120g SIERRA HPBT MATCH KING +AA2520
Has anybody here had any success with the 120g SIERRA HPBT MATCH KING and
AA2520 POWDER .
Or any other powder and did you load it to maximum magazine length of 2.260ish or what ALEXANDER ARMS web site has it at COAL 2.220 !!! with the 120g Sierra .
Why would this head have such a small COAL than say the usual 2.260 OAL that most of us use for the 6.5mm Grendel to have less pressure in the case with heads in the
120g and up .
The 120g Sierra HPBT is a normal shaped head and not a short stumpy head like a short hollowpoint so why the short over all cartridge length on the ALEXANDER ARMS web site .
I would have thought they would have had all their loads that they recomend all be in the 2.260 realm for OAL to keep presure signs down .
Or am I missing some thing here ???????.
I have been using LAPUA 123g heads for years , but the cost of them have went through the roof over here in the UK at £320 or $500 per 1,000 , so they are out .
The 120g Sierra`s are alot more afordable , so that is why I am looking at them .
Any help would be appreciated .
Here you go!
A COAL of 2.260" is the norm for 5.56 NATO, not so in the Grendel. With the array of projectiles in the 6.5mm, COAL is going to vary widely. For instance, when loading for the 100g Amax; if you seat it longer than 2.200" you begin to lose neck tension and the recommended per/caliber of support for the projectile. Make sure you have a COAL measurement (for the chamber in your rifle) for each type of projectile you plan to load for, or you my experience artificial over-pressure.
Last edited by Bwild97; 08-15-2012 at 06:56 AM.
The 120 SMK is shown in the AA data as having a max charge of 30.6 gr of AA2520 powder. It has proven to be a good load. By my measurements the Sierra 120 SMK is .036" shorter than the 123 gr Hornady "head". I measured a COAL of 2.37" with the SMK. What do you use for tails, AA recommends CCI450.
The 120 SMK does have a more rounded ogive than some of the others, 123 Scenar or Amax for example. In my gun I'm touching the lands at 2.25" with 120 SMKs but don't touch till 2.284 with 123 Amax's.
Originally Posted by Bwild97
Thanks for the quick replys guys .
I never thought of the difference in neck tension with the 120g Sierra compared to 123g LAPUA SCENARS what I had been used for years ,
Just gose to show you it is ALWAYS BETTER TO ASK SOMBODY BEFORE YOU DO SOMETHING STUPID .
Thanks again .