7.62x51, 175gr homeloads using CFE223 or Win StaBALL Match

[goddamnox]

Hi All,
I am just starting my first reloads for 7.62x51 (AW 1:12 26") and looking at using Ruag once fired brass, Magtech primers, Sierra Matchking 175gr. Powder choice is looking like CFE223 or Win StaBALL Match.

If I consult the Hornady data for the above powders using .308 I get very different grain wt/pressure etc to that if I use the .308 service rifle data ( which I assume is for 7.62x51) I was wondering if anyone can confirm that the Hornady service rifle data is indeed for 7.62x51 NATO (unless the M1A rifle in 7.62 had a specific load?) and that is what I should base my loads on or am I missing something!?...

I have tried searching for answers and I am not looking for a "load" to use rather come confirmation that loading for 7.62x51 needs to be done so that the pressures are lower as stated in the Hornady data?

Hope that makes sense! if not be nice as just starting out reloading

 

[diggler1833]

A lot of that 7.62x51 brass is thick, and the rifles were different, so you end up with 'service rifle data'. I got into pressure extremely fast shooting 168gr SMKs over IMR-4064 in LC brass a few years ago, and then basically repeated those pressures loading a buddy's 165gr SP with his components. Don't quote the exact amount, but i managed to pop a primer on his at ~1.5gr over Hodgdon's starting charge for standard .308. That was an eye opener.

Currently, I'm just starting to get a little ejector swipe using just 43.0gr IMR-4064 under a 150gr SST at 2.800. That's only about a grain over the starting charge.

I think a decent rule of thumb is start with the service rifle data if using military brass, and work your way up slowly over a chronograph. I have zero experience with the Ruag brass, so I'd either compare case volume by H2O capacity to commercial stuff.. or just assume it is military and go from there.

 

[RegionRat]

There are slight differences between 7.62 NATO and 308 WIN.
The Service Rifle loads are for the older NATO rifles that use a thicker case and lower pressure than the commercial 308 WIN.

If you are running a modern bolt rifle that is marked 308 WIN, then you can use the regular bolt gun data that is typically shown for a 24" 1:12 bbl.

https://www.accurateshooter.com/cartridge-guides/308win/

 

[Doom]

I hope @RegionRat won't be offended but the cartridge guide is not totally correct. For instance the pressures 50,000 PSI and 62,000 PSI are not equivalent. The 50,000 is actually CUP (copper unit of pressure) while the 62,000 is PSI as measured by transducer at a different location. But the pressures are different. The Service rifle data is meant to conform to the requirements of the M-14 Service Rifle for which the 7.62x51 NATO cartridge was developed. The rifle is semiautomatic and an upgraded design of the M-1 Garand. The key is protection of the gas operating system of the M-14. There is also a specification for port pressure as the gas port. It is important also for the M-14 to have the correct burn rate so powder selection is limited to prevent overpressure of the gas port. The differences in the chamber are mostly within the tolerances of the 308 Winchester. I'm assuming your AW is an Ai Arctic Warfare rifle which is bolt action and should be capable of handling full 308W pressure.

As for brass there is about 3 gr of H2O difference in capacity when going from Winchester brass to the military brass such as Lake City, PMC, or others which accounts for the comment on military brass. Be careful of Hodgdon data as it is based on the higher capacity Winchester brass.

 

[Doom]

A little more information on pressure measurement and the 308/7.62. In the 1950's when these cartridges were released the pressure measurement system was based on a system that used a piece of copper that would be compressed by a piston exposed to chamber pressure. The amount that the crusher deformed was measured and a pressure was assigned to that deformation, called a Copper Unit of Pressure. For both cartridges the chamber pressure for the military 7.62 is 50,000 PSI (CUP) and the 308W is 52,000 CUP. That is the current 308W SAAMI pressure based on that system. Latter, electronic transducers began to be used to measure chamber pressure and in the US SAAMI established a system to be used and determined pressures in pounds per square inch (PSI) to be used. In the case of the 308W the transducer pressure is 62,000 PSI. Ammunition meeting either of these specifications is considered safe in a 308W and SAAMI expected the same velocity from either specification.

To further muddy the water the 7.62x51 is a NATO round and as such is used and loaded in many European countries. CIP was the organization that was in charge of ammunition and weapon standards and also developed a different standard for transducer measurement that yields different results because the point of measurement and technique is different. This has lead to a lot of confusion, especially in the 223/5.56x45 world because the 223 and original 5.56 round were developed in the US using the CUP system and the 5.56x45 NATO round was developed by FN in Europe using the European Transducer method.

 

[goddamnox]

Thank you all for the info and thoughts!
I saw that the Hornady service rifle data seemed to be specifc to the M1A and was not sure how relevant that would actuallly be to a 2012 AI?

I also weighed some once shot/deprimed (not cleaned) PPU .308 cases and compared them to similarly treated Ruag 7.62 and the PPU were actually consistently heavier (about 5-6gr)!? I had assumed that Ruag were "mil spec 7.62" and as such would be slightly thicker brass and therefore heavier than commercial .308... Maybe the Ruag is actually just .308 with a metric label! and I was fooled by the fact they come in Swiss ammo tins!

 

[RegionRat]

What ever brass you select to work with, it is a good idea to take some measurements to know how you stand if you ever run out or need to make a change later down the road. As you improve, you will be able to tell the difference on the target.

Like Doom points out, the waters got muddy when the 308 WIN jumped into the market early, then the MIL, then the NATO. It is always hard to get a committee to do the right things, and near impossible to get three or four committees lined up when crossing so many boundaries.

Without a doubt, there is a difference in the listings and manuals between Service Rifle loads and 308 WIN loads, and it is significant. It is good to ask questions and do your homework for understanding all those others, but now you must pay attention to what is in front of you and in your hands.

Life it too short to screw around with crappy brass, so narrow down to the good stuff and take care of your workmanship, it will pay off.

Just because a manual shows speeds and/or pressures, doesn't guarantee your rig will match so always run your work-up.

Don't be too concerned with matching speed performance claims on the internet, let your target scores give you feedback on your recipe.

An Accuracy International is typically a fine rifle, but like anything else it needs maintenance and attention to run well. Make sure your ignition parts are free of dirt and wear and you will not waste time in the situation where things got wet and dirty.

There is only one problem with a good AI rifle. The driver cannot make excuses. Good Luck and in for the range reports.

 

[RegionRat]

I hope @RegionRat won't be offended but the cartridge guide is not totally correct.

Never, no worries.
It was a lazy move on my part to try and give the OP some background.

In my youth, we were already on piezo and we were still taught to interpret the copper slugs. When time passed and I owned the labs, I still kept the old equipment around to teach the young what CUP meant. It was a clever method for it's time, but none of us missed it.

 

[OkieMike]

Is your rifle chambered in 7.62x51 or .308 Win?

If it's chambered in .308 then use .308 load data... With the caveat that if you're using mil/7.62 brass, you're going to run into pressure sooner than with commercial brass.

If you really aren't sure then you can start with 7.62 load data and if you don't get pressure at max charges then you can keep going with .308 load data until you hit pressure or you're satisfied.

As far as the 2 powders you asked about... Just my opinion... I would choose StaBall Match. I haven't used it yet. But I have used CFE-223 and it isn't temp stable and can get erratic in warm temps and near max pressure.

PS: Nosler has 7.62 load data for their 175/their brass... But no data for either powder you listed.

Mike

 

[goddamnox]

Is your rifle chambered in 7.62x51 or .308 Win?

If it's chambered in .308 then use .308 load data... With the caveat that if you're using mil/7.62 brass, you're going to run into pressure sooner than with commercial brass.

If you really aren't sure then you can start with 7.62 load data and if you don't get pressure at max charges then you can keep going with .308 load data until you hit pressure or you're satisfied.

As far as the 2 powders you asked about... Just my opinion... I would choose StaBall Match. I haven't used it yet. But I have used CFE-223 and it isn't temp stable and can get erratic in warm temps and near max pressure.

PS: Nosler has 7.62 load data for their 175/their brass... But no data for either powder you listed.

Mike

Chambered in 7.62x51 but I think the Ruag brass I am using (labelled as .308 (7.62x51) is not mil/7.62 brass and I have shot this in its original factory form with no issues and decent results. But I think/hope I can get better results by homeloads but as I am new to this I just want to start with the best possible info hence my question. I am making some loads using StaBall Match so will see how they go, starting with conservative powder loads.

 

[goddamnox]

First loads tested, 43gr - 45gr in .5gr steps all 10 shots (44gr-9shots) @ 94yds. Win StaBall Match, Ruag once fired brass, Fiocchi LRP.

Nothing amazing but nothing too terrible. Best - SD-4.7 / ES - 17.9 was 44.5gr. But 44gr (SD - 5.3 ES - 14.4) had 5 shots all within 4fps.. Ill just have to make more and shoot more I guess, only way to be sure!

 

[MK20]

Could we all please stop pretending that 7.62 vs 308 will make a damn bit of difference in ANY modern rifle.

Work up a load using available data, and go shoot. Your AI will handle any reasonable pressure whether the barrel is marked in metric or imperial.