We developed a line of cartridges we call the "GPC" - (General Purpose Cartridge).  We have released and sold quite a few of the first offering (27 GPC), the 20 GPC is coming out next along with the 24 GPC, then the 25, 26, etc.

The 6.8SPC case is the parent case, which we have "improved" (sort off like an Ackley, but not as dramatic).  We relieved some of the case taper and changed the shoulder angle to 30 degrees (not like an Ackley at 40 degrees), so it still runs in a gas gun just fine.  The gain over the original 6.8SPC case is about 1.5-2.0 grains.  However, that isn't the main point, although it is a nice benefit.

We were a huge fan of the 6.8SPC and invested quite heavily in it in the past.  However, there was so much confusion out there for the end user at first about the SPC/SPCII differences, and then there are several manufacturers that created their own chambers as well.  It's fair to say there are probably 20 different "SPC II" type chambers out there depending on where you look.  Since only the original SPC chamber is SAAMI, the ammunition will always be to that spec.  We started out with the name "6.8 GPC", but that didn't really defeat the confusion so we have changed it to the 27 GPC, and, for consistency purposes as the entire line up is labeled 20, 22, 24, 25, etc.

Well, we can't just leave things alone so we decided to go with the GPC, and leave the original SPC/SPCII and its case behind - so there is no confusion about our GPC and what was the SPC.  We also wanted to offer sort of a "pick your poison" lineup using the GPC case as the standard/parent case, in other calibers.

As you can see we will have a full line from 20 cal up to 30 cal.  They will all carry the GPC name so there is no confusion.  The 27 GPC (6.8mm) case becomes the parent case for all the other GPC variants.  Some may require a slight shoulder bump and trim but otherwise the 27 GPC case is the parent case for the rest - neck up or neck down.  The only one available right now at the time of this OP is the 27 GPC, but the others will be out over the coming months.  For now, with the 27 GPC, you just fireform 6.8SPC brass into the GPC.  We are working with Starline to get 27 GPC parent cases done so folks can just use them to make the others - it should be done/ready in a few months.

Below are pictures of the GPC lineup and a standard 6.8SPC loaded cartridge (left) next to a GPC case (right).  The differences are subtle, but enough for it to be a different cartridge that we can move forward with as a standard.  Since it originated as a 6.8SPC case, it uses standard 6.8SPC bolts, mags, etc.

Load lengths for the GPC family are anywhere from 2.26/2.295 all the way out to 2.380" or more if you want to load long.  Once we finalize the development, we will actually "publish" each specific cartridge's load length.  The 20 GPC for example will never load all the way out to 2.38" so right now we just say 2.295" or longer.  As you know, most standard 6.8SPC mags allow a load length of up to 2.295" or so.  So really, it's a matter of how long "can" you load them and how load do you want to load them.

Performance?  Well, for the 27 GPC as an example, "6.8 SPCII" loads are the starting loads for the 27 GPC.  We'll get some charts and graphs up but at the end of the day it's easier to explain it to a lot of folks the first way.

Here's the GPC Lineup loaded to 2.295" for the most part (except the 20, that one runs shorter either way)




Here they are loaded to ~2.375-2.380" (where we intend to run them)



Here's a picture of my personal 27 GPC's, built on LWRC Six-8 receiver sets.  One is a 16" and the other a 22".



Here's pics of the lineup individually, most of them loaded to 2.375-2.380" (except the 20 GPC, that stays around 2.295" or less)










That's it for now and I guess we will just update as we release more of the lineup.  I'm sure I'll come back and edit this like I do all my OP's as more things develop, questions are asked that I didn't think of explaining up front, etc.

Thanks!

That's the 2nd time I've seen that "OST", what does it mean?  Thanks!

Ah!  Thanks!

I understand now, thanks!

We'll get range reports up as we release each one, but we can always provide some Quickload estimates if you like for those that aren't produced yet.  Yes, this standardized family will do well against their close-cousins like the 224V, 6.5G and 6.8SPC.... The 277 Wolverine uses a 5.56 case so it's completely different... the 27 GPC runs much faster than the WLV of course.  The benefit of the WLV is unmodified 5.56 mags, 5.56 bolts, 5.56 brass as a parent case and the supers/subs through the same barrel like the BLK.  The 30 GPC will run significantly faster than the BLK of course as well, just like the 27 GPC does the WLV.  Same-same there.

here are a couple of estimates for the 25 GPC

24 GPC estimates

We appreciate it but typo it's 30 GPC, the PRC is a Hornady cartridge. The 30 GPC should be around come end of summer or so. The 20 and 24 are coming out next then 25, 26, 30, 22... somewhere in that order.

Thanks!

There has been a lot of interest in the 25 cal actually  and for good reasons... 25 has been neglected somewhat but if you think about it, it is a 6.3mm to the 6.5mm and the options for bullets these days has improved.

It's marginal in 16" and under I would say. You start to see the real difference at 18" and longer as you are better able to take advantage of the additional case volume.

What bullet are you looking for data on?  I'll see if we have it. With the 27 GPC you can basically take SPCII data and work up, and, the GPC was designed to load long so while at the same time you are increasing case volume our freebore is set a bit long as well to keep pressures in check as you move the bullet further out. Therefore the 27 GPC will prefer some of the slower powders in the 6.8SPC range/window.

I know it sounds too simple, but basically start with SPCII loads and work up... there is a ton of SPCII data already out there to use as a baseline.

here is some of the testing data for the 27gpc

Don't know much about the Tac 6 but there are some 24 GPC estimates posted above... if you are referring to design again I dont know.

We dont have a ton of data on either of those yet, sorry. If you want to send me your load data for them in your SPC maybe we can replicate them as a starting point and see how we do?  We did some work with the 120SST with CFE223 behind it but we did not focus on it much at all to give a fair result.  As an example we were able to push the 130 grain Federal Fusion pulls 100fps faster than the 120SST using pretty much the same data so as you can see I cant offer much for that one yet.

all of the gpc calibers except the 27 and 20 will have the shoulder moved back a little and trimmed so more bullets can be fit.

While that may be true using standard mag lengths, please remember the GPC family is meant to be able to be loaded long...  that's why we added case volume instead of reducing it. While you can run it in standard mags without issue, yes, that will restrict the use of some of the really long bullets but not if you load longer than 2.295".  The baseline standard load lengths are ~2.295" (PRI, ASC, CPD and Six-8 Pmags).

And thanks!  We never know when we will cross paths with someone that has had experience with us and it's always nice when we do.

Whichever you are most comfortable with. Thanks!

Sure will, as long as you can load them that long in your platform.

Got it thanks!  Will come back with update.

the 105's will fit at 2.295 and longer loading

We try not to do "better" discussions, sorry.

If theres something specific you would like to know we are happy to help answer.

Alright just an update.

Since there has been enough interest in the 25 GPC we ordered the tooling and blanks for it as well...

So we will have the 20 GPC, the 24 GPC and the 25 GPC all available in a couple months, maybe less.

The 27 is out already.

We will probably do the 28, then 26 and 30 after that, then the 22 last.  We are still debating on final chamber for the 22.

some 28 GPC estimate data

27 GPC Brass from Starline is in process!  Should be available in a few months!

The 27 GPC Brass is the Parent brass for all the other GPC cartridges, so, this is good!

Timing is great as well since all the blanks and tooling are also ordered for the 24 GPC, the 25 GPC, 26 GPC and 28 GPC!  (30 GPC and 22 GPC will be the last two to launch).  Since we already have the 27 GPC running, and the 20 GPC testing done and available shortly, this is great!  Practically an entire family or cartridges all launched in a 6-month period, with "Factory" Starline brass available soon as well.