Problem first time loading subs

[DETCADER]

Hello--

First post here can you please help?

I loaded some 220gr bullets last night with Accurate 1680 powder starting at the published minimum of 10.9 grains and went up to 11.9 grains, with a COAL of 2.194" My results were not what I was looking for:

10.9gr
785.9 777 725

11.3gr
863 765 822 756

11.5gr
794 830 781 875 885

11.7gr
879 784 784 837

11.9gr
928 882 868 825 817

I believe the difference in FPS between shots is to be attributed to my first time using a specific powder measure, so im not really upset about that.

My question is, I went up to the max load for accurate 1680 with a 220 bullet at 12gr. Im trying to get around 1050FPS. Can I go higher or is my COAL affecting the FPS somehow? Should I seat the bullet to a different COAL or add more powder or what?

Thank you.

[dellet]

Not enough information.

Barrel length and exact bullet are needed to give any ore than general help. But genera l help may be all you need for this.

Where did your data come from?
If they list 12 grains as maximum, it’s probably not he best data since it is likely a max load for a 220 grain bullet in a 16” barrel to stay under 1100 fps. This comes from a very stupid assumption that no one will shoot a 220 as a super, and even worse that no one is interested in maximum pressure or exceeding it.

I will pick on Hodgdon because they recently bought Accurate powder and completely screwed up the old load data. Western powder had both super and sub data for many bullets, Hodgdon scrubbed that data and now only has sub data for heavy bullets. It’s garbage.

Hodgdon lists 10.9 grains as max load for a 220 SMK at 32,300 psi. That is only 60% of max load by pressure. COL is 2.089”.

Accurate’s old data uses the same COL as Hodgdon, with a max load of 12 grains and 41,000 psi.
https://accuratepowder.com/wp-content/u ... 7-2-13.pdf

Sierra lists the same bullet powder combination max at 17 grains at 2.230”. I would caution that load as being hot and component changes could get interesting.
https://sierrabullets.files.wordpress.c ... 052018.pdf

Hornady, Nosler, Sierra all have data for 220 weight bullets at a pressure or load density maximum.
Note the difference between Sierra and Accurate for The same bullet. Basically showing the pressure difference moving the bullet out can make.

On a side note your velocities seem very low for charge weight. This may be a bullet or even a bore issue. That’s why complete data is needed to really give any detailed helped.

Hope that gets you started.

[DETCADER]

Not enough information.

Barrel length and exact bullet are needed to give any ore than general help. But genera l help may be all you need for this.

Where did your data come from?
If they list 12 grains as maximum, it’s probably not he best data since it is likely a max load for a 220 grain bullet in a 16” barrel to stay under 1100 fps. This comes from a very stupid assumption that no one will shoot a 220 as a super, and even worse that no one is interested in maximum pressure or exceeding it.

I will pick on Hodgdon because they recently bought Accurate powder and completely screwed up the old load data. Western powder had both super and sub data for many bullets, Hodgdon scrubbed that data and now only has sub data for heavy bullets. It’s garbage.

Hodgdon lists 10.9 grains as max load for a 220 SMK at 32,300 psi. That is only 60% of max load by pressure. COL is 2.089”.

Accurate’s old data uses the same COL as Hodgdon, with a max load of 12 grains and 41,000 psi.
https://accuratepowder.com/wp-content/u ... 7-2-13.pdf

Sierra lists the same bullet powder combination max at 17 grains at 2.230”. I would caution that load as being hot and component changes could get interesting.
https://sierrabullets.files.wordpress.c ... 052018.pdf

Hornady, Nosler, Sierra all have data for 220 weight bullets at a pressure or load density maximum.
Note the difference between Sierra and Accurate for The same bullet. Basically showing the pressure difference moving the bullet out can make.

On a side note your velocities seem very low for charge weight. This may be a bullet or even a bore issue. That’s why complete data is needed to really give any detailed helped.

Hope that gets you started.

Thanks for the info.

Ya I forgot to add I’m using a 7” 1:5 barrel so obviously I’m asking a lot.

I shot some more today loaded with A1680 here are the results:
12.4gr 946, 920, 903, 878, 898
12.6gr 920, 933, 953, 921, 905
12.8gr 917, 933, 926, 927, 941
13gr 967, 927, 935, 953 957

So I guess from my start at 10.9 grains my average was 762 FPS and where I’m at now I’m at 13 grains and my average is 947 FPS

Should I adjust my COAL out to 2.250” and keep working up to 17 grains and see if I keep increasing in velocity, or what would you recommend?

[dellet]

Honestly with those velocities, I would be checking bullet diameter and bore diameter. If those check out, I would try a different chronograph. No reason to be that slow with that much 1680.

[DETCADER]

Honestly with those velocities, I would be checking bullet diameter and bore diameter. If those check out, I would try a different chronograph. No reason to be that slow with that much 1680.

Hmm.
I just measured 10 bullets all at .308
Chrono seems fine I shot some .22s and some 110 grain 300s if i remember correctly the 110s were at around 1900 FPS.

I’m leaning towards the fact that this is just a pretty darn short barrel.
Any easy way to measure bore size?

[cdl]

The Sierra 220gr Match King with 11.2gr of A1680 @ 2.120" COL is like the original Advanced Armament Corp (AAC) cookbook load. (300aacblackout dot com)

The 220 MK leaves a lot of room for powder behind it, and seems to like to be loaded to about 2.120" maybe 2.130" COL for reliability. Shorter and it gets "flaky", longer and you need a "grunch" of that gassy powder.

For me, that load at 2.120" COL gives me a 1000fps with an 8.3" barrel and 1050fps* 10.5" . A shorter barrel shouldn't need more than few tenths to hit a 1000fps.

I think 11.2gr of A1680 makes a lot noise, and the 220MK leaves way too much volume behind it at a reliable length. So I don't use the combo anymore. But hey, it's tried and true. Almost has to work.

* EDIT: Change 1100fps to 1050fps because I was looking at IMR4198...dumb.

[dellet]

I don't think I ever used more than 12 grains of 1680 to hit 1050fps with a 220 grain bullet, that would include a 5" barrel.

It's easy to push a lubed, soft lead bullet through the bore and then measure it, Same if you can recover anything you have shot. You can drive a jacketed bullet through but it has to be driven so a lot of care needed. The nice thing about pushing something through is you can feel loose spots where you would lose pressure and velocity.

Possibly a bad lot of powder?

[cdl]

in general. when I go from an 8.3" to a 5.5" barrel, I go from 1000fps to 950fps and live with it. I do download to 1000fps for my 10.5 though.

The weather man infers the speed of sound will be 1018fps at 8:00am tomorrow morning. It'll be a 5.5" barrel day... if I go out.

[popper]

too short of a barrel, too much powder burning after the muzzle. High pressure leads to early bolt opening and gas in your face.