Reloading 243

CCsour · March 8, 2019, 04:30 PM

Building a load for a rebarreled 243. 100 gr Sierra GameKing BT. started at 36gr Win 760 went up .5 each step 37.5 pretty fair 38 spread 38.5 spread even further 39 came back to the best group, however 38.5 and 39 had to work like hell to get the case ejected! Cases all spec out for length and diameter. 5 rds each step. about half of the last ten where the problem was had a lot of black on the case neck. Lake City Match Grade 308 cases resized to 243. Any ideas as to why the last ten cases stuck so bad? Every one loaded nice.

Reloadron · March 8, 2019, 04:46 PM

Black on a case neck is fine, as long as it does not extend down the shoulder, hard extraction not so much. Necking down 308 to 243 is a big jump and may require some neck turning. When necking down the case neck brass needs to go somewhere and the greater the change the more brass you have. Since I don't know your chamber it's hard to say why hard or difficult extraction exist but you may want to measure your case neck thickness. I would consider that just as a start.

Ron

GeauxTide · March 8, 2019, 04:46 PM

If it's mil brass, that's the issue. Mil is thicker and harder. If you have hard bolt lift and extraction, you're over max, A LOT! I get black on my case necks in all of the nine rifle calibers I load.

Reloadron · March 8, 2019, 05:12 PM

Looking at the Sierra 50th Edition you are getting close to their suggested maximum load of 39.2 grains even with hand individually weighed charges and allowing for scale inaccuracies. Try around 36 to 37 grains and see if extraction remains a problem. Finally, if you have it locally, invest in a box of factory 243 Winchester and see how the cases behave and then reload them. All of this assumes a nice clean chamber including chamber neck and throat.

Ron

std7mag · March 9, 2019, 07:29 AM

As was mentioned, going from 308 to 243 makes the necks thick.
It would be a good idea to inside neck ream.
Also military brass will be thicker yet.
There are a lot of good quality brass available for 243.
Maybe try some of them.
Hornady, Nosler, PPU, Winchester.

If you get a chance try some RL26 with those 100gr GameKings.
You'll be surprised at the velocity gain, WITH good accuracy.

Mobuck · March 9, 2019, 07:45 AM

I've made 243 cases from military (LC) 7.62x51 brass. If you don't ream or turn the necks, you'll have a tight neck situation. Add this to the possibly thicker mil-spec brass, you have to consider a much lower max load.

tango1niner · March 9, 2019, 08:21 AM

Generally when reloading US 7.62X51 military brass using standard .308 Win. reloading data it is recommended to reduce powder charges by one grain as military brass has less internal volume and will produce higher pressures.

What brand, type, rifle ?

hooligan1 · March 9, 2019, 08:34 AM

I use Winchester Supreme 780 with that vary bullet with a great deal of consistency.
Seems like it almost duplicated the Winchester power point gray box load, not quite the same but real nice in a couple rifles we had.

std7mag · March 9, 2019, 12:52 PM

Why duplicate when you can exceed?

RC20 · March 9, 2019, 04:56 PM

My take is you have jumped into the deep end of the pool.

You hit serious pressure signs and kept going.

Rather than resize cases, factory 243 would be the way to go unless you are experience at the craft of re-sizing existing. I can see doing that for ones you can't get but cases you can?

Nothing wrong with it but you did not understand you are no longer in an apples and apples case.

You have bolt sticking and that is a a serous pressure sign. That is immediate back off. It does not matter the groups got better.

As your cases are modified they are not exactly 243 cases (applies to oranges) the tables no longer apply as max and max alwyas was and still is something to be approached cautiously.

You need to drop back at leas half a grain.

Lesson learned hopefully.

March 8, 2019, 04:30 PM	#1
CCsour Junior Member Join Date: March 8, 2019 Posts: 1	Reloading 243 Building a load for a rebarreled 243. 100 gr Sierra GameKing BT. started at 36gr Win 760 went up .5 each step 37.5 pretty fair 38 spread 38.5 spread even further 39 came back to the best group, however 38.5 and 39 had to work like hell to get the case ejected! Cases all spec out for length and diameter. 5 rds each step. about half of the last ten where the problem was had a lot of black on the case neck. Lake City Match Grade 308 cases resized to 243. Any ideas as to why the last ten cases stuck so bad? Every one loaded nice.

March 9, 2019, 07:29 AM	#5
std7mag Senior Member Join Date: June 23, 2013 Location: Central Taxylvania.. Posts: 3,609	As was mentioned, going from 308 to 243 makes the necks thick. It would be a good idea to inside neck ream. Also military brass will be thicker yet. There are a lot of good quality brass available for 243. Maybe try some of them. Hornady, Nosler, PPU, Winchester. If you get a chance try some RL26 with those 100gr GameKings. You'll be surprised at the velocity gain, WITH good accuracy. __________________ When our own government declares itself as "tyrannical", where does that leave us??!! "Januarary 6th insurrection". Funny, I didn't see a single piece of rope...

March 9, 2019, 08:34 AM	#8
hooligan1 Senior Member Join Date: July 18, 2010 Location: Independence Missouri Posts: 4,585	I use Winchester Supreme 780 with that vary bullet with a great deal of consistency. Seems like it almost duplicated the Winchester power point gray box load, not quite the same but real nice in a couple rifles we had. __________________ Keep your Axe sharp and your powder dry.

March 9, 2019, 12:52 PM	#9
std7mag Senior Member Join Date: June 23, 2013 Location: Central Taxylvania.. Posts: 3,609	Why duplicate when you can exceed? __________________ When our own government declares itself as "tyrannical", where does that leave us??!! "Januarary 6th insurrection". Funny, I didn't see a single piece of rope...

March 9, 2019, 04:56 PM	#10
RC20 Senior Member Join Date: April 10, 2008 Location: Alaska Posts: 7,014	My take is you have jumped into the deep end of the pool. You hit serious pressure signs and kept going. Rather than resize cases, factory 243 would be the way to go unless you are experience at the craft of re-sizing existing. I can see doing that for ones you can't get but cases you can? Nothing wrong with it but you did not understand you are no longer in an apples and apples case. You have bolt sticking and that is a a serous pressure sign. That is immediate back off. It does not matter the groups got better. As your cases are modified they are not exactly 243 cases (applies to oranges) the tables no longer apply as max and max alwyas was and still is something to be approached cautiously. You need to drop back at leas half a grain. Lesson learned hopefully. __________________ Science and Facts are True whether you believe it or not

March 8, 2019, 04:46 PM	#2
Reloadron Senior Member Join Date: June 8, 2016 Location: Cleveland, Ohio Suburbs Posts: 1,750	Black on a case neck is fine, as long as it does not extend down the shoulder, hard extraction not so much. Necking down 308 to 243 is a big jump and may require some neck turning. When necking down the case neck brass needs to go somewhere and the greater the change the more brass you have. Since I don't know your chamber it's hard to say why hard or difficult extraction exist but you may want to measure your case neck thickness. I would consider that just as a start. Ron

March 8, 2019, 04:46 PM	#3
GeauxTide Senior Member Join Date: April 20, 2009 Location: Helena, AL Posts: 4,423	If it's mil brass, that's the issue. Mil is thicker and harder. If you have hard bolt lift and extraction, you're over max, A LOT! I get black on my case necks in all of the nine rifle calibers I load.

March 8, 2019, 05:12 PM	#4
Reloadron Senior Member Join Date: June 8, 2016 Location: Cleveland, Ohio Suburbs Posts: 1,750	Looking at the Sierra 50th Edition you are getting close to their suggested maximum load of 39.2 grains even with hand individually weighed charges and allowing for scale inaccuracies. Try around 36 to 37 grains and see if extraction remains a problem. Finally, if you have it locally, invest in a box of factory 243 Winchester and see how the cases behave and then reload them. All of this assumes a nice clean chamber including chamber neck and throat. Ron

March 9, 2019, 07:45 AM	#6
Mobuck Junior member Join Date: February 2, 2010 Posts: 6,846	I've made 243 cases from military (LC) 7.62x51 brass. If you don't ream or turn the necks, you'll have a tight neck situation. Add this to the possibly thicker mil-spec brass, you have to consider a much lower max load.

March 9, 2019, 08:21 AM	#7
tango1niner Senior Member Join Date: March 5, 2009 Location: NY Posts: 317	Generally when reloading US 7.62X51 military brass using standard .308 Win. reloading data it is recommended to reduce powder charges by one grain as military brass has less internal volume and will produce higher pressures. What brand, type, rifle ?