125 GR Sierra MatchKing Bullets

On Deck · December 4, 2015, 05:02 PM

Has anyone used 125 GR Sierra MatchKing Bullets in a SA SOCOM 16?
Too light of a bullet?

emcon5 · December 4, 2015, 07:35 PM

I am guessing this is some sort of M1a, and you are talking about .308 loads?

If so, seems awful light.

Kosh75287 · December 4, 2015, 08:00 PM

OFFHAND, I don't know why it would NOT work. One thing I'd wonder about is if the M1A rifling twist, which is optimized for 147 - 175 gr. projectiles, will stabilize the lighter projectiles. I'm also guessing you'd have to push them pretty fast, if you hope to operate the action. I did a quick search over at the Hodgdon reloading site, and most of the data I found, using service-rifle friendly powders, involved compressed charges. The exception, H335, might be the powder to work with.

I don't know what rifle powders you might have on hand, but if they're near the 4895s, you might try a work-up with those.

zeke · December 4, 2015, 08:15 PM

Have tried 125 Nosler Ballistic tips, and they gave surprisingly good accuracy and velocity with 748 (cci 34 primers). The socom owned has a slow twist, common to the standard M1A? Strongly advised to load dummy round, and cycle from bolt lock back. Likely you may find the bullet pulls out slightly from the cycling process. That may or not concern you, depending on your purpose.

Bought some hdy 125 sst's to try in various 308s, as they have a cannelure.

The poi may need to be adjusted, again depending on your purpose.

Kosh75287 · December 4, 2015, 08:33 PM

Zeke, is there not enough of a base to fully engage the neck tension? I'm trying to figure out why the 125s would move forward when chambered from bolt lock-back.

zeke · December 4, 2015, 08:58 PM

Kosh-that would be it, including setting the full dia of bullet out further for better accuracy. Not mentioned was that included not expanding the case necks after sizing. Was expecting the opposite, as in bullet set back.

Have the same scenario in some specific pistol loads, like the .380.

On Deck · December 5, 2015, 11:33 AM

Thanks all for your reply's!

30Cal · December 5, 2015, 06:50 PM

I shoot 125 TNTs a lot through a M1A Supermatch w/ 1:12". I use IMR4895 (I think maybe a half grain more than I'd use behind a 168 worked out well). It cycled just fine even down to around 39.0grs. Make sure you keep approx one caliber's worth of bearing surface inside the case mouth. I use 2.75" with the TNT, which is a little longer than what they recommend (2.7 if I recall), but after something like 2k of them fired, I've never had an issue. Cheap bullet, not fussy in the least, and brutally accurate.

10rds

As long as you have enough bullet in the case mouth, the bullets shouldn't move much at all (on the order of 0.005"). If they are moving, then you have inadequate neck tension (a die problem).

December 4, 2015, 05:02 PM	#1
On Deck Junior Member Join Date: November 14, 2015 Posts: 6	125 GR Sierra MatchKing Bullets Has anyone used 125 GR Sierra MatchKing Bullets in a SA SOCOM 16? Too light of a bullet?

December 4, 2015, 08:00 PM	#3
Kosh75287 Senior Member Join Date: October 15, 2007 Posts: 820	OFFHAND, I don't know why it would NOT work. One thing I'd wonder about is if the M1A rifling twist, which is optimized for 147 - 175 gr. projectiles, will stabilize the lighter projectiles. I'm also guessing you'd have to push them pretty fast, if you hope to operate the action. I did a quick search over at the Hodgdon reloading site, and most of the data I found, using service-rifle friendly powders, involved compressed charges. The exception, H335, might be the powder to work with. I don't know what rifle powders you might have on hand, but if they're near the 4895s, you might try a work-up with those. __________________ GOD BLESS JEFF COOPER, whose instructions, consultations, and publications have probably saved more lives than can ever be reliably calculated. DVC, sir. انجلو. المسلحة. جاهزة. Carpe SCOTCH!

December 4, 2015, 08:33 PM	#5
Kosh75287 Senior Member Join Date: October 15, 2007 Posts: 820	Zeke, is there not enough of a base to fully engage the neck tension? I'm trying to figure out why the 125s would move forward when chambered from bolt lock-back. __________________ GOD BLESS JEFF COOPER, whose instructions, consultations, and publications have probably saved more lives than can ever be reliably calculated. DVC, sir. انجلو. المسلحة. جاهزة. Carpe SCOTCH! Last edited by Kosh75287; December 4, 2015 at 08:43 PM.

December 5, 2015, 06:50 PM	#8
30Cal Senior Member Join Date: December 3, 2002 Posts: 1,264	I shoot 125 TNTs a lot through a M1A Supermatch w/ 1:12". I use IMR4895 (I think maybe a half grain more than I'd use behind a 168 worked out well). It cycled just fine even down to around 39.0grs. Make sure you keep approx one caliber's worth of bearing surface inside the case mouth. I use 2.75" with the TNT, which is a little longer than what they recommend (2.7 if I recall), but after something like 2k of them fired, I've never had an issue. Cheap bullet, not fussy in the least, and brutally accurate. 10rds As long as you have enough bullet in the case mouth, the bullets shouldn't move much at all (on the order of 0.005"). If they are moving, then you have inadequate neck tension (a die problem). Last edited by 30Cal; December 5, 2015 at 08:47 PM.

December 4, 2015, 07:35 PM	#2
emcon5 Senior Member Join Date: July 10, 1999 Location: High Desert NV Posts: 2,850	I am guessing this is some sort of M1a, and you are talking about .308 loads? If so, seems awful light.

December 4, 2015, 08:15 PM	#4
zeke Senior Member Join Date: November 17, 1999 Location: NW Wi Posts: 1,671	Have tried 125 Nosler Ballistic tips, and they gave surprisingly good accuracy and velocity with 748 (cci 34 primers). The socom owned has a slow twist, common to the standard M1A? Strongly advised to load dummy round, and cycle from bolt lock back. Likely you may find the bullet pulls out slightly from the cycling process. That may or not concern you, depending on your purpose. Bought some hdy 125 sst's to try in various 308s, as they have a cannelure. The poi may need to be adjusted, again depending on your purpose.

December 4, 2015, 08:58 PM	#6
zeke Senior Member Join Date: November 17, 1999 Location: NW Wi Posts: 1,671	Kosh-that would be it, including setting the full dia of bullet out further for better accuracy. Not mentioned was that included not expanding the case necks after sizing. Was expecting the opposite, as in bullet set back. Have the same scenario in some specific pistol loads, like the .380.

December 5, 2015, 11:33 AM	#7
On Deck Junior Member Join Date: November 14, 2015 Posts: 6	Thanks all for your reply's!