.243 Reloading Variance

[RiverRatMatt]

I took my pre-64 Winchester Model 70 out today. I have always shot 100g Remington Core-Lokt through it and it has performed well. I recently used almost all my 100gs and over the last month have been unable to find them in any store.

So I decided to break out my reloading gear and give it a shot again. Here's what I used:

80g Remington bullets
40g of IMR-4350
CCI #200 primers (unknown age... were my Grandfather's)
Once-shot Remington brass from my 100gs

So here's the problem. I chrono'd my rounds today. The three 100gs averaged about 2900 FPS. My 80g loads were as follows:

2964
3003
2760 (!!)
3136 (!)
2923
2966
2773 (!!)
2996

The difference between the fastest and slowest is a whopping 376 FPS. The largest difference in my factory 100gs was 60 FPS.

So what am I doing wrong? Maybe its the old primers? Every load was hand measured by me with my old Redding beam scale, each one was dead-on at 0.



BTW, for those interested, my Swiss K31 with mil-surp 174g ammo shot 2551, 2567, 2547 fps. That's a max variance of 20 fps for surplus ammo... that's crazy.

 

[Fuzzball]

"So what am I doing wrong? "

You're using too light a charge of a moderately slow powder behind a mid-weight (for caliber) bullet in a medium capacity case. All powders burn most consistantly at or near the max designed chamber pressure. Try a heavier charge or go to a faster powder.

 

[RiverRatMatt]

Anyone have recommendations for a better powder and load? The Lyman Reloading Handbook has IMR-4350 max charge at 41.5g for my 80gs, I didn't want to push too close to the safety threashold.

Also, I didn't do any case prep. I've read a bit and need to get an ultrasonic cleaner, measure the headspace, measure the shoulder length, deburr my primer hole etc etc.... ugh. I had no idea it was that important.

Bottom line for me seems to be that I need to find some factory loaded ammo in the next few days and sight in with that. My hunt is the 10th -.-

 

[JoeBUtah]

Anyone have recommendations for a better powder and load? The Lyman Reloading Handbook has IMR-4350 max charge at 41.5g for my 80gs, I didn't want to push too close to the safety threashold.

Also, I didn't do any case prep. I've read a bit and need to get an ultrasonic cleaner, measure the headspace, measure the shoulder length, deburr my primer hole etc etc.... ugh. I had no idea it was that important.

Bottom line for me seems to be that I need to find some factory loaded ammo in the next few days and sight in with that. My hunt is the 10th -.-

I use I4350 in my .243 and it seems to work for me. H414 is a popular .243 powder, and I just loaded up some 80 gr bullets with Reloader 15; haven't shot them yet though. A lot of guys use Varget.

With respect to your loads: did you see any signs of high pressure like flattened primers? What were your groups like?

I've seen .243 factory loads at the local wally's world here in Salt Lake, perhaps you'll get lucky in Boise...

 

[scatterbrains]

Ive had great luck with ramshot hunter and really great luck with Hybrid 100v. from 60gr to 100gr bullets hybrid gets me 3020fps in a 22" barrel with 105's

 

[Fuzzball]

" I've read a bit and need to get an ultrasonic cleaner, measure the headspace, measure the shoulder length, deburr my primer hole etc etc.... ugh. I had no idea it was that important."

It isn't. Adjust your FL sizer so you can close with just a hint of bolt handle resistance on your resized cases and you will have "measured" all the headspace and shoulder length you need to measure for accuracy and good case life .

Deburring flashholes and uniforming primer pockets MIGHT cut 10-20 thou off your best groups but it won't do a thing for safety.

Using an ultrasonic case cleaner (or steel pins in a wet tumbler) will give you some surgically clean cases which will only matter if you plan to do surgery with them. And it's a slow, wet mess to deal with, otherwise it's irrelivant. (Ditto a glittery high case polish from a dry tumbler.)

My .243s have liked 4350 for 100 gr. bullets but 4064 and Varget have done well with lighter bullets. At a full 1.5 gr under, you really aren't even close to your book's max.

"Flat" primers are the poorest thing you can try to guess excess pressure from, most primer flattening occurs due to excessive shoulder set back during FL sizing. Never mind die adjustment "instructions", you want to make your ammo actually fit your own chamber. If you want to KNOW if you're setting shoulders back correctly just prime an empty case and fire it in your rifle. If the fired primer is flush with the case head you're perfect, if it stands proud of the case head by more than 1 or 2 thou your shoulders are set back that many thousanths more than they need to be.