Making the most of a good rifle

[Love Life]

Also, might I suggest an actual drawing board for your tests and notes? It allows you to stand back and see the whole picture at once instead of flipping through pages. I currently have one up on the garage wall while I shoot coated boolits through as many different handguns as possible with both standard and polygonal rifling.

[runfiverun]

could come from the faster powders.
the trick is when does the shove come and when does it let off.
do you want muzzle blast affecting the release, or do you want to allow the boolit to get further down the barrel before being pushed hard.

[Love Life]

Yep. Stuff like 2400. Key is to use the 2400 for appropriate load levels. At 1750 fps the pressure is still low enough to allow decent accuracy. If I tried to go 2100 fps with 2400 the accuracy wouldn't be there, he bullets would be damaged enough on ignition to make it not worthwhile.

Trying to use a powder like RE 15 for full pressure loads will spike pressure a bit faster than I want. The RE19 will slow that down just enough to are the bullet more gently into the rifling. I also can get the most from a slower powder by having a longer than normal barrel.

2400 is actually fast in the grand scheme of things. At least according to the burn rate chart it is.

[btroj]

Also, might I suggest an actual drawing board for your tests and notes? It allows you to stand back and see the whole picture at once instead of flipping through pages. I currently have one up on the garage wall while I shoot coated boolits through as many different handguns as possible with both standard and polygonal rifling.

Handy thought of that. Makes sense though. Lets you see things side by side and you might notice someone you wouldn't have otherwise.

Good idea

[btroj]

could come from the faster powders.
the trick is when does the shove come and when does it let off.
do you want muzzle blast affecting the release, or do you want to allow the boolit to get further down the barrel before being pushed hard.

And how much of that is affected by barrel length? Mine will be around 28 inches so pressure has more barrel to drop off before the bullet leaves the muzzle. Totally different than what a 20 inch barrel might want.

[Love Life]

could come from the faster powders.
the trick is when does the shove come and when does it let off.
do you want muzzle blast affecting the release, or do you want to allow the boolit to get further down the barrel before being pushed hard.

If the crown is cut right, shouldn't release (from the muzzle) be stable across the spectrum?

[btroj]

If the crown is cut right, shouldn't release (from the muzzle) be stable across the spectrum?

Should but reducing muzzle pressure could make a slight difference. If my crown isn't right I know who can fix it.

I think Run is also looking at the relax point where the pressure drops below the level needed to fully obturate the bullet into the bore. He finds that a small lune smear often is found there, right Run? Something else to look at when do pairing burn rates. Barrel length makes a difference here too.

[Love Life]

I definitely agree that barrel length makes a difference. However; in getting the most out of the rifle, dropping to the old standby of 2400 seems kind of...I don't know...meh. Most of the rifle loading members here (who load with cast boolits) make that combo work, so it really wouldn't be a work out at all.

Pushing the envelope is where the learning will come in. They aren't my rifles, so all I can do is put forward my opinion.

So why would a lube smear be found at the relax point? If indeed that does occur, wouldn't a slow powder that pushes the bullet the entire time down the bore (no relax point) eliminate that?

What is the relax point? From what you posted it is the point where pressure drops below the level needed to fully obturate the bullet? Interesting. So would it be better to use something that keeps that pressure up during the entire trip down the barrel?

[btroj]

The 2400 would be no challenge at all. It would be used for times when I decide I don't want the noise and recoil of a 2400 plus fps load. Sometimes it is just fun to go pull a trigger.

The relax point, as Run calls it, is something new to me. My understanding is just what you said, where the pressure no longer fully obturates the bullet. The smear is because the lube is also held under pressure and at this point a small amount can escape the pressure and get left there.

Maybe we can get Run to chime in and more fully explain.

And yes, keeping pressure up the the trip down the bore reduces relax point troubles but increases muzzle pressure that can also be a problem, or so I am told.

In the end it all comes down to finding a balance.

[Love Life]

I don't understand. Leaves lube there? Doesn't the boolit impart lube the entire way down the bore? It's not like the boolit is shrinking at that point...or is it?

I mean once a bullet is obturated it's obturated...right?

[btroj]

Not entirely. If it was a soft, almost pure lead bullet then yes. A harder alloy has some spring. It will obturate under pressure but when pressure relaxes it will spring back to the initial size.

This is why most fire lapping write up suggest a very soft bullet. It squeezes in a tight spot and stays that size so it removes the tight spots. A harder bullets keeps riding the bore up and down the tight and loose spots so it polishes but doesn't remove tight spots.

What happens when we size a hard or soft bullet thru the same size die? They don't come out the same size, do they?

Think of annealing brass. It changes the final neck diameter, doesn't it? Has to do with spring back differences between the harder or softer brass.

[Love Life]

That makes sense. Now once the relax point is reached, and the boolit contracts, it has lost it's fantastic boolit to barrel fit. So, in my mind, keeping the juice on until the boolit leaves the barrel would be the way to go...I think.

[geargnasher]

Speaking of neck tension and neck expanding dies, here's something I started pondering a couple of years ago: Elasticity.

Cartridge brass is flexible, but it is also malleable. Squeeze it a little, it bounces right back. Squeeze it more, it stretches and bounces back much less. Anneal it, it loses a lot of its flexibility.

Sometimes we need hard, springy necks to improve boolit guidance, sometimes we need the brass to just blow up like an old sock and let go of the boolit with minimal influence on it. Sometimes we need a lot of neck tension to improve ignition or for mechanical reasons, sometimes we need as little as needed hold the boolit.

When we finally get worked out the thickness, preferred state of anneal, and tension for a particular gun, what are we going to do to prepare it for the next loading to minimize working? Also, does the requirements of the rifle system allow us to work within the elastic zone of the brass, or must we squish it past it's flexy limit to a smaller size to regain the tension needed? Are our necks of sufficient uniformity to allow effective use of a bushing die, or do we need to size a bit smaller and expand for uniformity? That all depends on the components and system, but generally I like to finish with some sort of expander, even if it's not doing anything except letting me feel how much grip the neck has on each case.

Here's an example: 7mm-08, brass made from '06 or .270 Win. Necks formed from the shoulder of the parent case, very hard, very tight clearance in the chamber. I made tools that would give 1.5 thousandths interference fit with the boolits. After firing, there was still 1.5 thousandths interference fit. The necks were hard, thick, and VERY springy. So, even with loads cooking along at over 2600 fps, the original VLD chamfer I used was all that was needed to seat boolits after every firing. No prep necessary, just deprime, clean the brass, reprime, charge, and poke a boolit into it. Five firings later not much had changed, no neck splits, only one or two cases showing odd springback out of 30.

Most of the time, that situation doesn't happen for me. I need to scrunch the necks a bit to get the tension the gun likes after each firing. So, I have to go about a thousandth or so UNDER what I need with the sizing die to allow for springback (this number varies greatly of course), and guess what? The necks usually don't all spring back the same. That's when I use the expanding mandrel to sort by state of anneal. The softer necks get grouped and fired more and the harder ones rested, or the soft ones worked in a factory FL rifle resizing die a few times until they match the hardest ones in the batch. Then I use the "finish" expanding mandrel to uniform the necks. How much to size down and now much to stretch them out again depends on the non-deforming elastic zone of the brass. Keeping under two thousandths interference fit in a bottleneck rifle cartridge generally makes it so that seating a boolit doesn't permanently stretch the brass when seated, but is still within the brass's elastic zone. This is ideal IMO, you can pull a boolit and the neck pops right back where it was, very consistent way to hold a boolit.

RCBS makes good expanding dies, and one can customize some of the other "M" style dies to do exactly what's needed, even flare a bit as required. Speaking of flare, I like just enough to get about 2/3 of the gas check to sit inside, and about 10-15 degrees of flare angle.

Gear

[btroj]

For belling I agree, get the check started smooth and no more.

So when sorting by neck tension it is all by feel? Sort of gauging the effort required to expand the necks? Interesting.

I also find it interesting that you end up with some cases being fired more times than others. Makes me wonder if some is because of differing hardness in the body of the parent brass that is now your neck?

Just shows that Bass was right, it only matters when it does. Key is finding when it does and what to do about it. Well, that and observing that a difference existed in the first place.

The devil is in the details, isn't it?

[geargnasher]

That makes sense. Now once the relax point is reached, and the boolit contracts, it has lost it's fantastic boolit to barrel fit. So, in my mind, keeping the juice on until the boolit leaves the barrel would be the way to go...I think.

Lube affects this to a very large extent. Using alloys that are springy is important, too. When the boolit goes through the throat it swages a bit, but maybe swage is the wrong word, maybe just gets squeezed like a balloon. When the pressure falls off, the obturation is maintained by the stored compression force of the boolit, like a spring. Also, the barrel is a spring, opening some under the pressure of the boolit and closing behind it, snake swallowing an egg syndrome. If the lube doesn't roll with the punches, it gets smeared behind as the sliding speed increases past its limit to flow. It's all a balance, just like a race car engine where each part must be tuned to work just so with every other part, the available fuel, air, and class rules.

Gear

[btroj]

Balance is sort of the key in all this, isn't it? Too much of a good thing isn't better, often it makes things worse.

[Love Life]

All this being said in this thread I have one question. Is the juice worth the squeeze?

[btroj]

Yes, it sure is.

Is there anything more satisfying than making a system work? Identifying problems, coming up with solutions, and seeing them thru?

Like I tell my daughter, anything worth doing is, by nature, difficult. Easy to do stuff is not very satisfying as anyone can do it. Accomplishing the difficult is what makes us different.

[geargnasher]

I like to feel the spring of the necks when expanding and when seating the boolit. The Forster seating dies mask the seating feel a bit, but it's a good trade-off. Sorting into batches doesn't make for even counts to be fired for groups, but when you can sort into three piles, shoot three small groups, and overlay the targets to find the aggregate size is double, or was half of what you were doing before when not paying attention to neck tension, lightbulbs start to come on.

I've use beam-type torque wrenches before, but once I got tuned in on the feel of the press handle, that has become my method. Every once in a while you'll find a dud case, one that just won't give good tension. Often, it will have a soft spot in one place that will show up when you check concentricity after seating a boolit. One time I took three duds from a batch and marked them. I shot some good groups, then fired one of those marked ones into the group......FLYER. I says Ahh---HA! It DOES matter! That's when I started paying very close attention to neck tension uniformity.

Gear

[Love Life]

With balance being the key, will the results be transferable? Is this NASA level knowledge only realized and benefitted from in custom rifles or can billy joe bob take the lessons learned here, fill his favorite cartridge with 'splody powder, seat is best cast boolit, and go get real jacketed performance.

When I smoke out the barrel on my rifle...again, I'll throw the 308 barrel back on. It is chrome lined and stuff and mebbe I can join the fray, albeit with a 308.

What is good for the goose (lessons learned here) should transfer to being good for the gander.

Now, neck tension, perfect brass, etc has been discussed. How are you going to get near perfect boolits? I wonder if cast and lubed boolits run into a swage die (so lube is retained, but voids and stuff eliminated) would be the ticket on that front.