I think bullet runout might be contributing to shoddy groups when loading long projectiles like Hornady 75gr OTM’s. Currently I’m using Lake City brass with an RCBS X-die and regular seating die. With lighter projectiles (55gr) I’m easily getting ~moa at 100 yards, but the 75gr’s seem pretty stubborn at around 2 moa. (1/7 barrel)
My specific concern is that the length of the 75’s is causing issues with the seating die, and adding runout, although I have no method to check that the full length sizing is making cases without silly runout in the first place. Every once and a while a 75gr will hang up in the seating die and go visibly off-center, requiring me to scrap the round and reprocess the case.
Would a different or better seating die possibly help? Are there seating dies better suited to longer projectiles?
Redding and Forster make straight-line seating dies and they are popular within the competition crowd.
If you know someone who has a concentricty guage, see if you can borrow it. These are useful indiagnosing problems at various stages of reloading and inherent brass issues/defects. Note that if your brass is the culprit, no seating die will correct it.
I’ve spun rounds of XM193 that have had a run-out of 0.010", though they tend to average around 0.005". For comparison, the run-out of my match-grade hand-loads averages 0.001".
Pappabear bought us the Sinclair concentricity guage. What a useful tool!
We’ve run factory loads through it and found interesting stuff. You can check EVERY step of brass processing to find out where you need to take corrective action.
In 308…
Black Hills 168gr Moly SMKs were all over the place. Averaging about .007… well outside of the .003-.004" max acceptable for precision.
Fed GMM was good around .002-.003, but I didn’t have a full box to check.
I was able to dial my Full length bushing die into getting us .001-.003, instead of a consistent .003-.004.
Imported surplus 308 ball was all over too. Some as good as .002 and some as bad as .008.
Our 69gr SMKs in .223 are as bad as .006, but they shoot 1/2 MOA most of the time.
I’ve heard good things about it. One of my Sgt’s suggested a concentricity tool to check factory ammo. Even if one were to use only factory loads, he said you can expect better groups.
As soon as the Schmidt gets in I’m going to pick up one of the Hornady ones and some different match ammo to see what the rifle likes.
Before we had the guage we just rolled some rounds on a reflective surface to double the visibility of runout.
We pulled out 5 wild looking 168 grain SMKs and shot them in a group. They actually shot pretty good. 1" at a hundred with 4 of them touching and a flyer taking the 5 group shot to an inch.
I was thinking of the Hornady tool too because they claim you can remove runout with it. But the guys on the precision gun forums thought the idea of doing that was absurd. So the Sinclair was the same price… We picked that one.
I don’t think runout is the problem I think your problem lies with the Hornady 75 grain OTM. I had the same accuracy issues last year with that bullet through my 1/7 16 inch barrel.
I tried 3 or 4 different powders, different primers, different brass, different seating depths all for naught. The best groups I obtained were about 2.5 moa. Average was 4 moa and the worst was 7 moa, all from a sand bag rest.
After doing a whole lot of reading both here and elsewhere on the net I discovered that many shooters get great accuracy from their AR rifles using Hornady 75 OTM’s and about just as many report abysmal accuracy.
At the same time I was getting 4 MOA from the Hornday 75’s I was getting 1 to 1.5 MOA with Hornady 55 grain FMJ’s. Go figure.
I have sinced sinced moved to 77 grain Nosler OTM’s. I get about 1.5 MOA from Nosler and Sierra 77’s but the Noslers are cheaper so that’s what I shoot.
I had to deepen the bullet tip hole in my RCBS 223 seater die stem because 75’s were bottoming out and getting seated crooked. The bullet seater stem is designed to hit some point between the tip and the ogive the full circumfrance of the bullet. If the tip bottoms out the bullet can easily be tipped during seating.
Check out www.zediker.com. He has authored a few books on shooting high power, the AR15 in High Power and Loading for HP. In his book reloading for HP there is a chapter on set up of presses, shell holder and sizing/seating dies. I learned a few things
On the quick, roll your rounds on a piece of glass. .005 runout will be noticeable. Keep adjusting your die until you get 0 runout or get a runout gauge. Redding makes a nice 223 Competition bullet seater but again, you need to check on a runout gauge. Reguardless of seating die used, you still need to QC your die set up until you are loading straight ammo then work from there.
For a run out gauge, everyone is making them now. I’ve got an old Necko which also measures case wall thickness, banana bend for indexing, case head squareness and runout. If I was to buy again, Sinclair has a basic runout gauge that uses a dial indicator which is fast for doing alot of ammo in a sitting and is about $60.00 cheaper. I generally use mine since it is slower for checking seating die set up and then occassionally from time to time during the loading process if I’m going for Match type ammo.
I just remembered this one that I also picked up in Reloading for Competition by Zediker.
When seating bullets, don’t seat them in one shot, Seat it about 1/3-1/2 a stroke, turn the case a little seat alittle more ect. I typically seat in three stokes with a third of a turn each stroke.
It sounds odd if your seating die is dead on but has helped me produce truer ammo with standard factory dies.
1" at a hundred with 4 of them touching and a flyer taking the 5 group shot to an inch.