223 75gr amax xbr8208 help

[vmaxpro]

Long story short, I ended up with 24.7gr of xbr8208 using the 75gr amax. 100yd group was really good, 4 shots were touching. Good enough!!! So I decide to chronograph the load, I was out of time tho so I just did three really quick. 2890,2960,2995? Thats quite a spread. I was only 5 or 6 feet from the chronograph, do you think I was too close?? Heres what I'm using

Lapua brass, full sized, 4 loadings on them
Rem 7.5
Xbr8208 24.7gr
75gr amax seated at 2.480

Accuracy was great, velocity was great ( from a 24"), and no signs of pressure. So what gives? Am I too close?

 

[MrMajestic]

4 rounds isn't a good sample. 40? Try going out to 5-600 hundred yards and see if you have vertical. If not question your chrono. FYI- I use N140 behind the 75 gr. A-Max and average 2980 fps from a 24" tube.

 

[Taildrag15X]

I always used N-135 with 75 A-Max until, in desperation Varget was in the dispencer. With a 28" tube, anywhere between 2,960-3,000 fps could be read on the screen if I didn't shoot exactly 1" above the eye, the higher the shot the lower the speed.

Check your placement, I'm at 20 feet from the muzzle, I have a frame holding a 1/4" grid note pad size "target" attached to the chronny so I know if a shot goes out of the "zone".

 

[GaCop]

4 rounds isn't a good sample. 40? Try going out to 5-600 hundred yards and see if you have vertical. If not question your chrono. FYI- I use N140 behind the 75 gr. A-Max and average 2980 fps from a 24" tube.

+1 for N140 and the 75 ga A-Max. I'm using it in my 223AI.

 

[flatlander]

I'd get the muzzle farther away from the skyscreens - minimum of 10' if you don't want the muzzle blast affecting the chrono's readings.

 

[FroggyOne2]

Using 24.0 grs of H4895 with the 75AMax = 3125 fps in my bbl.

 

[A_Gamehog]

I use a lot of 8208 with heavy bullets in the .223. 68, 69, 70, 75,80
That is a very hot load for that bullet. How are the groups at 200? or 300? that tells the whole story.

Best groups with 75's was with 23.0 grains of Varget,


Best groups for me today @ 300 is

8208 24.0
68 Hornady
Nosler Brass
Magtech 7 1/2 primers

 

[FroggyOne2]

I have shot 5 national records with that load.. and the brass is on it's 7th firing.. some of the pockets are starting to get a lil loose, but I believe it is because I used to shoot 90BT's with 25.1 grs of RL15.. the chamber wasn't cut right for that bullet, but I had to try it. I am building another rifle for the purpose of only shooting the 90's. I am not changing a thing with my current .223.. it just shoots way too good.

 

[A_Gamehog]

FroggyOne2, my question was directed to the orig. poster VmaxPro. Hey froggyone2, that is a great load and congrats, does your rifle have a std. chamber and throat? I need to try that load if it does. AR-15 or Bolt gun?

Thanks,

 

[FroggyOne2]

That is cool.. yeah.. it is a Wylde chamber for 80's.. I seat the bullet about 10 thou above the neck shoulder joint. It is a bolt gun, 7.2 twist Rock Creek bbl that is 30' long.

 

[vmaxpro]

Thanks for all the replies! I just found my load, and its awesome. 25.5gr varget seated at 2.525 ( jamed .020). This gun seems to shoot above max loads for some reason. I still have full radius on primers. I couldnt be happier, i was starting to think this barrel wouldnt shoot the amaxes. Its a 1:8.75 twist.
Also, at 27.0 gr of 8208 with 52 gr amaxes, jumping .030 is really a hammer too!

 

[MrMajestic]

Glad you got it worked out! That feeling is why we do what we do!

 

[vmaxpro]

Haha thanks! Ughh yea its been driving me crazy all weekend. I was smackin eggs @ 500 today. I sat the chrono at 20ft today and used the above advice. Big difference, single digit sd and es. The velocity was a little slow but i could care less. 2897 @ 20ft. So overall 2900fps and accuracy in the upper .1s to lower 2s.