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need help with W748 load

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rifle newb trying to work up a functional/semi-economical load to get me started. Not knowing too much about rifle loading in general, Here's what I'm using:

LC pre-processed brass

Hornady 55 grain FMJBT

WW748 powder

Winchester small rifle primers

Dillon 550

Lee die set

I'm loading for 2 guns (wife and mine) both chrome lined both 5.56 chamber. I was wondering if you guys might be able to let me know where an acceptably accurate load might generally lie with these components w/ my particular barrels.

18" and 16"

Some data I've collected on a cool, drizzly day ~67 degrees sea level (16" rifle 1/7 twist):

25 gr. 2616 fps

25.5 gr. 2674 fps

26 gr. 2771 fps

26.2 gr. 2801 fps

27.1 gr. 2899 fps

18" rifle 1/8 twist

25 gr. 2685 fps

25.5 gr. 2785 fps

26 gr. 2899 fps

26.2 gr. 2925 fps

27.1 gr. 3010 fps

I had powder gathering in my powder die. . . it didn't seem right to me so I took some sandpaper, twisted it up and sanded the inside of the powder die a bit to smooth it out. Now, I'm getting much more consistent powder throws. My OAL target is 2.235" but I noticed that the bullets themselves vary a lot in length, and my cartridges w/ the lee dies vary up to .01" sometimes. My extreme spreads average around 60 FPS. Is this normal? I don't have one of those comparator do-hickeys.

26.2 fps was the listed max load, so I approached it slowly and then went for ~27 grains (based on others here loading to 27.5) to see what the velocities would be and checked primers for danger signs. It was a cool day, and the velocities were not out of control, so I went ahead and tested. Primers seemed to all be ok. I was hoping for ~3100 ish but didn't get it. I don't even know what power factor I need to have for the game. Given these velocities, where's my range to focus on for a little bit of accuracy testing? What I'd really like to do is just make a bucket load of ammo and work on skills since I don't have any :)

at 27 grains, the cases were getting pretty much filled all the way up w/ just a little bit of space left it seems.

With these barrel twist rates, i'd assume my more accurate loads would be heavier bullets, but this is where I'm starting from and I'd like to see if I can get a functional load w/ the 55 grain and cheaper powder to build some skills before moving up to 75 or 77 grain bullets.

Edited by chunger

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Here's what I've found in my 16" Colt 1/9 HBAR.

I can get 3 shot MOA groups with the following combination:

Rem or LC case

Rem small rifle primer (6 1/2)

27.0 grains W748

Hornady 55gr SP

My velocities are about the same as yours in your 16" barrel. I didn't see any improvement in accuracy when shooting 69gr SMKs in this same rifle, but with a 1/7 or 1/8 twist you might. I've never used the Hornady 55gr FMJs, but I've heard of others getting good accuracy out of them, so I think with your choices in components you should be able to find something that shoots well. Your extreme spread seems about the same as what I got, but I don't record that information so I can't be certain.

I'm not sure I answered your questions - if you have something specific let me know.


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Looks like I need 2910 to make 160 minor power factor. This means I've not loaded up far enough for the 16" rifle. Wife won't be happy if she's disqualified because I made bad ammo :surprise: . Best avoid that situation altogether. Wife also won't be pleased if rifle blows up :blink:

Looks like I'm headed towards 27.4 - 27.5 grains to go for 3100 and 3000 fps in order to comply with the rules of the game. . . and then, the accuracy will probably have to either be there or not because I don't have much wiggle room. Hopefully the combo proves in both rifles.

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Did some more testing today w/ 27.4 grains 748.

18" gun

L 3005

H 3070

A 3038

ES 64.82

SD 22.56

16" gun

L 2898

H 2945

A 2929

ES 47.25

SD 14.07

Group 18" gun Meopta K-dot. I'm not the best group shooter, but I if I put enough bullets down range, I'd be able to get some useable info. Now that I know power factor is not 160, I may be able to back down a bit and shoot more groups. Very much hoping to get a ~MOA load. Maybe I'll still get there with some tweaking. For now, I have 1.3" and 1.8" . . . functional. These are 1/8 and 1/7 twist rifles so maybe the 75 grain Hornadys I have inbound will fair better.


Edited by chunger

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I have pushed a 55 grain win FMJ with 27.7 grains of Win748 out of a 20" stainless rock river barrel with an average of 3136, SD of 11.7, hi of 3153, and a low of 3119. Shooting at 1 moa. Using Remington Brass and showing very little pressure.

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Back when I had a 1-8, it really liked the Hornady, 68 grain, match hollowpoints(not moly) and would always shoot sub 1/2" at 100 yards. I don't remember far enough back to remember what my 1-7 used to like.

I have found that every barrel seems to have its own likes and dislikes.

good luck!!

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