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Posted: 8/23/2009 4:33:51 AM EST
[Last Edit: 9/7/2009 3:01:04 PM EST by murderman]
Two other long time arfcomer's and I spent most of last Sunday chrono'ing various SBR combinations. The data is presented below. It is safe to say that we all wish we could have run the additional 10 strings to complete the tables, but the heat/humidity was pretty rough, and time simply ran out.















Edited to remove duplicate data.
Link Posted: 8/23/2009 6:42:22 AM EST
[Last Edit: 8/23/2009 11:59:31 AM EST by Molon]
Excellent presentation!
Link Posted: 8/23/2009 7:04:32 AM EST
Thanks Molon; I know that you are one who can appreciate the data and the effort.

Roger that regarding the cans; take a look at strings 1 v 7, 2 v 8, and 3 v 9. I really wish that we would have been able to complete the tables during the same environmental conditions, but such is life.
Link Posted: 8/23/2009 7:07:10 AM EST
Sweet, great info!
Link Posted: 8/23/2009 7:34:52 AM EST
It was hot.

The sunshade pop-up blew away!

The Ammo was expensive.

The sound of bullet hitting steel at 100yards was great!

Getting to listen to the SPR/M4 and the SCAR-H SD - Priceless
Link Posted: 8/23/2009 7:36:38 AM EST
Wow!!

Thanks for doing this.



Link Posted: 8/23/2009 7:57:26 AM EST
Link Posted: 8/23/2009 8:32:54 AM EST
Did anyone notice the velocity drop between the 11.75" and the 12.5" 5.56mm barrels?
Link Posted: 8/23/2009 11:50:09 AM EST
[Last Edit: 8/23/2009 11:57:32 AM EST by Molon]
Originally Posted By murderman:


Roger that regarding the cans; take a look at strings 1 v 7, 2 v 8, and 3 v 9.



Duh! Right in front of my face. For some reason my brain was incorrectly thinking the Blackout was another can. Thanks again for taking the time, effort and financial loss to perform these tests and post your results.
Link Posted: 8/23/2009 12:33:24 PM EST
Originally Posted By Doc_Strangelove:
Did anyone notice the velocity drop between the 11.75" and the 12.5" 5.56mm barrels?


Yeah 200 fps in less than an inch is huge. That's why my AR pistol and future SBR sports a Noveske 12.5.
Link Posted: 8/24/2009 10:33:18 AM EST
[Last Edit: 8/24/2009 10:33:27 AM EST by Doc_Strangelove]
I really think that the sweet spot in bqarrel length on the 5.56mm weapons is 12.5 inches.
Link Posted: 8/24/2009 10:54:33 AM EST
Originally Posted By Doc_Strangelove:
I really think that the sweet spot in bqarrel length on the 5.56mm weapons is 12.5 inches.


This thread was the final factor to why I just ordered a 12.5" WOA barrel for my pistol. Thanks so much for the data guys!
Link Posted: 8/24/2009 1:39:34 PM EST
Originally Posted By Doc_Strangelove:
I really think that the sweet spot in bqarrel length on the 5.56mm weapons is 12.5 inches.


Probably even more so for the 6.8.
Link Posted: 8/24/2009 2:03:00 PM EST
Originally Posted By murderman:
Originally Posted By Doc_Strangelove:
I really think that the sweet spot in bqarrel length on the 5.56mm weapons is 12.5 inches.


Probably even more so for the 6.8.


I was going to say, the 12.5 6.8 is the real story, practically the same MV as the 5.56 but with a 110 vs a 77.
Link Posted: 8/24/2009 2:20:23 PM EST
As a fan and owner of 12.5'' AR's I really appreciate the time and effort you guys put into this. I'm saving this data for future reference.

Link Posted: 8/24/2009 2:24:45 PM EST
Originally Posted By 87GN:
Originally Posted By murderman:
Originally Posted By Doc_Strangelove:
I really think that the sweet spot in bqarrel length on the 5.56mm weapons is 12.5 inches.


Probably even more so for the 6.8.


I was going to say, the 12.5 6.8 is the real story, practically the same MV as the 5.56 but with a 110 vs a 77.


It gets even better though...

We received 700 rounds of 85 TSX's last night; they should absolutely smoke anything 5.56 with the proper chamber/twist combination in 12.5.

Link Posted: 8/24/2009 6:54:18 PM EST
This should be tacked
Link Posted: 8/24/2009 7:46:05 PM EST
Very nicely done. You have done a great service to all the data whores here. The 12.5" 6.8 is intriguing.

Link Posted: 8/25/2009 5:05:49 AM EST
[Last Edit: 8/25/2009 5:19:15 AM EST by DevL]
The SPR/M4s were three different units specific to the three rifle's owners. The two that showed the modest velocity boost were both the new/current style SPR/M4 baffles and the one that showed the veolcity drop was an older stlyed SPR/M4 baffle. I dont know if that was the cause of the velocity boost vs drop but it is interesting to note none the less. We will have to swap the cans around next time and see if it really is the baffle design of the can that made the difference. Although, I used to have an older styled SPR/M4 with the old baffles and it showed the same low ~15 FPS velocity boost that my newer baffels show when I did previous chrono testing.

The SCAR-H SD was REALLY quiet with .308 and a 20" barrel. I was very impressed. It was no louder than our 5.56 cans on the SBRs to the ear.

I am going to rebarrel my LWRC to a 12.7" barrel. The velocity change going from 12.5" to 11.5" is pretty much the same as cutting 2" from 14.5" to 12.5" so that last inch costs roughly twice the velocity per inch as the 14.5-12.5 cut. Those are also the hottest 12.5" chrono numbers I have ever seen on the Operator and N4 12.5" barrels. I dont know if thats just what those barrels do or if it was becasue it was hot and the barrels were new or what exactly, but those numbers are smoking. Both barrels put multiple XM193 rounds over 3000 fps. Half my 11.7" barrel's rounds were under 2800 fps.
Link Posted: 8/25/2009 8:20:13 AM EST
I'm not too deep into SBR and Suppressor information, but does the suppressor affect velocities at all?
Link Posted: 8/25/2009 8:26:20 AM EST
I would really love to know the results of SSA 85gr TSX combat loads through Denny's 12.5" 6.8mm barrel.
Link Posted: 8/25/2009 2:03:07 PM EST
Originally Posted By DevL:
The SPR/M4s were three different units specific to the three rifle's owners. The two that showed the modest velocity boost were both the new/current style SPR/M4 baffles and the one that showed the veolcity drop was an older stlyed SPR/M4 baffle. I dont know if that was the cause of the velocity boost vs drop but it is interesting to note none the less. We will have to swap the cans around next time and see if it really is the baffle design of the can that made the difference. Although, I used to have an older styled SPR/M4 with the old baffles and it showed the same low ~15 FPS velocity boost that my newer baffels show when I did previous chrono testing.

The SCAR-H SD was REALLY quiet with .308 and a 20" barrel. I was very impressed. It was no louder than our 5.56 cans on the SBRs to the ear.

I am going to rebarrel my LWRC to a 12.7" barrel. The velocity change going from 12.5" to 11.5" is pretty much the same as cutting 2" from 14.5" to 12.5" so that last inch costs roughly twice the velocity per inch as the 14.5-12.5 cut. Those are also the hottest 12.5" chrono numbers I have ever seen on the Operator and N4 12.5" barrels. I dont know if thats just what those barrels do or if it was becasue it was hot and the barrels were new or what exactly, but those numbers are smoking. Both barrels put multiple XM193 rounds over 3000 fps. Half my 11.7" barrel's rounds were under 2800 fps.


Great point on the SPR/M4 individual device apparent differentials; we need to swap them around next session to quantify if there is a velocity difference between the respective baffle stacks..

Let's do spend some more time with the SCAR-H SD on the bolt gun next outing when we are not so "distracted" and worn down by a long day of chrono work in the heat.....indeed, it was very pleasantly surprising considering that the loads are pretty hot producing 2700 FPS with 168 gr. projectiles out of that comparatively short barrel during previous testiing.. So, what have you got planned this coming weekend?

Just for reference, while I may have been the one to post this data, equal credit is due to DevL and SC-Texas; this was a Team effort, which could not have been accomplished otherwise.

Link Posted: 8/25/2009 3:39:15 PM EST
Originally Posted By timmy_mpls:
I'm not too deep into SBR and Suppressor information, but does the suppressor affect velocities at all?


Its supposed to have no effect or a very modest free bore boost to velocity. Murderman had a DROP in velocity, which was odd.
Link Posted: 8/26/2009 7:53:58 PM EST
Originally Posted By drw1006:
I would really love to know the results of SSA 85gr TSX combat loads through Denny's 12.5" 6.8mm barrel.


First, thanks very much, guys, for posting these data!

I have fired the older SSA combat loads in my Cardinal armory 1 in 11" SBR, 12.5" barrel , SPCII chamber, with a .30 cal JET suppressor and got an average velocity of 2968 FPS with a max reading of 2975.

I also have a 12.5" Denny's / WOA 6.8 X 43 mm barrel, w/ SPCII chamber, which I reamed myself. I expect the velocity to come in pretty close, and I will also be testing some 80 grain GS custom bullets.

I have never chrono'ed the new 85 Tactical Loads (using the new powder) yet, but give me one or two more weeks, and they will be posted.

Link Posted: 8/26/2009 7:54:54 PM EST
Originally Posted By 87GN:
Originally Posted By murderman:
Originally Posted By Doc_Strangelove:
I really think that the sweet spot in bqarrel length on the 5.56mm weapons is 12.5 inches.


Probably even more so for the 6.8.


I was going to say, the 12.5 6.8 is the real story, practically the same MV as the 5.56 but with a 110 vs a 77.


+1. I couldn't have said this any better myself.
Link Posted: 8/29/2009 8:40:58 AM EST
I ran a couple of boxes of the new SSA "TL" 85 TSX's this morning to sight in an optic on the SBR labelled J2 above. They are substantially more accurate than the crap Hornady stuff that I have in existing inventory; the fact that the brass all landed in a neat little pile is also indicative of their consistency.

As I went to the public range 1.5 miles from our home 20 versus the private one that is 35 miles away for time convenience, I did not get the opportunity to chrono; the other two members of the "chrono team" were also tied up anyway. We should be able to record some hard data next weekend, but subjectively these loads seem plenty hot.
Link Posted: 9/7/2009 3:10:15 PM EST
DevL and I ran 5 more SBR chrono strings today, and the results continue to be interesting. It was again extremely hot and humid, but after the chrono and suppressor POI shift testing, we had some fun at 300y; nothing quite like easily tagging the 8" steel with sweat, heat, and glare burning your eyes out!

Folks have asked for data on the SSA 85 TSX "TL's", and here you go:



Will post up the other data when time permits.
Link Posted: 9/7/2009 3:14:10 PM EST
Dang.
Link Posted: 9/7/2009 3:23:47 PM EST
[Last Edit: 9/7/2009 3:27:36 PM EST by murderman]
Originally Posted By 87GN:
Dang.



Indeed.... and when they hit the steel or the berm, you can definitely tell that they ain't no 5.56!

ETA: Also substantially more accurate than the old Hornady crap. This combination seems to be working very well.
Link Posted: 9/7/2009 3:38:49 PM EST
sorry I missed ths one.
Link Posted: 9/7/2009 3:54:50 PM EST
Here is the target; please bear in mind that this is shooting through a chrono, rather than explicitly shooting for a tight group. The 11th hole was a cold bore "fouler", but I don't remember specifically which the first one was.

Link Posted: 9/7/2009 4:09:12 PM EST
You guys are really selling me on the 6.8 SBR concept.
Link Posted: 9/7/2009 5:08:28 PM EST
It is an amazing little cartridge

Link Posted: 9/7/2009 7:45:17 PM EST
Fascinating. So, with an average MV of 2,900 fps, what could we expect from the same 85 grain projectile at around 100 yards?
Link Posted: 9/10/2009 2:54:52 PM EST
The 85gr TSX looks like a great load in the 12.5" barrel.

Same drop and drift, to 500yds, as M855, when fired out of a M-4, so you can use the 5.56 ACOG's.

Hits harder at any range. Hummmmm.

Looks like the 6.8 is living up to the hype, finally.

This gives me much to think about.....

Thanks for the information.
Link Posted: 9/10/2009 3:29:46 PM EST
Originally Posted By RedFalconBill:
The 85gr TSX looks like a great load in the 12.5" barrel.

Same drop and drift, to 500yds, as M855, when fired out of a M-4, so you can use the 5.56 ACOG's.

Hits harder at any range. Hummmmm.

Looks like the 6.8 is living up to the hype, finally.

This gives me much to think about.....

Thanks for the information.


B-I-N-G-O.....we have a winner here!

I have an 11J on order for the 6.8 SBR "hog gun", but the wait will probably be as long as an F4.

Link Posted: 9/10/2009 3:59:47 PM EST
Originally Posted By 87GN:
You guys are really selling me on the 6.8 SBR concept.


me too! Been thinking about building a 6.8 for hogs and deer. Since I already have a 12.5 in 5.56 ......a 12.5 6.8 with a acog or 1-4 would be kickass.
I'm going to start looking around for parts and see how much it's gonna cost me.
Link Posted: 9/20/2009 5:19:15 PM EST

tag.

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