Hornady .224 75gr Moly Coated BTHP

[SSN Vet]

I've read much about the need to have a 1-7 (or at very least a 1-8) twist barrel to stabilize the heavier bullets in an AR.

Went to buy primers today and noticed that the box on this bullet states "twist rate 1-9".

Does the factory moly coating on the bullet affect a given barrels ability to stabilize a heavier bullet?

Any one have experience with these?

I'm setting up to reload .223 for my new and first ever AR (a 1-9, chrome lined, 16" middy).

Should this rifle be able to get good performance out of this bullet?

I like to work up two loads for each of my rifles:
1. an inexpensive, yet accurate plinker/paper puncher
(I've ordered 55gr BTHPs for this purpose)

2. a premium best accuracy load.

Would this bullet be a good candidat for #2?

I've read that switching between copper clad and molly coated can cause problems in the bore. Is this primarily for guys applying their own molly coatings? is it over blown? or a bonified no-no?

 

[snuffy]

I doubt very seriously that the 1-9, 16 inch barrel is going to stabilize those heavy bullets. No the molly is not a factor. My 20" bushy in 1-9 twist will NOT stabilize the non-molly 75 hornady BTHP. Huge groups with slots instead of clean holes @ 100 yds.

Your short barrel equals less velocity, velocity is what produces bullet RPM, so less RPM = less stability.

 

[asknight]

SSN Vet, I think Hornady marks the boxes in that manner as a "minimum" rifling twist to use those bullets. My answer to the question is your 1:9" possibly can stabilize those 75gr, but not all 1:9s can.

For clarification, let me explain my conundrum. I have two AR barrels, both 16" HBAR configured. Too, both are Wilson 1:9" non-chrome lined though one was obtained through Rock River Arms and the other Del-Ton (DTI).

The RRA barrel is ~MOA with 60gr VMAX all the way to Hornady 75gr OTM. With anything less than 60 or over 75grs, the group opens (but not by much). This barrel is a bit more forgiving as far as bullet weights go, but doesn't shoot any into as tight of group as the DTI with it's favorite loads.

The DTI barrel is sub-MOA with Hornady 40gr VMAX, Win 45gr HP, Black Hills 52gr OTM, and Hornady 55gr VMAX. Anything over 55gr scatters like birdshot. Clearly, this barrel definitely has it's choices of bullet weight. It is more accurate than the RRA Wilson barrel with it's favorite loads, but useless without.

I know what you're thinking, as I thought it too... that darn DTI barrel is NOT a 1:9" from looking the traits that it's exhibiting. Well, I measured off 9 inches on my swivel head cleaning rod and fit up a nice, tight patch. The cleaning rod gets a full revolution for every 9 inches it's inserted... so I think it's safe to say it is indeed a 1:9".

Anyway, that's the long way around to tell you that every barrel is different, even same spec barrels. Try your recipe and note it's qualities (or lack thereof) and share the knowledge.

 

[SSN Vet]

thanks for the replies...

these loads are for my first AR build....which is a 16" Del-Ton middy.

though I origonally opted on the 16" DTI Chrome Molly (as I clean all my fire arms well,) I hit the panic button after reading some posts on AR15.com and changed my order to a Chrome Lined 16" DTI barrel......

If I understand correctly, the rifling is a little bit sharper on the non-Chrome lined barrels....

so if your 16" DTI can't shoot the 75gr bullets with Chrome molly, then it sounds unlikely that the chrome lined will be able to either.........

unless it truely is a crap shoot?

I guess I really don't have any reason to load >55 gr any ways....as the longest range at the R&G club I belong is only 200 yds.

ever try tho Sierra BlitzKings?

 

[asknight]

I think it truly is a crap shoot, as the 1:9" twist is a compromise or mixing of the original 1:12" (55gr M193 designed) and the newer 1:7" (extremely long for caliber 62gr M855/SS109 due to steel penetrator). The 62gr M855 is length-comparable (which determines rifling twist requirements) to the 75/77gr OTM bullets.

So by my calculations (guesses) if you assign a +/- 5gr range to the bullets for which certain rifling twists were designed it would calculate out to 50-60gr bullets for 1:12" and 70-80gr bullets for 1:7" twists. That leaves me guessing that the middle (60-70gr) would be the ideal for 1:9". That's just my thoughts, though. Fear not, as there are some excellent loads available in this range as all ammo companies have at least a few choices in the 60, 62, 64, 68, or 69gr bullets.

I have seen 1:9s that would drill the 75gr OTMs into the same ragged hole at 100 yards... but my DTI won't.

I have loaded a few 55gr BlitzKings in .223, but not enough to form a solid opinion on them. I was planning on trying that load out on coyote late this winter, but haven't yet. I'm getting about 1.25" @ 100 with them out of my DTI barrel sending them out at ~3100fps based on calculations. I haven't a chrony right now cause the screens are "disabled" at the current time.