243 Winchester and Pressure

ColColt · May 4, 2014

Has anyone heard or read of any pressure spike problems with the 243 Winchester? I got into a discussion with some others and this was brought up. I can't imagine one caliber causing this sort of problem more so than any other. If you load too little of a slow powder like IMR 4350 or H4831 I can understand there could be indeed pressure problems and we're warned not to go below recommended starting charges regardless the powder or caliber. It really doesn't make any sense to me hey the 243 would have any problems of this sort more than a 30-06, for instance.

If loading a 270 with half a case full of 4831 there could be a pressure problem. Following recommended starting/max charges in whatever caliber is not adhered to there could be a lot of problems. I just can't see how or why the 243 got singled out. I have read the 7mm Mag suffers the same scenario but, when I had one I used IMR 4350, N205 and H4831 and never had a problem with it in any bullet weight.

Darkhorse · May 4, 2014

I used to load a lot of .243 and the only pressure problems came from one powder, IMR 4831.
I also loaded a few in 7mag. with that powder and no pressure problems, at first.
What it would do in .243 was bulge the bottom of the case, just above the web and this was with book safe loads. This was the only pressure signs it showed.
Later I loaded some 7X57 with IMR 4831 and guess what? Same bulge, same location. So I dropped back to the minimum load and got the same results. Changed to IMR 4350 and the bulge went away.
I loaded a few in .300 Win Mag. and it was accurate, with no pressure problems, so I loaded some up for hunting. I shot a doe and I could hardly lift the bolt. Primer was a little flattened. It was a very hot, humid day for November, maybe that had something to do with it.
Anyway, when I got home I disposed of all the IMR 4831 and went back to good old IMR 4350.

ColColt · May 4, 2014

I've only used H4831 in a few caliber, one being the 308 Norma Magnum, 7mm Mag and the 270 Winchester. It seems that powder was made for the 270. I've owned four and they all loved it with close to max loads and zero pressure problems.

From all I've seen in the manuals it's mostly for the heavier bullets such as the 105-107 gr bullets from various manufacturers. I think 4350 may very well be one of the top best powders for the 243 from all indications...that and Reloaders 19 and 22. The only manual I have that even hints at pressure problems is in the Speer manual. None of the others even mention it. Speer's problem seems to stem from using cases other than Winchester as they specifically warn with their data to NOT use any other brand. Maybe they're getting kick backs from Winchester, who knows.

I'm surprised about the 7x57 in that in all my manuals 4831 is recommended in about all the bullet weights and seems to give the higher velocities.

Partisan · May 4, 2014

Who were the "Others" you were discussing this with and what did they site as their information source?

Ridgerunner665 · May 4, 2014

Avoid very low charges of slow powder...its not a big deal...just follow the load data from a reliable source.

I've never used 4831 in 243....the slowest powder I've used in it is Reloder 19....mostly use Varget and H4350.

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ColColt · May 4, 2014

Partisan":35mqnd1n said:
Who were the "Others" you were discussing this with and what did they site as their information source?

The other manuals I have...Nosler, Sierra and Hornady.

baltz526 · May 4, 2014

Never heard of this with the 243. But if you believe it, Solve the problem by using H414/W760 Or W780 Add LR magnum primers and all your Imagined/real pressure problems should go away. Unless you add Too much powder.

Oldtrader3 · May 4, 2014

H-4831 was developed as powder for the 20mm cannon shells during WWII. The .270 came out in 1925, long before H-4831 did. Both the .243 and the .270 are better utilized by the burning rate of H-4350 unless very heavy bullets are being shot.

SJB358 · May 5, 2014

I run alot of RL19 and RL22 in the boy's 243. RL19 with the 90 AB and RL22 with the 105 AMax's. Works excellent for me. Seems the 243 does real well with alot of powders and it has been one of the easiest to make accurate loads as well.