IMR 4227 in .243 - unexpected high velocity

[Bill*B]

Best gurus, I seek your thoughts. While working up a load for my 19.5" barrel .243 carbine, I loaded 16.5 grains (what my Little Dandy measure throws with a #20 rotor) of IMR 4227 power behind a SAECO gas check bullet, cast of linotype, weight 80.5 grains, with a magnum primer. The bullet was seated to contact the lands. This gave me 1884 fps, just about what I would expect. Moving on to the #21 rotor, throwing 17.3 grains, my chrono showed a velocity of 2179 fps. I was shocked that a 0.8 grain increase in powder would give 295 fps more velocity. Both loads are within Lyman/RCBS recommended ranges, and neither showed any pressure signs, but I still found the experience disturbing. Should I worry?

[BK7saum]

Is that based on only one load shot over the chrono. If 4227 is position sensitive and you only shot one load of each, I'd say that the results may not be surprising, but I shoot 3 loads to at least get a small average.

That is a wide change, but probably not accurate. Shoot a pair or 3 at each charge weight. I find having less case filled causes wider extreme spreads. I think the first was on the low side and second was on high side for that charge.

[Tackleberry41]

You did not say how many shots you ran over the chrony. There is a limit how hard you can drive a cast bullet. They get to fast suddenly you get these spikes in velocity. I have seen 600fps spreads on loads where if you backed it off just a little it settles back down.

Fiddle around with a load and you will find a sweet spot where the spread is under 10fps. Change powders or any other variables and you start over again.

[Bill*B]

Five shots averaged for the 16.5 grain load, velocity spread 1834 to 1951 fps. Eight shots for the 17.3 grain charge, 2171 to 2207 fps. I stopped the string early to take a couple home and pull the bullets - fearing I had used the wrong rotor - but the charge was correct, at 17.3 grains. I did not use a filler for either load. They were fired from a bolt rifle, magazine fed.

[Maven]

Bill*B, Could the odd result indicate a problem with your chronograph? I.e., there may not be any independent confirmation of results, or what Oehler calls a "proof channel." If this happened to me, I'd test the device itself with a box of expensive, but known velocity (1,040- or 1,080 fps) .22 LR ammo. With that done, I'd weigh the same brand of new .243Win. cases so that you have enough* to retest the 16.5 gr. and 17.3 gr. charges of IMR 4227. And I almost forgot, start with a new battery and under ~the same light conditions. Hope this helps!


*10 of each

[earlmck]

You're right Bill -- that is puzzling. I've been chronographing cast boolit loads for around 40 years, often using IMR 4227 and have never seen that kind of velocity jump with that little powder increase.

I looked at your load with QuickLoad and see that those are rather low pressure loads (like around 13 to 15k psi). My guess is that the 16.5 grain load had lots of unburned powder and the 17.3 grain load not as much unburned powder, so you are just starting to get the "push" out of your 4227 load. You probably need a faster powder so you get more normal pressure without exceeding desired velocity levels.

I don't shoot cast a lot in the 243, but the little I do has been with TrailBoss which fills the case much fuller. I've been using 10 grains and a Lyman 80 grainer for an nice tin can plinking load when getting younger kids used to the "youth rifle" they will use for their first deer hunts. QuickLoad tells me that 16 grains of the fluffy stuff would fill your case nearly 100% and get you over 1900 fps at moderate (34k psi) pressure levels, just in case the 4227 experience worries you enough that you wanted to try a different powder that would get you your desired velocity levels at mid-level pressures and fill the case to a much greater degree.

Another thought would be Unique or similar in the 9 to 12 grain range with pressures in the 20 to 30k psi range.

[Bill*B]

Thanks to all! Bill

[Dieselhorses]

Is the IMR 4227 the "new" stuff? Or the "old" stuff? The old, made by Dupont, was manufactured a little hotter. Also seating your bullet where it touches lands/grooves is going to produce more pressure. My 30-06, according to Lyman manual, calls for "2.984 COAL" for the Lee mold I use. Another .054 to 3.38" would put me touching. In my case, I'm going to step it up .009 6 times and compare results. Any reason why you're using magnum primers?

[Bill*B]

The 4227 is from a batch about a dozen years old. Using mag primers only because I though they would give more positive ignition with the small charge weight. Bill

[Maven]

Bill*B, The following link from the CBA Forum and posted by Joe Brennan, may help you determine whether the 300 fps velocity increase you recorded for 17.3 gr. IMR 4227, is anomalous or not: https://castbulletassoc.org/forum/thread/9-chronographs-es-and-sd/ Btw, I don't know why you used LR Mag primers with 4227 and CB's in the .243Win. case. I've always used standard LR primers with 4227, 4198, TVEN, 5744, Unique, and AA #9 in that cartridge, with CB's naturally with nary a problem. In short, I think we've narrowed the unusual result to either a chronograph problem or a propellant/primer problem, don't you think?

[Bill*B]

The hotter mag primers may well have contributed. Will have to try the load again with regular primers and compare, when my pulse settles down. Bill

[Dieselhorses]

IMO, I've had good luck with H4895. You can go as low as 60% of max load. It will be very close to 60% of max load velocity. If you load 70%, velocity will be 70%. H4895, for me anyway, is an excellent powder to use for reduced loads. I have used it in my 30-06, .270 and even my .223/556. Worked great.

[Bill*B]

Gentlemen, I have stumbled onto the awful truth - and since you have been kind enough to help me, I am going to hang my head in shame and share it with you. I pulled the bullet from one of my remaining unfired rounds and examined the powder with the 20X microscope from a Lee hardness tester. The grains had no perforation! That means they could not be IMR 4227. The power grains appear identical to, and almost certainly are, Alliant #2400. What a big "red flag" warning me to be more alert and careful at the loading bench.

[Maven]

"The grains had no perforation! That means they could not be IMR 4227. The power grains appear identical to, and almost certainly are, Alliant #2400. What a big "red flag" warning me to be more alert and careful at the loading bench." ...Bill*B

Bill*B, I'm not convinced the powder is Alliant 2400 since it is a flake (disc) powder whereas IMR4227 is an extruded or stick powder, albeit with very short "sticks." Is this not the case or have these two propellants changed their basic shape?

[Bill*B]

They are very close in appearance. I can't tell them apart. The #2400 "flakes" are a little shorter than the 4227 "sticks", but they look much the same even under magnification. 4227 has a single central perforation that #2400 does not. According to "Powder Profiles", John Wooters measured IMR 4227 at 0.025" in diameter, and 0.021" in length. He found that #2400 averaged 0.038" in diameter, and 0.013" thick. Now, this was published in 2009. I don't know if the dimensions have changed over time.

I am also implicating #2400 because I have only loaded 3 powders in my .243 - Steel, #2400, and IMR 4227. The huge flakes of Steel are unmistakable. Bill

[swheeler]

"The grains had no perforation! That means they could not be IMR 4227. The power grains appear identical to, and almost certainly are, Alliant #2400. What a big "red flag" warning me to be more alert and careful at the loading bench." ...Bill*B

Bill*B, I'm not convinced the powder is Alliant 2400 since it is a flake (disc) powder whereas IMR4227 is an extruded or stick powder, albeit with very short "sticks." Is this not the case or have these two propellants changed their basic shape?

The current 2400 is extruded, very small sticks similar to 4227

[44MAG#1]

Shoot five rounds with the powder positioned in the rear of the case and five with the powder in the front of the case and see how position sensitve it is. I think you will see the powder is very position sensitive. If it is I would do somerhing different regardless.
No need to use a powder like that unless you cant do any better.

Again I mean no hurt, harm, anguish or turmoil by my post I have posted on this posted subject. I am not baiting, trolling or calling out anyone. I am making a post based on my experience, knowledge and/or belief or opinion. That is all.

[Bill*B]

Thanks to you all. This episode has caused to pause, and reevaluate my loading preferences and practices. Bill

[Maven]

Thanks for setting me straight on Alliant 2400, Scooter! I now completely understand Bill's "unexplained" velocity reading.

P.S. I haven't seen or used 2400 in +20 yrs.

[swheeler]

Bill I think you have figured out what happened, eye opening experience! About a decade ago I moved my powder magazine probably 12 feet from my scale and press, only one bottle of powder on the bench at a time for single stage, and one bottle feet away for progressive. Maven, yes Alliant pulled a sneaky on us ;-), when 2400 was unattainable I started working with 410 which is extruded, then when I got my hands on some new 2400 I too did a double take, thought I'd grabbed the Alliant 410 powder by mistake.

[Dieselhorses]

Shoot five rounds with the powder positioned in the rear of the case and five with the powder in the front of the case and see how position sensitve it is. I think you will see the powder is very position sensitive. If it is I would do somerhing different regardless.
No need to use a powder like that unless you cant do any better.

Again I mean no hurt, harm, anguish or turmoil by my post I have posted on this posted subject. I am not baiting, trolling or calling out anyone. I am making a post based on my experience, knowledge and/or belief or opinion. That is all.

44mag, since we're on this subject were you referring to 2400 maybe being position sensitive or 4227? Just wondering because I'm trying to work up some 308's with IMR 4227. Is there some sort of reference that reflects powders sensitivity?

[44MAG#1]

44mag, since we're on this subject were you referring to 2400 maybe being position sensitive or 4227? Just wondering because I'm trying to work up some 308's with IMR 4227. Is there some sort of reference that reflects powders sensitivity?

Most powders are including 2400 and 4227. Try the experiment I mentioned. It can be an eye opener. Even fast pistol powders such as Bullseye can be in big pistol cases.
In rifle cases I would never use a powder that sloshed around much.

Again I mean no hurt, harm, anguish or turmoil by my post I have posted on this posted subject. I am not baiting, trolling or calling out anyone. I am making a post based on my experience, knowledge and/or belief or opinion. That is all.

[Dieselhorses]

Most powders are including 2400 and 4227. Try the experiment I mentioned. It can be an eye opener. Even fast pistol powders such as Bullseye can be in big pistol cases.
In rifle cases I would never use a powder that sloshed around much.

Again I mean no hurt, harm, anguish or turmoil by my post I have posted on this posted subject. I am not baiting, trolling or calling out anyone. I am making a post based on my experience, knowledge and/or belief or opinion. That is all.

No I'm totally with you. Another reason I asked was because, (and not to complicate things), I was debating on using a filler. If I establish a halfway decent load I don't think I'd be conscious during a hunt on whether I remembered to tip rifle back or forward but yes, I understand what you're saying. Most of the volumes in my other rifle cal's generally are 60% or more and that's another thing I need to be conscious of is powder volume-all powders are different. Thanks for your advice.

[44MAG#1]

While I have never used a filler in a bottleneck case since ive never used a powder charge that light I have in straight walled cases such as the 45/70. This with A2400 amd. 515 grain bullet . And the 458 win Mag using A2400. It worked great.

Again I mean no hurt, harm, anguish or turmoil by my post I have posted on this posted subject. I am not baiting, trolling or calling out anyone. I am making a post based on my experience, knowledge and/or belief or opinion. That is all.