Just started reloading - Question

nthrxx

nthrxx

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Me and my dad have finally got a set up and started getting around reloading for 308.

We tested various loads using 168gr sierra match kings, with Reloader 12 powder. When comparing our groupings with Federal Gold Medal Match ammo, we found our hand loads with 43.5 grain of powder had the same elevation and slightly tighter groups at 100 yards. Today, we went to the bush and stretched out to 415 yards. The issue we're having is that our hand loaded ammo is shooting 3 feet lower than the federal gold at 415 yards. We're getting ~30-60 more FPS with our hand loads, and the elevation at a 100 yards is fairly similar - so we're kind of puzzled as to why it's dropping significantly more at 415 yards.

Are we just using the wrong powder that doesn't have an appropriate rate of burn?
 
The FGMM you're using is 168 grain as well, right? If so your results are puzzling. The only thing I can think of is that the BC of the SMKs is much lower than that of the FGMM projectile...but that seems unlikely. 400 yards is really not that far...hmm. What size groups are you getting at 100 with your reloads and with FGMM? How big are the groups at 400?

I don't think the powder burn rate is an issue since you're getting more than the velocities needed and I assume that you're not seeing any pressure signs.
 
You say your handloads are faster than stated for the factory loads. Have you used a chronograph, or are you going by what the loading manual states they should be going?
If it is what the manual states they should be going, welcome to the magic world of the loading manuals!
 
The fgmm is also 168 grain. At 100 yards we're getting ~0.5 moa while with the handloads more around 0.4 and we get similar groups at 400 yards but the handload is shooting 3 feet lower which strikes us as odd. Speeds were measured with a chronograph.

Thinking we should be trying some varget instead as the powder we are using is fairly old and is no longer made.
 
nthrxx said:
The fgmm is also 168 grain. At 100 yards we're getting ~0.5 moa while with the handloads more around 0.4 and we get similar groups at 400 yards but the handload is shooting 3 feet lower which strikes us as odd. Speeds were measured with a chronograph.

Thinking we should be trying some varget instead as the powder we are using is fairly old and is no longer made.
Click to expand...

thats odd the burn rate shouldn't be affecting anything if your speeds are faster and they impact the same and are the same bullet they should be pretty dang close at 400. were the factory and handload 400 yard groups shot on the same day? have you chronied the factory loads? often atmospheric conditions can change bullet impact and often whats printed on the factory box is off by a little bit.
 
Factory and hand loads were shot same day and we did chrony the both the factory and hand loads the day before .

We're both quite puzzled.
 
I myself, would contact Sierra Bullets. I used to deal with a bullet tech there named Paul Box, he may be retired now, though.
They might be able.to help out.
 
Muzzle velocity is MV, doesn't matter on powder. BC may explain the change but isn't FGMM also SMKs, same 168 SMKs in handload.

Same MV and BC gets same trajectory (let's ignore wind). Check out any ballistics calculator. That's why many are going from 200gr 30 cal to 140gr .264
 
Did you chronograph the rounds shot at 400 or just the ones shot at 100? I wonder if the rounds used for the 400 yard shoot had the same velocity. Loading errors and peculiar powder batches do happen.
 
try it a couple different bullets to see if they do the same thing. also try cleaning the barrel maybe a bit of copper fouling can do strange things
 
We might be trying different types of bullets. I guess it is possible we had a loading error since this was our 3rd batch of hand loads. We didn't take the chrony with us in the bush. This happened with 3 of our rifles so I dont think its a cleaning issue.

I suppose we'll try again and if we have the same effect we'll try different bullets.
 
What chrony, and how far from the muzzle are you setting up the chrony? Too close = inaccurate reading from the muzzle blast.

Have you weighed the bullets to make sure they are 168gr?
 
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