Hey there, I am working up a varmint load for my 243 win. I am trying Nosler BT in 55gr. According to Nosler the range of charges for H380 is 49-53 grains.

The H-380 load in the Sierra manual for the 55 grain Blitzking is 43.6-46 grains.

My question is, how can a minimum load in the Nosler manual be higher than the max load in the Sierra manual for almost identical bullets? Is it safe to run the charges as listed in the Nosler?

Several data sources I have seen estimate speeds up to 4000fps with a 55gr bullet, but the Sierra manual is only estimating speeds up to 3600 since their charges are much lower. Any input would be appreciated. THANKS

This comes up all of the time, especially w/ new reloaders. The various powder & bullet manuf. test their handloads in different firearms w/ different barrels. The results are always going to be different. If you took two identical M700 in .243 & tested them w/ factory ammo as a base & then develope handloads for each, there could be as much as 100fps diff. between loads due to barrel bore finish, tolerence & chamber finish & tolerance.
Bullets of the same weight/dia. but diff. manuf. are going to perform diff. Changing the case & primer brand can also, sometimes significantly, affect your load. This is the reason you should always start below the max. load listed in the manual. Which manual? I have three, and will consult all when working up a new load for a new firearm. If you are using the NBT, then I would use the Nosler data as a guide & work up. BTW, you'll find that the 55grSBK will come apart @ speeds exceeding 3600fps. This is the reason that Sierra limits the speed of that particular bullet. Here is something else to add to your confusion, from the Hogdon website:
243 WINCHESTER
CASE: WINCHESTER

BBL: 24"
PR: WINCHESTER LR

TWIST: 1:10" TRIM: 2.035"


55 GR. NOS BT
COL: 2.650"


H414
50.0
3950
51,600 CUP


H380
51.0
4010
48,700 CUP


VARGET
45.0
4000
50,000 CUP


BL-C(2)
47.0
4025
49,400 CUP


H4895
44.5
4058
49,300 CUP


BENCHMARK
41.5
3815
50,100 CUP
Good luck be safe & keep asking questions.

Thanks for the input. I have used the Nosler 55 grain factory loads and my guns seems to like them. I am trying to atleast duplicate the performance of these loads. Never tried the Sierra's but I just bought their manual and was comparing data. Thanks again!

PS. That H380 is a pain to work with, that stuff bounces everywhere!

dogcatcher---I think it is indeed wise to cross reference. I got into trouble once by NOT doing so. The Lyman manual listed a charge well above the other manuals. I did not cross reference as the Lyman manual also listed a very low pressure. The max they listed would not even go into all cases and took some work to get it into the rest. I falsely thought it was a powder that an overcharge wouldn't be possible. Wrong! I cross checked it after the damage.

dogcatcher---I ran across one that I found to be most unusual. In my 1967 Lyman manual for a .243 using a cast 95 grain bullet listed a starting load of 13.0 and max of 18.0 for IMR 4227 powder. The Lyman cast bullet manual copyright 1980 same bullet and powder listed a starting load of 19.3 and max of 24.5. The newer START was 1.3 over the old max,and the newer max exceeded the old by 6.5.

The measurement systems used by the reloading publishers really aren't that good. They contain a fair amount of plain old random error. A 10-shot average in the CUP system is doing good to repeat within 1,000 PSI, given the same lot of ammo, same technician, and same barrel. Piezo stuff isn't a whole lot better. Add in variation from differences between labs, and the situation is even more bleak.

Cross referencing between several manuals is a very good idea. An average of 4 manuals will cut the random error in half.

Also, be aware that powder lots vary in burning rate, and bullet manufacturers buy in bulk. So, depending on when a manual is published, maximum charges will vary.

You should always start low and work-up, and use data from your bullet manufacturer as a reference.

Carpetman, cast bullet maxes are not based on safe pressures in the weapon, but on where the bullet fails. We rarely get close to pressures dangerous to the gun.

Change in alloy or barrel can make a big change in where the bullet fails. I find the Lyman Cast Bullet Handbook wildly optimistic with plain base bullets

leftoverdj---I knew cast bullet pressures were much lower and never gave it consideration that max would be where bullet fails. Makes sense.

Dogcatcher,

I've found that some rifles max out well before book max. I would start at the lower of the charges you mentioned and check out accuracy, bolt lift, primer flatness. Man, I didn't even know you could get more than 50 grains of 380 in a 243. Is that a Compressed load?

Good Luck!

Reloader