The 120-123 class won’t group what is going on

[Mesa1978]

I have a Lilja barrel in a PF upper that puts 123's in a 1/2 to 3/4" group. hrug

[Bobke]

The bullets you’ve mentioned have widely different base to ogive measurements, so if you’re only loading to overall length without consideration of distance off lands, would expect less than optimal results. Recommend the Hornady tool to determine distance from lands.
And I would not ‘get after’ my barrels with JB Paste unless the barrel tells me it requires so. BoreTech makes some very effective carbon or coppers cleaners, and once a barrel is properly broken in, see little if any need for JB or further aggressive cleaning.
Have had exceptional results with AR Comp and RP7.5, CCI 41 or 205M’s in both sorted Hornady or Lapua brass. I have same AR319 barrel and use 123SST and AR Comp for hunting and 123CC, Scenars or Sierras off season. It’s a good barrel-don’t give up on it just yet-it will shoot.
Run a seating depth test with Comp in the low 27gr range and will bet you find success, but you need to be aware of distance to lands for the process to succeed, and be repeatable.

[Dt219]

If I knew how to upload pictures from an iPhone I would show all kinds of pix but i don’t think it’s possible

[grendelnubi]

It’s mostly just shot gun printing. Once in a while it will put 2 close and set the 3rd one out bad but I’m certain it wasnt me. I’d even redo the group just to see and it would be the same outcome or even worse. Hard part is finding projectiles !! I can get most powders with ease although some is pricy they are on the shelf. I have plenty of brass and primers. Is it against the law to try normal small rifle primers Instead of the 450s ? My uncle is shooting a 6arc with 400s middle of the road charges and hasn’t seen any problems using them. No failures no slam fires and no piercings

In my experience, flyers are typically powder charge issues and usually occur at the higher charges. I gave up on CFE because of the flyer issues and have not had any issues since.

400's will work, they are not as thick walled as 450's but will work.

[myrifle]

Lilja barrel with under 200 rounds down the pipe can’t group any heavy bullets. 120 eldm, 123 smk, or hornady black 123 eldm. Bought the barrel new to zip the light bullets and it does with ease both 85gr Sierras and the 90gr tnt bullets across different powders and charges its almost like it can’t shoot a bad group. So I thought hey let me see what the Grendel is all about. Picked up some 120s and already had the 123smk from a 260 rem. I had. Well long story short I have tried benchmark for the hell of it, varget and lever with the 120eld about a 1.5in is all I could muster from those powders. So I picked up some cfe223 this wknd and tried it with the 123smk. Same result about 1.5in groups. Tried the hornady blacks. Maybe 1.25in group. Try different pills or powder ? It’s about to get old burning through stuff and combos that should group better than it is. Bumping shoulder back .004 full length hornady sizing and seating dies. CCI 450 primers, starline brass. Prob contacting Lilja in the morning.

Well did you try to work up a load based on what your barrel and chronograph told you it wanted or did you just pick a few charges ad one seat depth and go oh well it doesnt like 120 class weight bullets?

Not being a a@$ but your OP post doesnt tells us anything about what you tryed in the gun for a handload work up.

[Dt219]

Well first thing I did not use a chronograph, and next thing I went from the middle of a charge to book max in .3gr increments with 3 make it 4 different powders, varget which is not preferred bc it won’t get the speed some of you guys is hunting, lever because I had it on hand and it’s a favorite on here, and cfe 223 for the same reason. Oh and I left one out I also tried tac. Middle of the charge on up to max with 2 different bullets which is all the heavies I had on hand. I mean i don’t have a 1/2in group worked up and trying to shrink that with seating depth or voodoo rocket science I’m just curious why it is giving me a fit to get anything that resembles a decent group.

[Dt219]

Just made a fast test round. For the 120 eldm. CBTO using my hornady tool is 1.682 touching the lands . does that even sound remotely right ? And COAL IS 2.230 again it’s not an average of 5 or so just a good one time measure

[grendelnubi]

1.682 sounds reasonably accurate. My smallest chamber (18" Oden Works DMR) with 120 ELD-m is 1.702 to lands so yours is measuring a little smaller. If you loading mag length 2.26 then you are right on the lands with the 120 ELDM.

If I were you I would move the coal back to factory black 2.241 (1.661 OTB) which would give you about 20 thousands jump and use 30 grs of CFE (This is best CFE charge for me) and retest.

I bet it shoots better than it did before.

[Dt219]

I’m going to find coal for the 123 Sierra today at work I will post it also. I know I just assumed but my loads had to be in the lands with the 120. Again I’d have to measure a loaded round but the dummy I made last night does appear to sit further away from the magazine than the ones I been shooting. Those 120s are pushed way back into the case

[Old Bob]

This thread got me to thinking about my Grendel AR & Hornady 120gr ELD-M bullets - which I intend to load at some time. My barrel is by Wilson Combat. Using the Hornady comparator system: With the 120gr ELD-M hitting the lands, it's CBTO is 1.720" & it's COAL is 2.260" . So, if I were to seat the bullets at that COAL, they'd be touching the lands. If it weren't for these discussions, no telling what kinda trouble a shooter might find him/herself in. Thanks to everyone who participates & imparts vital information for the Hoard. :-)

[Bobke]

As this discussion applies only to AR Grendels, would surely want to start a minimum of .020 off lands, and work further back in .005 increments using appropriate tools-Hornady and Redding bushings work for my applications-and use strictly BTO data for its consistency, not OAL, as bullet tips are not consistent enough, even in a same lot, for precise measurement. Get your distance to lands and load a dummy round using same bullet to the same OAL and get your real BTO dimension, and use that for your datapoint for that lot of bullets. Now run your seating depth test.
Nothing more aggravating than loading close or on lands, intentionally or not, and sticking a bullet in chamber and dumping powder in your action and shutting down a range session, or a hunt, upon extraction of an unfired round from chamber. And ‘on lands’ is unwanted pressure, especially in AR setup.

[grayfox]

The 120 gr bullets have a fatter, tangent ogive and so should not expect them to load out to coal's of the 123's, like Hornady black for example. The 123's were designed with a more like secant ogive and have a longer taper.
And from another forum (6Arc) I've found that most bullets seem to do well at 60-100 thou' off the lands. There's an accurate shooter article talks about that. The "bestest", "absolutest" benchshooting length may go up to the lands or real close to it but that advantage falls off every 100 shots due to throat erosion. The 60-100 range offers a long-time depth that shoots very nicely.

So if your 120 eldm sits at 2.230 on the lands try it at somewhere 2.180-2.170. Just be aware that the fatter ogives will seat shorter than the 123's.

I measure all my bullets to find out where they hit the lands, even for other calibers (ok I don't worry so much about the 223's). Assume nothing from one bullet to the next.

[VASCAR2]

If I knew how to upload pictures from an iPhone I would show all kinds of pix but i don’t think it’s possible

You can post pictures directly to the forum from an iPhone, tablet or computer by following the instructions below. The pictures will be small and have to be a small size. On an iPhone you can email the pictures to yourself. When putting the pictures in an email you get an option on file size, select a smaller size. I find it easier to post pictures using a web hosting site like Flickr, imgur or postit.


How to post pictures
1. Go to the lower right corner of the "Quick Reply" section and click on the "Go Advanced" box.

2. In the next screen, below the "Your Message" section and in the "Additional Options" section click the "Manage Attachments" box.

3. In the new window that opens up click the "Add Files" box, and when that pops up another little window click the "Select Files" box. Go find the file(s) on your computer, click on them, and choose "Open." You should see your file(s) in the little window so click "Upload Files."

4. This brings you back to the main File Upload Manager window, and your file(s) should appear down in the Attachments area. Click "Done."

5. This brings you back to the "Additional Options" section and you should see your image file(s) under the "Manage Attachments" box. You can now either "Submit Reply" or "Preview Post."

Note: Make sure your picture is a standard picture file format is not sized too big.

[Dt219]

Ok the 123 smk CBTO length is 1.755 and COAL length is 2.355. So for sure that bullet was off the lands

[LR1955]

I have tried 120eldm hornadys and 123 Sierra match kings. I shoot off a bench with bags up front and the rear. Can only muster 1.25in - 1.50in groups at best with either bullet at 100 yards. And no I have not let anybody else shoot it yet. During testing I usually only shoot 3 shot groups to begin with going up in .3 increments. I wouldn’t think it’s me pulling or flinching since I have no problems shooting and stacking the 85s and 90s into a .5in group pretty consistently. Maybe I just have not hit on a decent combo. I did not expect a Lilja to be this picky. I have several powders I can try but not many bullets in there weight class. I can get my hands on some 123 eldm local but that’s all the options I have Thanks

Your lighter bullets use a tangent ogive which is very forgiving in a number of ways. The 120 ELD's and the 123 Sierra use more of a secant ogive which is far less forgiving to handloading techniques. When the 123 Sierras came out, very few guys could find a load that was consistent with a Grendel / AR-15. Bolt gunners had an easier time.

The 120 Sierra uses a tangent ogive like the shorter bullets you are having good luck shooting.

I suggest you buy some 120 Sierra's and try them. I bet they will shoot just fine.

LR-55

[Dt219]

I have tried numerous times to post pictures from my phone and I have had a couple Apple gurus try a couple different ways to post them. For what ever reason when I select a picture and hit upload files it disappears.

[Dt219]

Another question. A member mentions a seating test. I have seen where some people like to perform it first for a bullet with a set powder charge and different seating depths and they start with the depth that produced the smallest group is that how it’s done I’m sure there is pros and cons to it

[grayfox]

Bullet seating depth changes vary the MV only a little, assuming you’re not highly compressed. Seating depth affects exit timing the most (in relation to the pressure wave up and down the barrel). That’s why I vary charge first (over a chrony) then look at seating depth. Besides, in an AR you have more wiggle with delta-powder than you do with delta-Oal. Seating depth is more of a fine tune.

[Dt219]

Just a test for pictures

[VASCAR2]

Picture works!