit enough appropriately grained black powder in a 45-70 case to create a pressure situation in appropriate firearms.

In my Pedersoli Rolling Block, I find that 1/8th" compression is the sweet spot and I seat 500 gr paper patched slicks just into the lands and the Postel bullet just a little bit (highly technical BPCR terms) farther in. I determined compression based on A) how much of a powder charge I wanted and B) bullet seating depth required to lightly seat into the lands. It has taken a great deal of experimentation to get to a very accurate load. It is far more art than science. I use a small initial charge of 3F Old Eynsford under 1.5 F. In my experience, this has brought down standard deviation in velocity and "seems" to diminish fouling/induce fuller combustion. Other highly qualified and experienced BPCR folks will tell you my theory is a load of insane, Satanic rubbish. They may be right. Be safe. Don't be afraid to ask questions, as you have done. Experiment with components - it's half the fun.

[Blackwater]

Interesting thread, and thanks, martinibelgian for a great post.

My start with my 1885 Browning BPCR was kind'a frustrating. I tried to find a "hurry up" way to get a good load. It didn't work. Then I read voluminously on a BPCR forum that doesn't exist any more, going back into their archives and reading every post that seemed related to what I was doing. Here's what I found:

1. Whether your load needs compression or not probably depends a LOT more on WHICH of the BP's you're using. Swiss often doesn't need or want it. Goex (the older stuff) usually does. And as a side note, Swiss or other "premium grade" black powders tend to heat your barrel up faster than "musket grade" like Goex (older issues) does. With a hot barrel, you can't keep the fouling moist with a blow tube, so I went with Goex myself. Others argue for Swiss and have gotten great results with their gun and loads. If you can, you probably ought to try both.

2. BP is MUCH more sensitive to every facet of loading - crimp/no crimp; compression/no compression/how much compression; bullet wt. (heavier helps the powder burn better, usually); fit of bullet to barrel; whether the front driving band contacts the rifling; primer strength (generally - but not always - Swiss tends to work better with milder primers/is easier to ignite, while Goex usually likes WLRM or Fed 215's to get best accuracy); and other factors I'm probably leaving out.

3. You can never intuit what your gun and powder and bullet will need in order to perform, but when you DO find that, your accuracy can really be amazing! So it's really WORTH the time and effort to experiment with the parameters and find what YOUR rifle and bullet, etc., want, in order for them to make you really, really happy.

FWIW, I've known several who got good guns, but wouldn't do their due diligence and find the right load for their gun and bullets and powder, but when they sold it, often at a HUGE loss (!!!), the new owner simply did some experimenting, and found it to be a real tack driver .... literally!

Ctg. black powder guns may or may not be "one load" propositions, but they sure do give a good immitation of it to most users of the Holy Black. The things you'll need to try are:

1. Lube - use a good, proven BP lube like SPG or make up some Emmert's if you like homemade (I do, and use @ 3-4% anhydrous lanolin in mine); DO NOT USE CONVENTIONAL SMOKELESS LUBES WITH REAL BLACK OR IT'LL PLATE YOUR BORE WITH ASPHALT!!!! And that stuff is SO hard to get out! You are better off not to shoot it until you get the right stuff, because you'll be a LONG time getting all that asphalt out, and it does NOT "shoot out" over time!

2. Generally, most rifles (but not all) like the bullet to contact the rifling when you close the breech. This pretty much makes it much less possible for this factor to vary, for one thing, and may also tend to align the bullet a tad better with the bore.

3. If using Swiss, fill to the base of the bullet, but if using Goex, try from .1-.4" of compression, use a drop tube for all loads, and repour any that stack up in a case either higher or lower than the others. This makes all your loads very, very similar or near identical, and this helps accuracy, too.

4. Let the gun, via your targets, tell you what works for YOUR gun and don't let yourself give a fig about what anybody else does. It's more unusual for two guns to like the same loads than it is for two to differ in what they like.

So basically, each gun is a one-off proposition, and there may be "general guidelines" that are more likely to give you "acceptable" results, but you'll be one lucky dude if they work out to be REALLY accurate. Some folks are lucky, but I've never been, so maybe that colors some of my advice? But generally, I've never had a gun that shot the first load I tried the best, or at least don't remember one. And I think I'd remember such a thing, too.

Long stroy short: try your loads varying only one variable at a time. Start out with something like I described and vary each element singly. First outing, you might try bullet touching lands, and loads with the powder just touching the bullet base, then another few loads with +2 gr. and another with +4 gr. Use your compression die on the two heavier loads, and it doesn't hurt to use it just for drill on the lighter one too. Shoot those. Find your best powder charge, then vary your primers, trying those I listed above first. Shoot again with 5-10 rds. of each load, and let your target tell you what primer your gun/load combo likes best. Then try crimp, light crimp, no crimp, again 4-10 rds. each, and let your gun/load combo tell you what it likes there. Then try varying your OAL in .10" increments from -.30" contact to +.30" of solid contact.

This should let you find your gun's "sweet spot" and should keep you in the X-Ring. It's not nearly as laborious as people think, either, and you only have to do this once for each rifle. From there on, just keep using your specific load, and just sit and smile, and after you've cleaned your gun and cases after shooting, just sit and smile and pet it a while. I think BP rifles like that.