Same powder weights for different bullets?

[majestrate98]

Can I subsitute the 6mm Sierra 70gr Match for the 6mm Nosler 70gr Ballistic Tip using the load data from the Nosler manual? I'm shooting a 243 Win and neither bullet will come close to the rifling, so I don't see an inadvertant pressure build up from that.

[Demaiter]

Nosler's manual just gives charges that are equal for all bullets of the same weight... I'd assume then you can swap bullets in and out with the same load data... Just start with a low charge and work up...

don't change the bullet if its a max load... as who knows what differences you'll find...

[majestrate98]

I started with the Ballistic Tip and 40.0gr and I'm now at 42.3gr with no pressure signs. Max load per Nosler is 42.0gr. The accuracy isn't there, so I want to try the Sierra MatchKing. I don't want to start at the bottom again, but I don't want to start at the top either. Is there a recommended "new" starting point?

[Demaiter]

There is no "true" starting point... especially if your looking for accuracy. Things are different in every gun... funny thing is too, in my manuals most loads are most accurate at a full charge, however I see many that are most accurate at a mid to low charge as well. You just gotta try it out.

I'd try another powder perhaps too.

I assume your shooting a .243 probably

My books say generally speaking IMR 4350 and Varget are the best two choices...

My Nosler manual says 42.0 grains is max for Varget, starting is 38.0 grains - for a .243 win
IMR 4350 max is 47.0 grains and starting is 43.0 - for a .243 win

[majestrate98]

The accuracy group on the Nosler kept getting tighter as the load increased. When I hit 42.3gr with only a 1-1/2" group, I figured I needed to stop and try something else. I'm going to pick up some H4350 and work up with both powders and bullets. If it doesn't get better, I think I'll try fire lapping the barrel. I figure if it won't shoot now, fire lapping can't hurt. It's a bit cheaper than going to a new barrel at the beginning.

[PCJim]

It is recommended that you restart from the minimum charge level when changing components, even same weight bullets. Different bullet designs will have varying amounts of bullet to barrel friction, effecting pressure.

Curious if you know what your barrel twist is?

[flpirate]

M98; try IMR 4007ssc, 43.6 gn with the 70 gn Noslers, set OAL at 2.675 for mine and its loves this set-up @ 150yds.

[Unclenick]

The rule about starting over with new components is pretty much sacrosanct. However, you can load in half grain increments from the start load and check for pressure signs on each one fired just once. Chances are good you will end up at the same place with both bullets, but it can't be safely assumed. Especially not if the new bullet is longer and seats any deeper into the case to match COL. Deeper seating does raise pressure. Differences in jacket wall thickness will change pressure too, though the MatchKings tend to be on the thin side. But they also tend to be more uniformly at maximum width in the bearing surface than Noslers, and that can raise pressure a bit.

A manufacturer may put all their same-weight bullets over the same load, but they know their jackets and tooling form, and also will often just list the loads for the highest pressure situation. All others in the group achieve less pressure and velocity as a rule.

[majestrate98]

Just shot the test loads this morning. I ended up at the same powder charge with the Sierra's that I did with the Nosler's. The Sierra's did start into the pressure signs at 42.3gr - earlier than the Nosler's. That pretty much substantiated what Unclenick said.

The barrel has a 1-10" twist rate and made by Adams and Bennett. If the accuracy doesn't come around soon, that will set my opinion pretty hard on their quality. They claim MOA accuracy, but right now it's not even close. So, for loads from 38.5gr up to 42.3gr, the best group was at 42.0gr with 1-3/4". I'm getting the same relative accuracy with both bullets.

I'm working on some new loads with H4350 now and I'm going to try the IMR4007ssc (thanks for the info on those). After the next session, if the accuracy doesn't improve, it's going to be fire lapped. How can you ruin a bad barrel?

[PCJim]

Before you go to extremes like fire lapping your barrel, try a heavier bullet. In my Ithaca LSA-55, I get great groupings with 100gr Nosler partitions over IMR-4350. I have yet to find a powder and charge to get similar groupings with Nosler's 55gr VT. But, I haven't given up yet either.

Rifles are kinda like women. To get their best performance, you just have to take your time and work with them. Eventually you'll find that perfect recipe.

[jamaica]

I have found that as you approach max the accuracy often falls off. I think it is because the pressures may get a little eratic as you approach max. My rifles usually exibit a sweet spot a little below max, or even about in the middle of the charge range. Try the 100 grain bullet and 4350 powder before you give up. I don't load for 243, but my son does and that is the load that works for him.

My 222 Rem groups better with a 55 gr bullet than with a 50 gr.

What kind of accuracy do you get with factory ammo?

[majestrate98]

I've loaded both the 80gr Nosler BT and the Hornaday 87gr VMax and the accuracy from those was not good. The Nosler 55gr was the worse, but they were used to break in the barrel. Maybe I'll go back and try those again. The Nosler 70gr was showing the most promise, but pretty much stopped at 1-3/4". This morning, one group just over an inch.

Factory ammo, Remington 100gr Core-Lokt, were grouping just over 2", but they were consistent with no flyers (I used those as my baseline.)

I guess the frustration is that with every other gun I've had, my reloads always improved over factory loads regardless of the bullet used. This barrel now has over 300 rounds through it and it should have settled down by now. I really built this gun for predators, so the lighter bullets are what I want to shoot.

Give me a couple of weeks and we'll see what comes out of the oven with the other recipes. I've got new loads with H4350 and H4831sc made up for next weekend. I'll be playing with the IMR4007ssc if these don't show improvement. Thanks for the input.

[Alfahealey]

I recieved this reply from Paul at Sierra as I was looking for .243 accuracy loads for my Browning bolt action with a 22", 1 in 10 twist barrel:

"The 70 gr. MatchKing with H-322 uses a starting load of 32.8 grs. up thru a top of 34.8 grs. If you don't get the accuracy you're looking for try IMR-4350.It uses a starting load of 40.7 grs. up thru a top of 44.6 grs. Try 44.0 grs. for a good accuracy load."

I'm under an inch (barely) with 34.3 grs. of H322.
Too cold and windy to test the IMR-4350.

I have some old Lyman data in IMR-4895 that start at 36 grs. and go to a max of 40.0 grs which was their accuracy load. I made a batch of these but weather hasn't cooperated.

[majestrate98]

Well, I have not had any better success with other recipes. I did find a problem with the action screws and fixed that, but no better success. Right now, the gun is shooting two shots within 1/2" and a third 1-1/2" to 2" away. There is no rhyme or reason to the order of the flyer. I'm going to start a new thread in gunsmithing to try to find some more help. If you've got additional advice, the question I'm posting is:

I have a Mod 70 chambered in 243 with an Adams and Bennett barrel mounted in a Bell & Carlson Medalist stock. The gunsmith "floated" the barrel when he mounted the barrel. I was getting terrible accuracy and tore the gun down to check all components for tightness. The action screws were very loose, except the middle screw. So I thought the action was being torqued and causing the problem. When I tighten the action screws (front and rear to 65 in-lb, center is very light), the chamber area of the barrel became very tight into the stock. The gun is still not accurate and I'm wondering if this may be the problem.

What is the proper floating zone? Should it free float all the way to the recoil lug? Should the chamber area be supported as it is? Should there be some fore end pressure on the barrel?

Any advice would be appreciated.

Thanks for all the input on the original problem. Looks like I'm going a different path now until I need to change direction.

Regards