Brass Life Cycle Study

[Hoot]

I am about to embark upon a study I suspect some folks may have an interest in and because I love doing this kind of stuff.

A member who appreciates some of the work I've been doing sent me 25 new Hornady cases to play with. They were a random collection, not pre-graded in any way. Interestingly, do you suppose all shipped at 1.70 inches? How about 1.70 -.03 inches? Would you believe anywhere from 1.691 to 1.696 with the average being 1.694 inches. For what they cost, I must confess I expected them to be of closer tolerance than they were, but perhaps I just have high expectations. Anyway, I identified 15 of them that are 1.694 +/- .0005 inches, which is the accuracy rating for my caliper. They will be the test bed.

I will create and update a chart for 15 loads. The chart will contain both fired and resized length and maximum girth just above the web, velocity, AVG, SD and ES for each cycle. I will load one set of 5 repeatedly at what I consider to be a safe, lower charge for the 225gr FTX bullet, 5 at a somewhat middle charge where I previously got a good group and 5 at what I consider to be a safe, upper charge for the 225gr FTX. I don't own a Lead Sled, so despite my own skills being less than stellar, the chart will also have a score assigned to each shot for it's placement relative to the center within a group as best as I can deliver and measure. I may opt to just post images of the groups along with the chart and graphs, rather than meticulously measuring them and let you be the judge. Cases will be grouped in 5's by closest weight to one another. Ditto on the bullets. Rifle will be cleaned prior to each trial, but not in between groups of 5 to reduce fouling shots stringers. Scope POI will not be adjusted. All shots will be preceded by a rifle tip-up to try to keep the powder as rearward as possible. Due to availability, Remington Small Rifle Benchrest primers (7 1/2) will be used. They perform very close to the WSR primers.

Sound interesting? Worth the trouble? Any other metric, easily recorded, that you'd like to see included in the chart? The 100 yard range where I shoot is fairly well shielded from wind and I will strive to shoot under the same conditions as many times as my powder and bullets last up to. Not being retired, this will no doubt take a while to complete, but will be updated immediately after each trial run. why the 225gr FTX? They're the cheapest and the bullet I get my best groups with.

Hoot

[Siringo]

WHAT -- you simply can't take vacation time to provide this to us by Saturday???

All kidding aside -- this will be great information. I would suggest also measuring the diameter of the extractor groove. Another interesting measurement would be the inside base to outside base. These measurements may help provide data where case shrinkage is occurring.

[slash2]

Thanks for looking into this Hoot, I've been curious about how long one of these cases will actually last. I've reloaded my cases countless times, and I'm serious about countless because I haven't counted, (I'm not as disciplined about record keeping as I should be) but I bet some of mine have been loaded well over a dozen times with many having been side crimped multiple times and I haven't had a case failure yet.

Thanks again Hoot, you're a great asset to the group.

[BD1]

I quit counting after I sectioned one at 20 times through the process, (no sign of incipent failure). IMHO the Hornady brass will be like .45 acp, dying from mouth splits, or lost in the grass.
BD

[Hoot]

So, am I just doing battle with a windmill? That is to say, "Yeah they shrink, next..."
My ignorance of the 450b platform is going to show now. I assumed the design intent is that when the lugs are fully engaged, with the base of the cartridge sitting flat against the bolt face, the rim of the case is supposed to be up against the lip of the chamber. Also I assumed that if the case has shrunk to where the rim is say, 20 thousandths short of the lip, that's not a good thing for ignition. I have some brass that has shrunk as far as 1.679 now and still heading south. They do not appear to be structurally failing, just getting further and further out of specification. If the design intent for this caliber is that continued shortening is of no consequence, then spending time chronicling it seems kinda like busy work to no end. I have a few other experiments cued up and could do battle with one of them instead.

"I could be arguing in my spare time." -Monty Python

Hoot

[slash2]

I've not had a problem with shrinkage at all Hoot, I'm finding that I still need to trim about 1 in 5 after a range session, even after many many reloadings.

[Siringo]

Slash -- what is your load?

[BD1]

Only time will tell if the .450B brass will shorten beyond the point of a good firing pin strike. So far, none of mine has. To be honest I haven't checked OAL for a while. The last time I checked they were still all longer than 1.690

Slash, what dies are you using? IMHO it's the sizing that shrinks the OAL of straight wall cases, not the firing.

To be more precise I suppose it's the difference in dimension between your chamber and your sizing die. The more you are moving the brass, the more you will shorten a straight wall case.
BD

[Hoot]

Only time will tell if the .450B brass will shorten beyond the point of a good firing pin strike. So far, none of mine has. To be honest I haven't checked OAL for a while. The last time I checked they were still all longer than 1.690

Slash, what dies are you using? IMHO it's the sizing that shrinks the OAL of straight wall cases, not the firing.

To be more precise I suppose it's the difference in dimension between your chamber and your sizing die. The more you are moving the brass, the more you will shorten a straight wall case.
BD

That's just the opposite of what I'm experiencing. Mine grow back about .003 after resizing. My guess is my chamber is on the loose side as I get a lot of resizing resistance even with imperial lube. I can just feel them squeezing narrower and longer as I cycle the ram. I gain back another .001 if I cycle it 2 or 3 times, rotating the case a third turn each cycle. It does not exhibit noticeably more or less shrinkage with high versus low power loads. I have recycled two other fellow's once fired brass and no two guns yield brass with the same resizing resistance. Go figure... Makes me want to do a cast of my chamber with some cerrosafe.

No one weighed in with clarification on how the round is supposed to fit into the chamber.

Hoot

[gunnut]

Here is something I noticed awhile back working with 284 cases. But, never followed up on it. Plenty of factory brass now. Has to do with extractor groove expanion. viewtopic.php?f=5&t=65&start=0