What does this fire formed brass tell me?

[gifbohane]

I fired my 100 Lake City 223 reloads that I sized to 1.750 prior to firing. Shot it and all 100 still plonk afterwards. After shooting most of them measured 1.752 and some did go as low as 1.749 and a few were as long as 1.1757.

Does this mean that the chamber of my AR 15 is very similar to the case gauge?

Would you trim this brass back to 1.750 again before firing?

Any other significant information that I can get from this?

Thanks

 

[sequins]

.6" is a pretty wide variation. Is that a typo or did you leave the shoulder and neck at the range?

 

[gifbohane]

.6" is a pretty wide variation. Is that a typo or did you leave the shoulder and neck at the range?

Seq-

Thanks … I fixed the numbers

Gif

 

[243winxb]

Maximum trim length , after sizing, is 1.760" when brass reaches 1.760" length, trim back to the 1.750"

The different length is not a problem, unless you crimp the rounds.

 

[gifbohane]

243- I do give them a slight crimp/

 

[243winxb]

I do give them a slight crimp/

A taper crimp would be better then a roll, when brass is not trimmed to all the same length.

I dont crimp for auto or bolt guns.

 

[243winxb]

Does this mean that the chamber of my AR 15 is very similar to the case gauge?

A case gauge measures head to datum . The datum is a point in the middle of the case shoulder.
A fired case is placed in the gage. The location of the case head in the gauge is noted.
A fl sized case head should be same or a slight bit lower, but within the high and low indicators.
Some gauges also check case body diameters, like Lyman.

 

[Rule3]

I fired my 100 Lake City 223 reloads that I sized to 1.750 prior to firing. Shot it and all 100 still plonk afterwards. After shooting most of them measured 1.752 and some did go as low as 1.749 and a few were as long as 1.1757.

Does this mean that the chamber of my AR 15 is very similar to the case gauge?

Would you trim this brass back to 1.750 again before firing?

Any other significant information that I can get from this?

Thanks

But did you resize all of them after shooting and then measure them?

 

[fguffey]

You are measuring from the end of the neck to the case head. You are not measuring from the datum/shoulder to the case head.

A case gauge measures head to datum . The datum is a point in the middle of the case shoulder.

A case gage measures a case from the datum to the end of the neck and from the datum to the case head.

And I wonder; if the datum for the 25/06, 270. 280, 30/06 and 8MM57 is .375" how can it be in the middle or half way between the shoulder/case body juncture and the shoulder/neck juncture?

F. Guffey

 

[FROGO207]

You could get by not trimming until you hit max length and still crimping if you used a Lee FCD. This is one of the things it shines for when working with bottle neck brass. Not having to trim brass to the same length every time. Me, I still find my ammo shoots more accurately without a crimp. You may want to try some that way and see for yourself. Just make sure you have enough bullet tension to prevent setback if you do.

 

[gifbohane]

But did you resize all of them after shooting and then measure them?

Rule 3

No After shooting the rounds I did nothing but measure them for size and plonk. Still haven't sized, deprimed or done anything with them.

 

[Rule3]

Rule 3

No After shooting the rounds I did nothing but measure them for size and plonk. Still haven't sized, deprimed or done anything with them.

Then your measurements mean little to nothing. As 243win in post #4 mentioned the 1.750 is just a uniform trim length (size first them trim) Then after resizing you can measure and as long as the cases are not over the max of 1.760 go ahead and load them, You should not have to trim after every shot.
Brass stretches more when new, as it gets used not as much

 

[gifbohane]

Rule 3- Just to be clear. I sized, deprimed. trimmed the once fired rounds to 1.750, loaded them and shot them.

I then tumbled them and immediately after that I measured them what I reported above and was just surprised that they had not expanded more in length and width and still plonked. They have been fire formed and seem to need no further trimming.

 

[Blue68f100]

I have several min spec 223R chambered AR's. For simi-auto's you need to full length size for reliable feeding. My brass will do the same thing but it's a hair long <0.001" The only way I know is I have a chamber gauge cut from the drop off of the barrel blank with the same reamer. I can not detect the length by my running my finger over the case gauge. The only way to know it's there is with a straight edge across the top. The only way to keep them from stretching so they will chamber a couple of times before FL sizing is needed again, is to shoot the gas system off. And use it like a std bolt operated gun.

 

[Demi-human]

was just surprised that they had not expanded more in length and width and still plonked.

It takes about three full power firings, without sizing, to get brass fully expanded to your chamber’s diameter.
Lapua brass also resists lengthening remarkably. It took six loadings before it needed trimming. Which kind of dismayed me, as it came a bit too short for me when new.

Much of the trimming and expanding is from the resizing cycle. If the case is not excessively sized for the chamber it won’t have so much brass flowing to the neck, needing trimming.

Even though it “plonked”, after sizing it still may increase in length and need trimming after.

Any other significant information that I can get from this?

Well, it seems like your rifle isn’t over gassed, I suppose. Since they weren’t stretched.
Also, I would wager, you had fun.

Because you directly tumbled them, rather than rinse them first, I suspect your shooting area is dry, perhaps covered, with a flooring of massive non-loose material.

As you refer to them as “Lake City 223 reloads”, I surmise they are 55 grain bullets. FMJ being the most inexpensive, and that you are crimping them, I’ll make my guess for those, but prefer to use the soft points myself.

Would you trim this brass back to 1.750 again before firing?

No. I trim my .223 every single cycle, and to the maximum case length, which is still short of the end of the chamber by eight thousandths, which is double what I’ve seen my stretchiest case lengthen to after firing.

That tends to make a lot of work though...

 

[Walkalong]

Some brass cases stretch more than others. I trim after every firing with .223 with a WFT trimmer, not all cases get touched by it, most do.

"Fitting" the chamber is usually a discussion about sizing the body/shoulder. Case length is about being to long overall regardless of how it was sized. Poor sizing can mean poor case life, or cases that won't chamber.

Being too long for the chamber in the neck/case mouth can mean a pinched case and dangerous pressures. "Plonking" a .223 case means nothing.

You can get a case gauge and check your sizing and case length with it. A great tool to help reloaders stay out of trouble. A Wilson checks the shoulder position and length, a Sheridan also checks the body diameter.

 

[gifbohane]

Walk

I have one of those LE Wilson 223 case gauges... and use it on every cartridge before and after loading the bullet.

Have you seen a good video of proper use of same? Seems to me I usually underutilize, rather than maximize, my toys.