Looking for Same Accuracy but More Power

S

Stevesdl

Beginner
Feb 15, 2010
85
0
Now that I have all my variables coming together (NAB 225, Nosler brass, headspace, OAL), my groups are an exciting and consistent as this target. (shot a number of same hole groups as well last weekend)

..I am getting greedy, but down so close to the wire (3 weeks away) for the 10 day hunting trip.
338 Win Mag with NAB 225 71gr at 2738 FPS at the muzzle.

I also tested 9 rounds of the same but made two adjustments (72 gr and adjusted OAL -.004 than the previous 71 gr loads.) 100 yd accuracy dropped to 2" groups.

The question(s)
1. Was it the change in powder or the change in OAL or the change in both that caused me to loose the accuracy?
2. Does the optimum OAL stay the same regardless of the change in powder sizes?

I would like to get a little more power out of my 338 win mag if I can also keep the accuracy.
Thanks
Stevesdl
View attachment 10-13-2010 338 Win Mag 225 NAB 72gr 3.447 OAL0001.jpg
 
I am no expert, but I will venture a guess : In every rifle the bullet "jumps" to the lands. The OAL may have to be longer than factory ammo to be the best way of addressing that "jump" that the bullet makes. Therefore the powder load should not make a difference, given that you keep the OAL the same as you have determined with give best accuracy.
The mistake you made, was in making two adjustments to the load at one time. With two, you will not know what opened up groups until you reload the same as the accurate load and only change one feature. If the groups open up, you know that the one changed feature is the culprit.
Steven
 
Yeah, after the first group, I was mumbling under my breath on why I would do a stupid thing as change two variables for a new load. I just didn't think (at the time of reloading). My load's OAL are now custom to my rifle but I made the OAL a longer length. I started with .020 from lands. The last not-so-accurate group were .016 from the lands.

thanks
Stevesdl
 
One change at a time Grass-hopper :wink:

Did you chrony your load with the higher powder charge ? There are quite often instances where your FPS will
peak or close to it before max charge. Efficiency has been reached and in my eyes no reason to be burning
more powder ??

That one grain difference can make a drastic change in groups - My .300RUM showed me that this weekend -
86grs gave me great groups - 87grs opened up to 1.5 inch or so 88 closed back down slightly.

There isn't anything in N/A that will know the difference in 100 / 200 fps velocity from your .338 WM - It's all about confidence and at this point in the game, you don't want to be second guessing yourself.
 
"There isn't anything in N/A that will know the difference in 100 / 200 fps velocity from your .338 WM"

I know. :) I all of a sudden have that Tim the Tool Man power urge.
Unless there is a magical answer and a short cut, I have already started to accept 2738 and 71 grs. Especially with that repeated accuracy. Most likely will work on this again AFTER hunting season for next year.

Thanks
"Grasshopper"
 
Only changing one variable at a time is best.
With the group pictured above, I would move it right 2 clicks, verify POI and go hunt.
The 225 gr AB at 2738 fps MV is more than enough energy to take down the biggest of elk.
Determine you own personal max range and practice shooting from field positions.
After your hunt start playing with loads for next year.

JD338
 
ah JD338

I had forgotten about your slogan signature. :):)
I am back on track now. :):)

Thanks everyone for comments
Stevesdl
 
Barrel accuracy is mainly a matter of timing. That is timing the exit of the bullet from the muzzle when you have the least oscillation and the most consistancy. Both powder charge and seating depth will affect the barrel exit timing. Powder charge by a large amount and seating depth by a small amount.

Think of powder charge and seating depth as being analogous to the focus adjusments on a spotting scope that has a macro (large) and a micro (small) adjustment. For that reason I will load first for the velocity I want and then fine tune with seating depth. Sometimes you hit a velocity range that is a scatter group with a large group size and the fine tuning of the seating depth will not carry you outside the bad barrel timing range you are in with velocity. In that case you need to proceed further or back to a better velocity range and the fine tune with seating depth.

JMHO
YMMV
 
Stevesdl

I agree with woods but since you are 10 days out from your hunt, I say stick with what you have. You don't want to bog yourself down trying to find the sweet spot when you could be practicing longer ranges from field positions and building your confidence at longer ranges.

Just my opinion....

JD338
 
In your shoes, I'd go with the load that punched the iddy-biddy group in the photo. You're not going to realize an appreciable increase in velocity by bumping the charge a grain in so large a case. I shoot 225-grain ABs in my .35 Whelen and last time I checked, a half-grain increase in powder charge changed velocity by about 15 fps and a full grain change yields about twice that---hardly worth any sacrifice in accuracy.
 
With that combination of power and accuracy, I wouldn't change a thing. Not a thing.

I'd load up a mess of 'em at that exact load and happily hunt with it.

My most recent example of doing just that was working up a very accurate load for my .375, that turned out to be well under max. Still, it was more accurate than I'd ever expected from a Ruger Number One in .375 H&H, and with a 260 at 2620 fps, it wasn't exactly a wallflower for power anyway. I loaded up a mess of 'em, practiced at the range with that rifle and took it hunting. It worked just fine, even at 300 yards.

If I can clobber a bear with one shot at 306 yards, at a mere 2600 fps mv, you can do even more with your .338 load!

Just go load a couple hundred of those things, and hunt happily. You've got more than enough power and accuracy available.

Guy
 
I would take the itty bitty holes load hunting this year as well.
If you want to play after the season, you have all winter and summer to do so.
 
I have log on to post a question twice this week and I see someone has posted the same question only hours earlier. Without hijacking this post I hope I can ask another question about adjusting the powder charge and effect on accuracy. I have read a few times that you should pick a powder that will nearly fill your case. How important is this? If we choice to keep the lower charge weight for accuracy at the range where our rifle is held level will the less then full cartridge have any effect in the field when our rifle may be aim up or down a steep sloop?


George
 
I believe that propellant sloshing around inside the case, when the rifle is held at different angles, or just when the propellant settles in a different attitude just before firing, will have an affect on groups.
Propellants that fill, or nearly fill the case will group more consistantly than those that do not fill the case.
Accuracy is only relevant, depending on what the shooter wants. A case not filled with propellant, will likely not show a variance serious enough to have a affect on a deer hunter's kills, except at extreme ranges. Deer hunters are, in general, satisfied when they group all rounds inside 6" at 100 yards. So, whether the case is full of propellant or not, will not even be given a thought. Shooters who seek optimum accuracy, want to pull in every advantage, in order to get the best groups possible. The serious shooter will endeavor to find a load that fills the case, and provides the best accuracy and desired MV. Hitting the mark still remains the object. How one gets there is dependent on a number of details, of which filling the case is only a minor one.
Steven
 
Steve,

How are you measuring your groups? That target you posted looks far better than 2.00". Remember the easiest way to measure is outside edge to outside edge minus the bullet dia.

Listen to P/Stroke and JD. one varible change at a time. 8) 8)

And remember, when ever ToolTime Tim went for more "power/speed", look where it got him... :lol: :lol:

Rod
 
Hey Rod!!!

That is a group with 71 grns. Everyone's comment brought me back into reality. This weekend I will go out and zero in for 200 and practice with about 75 rounds. It is just incredible how a few thousands and 1 grn of powder can make such a difference in accuracy. All has to do with balance and harmonics along with all those other variables.

Another intersting few things while testing.

1. In one of my earlier posts when I was having issues with everything (all my fault BTW - but you guys saved me), on two different occasions with 72 gr loads my fps was averaging (6 round average - 2936 FPS (In the recent past with COAL at 3.334 - 2833 FPS), (and yes this is after correcting the chrony to being 100% extended and flat) but I immediately started getting head separation for both 2nd and 3rd round reloads. That is when I started to believe the way I was setting up my die was also incorrect. --> Now that I have the OAL and headspace corrected and "One with my rifle", the pressures and ratio of "FPS to bullet to powder" is starting to look maybe more normal to what many others get with that load. 9 round average with all corrections and Nosler brass is 2772 FPS. My 71 gr loads are averaging 2738.

2. This next thought might be a tad embarrassing but not sure if it is verifiably true yet. Just noticed this yesterday at the range. I mentioned in some earlier posts that with the 73 and 74 grain loads I was getting bolt stick on a few shot occasions. Rightfully so,some comments correctly mentioned this is a sign of excessive pressure. As I have some very specific things corrected now, I noticed the bolt still sticking on occasion. In addition to the high pressures before, here is what might be contributing to the bolt sticking now...

If I pull the bolt handle 100% up (not 99.999 %), i noticed that it is sticking drawing back ..... If I just almost pull the bolt all the way up but not quite (and we are talking extremely extremely slight off 100%), and then pull back, no stick! hmmmmmm might sound like a minor gunsmith adjustment but not sure since I just realized this on my last three shots yesterday and have not checked to re-verify this morning with everything cooled down. I will advise as I re-verify.

Thanks Rod

Steve
 
Hey Steve,

Stiff bolt lift is usually indicative of hi psi, "stiff" pull back is generally a brass issue. A- time to resize or in your case. But in your case, you may have reached the work life of the brass.

I remember you saying this is the 3-4-5th reloading on the brass. When new or annealed, it goes thru its expand & natural contract cycle without an issue. You on the other hand may have just "worked the brass to the point it expands, but no contract (work hardened, loss of elasticity, etc).

Just a thought from what we previously talked.. I think thats what you may be feeling. Time to buy some new brass buddy or an annealing machine... Thats it, then I know somebody I can send my brass to for annealing......

BTW: Hows the M.I.L. situation? Hope for the best....


Rod
 
The bolt is sticky pulling back this morning with no brass also the bolt is sticky pulling back this morning with brass (brand new and fired brass)

It all seems to be affected if I swing the bolt all the way up tight before pulling back. If I do not go all the way up super tight and then pull back, it appears to pull back without sticking.

I am not sure till I go out this weekend if it gets worse or different after firing or when the barrel\bolt get warm.

I am only just now realizing this because of the way I was ejecting my brass after each fire. I would stand up and work the bolt which would make me inherently swing the bolt all the way up tight. I was doing it this way so I could catch my brass before it fell to the ground amongst other old brass and other rifle brass at the range.
I never thought this bolt was smooth and actually have made comments to it a few times. The trigger is the best I have ever had but the bolt is not smooth like some other friends bolts.

Thanks Rod.
Steve
 
Heck Steve, you aint got it broke in...... 8) Got er lubed in the right places? Lug bottoms (& faces of course), raceways, fore & aft part of bolt body?

I have an old Shooting Times annual that has a great article on smoothing out you bolt action. If interested I could scan and email it to ya. I did it several times & works great... LMK..

Rod
 
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