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Re: 300 Blackout
Posted: Sat May 11, 2013 12:08 pm
by John MH
AR15 wrote:Whisper but not Blackout. The Saami print for Blackout is way too loose and a 1:8 is too slow for 220's at 995-1000FPS in short barrels, say 12''.
I have no experience with Whisper btw, only Blackout.
The 220SMK is a long bullet that will yaw and become Dynamically unstable before regaining stability down range, because of its length not much yaw is required for the tip or tail to get very close to suppressor baffles, run it through a long 7 baffle can and you will get interference from the last one or two baffles, not strikes but close enough for the pressure to effect accuracy. I have seen a 1:8 Twist rifle that grouped with factory220 subs at 1.0-1.5MOA, open up to 6MOA through a 7 baffle can with no visible strikes, run a S5 on it and it shot the same 1-1.5MOA group no problem. Most of the holes at 6MOA where slashed.
The same barrel would shoot 125Gr Factory supersonic at 3/4MOA with good, concentric holes on paper .
The key to all of this is Static and Dynamic stability, while modern ballistic programs will tell you that your bullet is Statically OK, ie it is being spun fast enough to be gyroscopically stable they don't factor in bullet profile, Ogive dimensions, boat tail shape etc... and the correlation between Static and Dynamic stability. Dynamic stability is not automatically guaranteed. Some bullets are dynamically unstable at the moment they leave the barrel (or close too), like the 220's, others may loose dynamic stability during flight after decelerating.
We spent an entire day getting a Windows7 PC to run a very old bit of original Windows code that we were given, to my knowledge its the only thing available that models both Static and Dynamic stability.
Every other bit of software including Brian Litz JBM calculator will tell you that the 220 is stable at a factor of 1.970 approx, in reality if you apply the Static data to the Dynamic you will find that due to the bullet shape and speed the RPM is not enough to counteract Yaw and that the stability factor is more like .800 at 995FPS with a 1:8 Twist.
We were able to plug in a whole load of different bullet shapes, twists, Quick Load and actual measured velocities to get the best setup for the job. For the first time it got close to simulating what we were seeing down range.
Also bear in mind that we were designing a rifle to shoot factory ammunition as accurately as possible, working with Remington 220Subs. Handloads are considerably more accurate.
After twist rate was figured out it quickly became obvious that the 'Sporting' style Saami Blackout print was way too loose for good accuracy in proper subsonic loads, those long heavy slow bullets need to be setup in the chamber tight, so each one is as close to the next as possible in alignment, we set about making that chamber better.
What we have now is the equivalent to a Blackout Match.
Far too much science for me but since factory ammunition is made to SAAMI specs changing the 300 Blackout spec is likely to be problematical and I do not see how a 'tighter' chamber is going to make a factory round any more accurate. As long as the bullet is concentric with the case and chamber its going to start its journey aligned with the bore. Start tightening the chamber and redefining it as Match or Tight Necked and your are heading down the road of having to hand load or procuring specialist factory ammunition. The 300/221 Whisper is so close to the 300 Blackout as to be almost the same. Running a tight match chamber in a suppressed semi-auto with a gas impingement system is IMHO going to cause reliability problems, less so in a bolt action of straight pull. I suspect the Military would prefer to get their ammo from someone like RUAG
300 Whisper P which is already proven to work subsonic rather than Remington Sporting Ammo.
Re: 300 Blackout
Posted: Sat May 11, 2013 12:25 pm
by saddler
My experience of Remington sporting ammo is far from good...I'd have been better with some dodgy blokes reloads or WW2 surplus ammo, etc.
The Remmy ammo I fired in one of my Remmy rifles (so you'd THINK that they may, you know, be compatible/tuned to each other) made the rifle group like a shotgun
Re: 300 Blackout
Posted: Sat May 11, 2013 1:41 pm
by AR15
Far too much science for me but since factory ammunition is made to SAAMI specs changing the 300 Blackout spec is likely to be problematical and I do not see how a 'tighter' chamber is going to make a factory round any more accurate. As long as the bullet is concentric with the case and chamber its going to start its journey aligned with the bore. Start tightening the chamber and redefining it as Match or Tight Necked and your are heading down the road of having to hand load or procuring specialist factory ammunition. The 300/221 Whisper is so close to the 300 Blackout as to be almost the same. Running a tight match chamber in a suppressed semi-auto with a gas impingement system is IMHO going to cause reliability problems, less so in a bolt action of straight pull. I suspect the Military would prefer to get their ammo from someone like RUAG
300 Whisper P which is already proven to work subsonic rather than Remington Sporting Ammo.[/quote]
Completely incorrect, the case is not concentric with the chamber because the chamber is too loose, therefore the ammunition is loaded at different angles each time, this translates into a loss of accuracy over distance.
Apply that to what I have already said and you may understand what is going on here.
Our work on the Blackout is exactly what Noveske and AAC have done on their own guns.
We also have one of the most reliable versions of this rifle in full auto/ semi auto with DI and running suppressed. With a first fail (short stroke) at near 300 rounds of suppressed subsonic, our gun is easily as good as anything on offer from AAC.
The fail is due to a build up of carbon and powder around the bolt, upper and buffer system causing friction and has nothing to do with the chamber. An application of lubricant and it operates as before. We have other mechanisms at work that keep the bolt locked up for longer, so that more powder is burnt before it unlocks, causing the rifle to run cleaner for longer.
Rounds feed and extract perfectly.
And for your information we were instructed what ammo to make our rifle work with and given criteria that it must fulfill.
Re: 300 Blackout
Posted: Sat May 11, 2013 1:55 pm
by AR15
saddler wrote:My experience of Remington sporting ammo is far from good...I'd have been better with some dodgy blokes reloads or WW2 surplus ammo, etc.
The Remmy ammo I fired in one of my Remmy rifles (so you'd THINK that they may, you know, be compatible/tuned to each other) made the rifle group like a shotgun
Exactly mine too, the Saami chamber spec and ammo spec are crap.
Re: 300 Blackout
Posted: Sat May 11, 2013 1:59 pm
by John MH
Sorry not convinced that your special reamer will be consistently more accurate than the standard 300 Blackout Reamer Spec used on 1000's of guns in the USA, what you need to do is send one to me to test myself. Unfortunately I and the majority of shooters on here can't own a Semi or Full Auto its still all pretty academic.
Remington Sporting ammo verses RUAG Swiss P is probably no contest, I have no experience with the quality of Remington Factory ammunition but do know RUAG from both personal and professional use, what I do know of Remington brass is that I wont use it when there is far better available.
Sounds like the 300 Blackout SAMMI spec is s*** from what you say and that sticking with 300/221 Whisper would be a better idea, as I'm hand loading for my needs I am able to produce Match Grade 300 Blackout ammo that shoots very well out of my rifle with as far as I know a standard 300 Blackout chamber. Maybe its because I'm using a Redding National Match Die set that mines so good, furthermore the load isn't quite tuned to perfection just yet.
Re: 300 Blackout
Posted: Sat May 11, 2013 2:01 pm
by John MH
AR15 wrote:
And for your information we were instructed what ammo to make our rifle work with and given criteria that it must fulfill.
Must have been specified by someone who knows nothing about anything then.
Re: 300 Blackout
Posted: Sat May 11, 2013 2:48 pm
by AR15
John MH wrote:Sorry not convinced that your special reamer will be consistently more accurate than the standard 300 Blackout Reamer Spec used on 1000's of guns in the USA, what you need to do is send one to me to test myself. Unfortunately I and the majority of shooters on here can't own a Semi or Full Auto its still all pretty academic.
Remington Sporting ammo verses RUAG Swiss P is probably no contest, I have no experience with the quality of Remington Factory ammunition but do know RUAG from both personal and professional use, what I do know of Remington brass is that I wont use it when there is far better available.
Sounds like the 300 Blackout SAMMI spec is s*** from what you say and that sticking with 300/221 Whisper would be a better idea, as I'm hand loading for my needs I am able to produce Match Grade 300 Blackout ammo that shoots very well out of my rifle with as far as I know a standard 300 Blackout chamber. Maybe its because I'm using a Redding National Match Die set that mines so good, furthermore the load isn't quite tuned to perfection just yet.
1000's of guns in the USA are cheap and crap, the really good ones, made by Noveske et al, use a chambering like us. You have already stated you have never shot heavy subs through 12'' barrels, why not give that a try and see what the Saami chamber is like then.
The simple fact is that our reamer makes a chamber that is consistently more accurate than the Saami Standard. If it was not the case then nobody would be able to improve anything and gun development would grind to a halt.
All this development goes into our straight pull guns John so you don't need a semi auto either.
At the time of development the only ammo readily available was 208gr A-Max and 220 Remy, we made it work with that as requested.
I think you can guess that Edgars could supply both brands quickly.
It is unlikely that SwissP will be any different in case dimensions but will have more consistent powder and burn and possibly a better shaped bullet, hence making it more accurate. It will also benefit from being shot through a better chambered barrel with a correct twist just the same as any other ammo would.
Re: 300 Blackout
Posted: Sat May 11, 2013 2:56 pm
by John MH
I can't shoot anything through a 12" as I don't have one. I think trying to get anything consistently better better than 1 MOA on a 300 Blackout is a mute point anyway as its a ballistically challenged short range round in any case, its not designed to be uber accurate but fills a niche market. Mine is for 100m and less, although I know it will happily knock down Fig 11s on a 300m ETR all day long it ain't going to win any 200m plus matches over here. I will work up a subsonic load using Lapua 200 grain though just to see how accurate it is.
Re: 300 Blackout
Posted: Sat May 11, 2013 3:25 pm
by AR15
I'm only interested in making things as good as they can be John.
I think the 200Gr subs will do OK in a 16'' barrel. They would be even better with an improved chamber though.
Who doesn't want a more accurate gun if they can have one?
I'm curious though, if the 12'' barrel shot supersonic fine at 3/4MOA, why go to a 16'' for 100m shooting?
I guess you wanted the flexibility for supersonic longer range in the future?
Re: 300 Blackout
Posted: Sat May 11, 2013 3:49 pm
by John MH
It's for CSR so may be used out to 300 on an ETR but not for scoring 5's on Fig 12's, 11's and 14's ant 200m or more. A 12" would not be optimal for my needs.