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If I were to switch from using IMR4350 in a 243 to IMR4451 using 85-87 grain bullets, approximately how much less powder would I need to use to get the same velocity (approximately 3070 fps) if my original load was 44 grains ? From what I've seen Qiuckload estimates say about 2 grains less powder, but just wondering what real-life testing might has shown to date ? Ben

Have you thought to check Hodgdon's online data for a comparison of the two powders for the bullet weight listed? For the 243 and 6mm Rem, 4451 has a slower burn rate, but seems to have more energy.

I've tried them both, exact loads. No difference in two 3006s.

HuntnShoot, Thanks for the tip, but unfortunately the online data from Hodgdon is for a 85 grain Barnes bullet, which is quite different then the Sierra and Hornady bullets which I use. Also the load listed for IMR4451 is way faster then the load listed for IMR4350. Ben

The difference depends on the particular load, but also on the particular batches of powder. The jug of 4451 I've been using has required a little more powder to match H4350 velocities in several cartridges, about half a grain in rounds with about 50 grains of powder room. The lot before that was a little different.

I'm no ballistics guru, by anybody's yardstick, But Big H's own burn rate chart shows 4451 as a whisker slower than IMR 4350. In the ol' '06 with 180 grainers it damn sure isn't according to the chronograph. The lot I tried is way too perky for grain for grain substitution. I fully realize bore sectional area, bullet weight etc cause powders to "move position" on a burn chart but my advice to anyone is to treat the new powders with common sense, and not pay a whole lot of heed to merchandising and advertising.

MD.

Have you noticed any difference in the accuracy of loads with IMR4451 compared to H4350?

So far IMR4451 has produced loads at least as accurate as H4350 in every rifle, and sometimes more accurate.

What I've done is reduce the charge for the load developed with H4350 a little, then work up to the same velocity achieved, using the same case, primer, bullet and seating depth. Probably have done this with 8 cartridges so far. In fact, have only one H4350 load still in use, for Eileen's .243, but she only uses the rifle every 2-3 years, and has enough loaded ammo to last a while longer.

The new Sierra manual has them within a tenth of a gr. up to 43 gr. with the 85 gr. bullet.

Just checked my records, and my first two batches of IMR4451 got the following average velocities with the same .257 Roberts and 100-grain Ballistic Tips, using 46.0 grains of powder:

Lot 1--3052 fps
Lot 2--3104 fps.

Lot 1 was the first batch of 4451 Hodgdon sent me for testing, as I recall 2-3 pounds. I was impressed enough with it that I bought an 8-pound jug afterward--which was Lot 2.

After that test I mixed both batches together, and not surprisingly the results were slightly slower than with Lot 2.

From what I understand from more than one powder company, this is the same method they use to try to approximate the burn rate of "new" batches of powders. They keep older lots on hand that are a little slower or faster, and mix them with new lots to keep things within a reasonable range, usually within 2-3% or previous lots--though some powder manufacturers try to keep the variation within 1%.

Obviously, the longer a powder has been produced, the more new batches can be "adjusted." I remember back in the earlier days of H4350 when published data sometimes indicated it was a little slower than IMR4350, and then "new" data appeared indicating it was a little faster. These days things seem to have settled down.

I've been mixing lots of powder for some time now. If I buy 6 one ib bottles in mixed lots I pour them into an old Aliant jug and mix them into one lot then pour them back into original cans. I color code the cans as one lot.

Yeah, that's what I generally do too--unless the new batch proves to be very close to the same burn-rate as the older one. They sometimes do.