Re: 6.8 or 300 blackout
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: rusty815</div><div class="ubbcode-body">Just for kicks, heres a CPD 25 rounder:
http://www.midwayusa.com/product/310959/...ess-steel-black</div></div>
25 rounds though. The Barrett is 30 and well reviewed:
http://www.midwayusa.com/product/163532/barrett-magazine-ar-15-68-remington-spc-30-round-matte
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: rusty815</div><div class="ubbcode-body">That one is out of stock though, and I can't really use that here in Cali, so heres the 10 rounder:
http://www.midwayusa.com/product/186454/...ess-steel-black</div></div>
No reviews. This one has 11 reviews, averaging almost 5 stars. People must feel it was worth it:
http://www.midwayusa.com/product/576975/..._vc=subv1186454
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: rusty815</div><div class="ubbcode-body">according to Mr' Paolo Santos on the 6.8 forums, the differene in pressure from a SAAMI to a Spec II chamber, all else equal, is 4k:</div></div>
That is not correct. His conclusion was 1500 psi:
http://paulosantos0922.wordpress.com/tag/6-8-spc/
"CONCLUSION:
The SPCII Chamber reduces the pressure by approximately 1500K PSI without the loss of accuracy."
The answer when lab tested is 1000 - 1500 psi, depending on the ammunition. This has been tested in actual ballistic labs by several larger companies, the US govt., and Western Powders Ballistic Lab.
From: Robert Silvers
Sent: Thursday, July 14, 2011 5:06 PM
To: Johan Loubser
Subject: Re: Western Powders Ballistic lab
Johan,
Have you ever done a test where you take a 6.8 SPC SAAMI test barrel, measure velocity and pressure, then ream the same barrel to 6.8 SPC-II - and add more powder to match the pressure of the previous test, and then see how much extra velocity there is?
Robert.
----------------------------------
Robert,
Yes we did exactly that and the difference was negligible as to be ignored ca 20-30Fps and <1000Psi.
I know there is a lot of claims out there regarding this.
Some apply the effects of other calibers (such as the 223Rem) with completely different expansion ratios to the 6.8SPC.
The 6.98Spc is not sensitive to the slight changes in dimensions between the std and SPEC II.
Regards
Johan Loubser
Ballistician
Ramshot.Accurate.Powders
----------------------------------
Robert,
Example is that with SAAMI reference ammunition we got a difference of Pressure: -2.5%/-1200Psi and -19Fps
If one consider that is equal or less than one standard deviation I consider it negligible.
Regards
Johan Loubser
Ballistician
Ramshot.Accurate.Powders
From Art at SSA:
I can not disagree with Bob's statement of only 1000 -1500 PSI reduction and <30 FPS increase with a given load and projectile with respect to the SAAMI VS the Spec II chamber
Then DocGKR posted: "The information Mr. Silvers has posted is the factual truth. Every professional ballistics facility, including USG, foreign military, and Industry, that I am aware of that has tested 6.8 SPC vs. 6.8 SPCII using industry standard equipment has reported only a 1000-1500 psi change."
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: rusty815</div><div class="ubbcode-body">Just for kicks, heres a CPD 25 rounder:
http://www.midwayusa.com/product/310959/...ess-steel-black</div></div>
25 rounds though. The Barrett is 30 and well reviewed:
http://www.midwayusa.com/product/163532/barrett-magazine-ar-15-68-remington-spc-30-round-matte
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: rusty815</div><div class="ubbcode-body">That one is out of stock though, and I can't really use that here in Cali, so heres the 10 rounder:
http://www.midwayusa.com/product/186454/...ess-steel-black</div></div>
No reviews. This one has 11 reviews, averaging almost 5 stars. People must feel it was worth it:
http://www.midwayusa.com/product/576975/..._vc=subv1186454
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: rusty815</div><div class="ubbcode-body">according to Mr' Paolo Santos on the 6.8 forums, the differene in pressure from a SAAMI to a Spec II chamber, all else equal, is 4k:</div></div>
That is not correct. His conclusion was 1500 psi:
http://paulosantos0922.wordpress.com/tag/6-8-spc/
"CONCLUSION:
The SPCII Chamber reduces the pressure by approximately 1500K PSI without the loss of accuracy."
The answer when lab tested is 1000 - 1500 psi, depending on the ammunition. This has been tested in actual ballistic labs by several larger companies, the US govt., and Western Powders Ballistic Lab.
From: Robert Silvers
Sent: Thursday, July 14, 2011 5:06 PM
To: Johan Loubser
Subject: Re: Western Powders Ballistic lab
Johan,
Have you ever done a test where you take a 6.8 SPC SAAMI test barrel, measure velocity and pressure, then ream the same barrel to 6.8 SPC-II - and add more powder to match the pressure of the previous test, and then see how much extra velocity there is?
Robert.
----------------------------------
Robert,
Yes we did exactly that and the difference was negligible as to be ignored ca 20-30Fps and <1000Psi.
I know there is a lot of claims out there regarding this.
Some apply the effects of other calibers (such as the 223Rem) with completely different expansion ratios to the 6.8SPC.
The 6.98Spc is not sensitive to the slight changes in dimensions between the std and SPEC II.
Regards
Johan Loubser
Ballistician
Ramshot.Accurate.Powders
----------------------------------
Robert,
Example is that with SAAMI reference ammunition we got a difference of Pressure: -2.5%/-1200Psi and -19Fps
If one consider that is equal or less than one standard deviation I consider it negligible.
Regards
Johan Loubser
Ballistician
Ramshot.Accurate.Powders
From Art at SSA:
I can not disagree with Bob's statement of only 1000 -1500 PSI reduction and <30 FPS increase with a given load and projectile with respect to the SAAMI VS the Spec II chamber
Then DocGKR posted: "The information Mr. Silvers has posted is the factual truth. Every professional ballistics facility, including USG, foreign military, and Industry, that I am aware of that has tested 6.8 SPC vs. 6.8 SPCII using industry standard equipment has reported only a 1000-1500 psi change."