243 win High pressure?


June 28, 2006, 08:52 PM
I loaded up some 100gr SP 243 for my TC Encore rifle and shot them the other day. I had loads (3 shots each) of IMR 4064 from 33.5 to 36 grains. The Sierra book says min 33 max 36.5 for 100grn bullets. I worked up and noticed when I got to 35grns the primers started to flatten pretty good. The brass is winchester once fired with federal primers. I cant figure why its doing this. I double checked everything I can think of. The only possible thing I could think of is I checked the OAL with a stoney point guage and it came out to be right on with the books. I think I may need to seat them a little deeper to get them aff the lands a little more. Does this make sense and could it work or should I just use a lighter load? Its not shooting too bad but it seemed the groups were starting to shrink then I noticed the primers were flattening. Any help or thoughts would be great.

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June 28, 2006, 09:47 PM
Id say if your seeing pressure signs reduce your powder charge and try different seating depths. Once youve found the seating depth that shoots best then increase your powder while watching for pressure signs.

June 28, 2006, 10:34 PM
I have three Encore barrels and they all display a tendency to max out well below book max. I can only presume that they just have tight throats. I have found that seating a little deeper rather than trying to push too far out towards the lands actually makes things a bit better - lowers peak pressures a bit in my 308 and 7mm08 loadings.

The Encores give good accuracy and the velocities that I get are still reasonable, so I'm not sad with the end result. It's just something to remember as you work up new loads - don't expect to get book max.

June 29, 2006, 01:11 AM
Just don't light load the .243. I was working up a load for my son's single shot Rossi and was trying to find something light for him to practice with then build him up to warm accurate hunting loads. I experienced extreme pressure signs including split cases. Loading warmer cured this, middle to upper edge of the book... I found some writings on the net discussing high pressures when light loading the .243.

The best thing I've purchased to accompany my reloading hobby is a Shooting Chrony. Along with pressure signs, or lack of, the Chrony tells me so much more. A good investment of a little more than a hundred bucks is really worth it.


June 29, 2006, 07:10 AM
Thanks for the replies and help. I think I will back down to where I had decent groups and play with seating depth. thanks again.

June 29, 2006, 09:46 AM
IMR-4064 is also pretty fast for 243 with 100gr bullets, and you'll max out pretty quickly. I'd expect 4350 or 4831 to be more appropriate, especially since you have either a 24" or a 26" tube.

June 29, 2006, 09:54 AM
I seem to have better luck loading slower powders in the .243 (AA 3100 is my favorite). Faster powders caused similar issues in my Rem 788.


June 29, 2006, 09:59 AM
CAUTION: The following post includes loading data beyond currently published maximums for this cartridge. USE AT YOUR OWN RISK. Neither the writer, The High Road, nor the staff of THR assume any liability for any damage or injury resulting from use of this information.

Your load of 36.5 gr 4064 100 gr 243 should be 50k per Quickload.

The max pressure for 243 is 60 kpsi per SAAMI, but SAMMI allows 65 kpsi for 270W, which has the same 7mm Mauser case head.

The following load should be 65 kpsi per Quickload:
This 308 brass necked down to 243.
100 gr 40 gr IMR4895
Although this should be about 65 kpsi, but some factors made each shot higher pressure:
1) neck walls too thick make bullets pinch
2) bullets seated very long jammed into lands
3) Addams and Bennet bull barrel blank has very rough bore is prone to Copper fouling
4) The 38 Turk Mauser bolt handle knob took 100 pounds of force to close on this ammo


June 29, 2006, 12:29 PM
"back down the loads to the best group". Do like I do, load for accuracy, not velocity. Can't bring home the game with velocity.......chris3

Smokey Joe
June 29, 2006, 12:58 PM
Jethro--I agree with Ball3006 as to this load. Also, you said "back down to where I had decent groups and play with seating depth."

Seating depth is quite important. You checked yrs with the Stoney Point--You want to be LESS than the absolute max for YOUR chamber, i.e, the bullet should be a bit short of the lands when the round is chambered. Exactly how much less than max has to be worked out for each individual firearm and each different bullet model you load.

One other thing--I agree with Rbernie on yr choice of powders. IMR 4350 is the classic powder for .243Win. Your results might improve with that. It works very nice in my .243Win. You will still need to experiment with seating depth, though.

Enjoy. As always, the journey is part of the destination.

June 29, 2006, 02:51 PM
Thanks again to everyone for their help. I ll first try playing with seating depth. The guy I bought my reloading kit off of had 2 1lb cans of 4064(unopened) and the Sierra book said it was good so thats why I used it. If I cant get any satisfaction Ill switch powder. By the way what else is 4064 good for since I have 2lbs?

Smokey Joe
June 29, 2006, 03:55 PM
Ahh, good old reliable IMR 4064!

Now, it ain't that it won't work in yr .243Win, it's just not the powder you'd start with for developing a load, given that you have to go out and buy whatever powder you decice to work with. (That'd be IMR 4350 for the .243Win.)

Since you have it, you might as well try to work up an excellent load with it. You might find it works great.

It was the powder I began with 100 years ago with a Lee Loader in .30-'06, so I'll always have a soft spot in my heart for it.

Paging through the Nosler reloading manual (just the first one I grabbed) I find IMR 4064 to be useful in a HUGE range of cartridges and bullet weights; it's just that it so seldom is the powder of choice ("Most Accurate Powder Tested" in Nosler-speak.) Much more often this honor went to IMR 4350.

IMR 4064 will work in pretty much everything from 6mmRemington to .300WSM, which is just the section of the book I happened to page through. It'll work in a wider range than that I'm sure. It was Most Accurate Powder Tested in 6mmRem with an 80 grain Ballistic Tip; in 240Weatherby Magnum with a 55 grain BT; in 260Rem with a 100 grain BT or Partition; in .300Savage with any of Nosler's 165/168 grain bullets, and in .300WSM with any of Nosler's 150 grainers. So IMR 4064 is decidedly NOT junk!

Rifles are finicky and unpredictable to some extent, which is why there is room for art as well as science in reloading. Your rifle might actually prefer IMR 4064 to anything else you try. Or not.

But for heavens' sake since you've already got it, give it a good thorough try.

Enjoy. As always, the journey is part of the destination.

June 30, 2006, 09:33 AM
I haven't loaded a lot for the .243, but I'll soon be working up some loads for a Stevens that I aquired from a pistol match.

My previous experience with the .243 is that it truly can be picky. Especially regarding brass, as I seen some considerable fluctuations in case thickness, and neck thickness. (ie: case capacity too)

I suggest you refer back to your data and look at such things as case selection of the source.

If they used Winchester brass, that is one clue, as it and Federal tend to be lighter and hold more powder, and hence lower pressures with a specific load.
Also, primers can make a HUGE difference in small bore, large capacity cases such as the .243.

Also, case length will matter with your T/C. My experience with T/C contenders is that they have tight chambers, and tight throats, and short throats. NONE OF THESE ARE BAD !!!! It simply indicates that T/C is building their firearms to very tight standards. They make excellent firearms.

Mine and my brothers experience indicate that IMR-4831, is perhaps the best powder for the .243. Just an instance of a particulary good match of propellent to cartridge.

With length trimmed and neck reamed cases, he found that IMR-4831 delivered as much as 150fps faster than factory standard velocities with similar pressures as either of the 4350's or H4831. I'm told or lead to believe that AA3100 is very, very similar to IMR4831, so should be an excellent alternative.

However, I got superlative accuracy from a Rem. 788 with 80gr bullets (Hornady and Speer) and H4895 back in the mid '70s. No idea about velocity, as chrono's weren't widely available back then, but suspect that it was relatively low, probably 3,100fps or so.

But the many crow's and several deer I shot with this load never complained !!!!!

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