H4895 with .223 77 gr SMK

[Luky]

I just got a new RRA 24" 1:8 varmint upper (Wyld chamber) and was going to start working up a load for it this weekend. I have a few pounds of varget and about 1/4 lbs of H4895 (enough for testing as this shows higher velocities for a 77 gr SMK). Using PMC brass with CCI 400 primers.

Looking at the Hodgdon website it says 20.0gr -22.6gr max for H4895 powder for 77 SMK. However I also have a Sierra "manual" specific for AR15 reloading (.pdf I downloaded) that calls out loads of H4895 of 22.2gr - 23.6gr max for the 77 SMK. It is not as great a difference for the Varget (Hodgdon says 21.0 gr-23.7 gr and Sierra says 22.6 gr-23.9 gr).

Any idea why this is? Is it the pressure difference delta between a .223 vs 5.56 Nato chamber? I already loaded rounds at .2gr intervals to run a first ladder test and started at 22.2 up to 24.0 (2 steps over max - depending on pressure signs if I actually shoot them).

I measured the chamber with my stoney point tool with a 77 SMK bullet and it looks like is would be 2.368 OAL to touch the lands. Even loading them as long as possible to still fit into a 20 round mag (which I modified by pulling out the metal strip at the front inside to allow another 0.010" clearance inside the mag) they will still need to jump about ~.090" to get to the lands. (I measure my reloads @ 1.890" base to ogive/2.278" OAL). Is that a typical "bullet jump" for an AR15 barrel?


Seems huge for a new barrel (my Savage .308 has a very small chamber to lands, right at minimum so I can't really load longer than 2.800").

 

[Paulyr450]

All of my ar 15 barrels are the same way with the jump your talking about. My two stag arms ,rock river,my brothers scar 16,and my buddys two armalites are all that way.

 

[1idCat]

The SMK 77s shoot fine with that jump, I wouldn't worry at all.

My 26" varmint upper (Wylde chambered 1:7) shoots the SMK 77s best, at just over 1/2 MOA. Even at 800 yards, they keep within a MOA if I do my part and read the wind right.

As for powders, try Varget, IMR4320, RE15, and TAC. My go-to load is 24.0 gr. of Varget at mag length. YMMV.

 

[1lnbrdg]

Somewhere right around 23gr of H-4895 you should find a really good node that isn't over pressure. It's always shot good for me but not always been the highest velocity load out there. One of the most accurate 80gr loads I've ever shot but not quite as fast as I needed for 600yd competition.

 

[ksthomas]

Luky,

The differences between the manuals is typical of what you see from one gun to another. This is especially true when we're discussing ARs, in which we may be dealing with 223 Rems, 5.56mm NATO or Wylde chambers . . . among others. The Sierra data was done in a Colt AR-15 HBAR, with a 5.56mm chamber. This will be markedly different from what results you'll see when the same ammo is fired in a Wylde chamber. The latter, incidentally, is what the vast majority of competitive shooters use, so most loads you hear being offered by competitive shooters will be tailored to that chamber. Normal variation, and precisely why we're always harping about starting low, and working up slowly in YOUR rifle.

No point at all in shooting the 77s seated out, as they were meant for magazine feeding. If you're going to go to the added trouble of single loading, then step up to the 80-82 grain bullets and take advantage of the improved ballistics they offer. These were designed to be used during the 600 yard slow fire stage, which requires the rounds to be single loaded. So, the added length allowed us to improve the ballistics with essentially no "cost" to the intended use of the bullet or rifle in which it was intended to be used. The 77s, on the other hand, were designed to feed and function through the magazine.

I wouldn't bother with the 4895 here, but rather go straight to the Varget or RL-15. These two powders are far and away the most popular among competitive shooters using heavy bullets in the AR platform. Very proven, easy to develop good loads with and both have the right pressure curve for this combination. The 4895 (either flavor) is a great powder, and still one of the best for 308 match loads, but not quite as good as the other two for the 223/5.56 applications. No point in reinventing the wheel, if you get my drift.

 

[nobearsyet]

Sorry to revive an old thread, but the information is pertinent to my current dilemma. Due to this shortage I have found myself with 8lbs of H4895, a 5.56 chambered 1:7 twist 14.5" pinned and welded comp with a midlength gas system and rifle length buffer. Did Luky ever try this load and what kind of velocity did you get? I'm trying to replicate MK262 Mod 1 and this has been the only powder available locally. If I can get them around 2500fps I'd say I did pretty good. To do so would take 2800 from a 20" rifle or 2700 from an 18". Have any you got there with H4895?

 

[Foul Mike]

I shoot 4895 pull down in my Sav. Mod 12 and RRNM .223 with good luck.
I have lots of it so that is what I shoot.
My Mod 12 shoots 4895 better than any other powder and I have tried a bunch. Varget will not do as well in that rifle at all.
I use 25 gr. and a 55 grn. bullet most of the time but do load heavier bullets with good results.
If you have lots of it figure a load up. I would not trade my 4895 for Varget at all. Regards, FM

 

[nobearsyet]

I looked at the Sierra AR specific data and it looks like I can get there. Guess I'm going ot just have to try it. I was trying to avoid a HAZMAT fee for 1 can of powder to work a load up and see if it'd shoot (then ultimately buy more after the workup was done) and was hoping somebody would have chimed in and said something to the tune of "Yup, worked for me" but looks like trial and error is going to be the way to go.