Help me understand this?

[littletoes]

Fired a friends hand loads-69 grn SMK out of my .223, a factory barreled Remington 700 VS.

This factory Remmy fires 52 grn SMK's exceptionally well, has a 1 in 12 twist, yet the hand loads using the 69 Match King, pushed by 20 grains of IMR 4198 shot really well.

Surprising yes! I thought a Match King of this weight wasn't supposed to stabilize out of a 1 in 12 twist barrel.

He was using Lee Dies too.

Now, tell me if you think I can duplicate this load with some H335 @ 23.9 grains, straight out of Sierra's newest loading manual. Both loads are supposed to travel at 2800 fps.

Input?

Thanks Guys!

PS-I only have Redding competition Dies, and Foster. Elevation is 2600 feet above sea level.

 

[dmickey]

DO NOT start at 23.9 grains of H335! That is near the maximum powder charge according to Hodgdon's online data! Always start at the lightest charge listed and work up from there. What you get and what they get for pressure and velocity may be drastically different! Again, start at the lightest load listed and work up from there. Your gun, fingers and other parts of your anatomy will thank you.

 

[littletoes]

I think you might have confused the "AR" load info for the "Bolt-Action" load info!

The 23.9 load in the Sierra 5th loading manual is more than half-way to the "light" end.

Check it out!

 

[TheSnake]

Surprising yes! I thought a Match King of this weight wasn't supposed to stabilize out of a 1 in 12 twist barrel.

Yes you are correct. The minimum twist rate for minimal stability of this bullet is listed as 1 in 9.

 

[dboyles]

I've had H335 and the 69gr SMK work well for me in the past. It wasn't out of a 1:12 barrel, but if it shoots 'em, why fight it?

 

[Erik Cortina]

If IMR 4198 shot great, why don't you load IMR 4198?
I would suggest using 20 grains! ;D

 

[RJinTexas]

Have you tried shooting those 69 gr bullets out to 300 yds, you may find out that your 12tw will not stabilizethe heavier bullets at farther distances. Then if you still like what you see I suggest you take Erik's advice and feed it what's it has already told you it likes, why fight it.

RJ

 

[queen_stick]

Have you tried shooting those 69 gr bullets out to 300 yds, you may find out that your 12tw will not stabilizethe heavier bullets at farther distances. Then if you still like what you see I suggest you take Erik's advice and feed it what's it has already told you it likes, why fight it.

RJ

+1

shoot the 69's at long range... that will tell you right away if they're fully stabilized

 

[littletoes]

That's the problem, we were shooting from 100 to 400 yards, and I can't remember if I had shot them to the 400 yard line, but like said above,I just need to get back out to the firing line and try them.

Haven't tried the 4198 yet because nobody seems to have any in town! Didn't realize it was such an "old" powder!

 

[Erik Cortina]

If you use a different powder you have to start over with load development. You shouldn't substitute powders, speed and pressure are two different things, just because two loads are going the same speed doesn't mean they have the same pressure, it could be dangerous!

Oh, and the same goes for shooting someone else's handloads, you got lucky apparently, but it too can be dangerous.

I don't mean to lecture you, I just want everyone to be safe.

 

[littletoes]

Absolutely!
But in all cases when considering factory rifles, I have never, nor have I ever heard of there being ONE case, where a low-end load from a loading manual has showed excessive pressures.

No, not one.

The ONLY exception that I can even imagine, is one where an individual has tampered with the factory chamber, for example-possibly "polishing" it.

I can imagine that every experienced hand-loader on this forum has experienced the same exact thing.

No, I wasn't lucky, but thank you for the concern.

When one experienced hand-loader, fires another experienced hand-loaders rounds, it is not luck, it is a hypothesis.

 

[Erik Cortina]

Absolutely!
But in all cases when considering factory rifles, I have never, nor have I ever heard of there being ONE case, where a low-end load from a loading manual has showed excessive pressures.

No, not one.

The ONLY exception that I can even imagine, is one where an individual has tampered with the factory chamber, for example-possibly "polishing" it.

I can imagine that every experienced hand-loader on this forum has experienced the same exact thing.

No, I wasn't lucky, but thank you for the concern.

When one experienced hand-loader, fires another experienced hand-loaders rounds, it is not luck, it is a hypothesis.

My bad, I didn't realize you were an experienced handloader due to the fact that you were trying to substitute powders based only on speed!

 

[littletoes]

Uh....."Low" speed......

Custom chambers with tight necks may be another example altogether!

So Mr. Erik, in your wisdom, are you telling me, that on each and every occasion, you have ALWAYS started at the lowest given load example, when loading for a factory chambered rifle???

ALWAYS??? I would imagine NOT.

Another question would be, have you ever exceeded a loading example's listed max pressure??

Yes, that's a "trick" question! If you go from the previous Sierra loading manual, to the most current, some of the "past" loads would indeed be considered above the max level in the newer manual.

Check it out.....

 

[Erik Cortina]

I don't use reloading manuals. So your question does not apply! ;D

 

[littletoes]

Now that IS interesting!

You must have favorite powders, and go with burning rates that you combine with bullet weight???

How do you figure out what your looking for?

 

[Erik Cortina]

Now that IS interesting!

You must have favorite powders, and go with burning rates that you combine with bullet weight???

How do you figure out what your looking for?

Is that another trick question? An experienced handloader like yourself should know exactly how to do it! ;D


Ok, I'll tell you. I use QuickLOAD.

 

[littletoes]

Guess I'm an old dinosaur!

A couple of friends of mine have and use QuickLoad, but I haven't tried it myself, or even talked to them about it. They have posted pictures, and data results, but I have never openly asked about it.

Care to give a brief review of how its impressed you with specific loading's? Or how specific powders stand out?

Confused on how it deals with custom chambers as compared to the "length" of factory chambers, with their excessive free-bore.....?

 

[Laurie]

Returning to the OP's question, no a 69gn Sierra MK will NOT stabilise normally in a true 1-12" twist barrel. Under standard ballistic conditions (59 deg F, 29.92" mercury atmospheric pressure), the 69gn SMK which has a 0.900" OAL produces an Sg (stability coefficient) of 0.95 at 3,000 fps, while 1.0 is the theoretical minimum required. Don Miller, Bryan Litz and other ballisticians recommend a minimum Sg value of 1.4 to cover the likely variations that can affect real as opposed to theoretical stability - low temperatures and high atmospheric pressures, marginally longer bullets in the box, the twist rate not quite what the manufacturer quotes, MV variations etc.

However, when Remington says 1-12" twist, that's not quite the same as Bartlein saying 1- whatever, that company sticking to the spec within a tiny set of tolerances. Your Remy barrel may actually be a little on the fast side, say 1-11.75", the 1-12 only being nominal. Rerun Miller at 1-11.75" and you're up to 0.99 Sg, so a slight air temperature increase would see the bullets apparently act as if fully stabilised.

Then you might be shooting on some high plateau 5,000 ft ASL that reduces atmospheric pressure significantly, and in 80 or 90 deg F temperatures, both factors thinning the air and reducing the 'overturning moment' on the bullet and therefore requiring a lower rate of spin to just achieve adequate gyroscopic stability. Run Miller again at 90 F and 24.9" mercury (the equivalent of the standard 29.9" at 5,000 ft altitude all other things being equal) and our 69gn SMK has an Sg of 1.21 at 3,000 fps MV in a true 1-12" twist rate barrel.

The fact that you hit the target with round holes doesn't mean the bullet is FULLY stabilised - its groups may be poor compared to an equivalent quality barrel and load in 1-10" twist which is optimum for this bullet. You'll likely also find that results are very inconsistent when your Sg is as marginal as this - that is it appears to shoot fine one day, then is all over the target the next time you shoot due to minor changes in atmospheric pressure and temperature.

Laurie,
York, England

 

[littletoes]

Thanks Laurie!

Isn't there a place you can also get a false "stability", or "just" stabilized in lower velocity, in a specific, lower velocity range?
Can't be so, since I'm well above the transonic range......I know that low bc bullets have been known to stabilize below the transonic range...but can't remember with med. to high bc bullets!

Elevation is around 2600, just for clarification, and no I haven't measured the true spin of this rifle.

 

[Laurie]

Isn't there a place you can also get a false "stability", or "just" stabilized in lower velocity, in a specific, lower velocity range?
Can't be so, since I'm well above the transonic range......I know that low bc bullets have been known to stabilize below the transonic range...but can't remember with med. to high bc bullets!

I've not heard of this one - the ballisticians say the key figure is 1.0, below that the bullet simply can't stabilise; on or marginally above it, it will but still may not group well until the Sg goes a bit higher. I suspect that your altitude is the key factor as whatever atmospheric pressure is being produced for your region at the time you're shooting, sees a 2.6 inches Hg pressure drop going up 2,500 ft compared to the sea level reading. Running Miller with 27.6" Hg and air temperature of 70 degrees F raises the Sg to 1.07 on a true 1-12" twist which will just let you get away with using this bullet, although it may not produce its best groups.

I have a couple of personal experiences that are relevant. Some years back the UK CZ importer loaned me a then newly introduced .223 Rem Cz527 Varmint which should have had a 1-9" barrel. I loaded up two lots of ammo, one with the 69gn SMK, the other with the longer 68gn Hornady HPBT Match and tried them at 200yd in a range that will be maybe 200 or 300ft ASL on a warm (by our standards, not continental North America) summer's day. The SMK loads (which were mild) would about hold the 3-MOA Inner ring of the UK NRA Target Rifle target; the 68gn Hornady loads would barely stay on the target frame and were going through it sideways. The answer was of course that the factory hadn't fitted a 1-9" twist barrel, it was still 1-12".

The other example is very close to yours despite being for .308 Win. I did a fair bit of testing with the 185gn Berger BT Long-Range in a 1-13.5" twist Bartlein a couple of years back and 100yd results were excellent despite Miller saying the Sg was only 1.07, similar to what you may be getting. This was in the autumn with temperatures in the low 50s. I was encouraged enough to try them in an 800yd F Class match on the same range a few weeks later now in early winter and with the air temperature having fallen to around 40, maybe the high 30s. While they hit the paper, there was 2-MOA plus vertical dispersion and I had to switch back to my usual 155gn ammo after a few shots. 800yd instead of 100? Temperature / pressure changes? Take your pick!

If the 69gn SMK loads work, keep on trying them and at longer ranges too, but take lighter bullet ammo along too just in case you find the heavy bullet loads don't perform on the day!