FPS Difference

[M36]

I have reloaded some .223 using LC brass, 25 gr. H335, WSR primers and 55 gr Hornady FMJ. Although I am trying to build this for my son's AR, he is out of town with it. Yes, I know it's better to have the gun here.

The FPS out of my AR with it's 10" barrel was an average of about 2575, and at 100 yards the round dropped 9". Nice group though. His AR has a 16" barrel. Does anyone have an idea of the FPS increase he may get out of this load with his AR? In the end, Im going to eventually test in his gun.

 

[jwrowland77]

I believe it's around 20-30 fps per 1" of barrel

 

[M36]

Thank you!

 

[rsrocket1]

That's my go to load for my 20" AR and I average 3010 fps when seated to 2.280". Quickload predicts 3065 so working down to 16", Quickload predicts 2894 fps so you can estimate about 2840.

He should really only have a little less than 2.4" drop at 100 yard if he boresighted it and you should only have a 2.5" drop at 2575 fps MV @ 100 yards.

Are you sure the bullet drops that far with your gun?

 

[M36]

Are you sure the bullet drops that far with your gun?

Yes, nice grouping though and 9" short of center where I was aiming. My load is 25 gr 2230, CCI 200 primer (small rifle may be wrong on number) non Hornady 55 gr FML w/o cannelure and I am dead on at 100 yrds with the 10" barrel. Dont have a crony of this load though.

Having a hard time finding 2230 here so he got the H335.

And I have researched and found the load is similar to some others using H335 with their AR's.

I guess Im not understanding how a difference of 265 FPS is going to result in a drop of only .1 ", between the two barrel lengths.

 

[steve4102]

I think you are mistaking a "Point of Impact" difference with "bullet drop".

It is not uncommon for a different load, with a different powder, with a different bullet to have a different POI. You bullet is not actually "dropping" 9 inches more than your 2230 load.

This test shows from 10-16 inches is just over 300fps.

http://www.accuratereloading.com/223sb.html