.223 velocities...does this sound reasonable?

[Dentite]

Hey gang,

Bolt action Savage Classic 14 with a 22" barrel. I'm using 55gr Hornady Vmax and H4895 in RP brass. A few years ago I settled on a load of 25.0gr H4895 that grouped very nicely and was about the upper limit of published data.

A year or two ago I chronographed a five shot sample and got an average of 3100 or so.

Today I chronographed some rounds with the same powder charge and change of brass. Got a bunch of once fired PMC brass from a friend. Resized the same way, same primers, bullets etc.

I was a bit surprised when they chronographed at an average of 3225. Still grouping well. Some primer flow around the firing pin but no visible ejector marks on the brass or heavy bolt lift.

Also I seat these about .040 off the lands so the OAL is greater than factory ammo so the combustion chamber if you will is a bit larger than factory ammo.

I don't know if the brass is actually that much different or my beam scale is a bit out of wack or if my chrono is out of wack but it was very consistent with the velocities.

So...long story short...you guys think I'm okay breaking 3200ft/sec or do you think I might be pushing the pressure a bit?

Thanks.

 

[Steve C]

You are pushing the pressure limits, the primer flow is the best indicator. As you and any one who has read a loading manual knows that any change in component can change the pressure and performance of a load, sometimes increasing pressure and other times decreasing pressure with the occasional leaving things the same. Rule of thumb has always been to work the load back up when a component has changed. In your case a slight reduction in charge weight is probably in order.

 

[RainDodger]

Pushing it a bit I'd say, but if you're within specs and it works.... my standard loads with 60 grain bullets out of a 20" AR are running right around 2900 FPS. I could go faster but I have no need to do so, since I have the consistency and accuracy that I want.

 

[243winxb]

no visible ejector marks on the brass or heavy bolt lift.

The difference in brass may make a difference. Compare the brass weights between RP & PMC. Heavy brass = more pressure/velocity. What primer? CCI 400 flow early for me in a Savage. The 3225 fps is in the area listed for a couple of bullets on Hodgdons website. Take about 30 fps off per inch of there 24" barrel. I would guess your at maximum.

 

[Berger.Fan222]

Great comments above.

I'd double check the reloading scale also as part of your due diligence. If you don't have a second scale to compare to, you can weigh the 55 grain bullets, VMAX bullets are usually within a few tenths of a grain from their spec. It's not perfect, but will tell you if the scale is off by more than a few tenths.

You may also consider whether you opened a new powder container. Powders can have some lot to lot variation, but the humidity of the powder matters a lot too. Working up a load with powder that has been acclimated to the humidity in your reloading area if it's a basement with 50-80% humidity will generate less pressure and velocity than working up a load with just opened powder or powder acclimated to 0-25% humidity. There are two reasons: 1) Powder with a higher moisture content contains less nitrocellulose per grain, because some of the weight is water. 2) Powder with a higher moisture content expends some energy converting water to steam which lowers temperature and pressure if other factors are equal.

Our practice has been to keep the reloading area in the 40-60% humidity range and leave a new powder container open for a few days before loading so that all loads have comparable moisture content in the powder.

 

[spitballer]

Amazing that there would be such a velocity difference when the components are essentially the same. The brass, of course, would be the logical first place to focus because it's the only component that has been altered. I'm not too familiar with different kinds of brass (and probably should be) but I've always used sporting brass in my bolt action .223. If the brass is mil-spec it may have a slightly smaller capacity in a sporting chamber but it can be offset by a longer OAL. I've never run into leaky primers but I always use Markron sealer. Factory velocity is around 3240 fps for a 55 grainer so I'm going to vote "safe" if you're still at 3225 with a bolt action.

The leaking primers still throw me, though. Consider some sealer, it tends to cushion the primer as well as sealing it. The latest Markron instruction sheet says to apply sealer to the pocket before seating the sealer for best performance, but the stuff dries so fast I don't see how this would be practical; I still use a dab on the primer after seating and let it seep around the edge. A can of lacquer thinner is a must, for thinning and cleanup.

 

[Dentite]

Thanks guys for the responses.

When I said primer flow around firing pin, I was referring to cratered primer marks, not gases leaking around the primer.

I just weighed a 55gr vmax bullet and my RCBS beam scale was right on.

I think the chronograph is close to accurate as well because I tested some .300WSM loads and they were not faster than I expected.

I guess the brass made a bigger difference than I expected, and this is a new lot of powder and that could be a factor as well.

I think I'll drop it a grain or two and do accuracy testing again.

Thanks again.

 

[Laphroaig]

DT - Do you level your chrono when you set it up? Doing the math indicates that a 2.2 degree difference between chrono setups could explain the velocity difference. That's not much of a difference to detect with the naked eye.

arcsine (3225-3100)/3225=2.22 degrees.

That could explain at least part of the difference, along with a different can of powder and brass.

Laphroaig

 

[Rule3]

Easiest thing to check (and the only change) is the brass volume.

Any PMC brass I have was military crimped. Measure the volume of PMC and RP brass. I am guessing the PMC is heavier wall and less internal volume.

What about outside temp? It was over a year ago so where the tests done the same outside temp, humidity, altitude etc?

 

[Sunray]

25 of H4895 is the starting load for a 55 grain SP bullet. There should be no pressure issues. 3200 fps is about low for 25 grains. Hodgdon says 3176 fps.
Something else is going on. Just changing cases shouldn't do anything. Start by pulling a few and checking the charge's weight.

 

[JDGray]

Different powder lots can vary 10%, could very well be your problem.

 

[shooter1niner]

Not a big fan of the primer flow... It's an indicator in any case.

 

[coonbait]

different temperature will also change your loads velocity

 

[Rugg_Ed]

I just checked some of my data.
RP brass 60 Hrndy Vmax 2891/fps
Mill LC 60 Hrndy Vmax 3092/fps
I would suggest start at:
Component change
Power Lot
Temperature

 

[Dentite]

Thanks guys.

I have always tried to get the chronograph set straight and level to avoid errors.

The brass is commercial brass with non crimped primers.

The temp can vary significantly here, temps from 30s to 115+ but the day I chronographed these loads it was 85 degrees and I'll have to look up exact conditions but I'm sure the last time was 65-85 degrees.

Thanks again for your input guys...I'm going to back it off and do accuracy testing again. Kind of a bummer because I did have a nice accurate load worked up.

 

[Dentite]

Just to follow up....I did weigh a small sample size of the two different types of brass. The RP brass I was using was an average of 93gr and the PMC brass I just started using was 97gr. So the PMC does seem to be thicker which is likely a factor.

 

[paul105]

Manufacturers change specs without notice, so use this link with that in mind. Scroll about 1/3 the way down the page. There is a list of 223 Brass by mfg, weight, and water capacity.

http://www.6mmbr.com/223rem.html

Changes in ammo/air temperature can cause velocity differences. There's a possibility that, if your powder was stored in less than ideal conditions, it might lose a bit of moister, causing a slight incr in charge weight if you are using a scale to set powder charge.

Any change in component lots can/will change ballistics.

All of the above could be causing a stacking effect to increase pressure/velocity.

FWIW,

Paul