Tried using higher quality, heavier ammunition for my Sig M400 with 3.5x ACOG, including some quasi-match ammunition, and was happily shooting 2-3" groups at 100m. Even the crappy Field & Stream 55 gr that I was working hard to shoot 8-10" groups last time (which irritated the shite out of me) was more like 6". 62gr or heavier only from now on...

My CCR refinished BHP spun like a top. I always have to relearn that it shoots a true 12oclock hold. Great day, almost 60F in February.

Nice to hear that the M400 is producing better accuracy. It's almost certainly from the type of bullet, rather than the bullet's weight per se. Bullets that tend to be accurate in most barrels include:
53 Hornady Vmax -- as long as it's not pushed too fast
55 Hornady Vmax
55 Sierra Blitzking
69 Sierra Matchking
75 Hornady HPBT
77 Sierra Matchking

If you hand load, others here can help you with powders and charges.
If you buy factory ammo, expect accurate ammo with the above bullets from Hornady, Federal, Aussie Outback, and Black Hills. Sometimes Fiocchi, too.

quote:

Originally posted by Batty67:
Tried using higher quality, heavier ammunition for my Sig M400 with 3.5x ACOG, including some quasi-match ammunition, and was happily shooting 2-3" groups at 100m. Even the crappy Field & Stream 55 gr that I was working hard to shoot 8-10" groups last time (which irritated the shite out of me) was more like 6". 62gr or heavier only from now on...

My CCR refinished BHP spun like a top. I always have to relearn that it shoots a true 12oclock hold. Great day, almost 60F in February.

As Fritz has alluded to, bullet weight is not always the cause/solution. If you bought some match grade ammo with a light weight bullet like the 53 gr VMAX, it might shoot great.


Accuracy has more to do with consistency of the components than it does with a particular bullet weight. Although of course there are situations where a barrel will like a heavier bullet for reasons of harmonics, or just the strange conglomeration of voodoo that contributes to accuracy.


Also, while an ACOG is a great optic for a great many things. It isn't the best choice for drilling tiny groups at 100 yards.

The M400 has a tighter twist rate so I was informed on these boards that it will generally do better with heavier bullets.

As far as the ACOG goes, it is a blast, and I understand it is not a precision optic. I got it almost new for a great price. Could not resist and did not really try either. As I noted, I was quite happy with 2-3" groups at 100m. I was also able to hit 4" diameter hanging targets at 100m most of the time, and knock-down lead pig and chicken targets (12" x 18" or so) at 300m + m most of the time.

quote:

Originally posted by Batty67:
The M400 has a tighter twist rate so I was informed on these boards that it will generally do better with heavier bullets.

It might.

I have a 1-8 twist 18" barrel that likes the 50gr Vmax just as well as the 75gr Hornady HPBT.


Twist rate doesn't necessarily correlate directly to accuracy with a given bullet weight except in instances where the twist rate is too slow to adequately stabilize a projectile.

For example, a 1-12 twist 223 wouldn't stabilize a 73gr Hornady ELD.


If you tried a match grade load with a light bullet, even a 1-7 twist barrel might like that just fine.

quote:

Originally posted by Batty67:
The M400 has a tighter twist rate so I was informed on these boards that it will generally do better with heavier bullets.

I believe the M400's barrel has a 1:8 twist rate. That's tighter than the old school AR15 1:9 and the really old school 1:12 varmint bolt actions. But now a 1:8 twist is pretty common. A tighter twist of 1:7 is pretty common on AR15s, too. 1:8 and thereabouts is common for match-grade stainless barrels, and it will stabilize common bullets of at least 77 grains. Most of my 223 barrels are 1:8, although a couple are a touch faster at 1:7.7 twist. I have retired 1:9 and 1:7 twist barrels. Even the 1:7 twist barrel shot quality 55 grain bullets with great accuracy.

My 1:8 barrels shoot quality ammo accurately -- with bullets as light as 40 grain VMax, and as heavy as 77 grain SMK.

Bullets heavier than 65-ish grains tend to be made for better accuracy. These heavier bullets tend to be more efficient in the wind (i.e. higher ballistic coefficients), therefore they fly better for long distance targets.

Many people associate the crappy accuracy of lighter bullets with 55-62 grain FMJ ammo. It's the cheap manufacturing process of the FMJ round that causes the crappy accuracy, not the weight of the bullet per se. Hornady's Vmax bullets are well made, and I've seen great accuracy from bullets of 40 to 60 grains. Sierra's Blitzking bullets are light, but also very accurate. In fact, a number of manufacturers have plastic-tipped varmint bullets that exhibit match-quality accuracy. The downside to these light bullets is their low ballistic coefficients, which means they get tossed around in the wind at extended distances.

quote:

Originally posted by Batty67:
My CCR refinished BHP spun like a top. I always have to relearn that it shoots a true 12oclock hold.

That's interesting.

What distance is your Hi Power from the target, for a twelve O'clock hold?

What kind of loads?

quote:

Originally posted by RichardC:

quote:

Originally posted by Batty67:
My CCR refinished BHP spun like a top. I always have to relearn that it shoots a true 12oclock hold.

That's interesting.

What distance is your Hi Power from the target, for a twelve O'clock hold?

What kind of loads?

I first note that I had Novak install night sights, so this is not a BHP with OEM sights (which my 52-YO eyes have a hard time with!). I was shooting 8" pie plates at 20 yards (the only choice I had that day).

I had an early model M400 but wound up selling to a family member at a discount. It was a quality made gun for sure and shot perfectly. I didn't want to sell it but the two ar's I had, I couldn't afford to sell at the price I gave him.

Sig makes an innovative lower with ambi mag release built in and the availability for a sling to be mounted to your lower. I thought for sure other manufacturers would start copying it by now.