Trying to pin down some inconsistencies in OAL bullet length. I currently am using a lee turret press with Lee Carbide dies for 9mm using 115g extreme rn bullets over 4 grains of tight group.

According to Hodgden COL should be 1.100 I have the die set at 1.004. Some will occasionally be 1.106 and even 1.107. Without adjusting the seating the next rounds have been back to the 1.004 and then every so often back out to the above ranges.

My conclusion is the bullet not being exact in measurement, any thoughts?

Looks to me like you are still within suggested tolerances with your loads. Brass height, thickness or thinness all effect oal.
For advice on using the Lee Turret press Rule3 is very knowledgable on that subject, maybe he will chime in here. Make sure your dies are clean and use a full stroke of the handle.

A lot of manuals have this and that for a OAL.

Some pistols need the short 1.09 to function............
My C9 did not get good results with the Extreme plated bullet
until it was at 1.12" oal.

At the OAL of 1.10" Green Dot at 1012fps got 2.91" and CFE at
1172fps had 1.79" at ten feet off the sand bag with a 115gr.

At a OAL of 1.12 the same loads shot under 1.08".
At a long 1.14" OAL I had four powders shoot under 1" with the plated RN bullet.

Each weapon is different.
If yours likes a short OAL, great.

Based on the brass I'm using, oal will almost always vary. I set up my oal for the brass I have the most of.

After upgrading to the 4 hole Lee Classic Turret and using separate seating and crimping, my COL stayed within +/- .002". Not sure you can get much better than that using untrimmed mixed headstamp brass. I was thrilled with those results and I also use Xtreme plated in 9mm, 40 S&W and 45 ACP. Just my 2 cents....

Using a Redding T-7 and RCBS dies O.A.L. will vary +/- .002 for me also with pistol rounds. I think that's pretty good using untrimmed mixed brass.

It's a Handgun Caliber, don't sweat a variation of less than 0.010 inch because it won't have any noticeable effect on accuracy or pressure.

As for the cause, just consider the variations of all the components involved, bullet length and profile will vary slightly, the clearances in the toggle links, ram, and shell holder will stack up and the end result is a variation that typically runs somewhere in the range of +/- 0.003-0.005 inch.

Unless the seating stem in your die actually hits against the tip of the bullet (not very likely), I agree that the small variation you're seeing is most likely due to the difference in bullet profile from mfg. The small variation you are seeing shouldn't be a problem.

Why not trim all of your brass to the same length?

If I was loading for bullseye accuracy I could see trimming the cases. Loading lots of pistol rounds I just don't see the need. I don't have problems with feed, accuracy or anything else caused by case length.

Because it's generally a waste of time.

It's not like you can take a bunch of mixed-headstamp, mixed-usage brass, trim it, and expect match performance. Does it get better? Maybe, maybe not.

BE shooters usually use unfired, trimmed brass for match ammo. Maybe once-fired. But after that, it either gets pitched or goes in the practice bin.

COAL is the distance from the tip of the bullet to the base of the case. It's determined by (but not the same as) the distance from the contact point of the bullet with the seating stem to the surface in the shell holder that supports the case. It has nothing to do with case length, brass or rim thickness, and won't be affected by trimming or segregating brass.

Variations in COAL are normal and are due to variation in bullet ogive shape and loading technique. Your variations are acceptable for normal shooting; 50 meter Olympic slow fire is another story!

If your using a die that seats AND crimps at the same time, brass length and thickness most certainly does affect COAL!!!! This is mostly eliminated if you trim your brass!!!

Do I advocate trimming pistol brass... NO

Do I advocate seating and crimping in separate steps... YES

Will the OPs groups or firearms functionality be affected by the variations he's seeing, its doubtful....

As a note;

Hodgdon does not have data for the Xtreme bullet.

It only list the 115gr Speer Gold Dot and............

a Lead Round Nose bullet.

Take care and get the correct data.

I have an LCT been using it for years. It's not the press or the bullet measurements, it's your human condition. We aren't robots we can only try to be as consistent with our press strokes as we can. Your COAL is actually pretty good for pistol. Measure some factory practice ammunition some time, yours is likely better than factory. I find that seating and crimping separately and using the same headstamp for a run is helpful. I get a more consistent feel for the brass when it's all the same headstamp.

__________________
Trucks and guns.