The UK's Finest Independent Forum for Shooters and Gun Owners. Est 2010.

Following Dromia's advice (although I have now been labelled as cavalier ) I thought it a good idea to get some feedback from the powder manufacturers regarding my choice of powder (IMR 4350) for 243.

here's how the conversation went…

Me:

Good day,

I recently purchased some of your IMR 4350 in order to develop a load for the 70gn Noselr Ballistic Tips bullets in .243 win. At the time I relied on Nosler's published data here: http://www.nosler.com/nosler-load-data/243-winchester/

Starting at 43 grains and working up to 45 grains by far the lower value was acceptable to my rifle, producing a sub 3/4'" group at 100 yards. However, I was interested to see if you yourselves provided any data for the IMR 4350 in 243 and was surprised to see that your data only starts with the 85gn Bar TSX.

Can I ask if this is because you feel the powder unsuited to a 70gn bullet and that Nosler's data should be treated with caution? Or is it simply that this isn't a load/ powder combination that you have gotten round to testing (I would imagine that there are many thousands of combinations and that you cannot provide data for each and every combination).

Best regards, Mick

Hodgon's :

Mick,

The IMR 4350 usually performs better with heavier bullets in that cartridge. When we did our testing the faster powders did better with that bullet weight. You are correct in saying that we cannot test every single combination that is out there. Sounds like a good load.

Mike

All good then. I have my new load which is 43gn of IMR 4350, definitely the best performer over two separate days. I just need to do a like for like at 200 and 300 yards.

Onto developing a load for the 55gn Nosler's now using the old N150, which should be fun!

The reason that Hodgdon likely don't quote this combination is that as advised IMR-4350 is too slow burning for 70gn bullets. Running your favoured load through the QuickLOAD program gives a predicted 92.9% charge burn figure in a 24-inch barrel, ~90% in a 20-incher. So, nearly 10% of your powder charge goes out of the muzzle unburned.

The calculated peak pressure from 43gn IMR-4350 is 44,548 psi, that is the normal value for military firearms and cartridges developed during the 1880/90s while the SAAMI MAP allowed for the cartridge is 60,191 psi and factory ammo will be loaded to somewhere between 57,000 and 59,000 psi.

Doing a propellant charge table run for the cartridge and bullet set for a peak pressure of 58,000 psi sees the following powders as being better matched to the combinations

(1) High energy / double base ball: Alliant Re17 (Reload Swiss RS70); Ramshot Hunter; Ramshot Big Game; Viht N550; Alliant Re15; Viht N540

(2) single-based extruded: IMR-4895; IMR-4064; IMR-4320; IMR-3031; H. VarGet; Lovex SO62; Viht N150; Viht N140.

All give charge burn values of 98-100%.

An inefficient combination can sometimes give good results, but equally often may be inconsistent working well on one occasion but failing to produce full case obturation in the chamber (sooted-up cases, chamber and bolt-face) or burn efficiently on another. One often needs to chronograph test loads as well as look for good groups to see what is actually happening in the rifle.

Having played around with the 243 on paper with 55-100gn bullets some years ago, my killer load with the 70gn Sierra MatchKing in an ex-police Parker-Hale M87 tactical rifle was the relatively fast burning and dense Viht N530, a powder I've never seen recommended or listed in a reloading manual probably because it uses less than 90% of the available case capacity. This pairing consistently produced the smallest groups of any combination tried.

Many people use Viht N140 because (a) it works, and (b) it's a very useful powder so they hold it for other cartridges too.


N140

Cartridge : .243 Win.
Bullet : .243, 70, Nosler BalTip 39532
Useable Case Capaci: 51.115 grain H2O = 3.319 cm³
Cartridge O.A.L. L6: 2.700 inch = 68.58 mm
Barrel Length : 24.0 inch = 609.6 mm
Powder : Vihtavuori N140

Predicted data by increasing and decreasing the given charge,
incremented in steps of 1.0% of nominal charge.
CAUTION: Figures exceed maximum and minimum recommended loads !

Step Fill. Charge Vel. Energy Pmax Pmuz Prop.Burnt B_Time
% % Grains fps ft.lbs psi psi % ms

-10.0 82 37.80 3113 1507 43758 8498 100.0 1.178
-09.0 83 38.22 3141 1534 45088 8543 100.0 1.162
-08.0 84 38.64 3169 1561 46454 8584 100.0 1.146
-07.0 85 39.06 3197 1588 47858 8624 100.0 1.131
-06.0 85 39.48 3224 1615 49300 8664 100.0 1.116
-05.0 86 39.90 3251 1643 50781 8704 100.0 1.102
-04.0 87 40.32 3278 1670 52303 8742 100.0 1.088 ! Near Maximum !
-03.0 88 40.74 3304 1697 53867 8781 100.0 1.074 ! Near Maximum !
-02.0 89 41.16 3331 1724 55473 8819 100.0 1.060 ! Near Maximum !
-01.0 90 41.58 3357 1751 57124 8856 100.0 1.047 ! Near Maximum !
+00.0 91 42.00 3383 1779 58820 8893 100.0 1.033 ! Near Maximum !
+01.0 92 42.42 3408 1806 60563 8929 100.0 1.020 !DANGEROUS LOAD-DO NOT USE!
+02.0 93 42.84 3434 1833 62355 8965 100.0 1.008 !DANGEROUS LOAD-DO NOT USE!
+03.0 94 43.26 3460 1860 64196 9001 100.0 0.995 !DANGEROUS LOAD-DO NOT USE!
+04.0 95 43.68 3485 1888 66088 9035 100.0 0.983 !DANGEROUS LOAD-DO NOT USE



Starting with a clean sheet of paper, I'd likely try N150 first with this bullet weight as it ticks all the boxes -near 100% case fill-ratio alongside 100% charge burn and I know it works well in this cartridge with light to mid weight bullets, it being my favoured option for 80-87gn bullets.


N150

Cartridge : .243 Win.
Bullet : .243, 70, Nosler BalTip 39532
Useable Case Capaci: 51.115 grain H2O = 3.319 cm³
Cartridge O.A.L. L6: 2.700 inch = 68.58 mm
Barrel Length : 24.0 inch = 609.6 mm
Powder : Vihtavuori N150

Predicted data by increasing and decreasing the given charge,
incremented in steps of 1.0% of nominal charge.
CAUTION: Figures exceed maximum and minimum recommended loads !

Step Fill. Charge Vel. Energy Pmax Pmuz Prop.Burnt B_Time
% % Grains fps ft.lbs psi psi % ms

-10.0 89 39.60 3060 1456 41134 8752 98.8 1.219
-09.0 90 40.04 3091 1485 42463 8823 99.0 1.201
-08.0 91 40.48 3121 1514 43833 8889 99.2 1.184
-07.0 92 40.92 3152 1544 45245 8951 99.4 1.167
-06.0 93 41.36 3182 1574 46701 9009 99.6 1.150
-05.0 94 41.80 3212 1604 48203 9062 99.7 1.134
-04.0 95 42.24 3242 1634 49751 9112 99.9 1.118
-03.0 96 42.68 3272 1664 51347 9157 99.9 1.102 ! Near Maximum !
-02.0 97 43.12 3301 1694 52993 9197 100.0 1.087 ! Near Maximum !
-01.0 98 43.56 3331 1724 54691 9233 100.0 1.072 ! Near Maximum !
+00.0 99 44.00 3360 1754 56443 9267 100.0 1.057 ! Near Maximum !
+01.0 100 44.44 3388 1785 58250 9299 100.0 1.043 ! Near Maximum !
+02.0 101 44.88 3417 1815 60114 9331 100.0 1.028 !DANGEROUS LOAD-DO NOT USE!
+03.0 102 45.32 3446 1845 62038 9362 100.0 1.014 !DANGEROUS LOAD-DO NOT USE!
+04.0 103 45.76 3474 1876 64023 9393 100.0 1.001 !DANGEROUS LOAD-DO NOT USE!
+05.0 104 46.20 3502 1906 66073 9423 100.0 0.987 !DANGEROUS LOAD-DO NOT USE!

Thanks Laurie,

Some notes in case you missed them from my previous posts.

The barrel length is 22", not sure if that makes much of a difference.

I have already got a load for N150. In real world tests I could only use a charge of 39.5gns, this gave the best group over several different days. But by my calculations that only represents a 77% fill, I thought that that would be a problem. I cannot go anywhere near the 42gn mark as that is where I will start to gets marks on the case head from the ejector pin and a stiffening of the bolt on extraction, all indicators that I've used an over pressure load.

You are right what you say about the failure to fully obturate with IMR 4350 though, as I did notice that the cases were sooty, Something that wasn't as evident when using the N150. It's interesting what you say about the factory loads too, I have never been able to get better than a 1 1/2" group out of any of the factory ammunition I've tried. It always wanders around the bull, that is regardless of firing consecutively one after the other, or firing a single round, removing the moderator, allowing the barrel to cool and firing again.

Because I was going from a combination of Nosler's and Sierra's data for the 70gr Ballisitic Tip and 70gr Blitzking (very similar in design but not identical) I only considered powders listed in both sets of data. The powders I do have two sets of data for are (in order of burn rate):

IMR3031
H380
Big Game (Going from Western Powders burn rate chart)
IMR4064
IMR4895
Varget (good luck getting hold of that!)
IMR4350 ( AA4350 & N150 is just above this in Hodgons chart)

I can check later with the Hornady manual to see if I can expand that list, but the Kindle is on charge! But it looks like I'm at the bottom of the burn rate chart and you suggest I should be nearer the top so, IMR3031, H380 may be better choices?

The N150 data I used was single source (I know now bad practice) from Vihtavuori's site, I'm under their own recommended minimum load which I think was 41gns, it's in the other thread.

So, should I assume that the IMR4350 is a) dangerous or b) simply inefficient? And further, as I never managed to find a factory load that suited the rifle in the first place, would it be a consideration that this particular rifle doesn't seem to like loads at the faster end of the scale? If it's inefficient, but accurate, is that a problem other than cost? In other words will it damage the rifle or bore in anyway, excessively soot the sound moderator or cause other issues?

I can easily switch back to the N150, not a problem, but maybe what you suggest could be worth trying, a faster powder and less of it, but I have read that having a lot of excess space (>55%) in the cartridge can be dangerous.

Sorry, I should add that I used Nosler's data for case capacity (as I assume that the bullet type will make a difference on case capacity?) they state a capacity of 50.8gns h2o; and so I worked on that figure which means that 39.5gns is a 73% fill.

I think I'm going to take your advice and go for the faster N140. It's easy to get hold of, all I need to do is find a couple of sources of data for a 70gn bullet, that is, Viht's own and one other. The N150 can be reworked for the 100gn soft point, it seems more suited to a heavier bullet. The IMR4350, well, I can pass that onto someone local and recoup some value.