Need some help figuring out what's going on

[mugsie]

This is driving me crazy!:banghead:
Try to bear with me as I am going to make this as through as possible.

I'm shooting a Savage 12BVSS 26" barrel .223 bolt action for which I'm handloading. I had loaded 26g of H335 under a Winchester 55g FMJBT bullet with CCI small rifle primers. The rifle has a 1:9 twist rate.

This combination exhibits tremendous over pressure signs, blowing holes in the primers and sometimes blowing the primers completely out of the shell! My groups however are sub MOA.

I was following the recommendations on the Hodgdon container which said max 26g and small rifle primers. Incidently, so no one thinks I went right to the max, I worked up from 24g in .2g increments. 24, 24.2, 24.4 ... up to 26 grains. As I said, the 26 grains yielded great results but with lots of over pressure. (I know I know - I don't have a chrony but will sometime in the future - as it stands now, I don't have one.)

I called Speer, because the say in their manual, which I have a copy of, to use small rifle magnum primers. My thinking was it would be that much more pressure but they Speer rep said no it wouldn't, it would be a more even burn. I decided to try it. Yup - he was right, no signs of overpressure even with 26 grains.

The way I found this out was tonight I started at 25 grains, 4 shots. Then 25.2g's, 4 shots etc and worked my way up to 26, looking for telltale signs along the way but there were none.

So here's the problem - at 26 grains I'm closing in at one MOA but I'm not there yet. The rifle seems to want more speed (I know I know - get a chrony but as I said - I don't have one yet. How does one reconcile group size with velocity anyhow?). Have any of you continued up the ladder in maybe .1 or .2 grain increments till signs of overpressure appear? My reasoning is that maybe another .2 or .4 grains would be it. What do ya think?

My AR - she loves 55g FMJBT with 26g H335 and mag primers and shoots 3/4" groups all day long. The Savage, when it was showing the overpressure signs, I was shooting a nice cloverleaf pattern. Sometimes I could put 8 shots inside a nickle sized circle (benched of course with a 12x scope). Now I'm lucky to be shooting 1 1/2" groups. So whatta ya all think (besides get a chrony). (BTW - the chrony will tell me the speed and consistancy but it's not going to tell me what the rifle likes for smallest group sizes will it?)

I'm open to suggestions.....
Tanks....

 

[NuJudge]

Some thoughts

I went to the Hodgdon website, and with a different bullet (that probably has more bearing surface) and probably a different primer, they say 23gr H335 starting loads, and 25.3gr maximum loads. That might be part of the problem, and it might not.

http://data.hodgdon.com/cartridge_load.asp

I started shooting .223 in competition three years ago after shooting .308 and .30-'06 for 25 years. There are a lot of discussions on the Service Rifle websites about just this kind of pressure excursion in .223 ARs. It is many times blamed on bore carbon build-up just ahead of the cartridge case. Application of JB compound with a plastic-bristled brush is what is spoken of as the cure. Normal bronze bristle brushes and solvents are spoken of as not touching the stuff.

I don't like the idea of abrasives on my bores, so I do not do this, but then I have not had this problem Can I suggest you ask gunsmiths around you if they have a borescope to look at your throat?

Can I suggest you run a round or two accross a chronograph to see what the bullet is doing?

 

[Ol` Joe]

Any time you have pressure signs you are well past the safe limit SAAMI recommends. Primers flatten and pierce at 70K+ and pockets expanding to the point primers fall out are a sign of a gone case. You say you worked up, you should have stopped at flat primers and not pressed it until they started to blow. A crony will help, but remember to take barrel lenght in concideration and not expect to reach 26" barrel velocities with a 20" barrel.
I`d drop the load a couple grs until you figure it out and keep in mind the book max is only a guide line. They reached it in their test with their components and their chamber/barrel. There is no promise you can do the same.

 

[SUBMOAS]

Hodgdon....

The site says max load is 25.3... I think you might be alittle over.
Look at your previous loads and find the one that shot the best without over-pressure. Play with the OAL.


Cartridge: 223 Remington
Load Type: Rifle
Starting Loads

--------------------------------------------------------------------------------
Maximum Loads

--------------------------------------------------------------------------------

Bullet Weight (Gr.) Order BW Powder Bullet Diam. C.O.L. Grs. Vel. (ft/s) Pressure Grs. Vel. (ft/s) Pressure

--------------------------------------------------------------------------------

55 GR. SPR SP 55 H335 .224" 2.200" 23.0 3018 40,800 CUP 25.3 3203 49,300 CUP

 

[dcloco]

You are lucky to get in the 1 moa range with FMJ bullets and a 1:9 twist. I can shoot 40, 50, 52, 53, 55, 60, 65, & 69 quality bullets...and get great groups...but FMJ...forget it. Turns a 3/8 moa rifle into a 2 moa rifle.

Better yet....try shooting groups at 300 yards...your FMJ's will group in the 6" to 12" range.

 

[asknight]

Here is a short version of a theory that's been discussed.

If your groups are tightening up as you're working UP to 26gr, then try working down in predefined increments of 0.5 gr or so until your accuracy tightens up again. With a rifle that is capable of sub-moa groups as yours proved, you can time the bullet to leave the barrel while the barrel is in a different phase of "whip."

It's cyclical with many rifles. As an example, my 700 ADL .223 is accurate at 21.4, 23.3, and 25.2grs of H335. I stuck with 23.3 in my rifle as it was the most accurate with the highest velocity without pressure signs. The accuracy literally disappeared with a load between the listed charges above. The more accurate the rifle is, the more noticeable timing of the "whip" will be.

My .223 is accurate, but like yours, my most accurate load was showing pressure signs. I began working down in 0.3-0.5gr increments and around 2.0gr below max listed load my groups got tight again. I'm currently testing this theory with another rifle.

Any thoughts from the real guru's out there?

 

[mugsie]

Asknight - I think you're right on the money. It's exactly what I was thinking of doing this weekend. Tonight I'll begin working down from 25g's in .2 or .5 grain increments and let's see what happens.

Thanks....

 

[243winxb]

.223 Remington VS. 5.56x45mm Not the same

What brass are you using? Military may make more pressure? There is a good article in the NRA's American Rifleman thats worth reading. http://www.nracentral.com/american_rifleman.php

 

[cpttango30]

Yah I think your over the max a bit, and if you are using military brass or laupa brass which is thicker than rem and win brass this will raise your psi as well. I would back it off some and look in your manual for a most accruate load and see if it that powder. I have found that you will be within +-1gr of the book listed most accruate load.

Now looking in my sierra manual it lists the max load for h335 with a 55gr bullet as 27.5gr.

My lyman 48th edition manual list 27gr as a max load for the 55gr h335 combo.

So take that hodgdon max load as you will.

If I am right h335 is a ball powder and ball powders tend to be a little more temp sensitive that other (Stick and flake) powders. You might want to try varget or Viht n133. or even acc XMR 2015 I get good results with it in my rifle.