What am I missing here?

[vicpinto]

So today I took the 223 rounds I loaded to the range and ran them through the chrono. Hornady VMAX 55 gr and Sierra TMK 69gr bullets over various loads of Varget and A-2460 as describe below - very conservative loads BTW as these are my first and I didn't want to "shoot my eye out kid". My question is regarding the two 5 shot strings highlighted below. I was under the assumption that, everything else being equal which in this case it is, the heavier bullets would have a slower muzzle velocity. What could cause this?

 

[mac1911]

Slightly more pressure with the 69s maybe a better complete burn of the powder at that charge weight and bullet?
Maybe the lighting changed for the chrony?
Lots of variables, barrel temp? Air temp change...
Now the important stuff, what grouped best and what powder charge range kept your point of aim point of impact closer to the same?

 

[50wt]

Seated depth of the bullet , crimp?

 

[EddieCoyle]

Higher pressure on the heavier bullets gave you higher velocity. The bullets could also have less bearing surface. Also, it's not that big of a difference.

That's really low velocity for a 223 too (on the 55s. Too low)

 

[Arto]

only 14 fps difference... looks like the 69 TMK's have tighter velocities (std deviation ~2/3 of 55's) - are they more accurate too?
the avg +/- std deviation
2598 +/-20 = 2578 to 2618 for the 55's
2612 +/-14 = 2598 to 2628 for the 69's

 

[Bmcl322]

Ceteris Paribus???? I blame the Dems for the irregularities in your rounds!! I especially blame Kamala Harris!! She is the new Hillary, but only worse!! More evil!! She is to blame!!

 

[vicpinto]

Seated depth of the bullet , crimp?

No crimp on these. As far as seating depth and COAL - I didn't use a value from the book. I'm trying to come up with an accuracy load so I used some of Hornady's tools and gauges to calculate a CBTO 20 thousands off the lands to start. There is a difference COAL between the 2 different types of rounds I put together due to differences in bullet shape and it is easily seen. The Sierra Match Kings just barely fit in an AR-15 magazine but no problem in the bolt gun.

 

[vicpinto]

Higher pressure on the heavier bullets gave you higher velocity. The bullets could also have less bearing surface. Also, it's not that big of a difference.

That's really low velocity for a 223 too (on the 55s. Too low)

Jim, I noticed that as well. Hornady calls for Winchester primers but I only have Federal and Remington 6 1/2s. Then I read not to use the 6 1/2s on 223 Remington due to thinner primer cups - use the 7 1/2BRs instead. I don't have those either. In your class you mentioned Federal primers are not as strong as Winchester so I wonder if that could also account for the velocity disparity. Also, I just remembered, when seating that longer 69gr bullet with 22.8gr of Varget I got a slight crunch when seating the bullets so I may have been on my way to a compressed load at that point.

 

[Mountain]

Your powder charges for Varget are too low. Your ES and SD for the 55's is a bit on the ugly side. 69's a little better but still not great. SD's in the single digits and ES's in the teens are attainable. Powders are not going to have consistent ignition below the minimum unless it's one of the known exceptions. Stay at or above the minimums and use the COAL's recommended by Hodgdon for those Varget loads. You should get better results from that. Let's ask that why is the heavier bullet faster question once you have a proper load at or above the published minimum powder weight.

Sorry, not familiar with A-2460 performance, but same principals apply.

You should not be getting a compressed load with Varget at those weights. What type of cases are you using and what was your actual COAL for those loads? Possibly your powder measure and/or scale is off? COAL shorter than it should be?

I use Varget for all of my large bore competition loads and other stuff too. I tried it for .223 but settled on Benchmark because it's much easier to meter and achieve greater accuracy from the small .223 case. Easy sub-MOA groups in a AR service rifle with Compass Lake barrels.

 

[mac1911]

Jim, I noticed that as well. Hornady calls for Winchester primers but I only have Federal and Remington 6 1/2s. Then I read not to use the 6 1/2s on 223 Remington due to thinner primer cups - use the 7 1/2BRs instead. I don't have those either. In your class you mentioned Federal primers are not as strong as Winchester so I wonder if that could also account for the velocity disparity. Also, I just remembered, when seating that longer 69gr bullet with 22.8gr of Varget I got a slight crunch when seating the bullets so I may have been on my way to a compressed load at that point.

really , you where getting crunch with a 69 and 22.8 Var? I get crunch with 77s and 24 grains? I have heard guys say if you aint crunching varget you dont have enough in the case

 

[Mountain]

really , you where getting crunch with a 69 and 22.8 Var? I get crunch with 77s and 24 grains? I have heard guys say if you aint crunching varget you dont have enough in the case

All of my .308 and .30-06 loads with Varget have a little extra space. I give each cartridge a little shake once done loading a batch as final squib prevention. I may have tried some compressed loads in .223 but that's it- nothing compressed in any other caliber.

 

[mac1911]

All of my .308 and .30-06 loads with Varget have a little extra space. I give each cartridge a little shake once done loading a batch as final squib prevention. I may have tried some compressed loads in .223 but that's it- nothing compressed in any other caliber.

maybe cause we are loading mostly for gas guns? I know a few bolt gunners running compressed loads of varget in 308 , 30-06 theres probably better powders for case filling in 30-06 ...I think compressed loads in 30-06 might be pushing it?

 

[TrashcanDan]

Burn rate may or may not have anything to add to the issue as well. Might be one piece of the puzzle.
2 different rates and the proof is in your data.

Notice how varget works better with the 69's and has better overall numbers vs. the 55's?

 

[TrashcanDan]

Jim, I noticed that as well. Hornady calls for Winchester primers but I only have Federal and Remington 6 1/2s.

I can help you out with that. I can give you 3 or 400 win sm rifle if you want to try em out.
How far are you from west bridgewater, and what are you doin tomorrow

 

[vicpinto]

I can help you out with that. I can give you 3 or 400 win sm rifle if you want to try em out.
How far are you from west bridgewater, and what are you doin tomorrow

I just saw your reply today and I tank you. I'm 20 minutes away in Swansea. Would love to get some Winchester - even swap with some Federals or Remingtons if you'd like. PM me.

 

[TrashcanDan]

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