Old globe firearms 308 norma mag : .024 neck expansion ? Load data help please.

[Kryogen]

(I have a pound of RL19 and 100 hornady SST 180 grains so that's what I'll use)

My father in law has an old globco centurion in 308 norma magnum. I want to reload for his rifle.

One thing that bothers me, is that factory cartridges measure 2.166 headspace with my hdy gauge. Fired cases average 2.190. That's a .024 headspace "jump". Aint that quite a lot?
Because I reload, I will probably just anneal, and then FL the cartridges only .002 and hope that they last a while. factory cases have never failed shooting once, though.

Also, funny thing, HDY lists a COAL of 3.345 or so but I measured the lands approximately at 3.305 with that rifle and bullet.
Norma data suggests an OAL of 3.307 wich is way more accurate.

Now, HDY lists 65-72 RL19 loads (with a 3.345 COAL), and nosler states max 69.

Max velocities are approx 3000 fps.

Sooo, I made 2 of each going from 68.0 to 72.0 in 0.5 increments. Because the bullet is .040 pushed in the case, I guess that I will hit max pressure before published data.
My plan was to start with the 68 load, and chronograph, and just stop with a load that gives me 3000 fps or so if I don't get pressure signs.
Or shoot a factory round with 180 grains bullet, chrono, and test loads until I get same velocity and not more (because velocity will depend on twist rate and barrel, so using a factory round as a benchmark for velocity seems reasonable?)

Opinions?
Thanks

 

[rokoro]

I have had several 308 Norma's and there has been a wide variety of the throats (freebore) which resulted in several grs difference in max load from one rifle to another. Factory ammo is headspaced on the belt of the case and you will find the shoulder of the case may move forward a considerable amount when fired. I do NOT move the shoulder back when resizing belted cases so the case is now headspacing on the shoulder , not on the belt. This results in cases lasting much longer plus it has a positive effect on accuracy. I would also suggest you seat your bullets so they are just short of touching the rifling. Nothing wrong with shooting a couple factory loads and chronograph them. Also measure case head expansion with a mic on the factory round. Then measure the case head expansion of the reloads. When you find the head expansion of the reloads has increased even one or two thou you have reached chamber pressure that is higher than factory. I would suggest consider that as absolute max. You may want to drop back 1 gr of powder. Hope this helps

 

[Dogleg]

Cases don't separate because the shoulder filled out, or we'll have to quit blowing the shoulders right out straight making 375s into Lotts, 338s into 458s, 375s into .375 weatherbys , and just about everything into an AI. The reality is that the separation line come from the case head blowing back against bolt face not the shoulder filling the chamber. That's why magnum headspace don't have a shoulder or a body. New cases headspace on the belt.

If, and it's a big "IF" there is too much stretch on the intial firing it's because the distance from the belt recess to the bolt face is excessive. Lots of them are. When we set up magnum chambers you can't even close the bolt on a go guage but they will take any brass we've ever tried. New cases don't stretch much because the head has almost nowhere to go. If there's too much stretch on the first firing due to a sloppy chamber, put a false shoulder on the new case to force the case head against the boltface where it belongs.

 

[Kryogen]

Ok, thanks, so should I use the velocity of the factory round as a max speed for my reloads, and keep it 50 fps below that for safety?
Any point in loading 20 mils back of the lands, or just load at lands length or closer?

I have an issue with knowing when I am near the real max charge, and it seems to me that the only close way I have is to check speed vs a factory round in the same gun.

 

[Eagleye]

Even Factory loads will vary considerably, depending on barrel, throat, Chamber dimensions, etc. Rokoro has given good info in post #2 above.

I have several 308 Norma Magnums.....two are custom rifles with aftermarket barrels, one is a rechambered 30-06, and two are factory rifles.

One lot of Norma factory 180 grain ammo I have here graphs right at 2990 in my "slowest" rifle, but is moving at 3122 in my "fastest" rifle. [No surprise this is a Custom rifle]

However, by reloading, each one of these rifles will make 3100+ fps with a 180 Partition or Accubond, just with varying amounts of powder.

As has been mentioned, once you have a fired case, adjust your FL die to headspace on the shoulder, so as not to push the shoulder back and risk case separations.

Regards, Dave.

 

[rokoro]

Ok, thanks, so should I use the velocity of the factory round as a max speed for my reloads, and keep it 50 fps below that for safety?
Any point in loading 20 mils back of the lands, or just load at lands length or closer?

I have an issue with knowing when I am near the real max charge, and it seems to me that the only close way I have is to check speed vs a factory round in the same gun.

The max charge will vary from one rifle to another. Some indicators that you are approaching max in a particular rifle are (in no particular order), Primer cratering, the primer material will flow back around the firing pin. This indicates excessive pressure. 2/ Extractor marks on the case head, this is often accompanied by stiff extraction. Case head expansion greater than the expansion of factory loaded ammo. Some new powders deliver top velocities which MAY exceed factory loads so suggesting you have to settle for 50 fps less than factory loads is not a valid assumption. At one time factory 308 Norma ammo was loaded with N204 powder. What they load todays 308 Norma ammo with I can't say. N204 would be very close to RL 19 in burning speed so may achieve close to factory ballistics at a safe pressure. If you use a faster burning powder you will likely reach max pressure before you reach factory vel. A slower powder may give you less pressure but you may not have room in the case to put enough powder in to obtain factory velocity or better factory velocity.

 

[Kryogen]

ok, so when resizing, adjust the die in until I get 1 mil of shoulder push, and then back just a hair and thats it?

I'll shoot those rounds, and I'll have a closer idea of what max pressure is around.
Then I'll resize without pushing the shoulder back next time, and I'll load closer to lands, and then figure out what max load is around.

Makes sense?

My fear comes from the fact that one published max is 69 and one is 72. I fear "going over max" without knowing it and having the rifle explode in my face. Not going to happen with .5 grains increases right?

 

[Eagleye]

At one time factory 308 Norma ammo was loaded with N204 powder. What they load todays 308 Norma ammo with I can't say. N204 would be very close to RL 19 in burning speed so may achieve close to factory ballistics at a safe pressure.

Definitely not being confrontational here, but........
Just a small correction on the original loading for the 308 Norma Mag. The 1st generation factory loadings used a dual-Core, 180 grain bullet over
76.7 grains of [now obsolete] Norma 205. the muzzle velocity of this load was advertised at 3100 fps, and in at least two rifle in that chambering
that I owned in that era, they exceeded factory velocities by from 25 - 60 fps. These loads were plenty warm in some rifles.

After Norma 205 was replaced by Norma MRP, it became the powder of choice for factory loadings, but Norma also softened the load slightly.
The new loading became [and still is, AFAIK] 75.0 grains of Norma MRP, and the advertised velocity went to 2960 fps.

I have broken down some recently manufactured 308 Norma Mag ammo, and the charge weight was 75.1 grains and 75.2 grains of what
appears identical to the MRP I have here. At present, I own 5 - 308 Norma rifles, and this lot of factory ammo's velocity varies as noted in
post #5 above.

I have never seen any bullet weight other than the 180 grain in factory Norma ammo.

Several years ago, when I spoke to Nils Kvale at Norma Precision in Amotfors, Sweden, he verified the loadings I have listed here, with the caveat that the actual weight of charge might vary slightly, due to slight variances in the powder, lot to lot.

Regards, Dave.

 

[rokoro]

Eagleye As you have indicated Norma only loaded the 180 gr bullet in the 308 Norma. I have an old Norma loading pamphlet that shows some load data for Weatherby calibres and a few others, the 308 Norma and 7x61 S&H being a couple of the others. In this pamphlet it lists a start load a max load and a factory duplication load. In the 308 Norma the factory duplication load was listed with N204. I had assumed that Norma was using N204 to load the 308 N when they listed a factory dup. load with that powder. That may well have changed when MRP came on the market.

 

[Eagleye]

Eagleye As you have indicated Norma only loaded the 180 gr bullet in the 308 Norma. I have an old Norma loading pamphlet that shows some load data for Weatherby calibres and a few others, the 308 Norma and 7x61 S&H being a couple of the others. In this pamphlet it lists a start load a max load and a factory duplication load. In the 308 Norma the factory duplication load was listed with N204. I had assumed that Norma was using N204 to load the 308 N when they listed a factory dup. load with that powder. That may well have changed when MRP came on the market.

Yes, I have the same loading pamphlet, and there is a factory duplication load with N204 listed, but apparently it was there for reloaders who wanted to use [or only had] the slightly faster powder.
Nils told me that all the factory ammo was loaded with N205/MRP. I have a quantity of N204 here, and it is [as you stated earlier] similar in burn rate to Reloder 19.
I have a fair quantity of Norma MRP on hand, and my best loads with the 180 Partition usually land right at between 75 and 76 grains of that propellant.

I have one custom 308NM that is very "fast", and achieves the 3100 fps target with only 72.5 grains of MRP. Even the later, milder, factory ammo is plenty fast in it.

Regards, Dave.

 

[rokoro]

Eagleye Thanks for sharing that.I stand corrected. Hopefully Kryogen will gleen some useful info out of all this. Mostly that due to a wide variation in throats (freebore) and just different barrels loads & velocity can vary considerably. In real life there will be little difference in effectiveness between a good 180 gr bullet travelling anywhere from 3000 right up to about 3150 fps. You don't necessarily need the absolute fastest load,you want the one that groups best in your rifle.

 

[Eagleye]

Eagleye Thanks for sharing that.I stand corrected. Hopefully Kryogen will gleen some useful info out of all this. Mostly that due to a wide variation in throats (freebore) and just different barrels loads & velocity can vary considerably. In real life there will be little difference in effectiveness between a good 180 gr bullet travelling anywhere from 3000 right up to about 3150 fps. You don't necessarily need the absolute fastest load,you want the one that groups best in your rifle.

Quoted for truth!!

 

[Kryogen]

I just want a load that performs well for my father in law. I don't have the time and willingness to really tune the load.

For some reason, factory ammo will group like 3-4 inches in that rifle at 100Y. I don't know if I can get an accurate load out of it.
I'll see how OAL affects it.

 

[Boomer]

Anal load tuning shouldn't be necessary provided the accuracy issue you face is an ammo problem and not a rifle problem. You should work up loads in once fired brass, that is full length resized, but sets back the shoulder only enough to ensure effortless feeding. Do not tolerate loose primer pockets. Choose a powder that is appropriate for the cartridge, and takes up approximately 90% cartridge capacity; typically 4350 to R-22 delinates the range of burning rates you should consider. Choose a bullet known for accuracy, Nosler Accubonds comes to mind. Choose a brand and grade of primers, and try not to deviate from them once your load is established. You might find that CCIs give you an extra loading or two over other brands. You shouldn't have to mess around with bullet seating depth to achieve acceptable field accuracy; for the sake of argument lets define that as being no greater than minute and a half for 3 rounds, but neither should there be excessive freebore. Ensure the chamber throat is not badly eroded, if it is you might find that round nose bullets, seated long, produce the best accuracy.

Ensure the scope holds zero. Ensure the scope mount screws, and the rifle's action screws are tight. Ensure the bedding surfaces between the stock and the barreled action are even and there is no binding of the barrel against the barrel channel. Zero the rifle to the cold bore shot, if the following 2 rounds form up around the cold bore shot, you're golden.

 

[Kryogen]

will test loads this weekend, will report once I have shot those.

As a matter of fact, I had a few cases with tighter primers, and a few with primers that easily went in.
What do you mean by do not tolerate loose primer pockets? Define loose?

 

[Boomer]

Opinions may differ, but my litmus test is when I can't feel resistance when seating the primer, with my bench mounted priming tool, I cull the case. Under no circumstances should you be able to seat a primer with your thumb. If you say to yourself, "Huh, that felt weird." err on the side of caution, and cull the case.

 

[Eagleye]

Opinions may differ, but my litmus test is when I can't feel resistance when seating the primer, with my bench mounted priming tool, I cull the case. Under no circumstances should you be able to seat a primer with your thumb. If you say to yourself, "Huh, that felt weird." err on the side of caution, and cull the case.

I agree with Boomer. I hand prime everything, and if a primer seats with very little or no pressure on the handle, the case gets discarded.

A loose primer pocket is an indication of enough pressure to expand the head of the case beyond normal limits.

If you have some older brass for that 308 Norma Mag....be careful. Look at the headstamp, If it reads 308 Norma with a little "re" included,
these are early cases, and are considerably heavier than later cases without the "re" on them. They are good cases, but will require that
you adjust your load down about 1.5 - 2 grains if you have a max working load in the regular cases.

The 308 Norma is by far my favorite "big" 30 cal, and I own several. Regards, Dave.

 

[Kryogen]

Will look into this. I had a few that were not so tight. Probably their last reload.

 

[Kryogen]

ok did some testing
(I have old cases 10-20 years, and new cases, and I am starting to wonder if they have the same capacity because I got a lot of speed variation with quite precise powder loads) (mixed cases)


old factory ammo clocked at 3126, primer quite flat, extraction not hard (slower powder maybe)
new factory ammo clocked at 3077/3053 smooth extraction

Speed was read with a chrony, next results will be read with a lab radar next time.
OAL was 20 mils short of the lands(3.285), and quite a bit short of the advertised HDY COAL (3.345, but that doesnt fit the lands, and norma lists a coal of 3.307 which does make more sense).
Will test another batch at 70.5 loaded to lands (3.305) vs 20 mils back (3.285) for accuracy.

results
started at 68.0 (2891/2908)
.5 increments
[....]
70.5 grains of RL19 clocked to 3042/3042
71.0 clocked to 3086/3105, no pressure signs.
71.5 bolt opening hard. 3116(stiff)/3137(really stiff)
72.0 not tested as 71.5 was over max

So, it tells me that the OEM load probably has a similar powder to rl19, and they determined a max of 3050 fps, and that does make sense to me. Max is somewhere between 70.5 and 71, but I'll just keep it safe at 70.5 like the OEM load and that's it.

Thanks
(HDY SST 180 grains, WLRM, RL19, loaded to 3.285 OAL, slightly crimped with lee FCD)

funny thing is that I got a 70.0 that clocked to 3051, faster than both my 70.5 loads, and the other 70.0 clocked 3019. case capacity maybe?

 

[rokoro]

Kryogen The older Norma cases re on the headstamp are heavier than the newer cases. Internal capacity is slightly less .so pressures will be higher. Personally I drop back 2 grs of powder when using the cases with re on the headstamp.