New can of powder and changing primers: Should I back off?

[GAJoe]

I'm down to 20 rounds of ammo so I'm going to load up another batch. My load is 40gr Noslers pushed by H4895 using CCI BR-4 primers. I got Remington 7 1/2 primers to try in this batch and I was out of powder so I'll be getting a new can. Should I back off on my powder load or would it be safe to use the same amount as before and check it with a chrony. My load before had no signs of being "hot".
GAJoe

[futuretrades]

basically, you are changing 2 components. using different primers and probably 2 different batches of powder. you did not state how much powder you are using, but IMHO, i would back off at least .5 tenths of a grain on the powder, and work back up to your load carefully. you may even find that you will need more or less powder to get the same results you were happy with before. above all, be careful and safe and enjoy the process all over again.

[Rick in Oregon]

Good advice there, I agree. In most manuals, it is stated that when changing any one component in a given load, to back off 5% from the previous charge. Load up a few rounds, chrono them, and look for pressure signs versus the same velocity you were getting before.

You're down to 20 rounds? That would last us about 1/2 hour or less in our ground squirrel environment. Goes to show the vastly different conditons that exist in our shooting world. We normally have at least 500 rounds loaded at any one time for each varmint rifle we take afield. You should feel fortunate, as you probably spend alot less money replacing rifle barrels!

Good luck finding an even better, more accurate load this time.

[GAJoe]

That's what I was thinkin' I should do. Thanks for the responses.
Yea, around here coyotes are the only critters I shoot with the .204. (A box of 100 will last me a while) That's only required 12 rounds in the last 18 months to take 9 coyotes. The rest were used to check zero when I felt the need. No danger of wearin' out my barrel here.
GAJoe

[futuretrades]

GAjoe
man, I think I would be pullin some hair out, and having withdrawal symptoms, if that was all the shootin I did with any rifle I own. I keep at least 600 rds of both 204 and 223, and have 100 rds of 270 loaded and ready to go. and I have on hand about 10,000 rds for my .22's. and about 30lbs of powder.
If this place ever caught on fire, I would tell the fire dept. to enter at your own risk, and see if you can beat me to the next county!

[GAJoe]

Well I got my powder load worked up again and it turned out to be the same as before. 40gr Nosler BT's at 3880fps gave me a group just under 3/8":

After 3 shots I knew I had a winner so I fired one from the last batch and it fell right in there. I got a better group than before, so it was worth the trouble. Probably less wind today.
GAJoe

[Silverfox]

GAJoe--Was that new can of powder from the same lot as the old can? If not, your new lot of powder must have been pretty consistent with the old can. Nice shooting!!! I'm glad to see you are having good luck with the 40 gr. Nosler BTs too. Not many shooters seem to be using that bullet, but it sure works good for me. It gives me a bit more hang time on prairie dogs than the 39 gr. Sierras and is pretty close to as good in accuracy as the 39 gr. Sierra.

Last year, I sighted my Savage 12VLP in for .8" high at 100 yards with the 39 gr. Sierras. That load had a muzzle velocity a tad over 3,900 fps and the 40 gr. Nosler BTs, with a muzzle velocity of about 3,884 fps, were hitting the target right in that same area!! I don't know how I got so lucky This year, the 39 gr. Sierras are hitting 1.004" high at 100 yards, but the 40 gr. Noslers are striking the target about 1/2" left of where the 39 gr. Sierras impact and not quite .4 of an inch higher. I will crank the windage knob right two clicks when I shoot the 40 gr. Noslers. I'll leave the vertical adjustment alone because I have a trajectory chart made out for the 40 gr. Noslers with the bullets hitting 1.4" high at 100 yards. I can work with that.