.45ACP case length and impacts on accuracy

Previous thread got shut down due to misbehavior, apparently. There was some good info there, which was lost, unfortunately.

Thoughts, or more importantly, data?

Damn, what did I miss?!?

Dave

Dcforman wrote:Damn, what did I miss?!?

Dave

TLDR: case length may or may not matter, incomplete data/different testing methods. Basically.

I'd guess there may be a self compensating effect that we don't understand or can't measure. A long case shoots well for one reason, a short case for another, and the tradeoff happens between the two without our knoledge.

Say for example initial internal case pressure was the important factor, a long case may meet whater psi by having more neck tension, and a short case my get close to the same psi by having less internal volume.  

Or another hypothetical example with two factors; a lightly crimped bullet in good condition over a poorly ignited charge from the low crimp may well be indistinguishable on target from a lightly mangled hard crimped bullet over a charge that ignited well.

Or it just might not make a difference.

There is some data in this forum from Jerry Keefer on this topic. 

Around the same time as he was sharing his data, I had a match where I was 20 rounds short on 45 ammo s o I took 20 rounds of ammo with split cases, some of which was so worn that you could hardly see the headstamp and used it in slow fire. You all know I'm no John Shue, but I still pounded a 96...and that 8 (and the rest) went right on call. The other 10 were a 94. No flyers.


There is a hell of a lot more to gain in training, mental management, dry firing, and conditioning.

Founder wrote:There is some data in this forum from Jerry Keefer on this topic. 

Around the same time as he was sharing his data, I had a match where I was 20 rounds short on 45 ammo s o I took 20 rounds of ammo with split cases, some of which was so worn that you could hardly see the headstamp and used it in slow fire. You all know I'm no John Shue, but I still pounded a 96...and that 8 (and the rest) went right on call. The other 10 were a 94. No flyers.


There is a hell of a lot more to gain in training, mental management, dry firing, and conditioning.

I have missed culling split cases and found no difference when shooting. To me overall bullet length is more important than brass case length. 
Shoving an over length loaded cartridge into a chamber jamming the bullet into the lands and grooves of the barrel changes breach pressure and will cause a flier quicker than anything else I can think of. 
You can feel the difference when it is discharged.

Founder wrote:John Shue

Q: How many times do you have to win Camp Perry to get your name spelled correctly?

A: Apparently at least one more time than Jon Shue has.

If we want people to test and post results we should more appreciative for the time and money they put into getting the results.

Something like this happens and makes me less willing to share what I find.  Sometimes it is better to not hit SEND.

Not everyone understands the scientific method but we can help guide them.

Maybe next time we suggest a similar test instead of telling them they did it wrong. If they are willing to spend the time and money on primers and bullets they might do the test and post the results for us all to see. Another option is if someone is willing to provide something to test to someone will and maybe post the results.

From what I remember, Chase's test was exactly what the topic title said it was. It demonstrated the effects on case length, and case length only, by using the same headspace on each round from a barrel tester. 

I don't know that his intended test was to determine "1911 case length and impacts on accuracy", which some interpreted it to be a test of.

Just a thought...

I’m not 100% sure exactly what the headspace was set to during the test.  That data was destroyed by the OP prior to me deleting the thread.

I did propose a test method of 2 series of 7 ten shot groups to be fired one series with cases at long length and one series at minimum case length.  The headspace would have been set for the longer cases.

I’m not fully convinced that headspace in a pistol truly affects accuracy.  I know in rifle that benchresters no longer neck size only.  And an auto loading pistol is not like a rifle at all.  But a series of tests might put that notion to bed.

Wobbley wrote:I’m not fully convinced that headspace in a pistol truly affects accuracy.

If history is right, the 38 Super is an example of the importance of headspace. The 'old' guns were chambered to headspace on the semi-rim, and was reported to be the cause of poor accuracy. Accuracy improved when the barrel was chambered to headspace on the case mouth.

The original report is in the 1961 American Rifleman. Rollins, John and Shockley, Richard 1961. Accurizing The Colt Super .38. American Rifleman, 109 (6), 40-41.

Looks like this is going down a rabbit hole comparing a straight wall case to a bottle neck rifle cartridge.
It has been proven that Rim thickness in pistol cartridge case manufacture is one of the main causes for inaccuracy for head spacing off the rim instead of the case mouth. The reasoning for the 38 Super and .38Spl head spacing off the case mouth in 1911 semi auto pistols.

I've always assumed case length was one of the many things in bullseye that if you think it will affect accuracy, then it does. If you don't think it matters, it probably won't.

Dcforman wrote:Damn, what did I miss?!?

Dave

Apparently someone misbehaved, David.

You've shot shoulder-to-shoulder with me at various venues. Have you ever known me to misbehave?

Stop. Don't answer that.

Another variable to consider… generally, all things being equal longer cases will be newer brass with less firings, and shorter cases will have more firings and therefore more resizing and be work-hardened (unless you are annealing your pistol brass… im sure theres at least 1 person on this forum that has done it).

My educated guess, based on the excellent accuracy observed with both long and short brass, is that softer brass shoots better, not necessarily longer. Brass minimally resized (i expand and resize with .45 colt dies, barely squeezes the brass either way with no belling of the mouth) gets less work hardened and lasts far longer… does that equate to more consistent groups? Conversely, if you bust your brass down violently with an undersized die then blunderbuss out your case mouth repeatedly… you get where im going with this.

New starline is usually .893, and most of mine has shrunk into the .880s, i would be curious to pull bullets from unfired rounds of the usual suspects headstamps and see what other new brass measures.

Fired brass expands radially and hence becomes shorter. I have heard that new brass was a key to the best longline ammo but failed to understand all the reasons why. Perhaps New star brass is best because a) it’s longer,  b) smaller diameter so it can settle up correctly in the chamber , and c) hasn’t workhardened

bruce martindale wrote:Fired brass expands radially and hence becomes shorter. I have heard that new brass was a key to the best longline ammo but failed to understand all the reasons why. Perhaps New star brass is best because a) it’s longer,  b) smaller diameter so it can settle up correctly in the chamber , and c) hasn’t workhardened

I had some new starline brass and when I weight sorted it, it was two distinct lots and one was more than a sd lighter than my motley range brass collection.