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BIGGDAWG

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Reply with quote  #1 
The first gpc barrels showed up today so i have the parts collected to build the upper and have brass and bullets so i am going to get it assembled and shoot some 130 fusion pulls to fire form some brass and see what it might do. 

I will keep data posted here, i won't be using any fire formed brass for a week or so still waiting on the size die.

edit to add, shot the first rounds and started way conservative. but our plan worked out just right. i started with new 6.8 spc brass i through primers, powder and a bullet in and they chambered and shot perfect.

looks like we will gain 1.8-2 grains over the spc , cases look good i am at 2580 with a 130 with room to spare and that isn't even shooting the fire formed case yet.


20171204_115650.jpg 

24651131_1819267194782644_421479618_o.jpg 

20171204_202150.jpg 



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BIGGDAWG

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a good night of testing. i modified a 6.8 bushing die to just size the body of the case it sizes a little too much but i get to fire them the second time with the new shoulder angle.

I ran the 120 sst at 2.295 and man it eats up case length. personally if i run this bullet i will be loading to 2.34 with a windowed mag.  i can push the 130 pulls i have faster.

so i did first test with the sst with fresh cases then i loaded a few in the fired cases to try to get to max.  i did not get there with cfe223 i was compressing pretty good at 2.3 so case was full es and sd looked awesome velocity just wasn't where i wanted it yet.

the 130 federal pulls i have ran great and love cfe223 i hit 2750 with room to go yet. they just started compressing at 25.2

120sst cfe.jpg  130 cfe.jpg 


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BIGGDAWG

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Reply with quote  #3 
data place holder
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BIGGDAWG

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Reply with quote  #4 
data posted for 120sst and 130 federal
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lapriester

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Reply with quote  #5 
Quote:
Originally Posted by BIGGDAWG
data posted for 120sst and 130 federal


Wow. I'm impressed by the velocities with this. So close to my 270 Win accuracy load it's amazing. Now I really NEED one of these. Destined to make me sell off my 6.8's.
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BIGGDAWG

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Reply with quote  #6 
got some testing in and started testing a 16 inch barrel also.

these tests were all with the 90 tnt tried some h335 and aa2200 and got some awesome velocities.

90 tnt h335 16 and 23.jpg 
16" 36.4 grains h335 max charge

36.4 h335 16 (2).jpg 






36.4 h335 90 tnt 16 inch                        34.3 h335 90tnt 23 inch                           36.1 h335 90tnt 23 inch

36.4 h335 16.jpg  34.3 h335 23.jpg  36.1 h335 23.jpg 



36.1 top and 36.4 bottom from 23 inch barrel

36.1 36.4 h335 23.jpg 



36.4 h335 90 tnt 23 inch barrel

36.4 h335 23.jpg 




90tnt aa2200.jpg 

26036968_1844196375623059_1725362656_o.jpg  26026842_1844223825620314_1598810608_o.jpg  26060884_1844226612286702_322668036_o.jpg 


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lapriester

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Reply with quote  #7 
Awesome isn't giving it justice.  That is some pretty impressive data.  I'm excited about this one.  36.4 of H335 looks a bit hot, huh?  LOL.  Hey...it's only brass.
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BIGGDAWG

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Reply with quote  #8 
Quote:
Originally Posted by lapriester
Awesome isn't giving it justice.  That is some pretty impressive data.  I'm excited about this one.  36.4 of H335 looks a bit hot, huh?  LOL.  Hey...it's only brass.


it was warm in the 16 but not the 23 but i would consider it max for sure.

this round has impressed me i must say. wade just got some great numbers with shooters world tactical so i will run some of them tonight too.

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RangerJoe

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Reply with quote  #9 
So why is there worse pressure signs from a 16" barrel (with less time for the pressure to act against the case) than 23"?  Hmm... [confused]  I presume these are from the same blank supplier and chamber reamer?
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BIGGDAWG

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Reply with quote  #10 
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Originally Posted by RangerJoe
So why is there worse pressure signs from a 16" barrel (with less time for the pressure to act against the case) than 23"?  Hmm... [confused]  I presume these are from the same blank supplier and chamber reamer?

The 16 is a rechambered wolverine barrel that someone messed up the chamber on trying to get a separated case out of. so they are both 11 twist but the port on the 16 is too big i am running an adjustable gas block but i think it has to do with the extra gas but it is hard to say maybe the brass fit the other chamber better.

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RangerJoe

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Reply with quote  #11 
Got it!  Only takes a tiny bit of variance in chamber, headspace, bore, etc. to manifest in a fairly big differences when dealing with this kind of pressure!
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44Joe

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Reply with quote  #12 
I'm interested in this one too.
who will you have make the barrels? Any time line?

I would like to see what it does with the 110 g AB.

Ty 
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RangerJoe

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Reply with quote  #13 
44Joe: Welcome to the forum!  MDWS turns their own barrels.  We buy high-quality rifled blanks and have a dedicated machine shop do the rest.  I believe there are only a couple GPC beta-test barrels now.  Typically after successful beta-testing, a limited run of first production barrels become available for experienced wildcatters to run with various twists, lengths, brass, primers, powders, bullets, magazines, etc. to really identify and iron out any wrinkles.  Then any tweaks can be made, and stock production barrels are listed for sale.  Mark can confirm or correct me, but that process can take from a couple months to half a year or better... just depends on how all the 1,000s of variables come together.
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44Joe

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Reply with quote  #14 
Ok, sounds like it will be a little bit.  I'll check on the progress and look forward to reading about it.  I think it's a good idea and a worthwhile upgrade.

Ty 
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MDWS

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Reply with quote  #15 
Quote:
Originally Posted by RangerJoe
44Joe: Welcome to the forum!  MDWS turns their own barrels.  We buy high-quality rifled blanks and have a dedicated machine shop do the rest.  I believe there are only a couple GPC beta-test barrels now.  Typically after successful beta-testing, a limited run of first production barrels become available for experienced wildcatters to run with various twists, lengths, brass, primers, powders, bullets, magazines, etc. to really identify and iron out any wrinkles.  Then any tweaks can be made, and stock production barrels are listed for sale.  Mark can confirm or correct me, but that process can take from a couple months to half a year or better... just depends on how all the 1,000s of variables come together.
Pretty much spot on! Usually. With this one, however, a lot of the variables have already been ironed out since it is a 6.8SPC improved... We just play with new load data, make sure the chamber and gas ports are good and done. This one, will be ready for production in no time.

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44Joe

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Reply with quote  #16 
what kind of rifling will you be using?  Hopefully not the old straight cut types, a 5R or 3R would be my preference.  Thanks 
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MDWS

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Reply with quote  #17 
Quote:
Originally Posted by 44Joe
what kind of rifling will you be using?  Hopefully not the old straight cut types, a 5R or 3R would be my preference.  Thanks 

They will be 5R.

Most likely a 10-Twist instead of 11 since the 130's are doing so well.

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bbbrownfield

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Reply with quote  #18 
+1 on the 10-twist
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44Joe

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Reply with quote  #19 
I think the 10 twist is a good choice too, when can I order a 20" !  LOL

What 130gr bullets?  I didn't think that there were any that worked well due to length or being constructed too tough(made for 270 Win)

Thanks
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sleddoc

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Reply with quote  #20 
I have used the 130 nosler ballistic tips in a regular 6.8spc and built a chart for my gun. ogive is a little different so everything fits well. I will look up my info and post when I get a moment. I have shot these out to 400 in really high winds and had good results
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MDWS

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Reply with quote  #21 
Check the performance of the Sierra 130 Game King/SBT.  I am EASILY getting 2550fps with them out of my 18" GPC barrel only loaded out to 2.26" COAL!!!  I think I can get 2600 if I use a different powder, which I will try soon.  Minimum expansion on them is 2000+fps (according to Sierra tech).  BC of .436, beautiful thing.

If I can get to 2600fps out of the 18" barrel loaded at 2.26, imagine what we can do at say 2.295".  Unstoppable.  Might not be the "best" hunting bullet for the GPC due to its threshold, but man does it buck the wind and reach out there.

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lapriester

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Reply with quote  #22 
So Mark. I see on your Website you will be, or are currently, offering a service to ream stainless 6.8 barrels to this caliber. Since I have 2 6.8's, one with a Bison barrel and one with a lightweight PSA CHF barrel, I might just consider that option after all the testing is completed. That way I won't have to figure out how to stuff another upper into one of my safes.

A thought. Would reaming the shoulder of my 6.5X6.8 barrel be a possibility? Now there's a notable idea. :-) A 6.5X6.8 GPC screamer. Now I've really opened a can of worms. LOL, AR15 6.5 Creedmoor clone.
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lapriester

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Reply with quote  #23 
Quote:
Originally Posted by MDWS
Pretty much spot on! Usually. With this one, however, a lot of the variables have already been ironed out since it is a 6.8SPC improved... We just play with new load data, make sure the chamber and gas ports are good and done. This one, will be ready for production in no time.
Oh God, don't mention the term "6.8SPC Improved" on the 6.8 Forums. The last person who did started a $hit storm.
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BIGGDAWG

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Reply with quote  #24 
Quote:
Originally Posted by lapriester
Oh God, don't mention the term "6.8SPC Improved" on the 6.8 Forums. The last person who did started a $hit storm.

isn't that the truth, turned into a bashing show

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mixednuttz

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Reply with quote  #25 
Quote:
Originally Posted by lapriester
Oh God, don't mention the term "6.8SPC Improved" on the 6.8 Forums. The last person who did started a $hit storm.
Biggdawg and I were just talking about a few hours ago. That thread got ugly quick on that forum.
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