.223/556 loads for my AR15/SPR

chrisward3

chrisward3

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Looking for ideas on where to start for bullets/powders/loads.

It has a 1/8 twist 18" SS barrel.

I am trying to decide between 69 or 77gr Sierra Matchkings, or 75gr AMAX bullets.

I had the rifle out today for the first time grouping MOA with cheap 55gr American Eagle bulk ammo...so im optimistic that I can tighten this gun up with some proper ammo.

Please let me know your experiences and what works for you so I at least have a base to work of until I perfect a specific load for my SPR!

Cheers,
Chris
 
If you go with the 75gr. Amax you will have to seat them too long to fit in the magazine; therefore that load will be single feed only. (don't believe those that tell you you can safely load them with an OAL of 2.260" - at that length the bullet bearing surface is almost non-existant and the chances of bullets setting back into the case could create a dangerous situation.)

The only real difference between the 77smk and 69smk is the length and bearing surface. The 77s have a higher ballistic coefficient and fly a bit better in the wind (less wind dope at longer ranges), so it really depends on how far out you shoot. If all or most of your shooting is done inside 400m, the 69s will perform very well. If you do a lot of shooting beyond 300m, then the 77s are the way to go.
It should be mentioned too that the 69s can be driven quite a bit faster than the 77s (200-300 fps) so the 69s will also give you less elevation to dial in the further you go.

Starting loads for each:
77smk / 24gr. Varget / Federal 205m primers / Winchester brass / 2.255" oal

69smk / 25gr. Varget / Fed. 205m primers / Win. Brass / 2.255" oal

Good luck!!
 
beltfed said:
If you go with the 75gr. Amax you will have to seat them too long to fit in the magazine; therefore that load will be single feed only. (don't believe those that tell you you can safely load them with an OAL of 2.260" - at that length the bullet bearing surface is almost non-existant and the chances of bullets setting back into the case could create a dangerous situation.)

The only real difference between the 77smk and 69smk is the length and bearing surface. The 77s have a higher ballistic coefficient and fly a bit better in the wind (less wind dope at longer ranges), so it really depends on how far out you shoot. If all or most of your shooting is done inside 400m, the 69s will perform very well. If you do a lot of shooting beyond 300m, then the 77s are the way to go.
It should be mentioned too that the 69s can be driven quite a bit faster than the 77s (200-300 fps) so the 69s will also give you less elevation to dial in the further you go.

Starting loads for each:
77smk / 24gr. Varget / Federal 205m primers / Winchester brass / 2.255" oal

69smk / 25gr. Varget / Fed. 205m primers / Win. Brass / 2.255" oal

Good luck!!
Click to expand...

thanks for the great info beltfed!
can you confirm that the 77smk requires less powder than the 69gr? just seems a bit backwards to me.

ill definitely be starting there though!
 
From what little I know about reloading I believe it has to do with pressure. Firing a heavier bullet creates more pressure so you have to back off on the powder. Maybe I'm wrong.
 
can you confirm that the 77smk requires less powder than the 69gr? just seems a bit backwards to me.
Click to expand...

Lighter bullet = more powder, heavier bullet = less powder if all else is equal. It's a pressure thing AFAIK.
 
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