Another Variable For Us to Lose Sleep Over!

[918v]

While trimming my 9mm brass, I found that some cases were very difficult to slip over the cutter pilot, while others slid on loosely. This tells me that some rounds will have more case tension on the bullet shank than others, and this will surely affect accuracy.

So I decided to sort by case tension.

Where can I get some nice plug gauges? I don't want Chinese. I want Made In USA (by undocumented workers).

[MakeMineaP99]

How fat is your wallet? American is $$$.

McMaster-Carr, MSC, etc. probably have what you want.

Have you determined run out in the 210 yet?

[ISUSteve]

Nothing like McMaster Carr to drain your wallet.

[918v]

There is no runout.

That sucker is dead on, when eyeballing it anyway.

[ISUSteve]

I've noticed this the first time I reloaded. When is too much accuracy for a pistol. I mean the only time you can really see how well a pistol can shoot is shooting off a bag or rest. Thats cheating. Nobody can hold a handgun steady enough to have the guns accuracy into play. I've put 5 shot groups into 4" at 25 yards with my P3AT off a bag. Theres no way I could do that standing. Isn't sorting by neck tension a waste of time?

[918v]

But that is the focus of my reloading. I know and accept that I will never be able to shoot a .5" group off hand, but I still want my gun to be capable. Look at it this way:

If your handload shoots 1" groups at 15 yards, and you add 4" of shooter error, then you can hold 5" groups at that distance. If your handloads shoot 3" groups, then your target will look like a shotgun pattern. Why even shoot at that point?

[Oreo]

I like the way you do things 918v, but Lord knows I don't have nearly the stamina to chase it the way you do.

[BigSlick]

Gimme a day or two an I a get ya da info.

I got some last year from Southwestern Gauge in DFW, got a few dat are certified -.0001

Cheap to, like $2-3 each

They a do lil orders if ya don't want a set

Top quality, Made in USA by undocumented guest workers

[Tailgunner]

Gauges wouldn't be your beat answer, What you need is a custom ground (with a lead in taper) pin mounted to a strain gauge to measure the grip (this will be capable of measuring both insertion and withdrawl force). Drive it with a bi-directional hydrolic cylinder that's ben fitted with a shell holder and a travel rate in the .063"/minute range.

[ede]

i was thinking along the same lines as tailgunner, but didn't really have a good handle on what you'd need like he does. my second idea would be to have a gauge made with a lead in then a go no go, or more likely a no go go step on the pin gauge. i think all things considered this will be something i never worry about.

[Oreo]

Tailgunner's thinking fancy. You could accomplish the same thing in a simpler design.

[918v]

Thank You for your responses. I was thinking of plug gauges rather than a strain gauge because they would be a simpler endeavor. But please tell me more about the strain gauge/neck expander thingy. Where? How? That would be the ideal solution. K&M makes a seater with a strain gauge, but seating 9mm with an arbor press? Hmm...

[918v]

OK, I googled strain gauges and found this amongst other things:

http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=1311092

WTF is the world comming to???

[colorado4wheel]

Just use the Lee cutter as your gauge. Any tight ones get thrown in bucket. It's about 10%. Before you do that I would run then through the Dillon Press. It's not really a issue with that powder measure because it sizes the case from the inside when you throw the powder. Another good reason to go Blue.

[creophus]

Wow 918, you should be your own gunsmith, then you'd be in heaven!

[AdamN]

Even gunsmiths think he's nutso, a quality 9mm handgun, I mean QUALITY will do 1/2" @ 50 yards with off the shelf unsorted reloading components.

Your time is better spent practicing if you want YOUR groups to improve.

What 918 states here has a lot of merit.
""" If your handload shoots 1" groups at 15 yards, and you add 4" of shooter error, then you can hold 5" groups at that distance. If your handloads shoot 3" groups, then your target will look like a shotgun pattern. Why even shoot at that point?"""

The thing is about any decent gun will shoot 1" at 15 yards with a good handload.

Ive seen several Glocks off the shelf get under 3" at 25 yards with good old mixed brass and bulk bullets.

If the gun is shooting 3" at 15 yards youve got other problems,

[craig110]

If the gun is shooting 3" at 15 yards youve got other problems,

That was my thought as well when I read the post. Hyper-tweaking (IMO) the reloads seems like optimizing the wrong element in the total grouping = base gun type + barrel length + barrel condition + ammo quality + shooter equation if the current grouping using carefully crafted reloads is 3" at 15 yards.

[ISUSteve]

If your handload shoots 1" groups at 15 yards, and you add 4" of shooter error, then you can hold 5" groups at that distance. If your handloads shoot 3" groups, then your target will look like a shotgun pattern. Why even shoot at that point?

If a shooter could shoot 4" groups and the handload groupings were 1" groups, wouldn't the max error be 3", not 5"?

[Mogollon]

918V,
Do you size your cases before trimming? Have you measured the case wall thickness at the neck to compare uniformity?
Inquiring minds want to know...:ow:

[AdamN]

If a shooter could shoot 4" groups and the handload groupings were 1" groups, wouldn't the max error be 3", not 5"?


Every shooter has a "wobble" area, some are better than others.

In theory if you had a 4" wobble and the gun was 100% accutrate every shot would be exactly where aimed, and you would have a group exactly like your "wobble" a 4" group.

If the gun shoots 1" you have no control where that shot will fall in the 1" area. It could be high, low, left or right.

Adding that error to your 4" group you would need to go the 1" of gun error added to the shooter error, and you would eventually end up with a 5" grouping if enough shots were fired.

Some shots may fall inside the "wobble" area but some will also fall outside of the area.

[craig110]

If a shooter could shoot 4" groups and the handload groupings were 1" groups, wouldn't the max error be 3", not 5"?

You're right, if the '4" groups' refers to the end result seen on the paper. The way I read the post, though, I think what he was describing in the example was adding together the group size of the ammo if the gun was strapped to a shooting rest (1") to the group size he would get if he was shooting perfect "one ragged hole when in a rest" ammo (4") to get an effective realized group size of 5".


ETA: Yeah, like ANeat said since we were both replying at the same time!

[AdamN]

Here are a few graphic examples Ive pulled from another site. Craigs got the idea

These are 50 yard targets but the principle is the same

http://i64.photobucket.com/albums/h165/aneat/Targets/lla02.jpg

http://i64.photobucket.com/albums/h165/aneat/Targets/lla03.jpg

http://i64.photobucket.com/albums/h165/aneat/Targets/lla04.jpg

[craig110]

I see there is no "Figure 1." Is that the one where the white lines entirely cover the paper? If so, it might look mine. :banghead:

[AdamN]

Here is the complete article http://www.bullseyepistol.com/cstomgun.htm

[918v]

918V,
Do you size your cases before trimming? Have you measured the case wall thickness at the neck to compare uniformity?
Inquiring minds want to know...:ow:

Yes, I size them before trimming, otherwise they won't trim evenly. When a case sits in the chamber, it is not centered with respect to the bore centerline. It is being pushed against the left side of the chamber by the extractor. When it fires, it expands unevenly, with one side of the case bulged more than the other. onsequently, the case mouth is out of square with the case body, so trimming at that point is not a good idea. Besides, fired case measure about .743" and I trim to .750" right now.

I have no way to measure for case wall thickness uniformity. A dial caliper is not the right tool for this, and benchrest measuring tools don't work with the 9.

[colorado4wheel]

What powder measure are you using?

[Mogollon]

918v,
I assume by benchrest measuring tools you are refering to a dial indicator? If you could set up any diameter mandrell to slide the case over so the upper inner side of the case is resting solely on the mandrell, then you could align the arm of the dial indicator onto the case, zero it, and slowly spin the case to check for variation.

[ISUSteve]

I don't know what I was thinking. I was only taking half of the error, but once you add the error to the other side, it does become 5".

[918v]

What powder measure are you using?

RCBS Chargemaster 1500.

[918v]

918v,
I assume by benchrest measuring tools you are refering to a dial indicator? If you could set up any diameter mandrell to slide the case over so the upper inner side of the case is resting solely on the mandrell, then you could align the arm of the dial indicator onto the case, zero it, and slowly spin the case to check for variation.

But that would be alot of work, and i wouldn't be able to correct the problem. I would just have to cull the case.

I suspect that case tension may be the cause of fliers. Nearly every case slid over the pilot. Some gave little resistance, come none at all, while others just refused to slide onto the pilot. I'm gonna run a test where I'll load a batch using a zero resistance brass and a batch using a super resistance batch to see if POI shifts.

Let me tell you a story:

I bought a bag of Magtech brass once. I was excited to get $500 new cases for $28. I proceeded to load-up some test loads. To my dismay, my starting loads were blowing primers. I found these cases to be excessively hard and it was difficult to expand/flare the case mouth. it was equally difficult to seat the bullets without mangling the bullet nose. I ended-up trashing most of this brass.

I believe that brass hardness and case tension on the bullet do in fact influence the pressure curve and POI.

[MakeMineaP99]

I believe that brass hardness and case tension on the bullet do in fact influence the pressure curve and POI.

Naturally. However, you have to realize the variables you are after are all but negligible outside of lab conditions.

[918v]

Well, I am seeing groups where four shots are in a dime-sized cluster and a fifth a quarter-inch or a half-inch away. I think the flier may be due to a case that has different properties than the rest. Isolating these weird cases is what I'm after. I just want to eliminate as many variables as possible.

So far, among the sorted cases, I see different degrees of case tension completely unrelated to case weight. In addition, I see that primers are being flattened during seating to various degrees despite all the primer pockets having been reamed to the same depth and the seating pressure being the same. This means that there are differences in anvil height between individual primers, another freaking variable!

So I assembled some rounds just now, sorted them for case tension and primer anvil height. I believe I now have rounds that are pretty much identical: Case weight is within .1 grains. Case length is within .001". Powder charges are within .1 grain. OAL is within .001". I guesstimate case tension is similar and so is primer anvil height.

[AdamN]

Well, I am seeing groups where four shots are in a dime-sized cluster and a fifth a quarter-inch or a half-inch away. I think the flier may be due to a case that has different properties than the rest. Isolating these weird cases is what I'm after. I just want to eliminate as many variables as possible.


A few things you could do, get a Ransom rest, hell if you were close to me Id let ya borrow mine....or are you using a Ransom rest or some other mechanical rest??

Another , fire about 10 or even 20 rounds for a group. Ill bet those "flyers" will dissappear and the actual group will slowly enlarge to a point where youre seeing the actual accuracy of the gun/ammo combination.
The group will grow to a point and stop.

One more thing is, take a Lee loader or even a single stage press to the range and try a group either loading the same 5 cases or even loading a single case several times and see what the grouping is.

You would eliminate the variable of the brass anyway.

[MakeMineaP99]

Why not isolate the cases from the flyers like in rifle shooting and continue to work with the good cases?

[918v]

I'm shooting from a bitchin' mechanical rest, but it is no Ransom. I gotta get me one of those.

I thought about shooting a longer string, so I tried a 15-shot group. I had 12 in a group you could cover with a quarter and three fliers that opened the group to one inch center to center. Pissed me off.