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Posted: 2/9/2013 6:25:58 PM EDT
[Last Edit: 4/1/2018 7:56:53 PM EDT by MRW]
Link Posted: 2/9/2013 6:32:59 PM EDT
A free float tube under those handguards wouldn't hurt.
Link Posted: 2/9/2013 7:01:16 PM EDT
Link Posted: 2/9/2013 7:41:04 PM EDT
That is some nice shooting.
Link Posted: 2/10/2013 11:03:58 AM EDT
[Last Edit: 2/13/2013 8:59:02 AM EDT by JeffinVAB]
MRW:

You seem to have assembled what happened to turn out to be an excellent combination of parts. You also obviously have an excellent barrel and shooting capabilities.

Altering your setup in any way, like a free float tube, would almost surely degrade the accuracy, as the barrel harmonic is obviously working for you.

Using the double sided gaussian gaussian distribution as a probability density for shot dispersion, and the correction factor for 10 shots of 0.667, you are shooting 1.03 MOA accuracy (1.543 X 0.667 PDCF = 1.029).

Thats awesome, good job. I have a $3K Lilja barreled rifle that only shoots 0.7 MOA.


Link Posted: 2/10/2013 11:15:00 AM EDT
Originally Posted By JeffinVAB:
MRW:

You seem to have assembled what happened to turn out to be an excellent combination of parts. You also obviously have an excellent barrel and shooting capabilities.

Altering your setup in any way, like a free float tube, would almost surely degrade the accuracy, as the barrel harmonic is obviously working for you.

Using the double sided gaussian gaussian distribution as a probability density for shot dispersion, and the correction factor for 10 shots of 0.667, you are shooting 1.03 MOA accuracy (1.543 X 0.667 PDCF = 1.029).

Thats awesom, good job. I have a $3K Lilja barreled rifle that only shoots 0.7 MOA.




I never understood correction factors, in guns or cars. A car sets a time down the 1320 and that's as fast as it goes. A gun and a shooter make a particular sized group and that's how accurate the two of them are.
Link Posted: 2/10/2013 11:24:20 AM EDT
[Last Edit: 2/10/2013 11:24:48 AM EDT by Sinister]
I would guess that adding a DD Omega 12.0 (free-floating with NO modification to the base upper) and switching to a Geissele trigger you could shrink that group even more.

Excellent performance from a stock trigger and barrel!!!

Bravo, man, bravo.
Link Posted: 2/10/2013 12:20:08 PM EDT
Good shooting. I wish Molon would come back, too. Those were the best posts on this board. I would say you should only put a free float tube on the rifle if you actually want one for weight/aesthetics/mounting options/etc. Even if it does improve precision...what does it matter? On-target is on-target, and that paper is just as dead with a 1.543 group as it is with a 1.443 group.

I've almost got my 20" SPR build finished, but it's going to be a while before I can see what it does. Once I have time, I'll replicate some of Molon's testing with it.
Link Posted: 2/10/2013 1:05:55 PM EDT
That's a nice set-up. Don't change a thing if it's working for you.
Link Posted: 2/10/2013 5:38:34 PM EDT
[Last Edit: 2/12/2013 11:28:31 AM EDT by JeffinVAB]

Originally Posted By nightshade1:
Originally Posted By JeffinVAB:...


I never understood correction factors, in guns or cars. A car sets a time down the 1320 and that's as fast as it goes. A gun and a shooter make a particular sized group and that's how accurate the two of them are.


The only way to understand shot dispersion is with statistical analysis. It can be tough to figure out.

It does make sense that if you keep shooting a 1 MOA rifle over and over there is going to be some ocassional increased dispersion. You have to use statistics to sort out the noise.

This is a good site to read for a basic understanding of understanding groups.
http://www.the-long-family.com/group_size_analysis.htm
Link Posted: 2/10/2013 6:45:16 PM EDT
I did a similar build with my old AR-15 SP1 barrel. I used a lightweight carbon fiber free float tube from DPMS and a Cav Arms polymer lower to make the lightest possible rifle I could build.

I replaced the Cav Arms butt plate with an A2 model which had to be fitted a little to work. That barrel/bolt always shot well and continues to do so despite thousands of rounds down the tube.

20.5 grains of H-4198 under a 52 grain SMK seated @ 2.250" works for me. 23.5 +/- grains of H-322 works as well.
Link Posted: 2/10/2013 7:37:48 PM EDT
I had found a barrel at a gunshow and built a similar upper to use with my Ciener rimfire conversion. It shoots ok but no better with rimfire than several different 1:9 Bushmaster (Maine) barrels and actually my 1:8 Rock River National Match shoots the rimfire better at 100yds

Those little sierras shoot nice.

The point I really want to make is the 20" pencil barrel has great ballance and feeling and I appreaciate the longer sight radius with my 59 year old eyes

My first AR was a bushmaster 20" h-bar, then I got into carbines because the Bushmaster was "too long" It turns out it wasn't too long,it just had a crowbar for a barrel when it should have had a pencil.

Seems like the original guys got it right in the begining
Link Posted: 2/10/2013 9:17:43 PM EDT
Looks like your flash hider timing is off. Is that a optical illusion?

Nice shooting!!
Link Posted: 2/10/2013 9:41:28 PM EDT
Link Posted: 2/10/2013 9:55:07 PM EDT
[Last Edit: 2/10/2013 10:18:44 PM EDT by DefaultUsername]
I think he means how the flat sides of the hider are not vertical.
Link Posted: 2/10/2013 10:30:43 PM EDT
I quit reading out of jealous anger when he said "75 degrees with a slight breeze..."

But was also glad to see some inspiration for my winter projects (two A1 barreled rifles: one with a Colt veteran 1/12 barrel, and one with a new Colt A1 barrel but in 1/7 for a little variety).
Link Posted: 2/11/2013 5:38:02 AM EDT
Link Posted: 2/11/2013 5:40:44 AM EDT
Link Posted: 2/12/2013 12:09:23 AM EDT
20" chrome lined, 1:8, pencil barrel.

Swap your barrel for ^this^ one, free float it and I can pretty much guarantee you'll cut your group size in half, or better. I've got one, and it shoots.

1:7 pencil barrels are out there but they're rare. 1:8 will stabilize any projectile that can be loaded to feed in an AR mag.

Link Posted: 2/12/2013 5:42:48 AM EDT
Link Posted: 2/12/2013 11:36:19 AM EDT
Originally Posted By MRW:
http://i1011.photobucket.com/albums/af236/onehalfmvsquared/hobby/IMG_0334_zps24c3db4c.jpg

Inspired by Molon (come back!), I built a flat top upper with an old M16-A1 Barrel. Barrel is marked C MP CHROME BORE and built on a generic upper with generic BCG, Stag Lower, generic LPK, and a CavArms A1 stock. The barrel is NOT free floated. The first time I tried to shoot this rifle for groups it do not work out so well. I changed the set-up.

I mounted a SWFA SS 10x Mildot scope in an ADM mount and headed out to the range today in Central Florida. Temperature was 75 degrees with a slight breeze. Shooting bench was arranged the same as shown here. Targets at 100 yards, 10-shot group. I waited about 10 regular breaths between each shot.

The results, Extreme spread:

1.543" Hornady 52gr HPBT Match
1.661" Hornady 55gr Steel Match (1.058" without one flyer!)
2.124" Handloaded Winchester 55gr FMJ
2.313" Handloaded Sierra 52gr HPBT (1.625" without one flyer)

I tend to throw one or more down to the right from time to time. I have to work on that.

Evidence:

http://i1011.photobucket.com/albums/af236/onehalfmvsquared/hobby/IMG_0346_zpsc4d9bfb4.jpg

http://i1011.photobucket.com/albums/af236/onehalfmvsquared/hobby/IMG_0345_zpsde3b776d.jpg

http://i1011.photobucket.com/albums/af236/onehalfmvsquared/hobby/IMG_0347_zpsf884c9fc.jpg


I really like the lightweight 20" design and I was getting ready to remove the barrel and sell it due to all the hysteria and retro demand, replacing it with a barrel with a faster twist, but now I don't know...


http://i1011.photobucket.com/albums/af236/onehalfmvsquared/hobby/IMG_0341_zpsfbc57a29.jpg


Is that one of the old 1/12 barrels?
Link Posted: 2/12/2013 3:09:08 PM EDT
[Last Edit: 2/12/2013 3:10:13 PM EDT by MRW]
Link Posted: 2/12/2013 4:32:45 PM EDT
Hm... from reading this thread, am I assuming that my 1/7 Colt hbar is pretty decent? I've only had this AR for a month, so I'm still in the "holy crap look at all the info" stage.
Link Posted: 2/12/2013 4:36:45 PM EDT
Nice report.

Never worked up a load for my retro SP so good inspiration.
Link Posted: 2/12/2013 5:00:53 PM EDT
[Last Edit: 2/12/2013 5:01:52 PM EDT by JeffinVAB]

Originally Posted By Doppleganger871:
Hm... from reading this thread, am I assuming that my 1/7 Colt hbar is pretty decent? I've only had this AR for a month, so I'm still in the "holy crap look at all the info" stage.

A Colt HBAR like the current 6721 is 1/9" twist. A 6920 is 1/7" twist and has the light barrel.

Which model do you have?

The OP, MRW, has put together an excellent shooter. IMO, this AR is shooting better than 95% of similar ARs out there. However, you never know what you have until you try it. You are going to need a good mount and good scope to get started. Break in your barrel mildly and I think it will group and clean better down the road.
Link Posted: 2/12/2013 11:03:20 PM EDT
Originally Posted By MRW:

Originally Posted By Jeepy2013:
Is that one of the old 1/12 barrels?

Yes. It is a surplus 1/12 M16A1 barrel made by Colt


They do shoot great with 55gr ammo.

I had one that would keyhole 62gr green tip though.

Great shooting OP.
Link Posted: 2/12/2013 11:39:07 PM EDT
Originally Posted By CROWDLG:
Originally Posted By MRW:

Originally Posted By Jeepy2013:
Is that one of the old 1/12 barrels?

Yes. It is a surplus 1/12 M16A1 barrel made by Colt


They do shoot great with 55gr ammo.

I had one that would keyhole 62gr green tip though.

Great shooting OP.


62gr is too heavy for any 1 in 12 twist barrel to stabilize.
Link Posted: 2/13/2013 1:27:35 AM EDT
Originally Posted By MRW:
I've really been looking hard at that barrel since last December. Will Fulton install the Front sight base on it too?


I couldn't say for sure but I would be very surprised if they are not set up to drill front sight bases.
Link Posted: 2/13/2013 10:22:07 PM EDT
[Last Edit: 2/13/2013 10:23:00 PM EDT by buckandball]
I too thought long and hard about the Fulton (what was it, criterion made) 1/8 pencil barrel. But I found the still in wrap new 1/7 A1 barrel, and despite its price, liked that "all Colt" aspect. Though all that really means is the extra $300 or so I spent on the Colt barrel could have been the Fulton barrel and a case of ammo... but such is the wicked nature of this hobby and the word "want"...
Link Posted: 2/14/2013 9:17:27 AM EDT
Originally Posted By Lumpy196:
Originally Posted By CROWDLG:
Originally Posted By MRW:

Originally Posted By Jeepy2013:
Is that one of the old 1/12 barrels?

Yes. It is a surplus 1/12 M16A1 barrel made by Colt


They do shoot great with 55gr ammo.

I had one that would keyhole 62gr green tip though.

Great shooting OP.


62gr is too heavy long for any 1 in 12 twist barrel to stabilize.


Link Posted: 2/14/2013 12:37:28 PM EDT
Originally Posted By Doppleganger871:
Hm... from reading this thread, am I assuming that my 1/7 Colt hbar is pretty decent? I've only had this AR for a month, so I'm still in the "holy crap look at all the info" stage.


Yes, if you have the Match HBAR 1/7, they are pretty damn decent. I used to shoot NRA high power with my pre-ban Colt Sporter Match HBAR, I used to do pretty well too.
Link Posted: 7/3/2013 10:13:02 PM EDT
Link Posted: 7/4/2013 9:54:30 AM EDT
If the gun is to be a dedicated group shooter free float may help although if just doing bench shooting hard to say how much. When looped up in a sling prone free float definitely helps. For 99% of the rifle/ carbines which are used as close quarters and 100 yard and in blasters probably not worth the effort.
With out match grade ammo and slow fire bullseye technique the advantages of free float are lost. Anyone who thinks free floating is going to be a significant advantage then shoots nothing but 55 grain ball ammo is missing the boat
Link Posted: 7/4/2013 11:00:29 AM EDT
Link Posted: 7/4/2013 11:06:53 AM EDT
Originally Posted By GeneralPurpose:
Good shooting. I wish Molon would come back, too. Those were the best posts on this board. I would say you should only put a free float tube on the rifle if you actually want one for weight/aesthetics/mounting options/etc. Even if it does improve precision...what does it matter? On-target is on-target, and that paper is just as dead with a 1.543 group as it is with a 1.443 group.

I've almost got my 20" SPR build finished, but it's going to be a while before I can see what it does. Once I have time, I'll replicate some of Molon's testing with it.


they really were the best threads
Link Posted: 7/4/2013 2:29:49 PM EDT
Nice rig and shooting


(What happened to Molon?)
Link Posted: 7/4/2013 8:42:30 PM EDT
[Last Edit: 7/4/2013 8:44:41 PM EDT by EVR]
A really enjoyable thread. Thanks MRW and others.

It's funny, I used to be a bench shooter and was obsessed w/ great sub-moa groups.

Then, for some reason many years ago, a rifle just seemed to me to be a tool of the field and I steered clear of bench shooting except for zeroing, and frankly, I haven'y changed much since then. So I shoot off the bench only a little and from field positions mostly on my range.

From a practical standpoint, what MRW has here {remember, he shot ten shots} is a really accurate rifle that would make a dandy "walk-around" varminter. That's my own "standard", I guess.

You did well, OP, and made a very fine rifle. I'd say keep it as-is and worry the local ground hog population some with it.

We don't have g-hogs here, just their little cousins, ground squirrels, and it would do fine on them, too.
Link Posted: 7/4/2013 10:11:09 PM EDT
For many of my rifles (even the faster twist ones) the most accurate factory ammo I have seen is the white box Winchester "Varmint" 45 gr

This works well in my 1/12

I agree that the free float is not the be all , end all that many folks think it is.

If the OP only has a regular military trigger (I believe this is the case ) his groups are very impressive . If he is looking at the best bang for the buck on improving his fine results I would think his trigger might be his best bet
Link Posted: 7/5/2013 9:16:24 AM EDT
[Last Edit: 7/5/2013 9:18:01 AM EDT by EVR]
Just another mention that I think it is safe to say that most fellows do not know the relationship between 10-shot groups and other smaller shot groups often dubbed "MOA". Many think a sub-1-inch 3-shot group is impressive but sort of yawn when they see a 1 to 2 inch 100 yard 10-shot group. We see mention of "MOA" groups all the time, with no mention of the number of shots in the group, whether one or more flyers was ignored, etc. I've posted a million times that we use 3-shot groups for various zeroing purposes here but for determining the true shooting accuracy of a rifle and the shooter, 10 is pretty much where it's at for determining accuracy of shooter, rifle and POI.

Somewhere I have seen a statistical analysis between the various shot numbers and how they impact group size. I do not recall exactly, but gist was the ten-shot group will often measure nearly 2x's what best 3 shots will. Maybe some of the High Power shooters can comment.

Anyway, in this thread we see here an example of skilled shooting from an accurate rifle. With the accuracy being quite useful for a variety of purposes. Nice job, OP.

If I ever get myself another AR it will be for sure a A1-weight barrel, probably in 1/9 or 1/7 twist but nevertheless of lightweight configuration. Thanks again for posting OP!
Link Posted: 7/5/2013 9:39:14 AM EDT
Link Posted: 7/5/2013 11:13:15 AM EDT
Originally Posted By rauchman:
Originally Posted By Lumpy196:
Originally Posted By CROWDLG:
Originally Posted By MRW:

Originally Posted By Jeepy2013:
Is that one of the old 1/12 barrels?

Yes. It is a surplus 1/12 M16A1 barrel made by Colt


They do shoot great with 55gr ammo.

I had one that would keyhole 62gr green tip though.

Great shooting OP.


62gr is too heavy long for any 1 in 12 twist barrel to stabilize.




it's not like .223 ammo gets fatter as grain wt goes up.
Link Posted: 7/26/2013 12:04:58 AM EDT
Link Posted: 11/28/2013 1:58:54 PM EDT
[Last Edit: 11/28/2013 2:02:10 PM EDT by MRW]
Link Posted: 11/28/2013 5:02:21 PM EDT
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By rauchman:


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Originally Posted By rauchman:
Originally Posted By Lumpy196:
Originally Posted By CROWDLG:
Originally Posted By MRW:

Originally Posted By Jeepy2013:
Is that one of the old 1/12 barrels?

Yes. It is a surplus 1/12 M16A1 barrel made by Colt


They do shoot great with 55gr ammo.

I had one that would keyhole 62gr green tip though.

Great shooting OP.


62gr is too heavy long for any 1 in 12 twist barrel to stabilize.



This, but only if it's steel core. Lower density steel creates need to elongate the projectile. Otherwise, 62 grain is fine but pushing the limit
Link Posted: 11/28/2013 5:17:02 PM EDT
For the OP, geeze, damned fine shooting, particularly with 10 shot groups.
I took my future father in law trap shooting years ago; he broke his first two birds and quit. He noted he was at 100% and wasn't apt to get any better than that.

Happy to see you shooting that well with a pencil barrel; concur with other posters who suggested that a better trigger might work in your favor, or at least make the shooting less work.
Moon
Link Posted: 3/29/2014 12:06:09 AM EDT
Link Posted: 3/29/2014 2:38:40 AM EDT
I would pull the flash hider off and inspect the muzzle for defects or excess build up of copper or other jacket material.I've had a few rifles with no crowning and jacket material build up that affected accuracy, it was common with those barrels I've seen to frequently have no crown, something that's was easily damaged by an untrained owner.fwiw
Link Posted: 12/7/2014 12:57:49 PM EDT
Link Posted: 12/7/2014 3:06:11 PM EDT
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Originally Posted By MRW:


Yes. It is a surplus 1/12 M16A1 barrel made by Colt
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Originally Posted By MRW:

Originally Posted By Jeepy2013:
Is that one of the old 1/12 barrels?

Yes. It is a surplus 1/12 M16A1 barrel made by Colt


I would love to find a standard (pencil) profiled 14.5" barrel in 1/12 twist with a standard FSB. I really like your 20 inch version...
Link Posted: 12/7/2014 3:09:41 PM EDT
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Originally Posted By brewsky101:


I couldn't say for sure but I would be very surprised if they are not set up to drill front sight bases.
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Originally Posted By brewsky101:
Originally Posted By MRW:
I've really been looking hard at that barrel since last December. Will Fulton install the Front sight base on it too?


I couldn't say for sure but I would be very surprised if they are not set up to drill front sight bases.


I'm betting Fulton can/will do it for you OP... If not, I KNOW Adco will do it for you and get it on true...
Link Posted: 2/8/2015 8:03:05 PM EDT
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