Sorry if this is already posted somewhere.  I searched and checked the ammo forum  


So, what is the best you can expect from XM193?  1-2 MOA, or is it better than that?  Is there some kind of factory spec from L.C.?  Or what is the general experience of you guys that have used it?

Bro,  I've always like XM193 and have shot it for years.  I usually shoot 2 MOA with my SP1 carbine and my 1/12 M16 clone.  Shoot a little better with my A2 1/9 clone.  

I like it too, and it's always been reliable for me.

The reason I ask is that I finally free-floated one of my 20" ARs, and put a decent scope and bipod on it.  So I was shooting it with XM193, and I wondered what the limits of the ammo were.  I thought the groups were pretty good.

In other words - I'm wondering if better ammo or improving the rifle (trigger?) is the way to get better groups.  The rifle is just a regular Eagle Arms, with regular trigger (and no chrome lining)

i have shot it through dennys recon bbl. and it was grouping around 1.5moa

OldPainless did some tests to prove to himself that people claiming 1MOA or better with any military ammo were (at best) deluding themselves.

His results were as expected - rather large groups.

If you are getting 2MOA you are doing really well.

Quoted: OldPainless did some tests to prove to himself that people claiming 1MOA or better with any military ammo were (at best) deluding themselves.

Now that you mention it, I DO remember that.  I wonder if the results are posted on Box O'Truth?

His results were as expected - rather large groups. If you are getting 2MOA you are doing really well.

Here's what I was getting at 100 yards





So I should be pretty happy with that from XM193 - and try something like Black Hills, before I do anything to the rifle?

I was getting a hair over 1 MOA with it. I have the target around here somewhere to prove it.  

You might want to try it with a 2 stage match trigger.  I found it helps shrink my groups somewhat, due to its consistent pull length and pressure.    

Didnt Old_Painless do a test on NATO ammo accuracy a while ago?  IIRC, it was found that it was good enough for combat, but not same hole accuracy type stuff.

ETA:  PhilipPeake beat me to it.

ETA2:  I'd say your groups are good for M193.  Try some better ammo before changing stuff out.  Thats my opinion anyway, you know what you want to do.

Quoted: ETA2:  I'd say your groups are good for M193.  Try some better ammo before changing stuff out.  Thats my opinion anyway, you know what you want to do.

Thanks - I think that's exactly what I'll do.  I've never bought "better" ammo than XM193 or white box, so it'll be a treat to try something like Black Hills.

Quoted: I wonder if the results are posted on Box O'Truth?

Why, yes they are...

XM193 is great ammo. Hot and reliable but it's not going to win you any competitions. If those are the groups you are shooting with XM switch to Black Hills blue box and you will be quite happy with your groups.

Quoted: Quoted: I wonder if the results are posted on Box O'Truth? Why, yes they are...

I swear I looked and couldn't find it.  I'm a maroon


Thanks for the link.  Looks like I lucked out with my batch of Xm193, since my rifle is NOT as nice as his!

I was getting pretty inconsistent grouping with XM193 and XM855 shooting with a 16" barrel with 1:9 twist. I found I did better using Georgia Arms .223 reloads and did even better with their Precision Plus match ammo.

Below targets shot using 3-9X42 scope at 9x, rifle benchrested all at 100 meters.

Target #1, G.A. .223 standard reloads, 55gr


Target #2 G.A. .223 Precison Plus, 55gr, Nosler point


Target #3 G.A. .223 Precision Plus, 60 gr, VMax point


Some of the flyers in the first two targets are a result of movement on the benchrest, some are because of me

I haven't the chance to try Blackhills ammo. I'll have to order some to compare. The accuracy guru at the range said the XM855 and XM193 is spec'd for 3" groups at 100 meters. YMMV

Regards,

Zip

Looks like you found my test.

I like M-193.  It is good stuff.

But, like all other military Ball, it is not as accurate as well developed handloads.

But it is plenty good enough for most uses.


(And P.S. - DK, you're not maroon.  You're just a shade of reddish purple. )

Quoted: Looks like you found my test. I like M-193.  It is good stuff. But, like all other military Ball, it is not as accurate as well developed handloads. But it is plenty good enough for most uses. (And P.S. - DK, you're not maroon.  You're just a shade of reddish purple. )

 Thanks.

Give what I've now read (and seen on your page), I'm very happy with my almost Minute-Of-Quarter accuracy I got.

But I have ordered some Black Hills Blue and Red Box, which will probably let me see how accurate the rifle (and myself) is/am.  Since I just have a regular trigger, and a regular barrel (and I'm just a regular shooter) - it'll be interesting to see if I can do much better.

Have you ever noticed that when someone tells you that they are getting minute of angle accuracy with XM193 they usually fail to mention:

a) the distance the groups were fired from
b) how many shots were in the group
c) whether or not they discounted "flyers".

U.S. military specifications for M193 require 10-shot groups for accuracy testing.

Below are two 10-shot groups fired from a Colt 16" HBAR (NATO chamber, chrome lined) at 100 yards using handloaded 55 grain Sierra BlitzKings.  All ten shots were counted when measuring the groups.  Group one measures .948" and group two measures .969".  

Now, the third group shown below is the best 10-shot group from 100 yards that I have obtained using XM193 fired from the same Colt barrel.  It measures 2.32".  XM193 has many positive attributes but minute of angle accuracy is not one of them.

Quoted: Have you ever noticed that when someone tells you that they are getting minute of angle accuracy with XM193 they usually fail to mention: a) the distance the groups were fired from b) how many shots were in the group c) whether or not they discounted "flyers". U.S. military specifications for M193 require 10-shot groups for accuracy testing. Below are two 10-shot groups fired from a Colt 16" HBAR at 100 yards using handloaded 55 grain Sierra BlitzKings.  All ten shots were counted when measuring the groups.  Group one measures .948" and group two measures .969".   Now, the third group shown below is the best 10-shot group from 100 yards that I have obtained using XM193 fired from the same Colt barrel.  It measures 2.32".  XM193 has many positive attributes but minute of angle accuracy is not one of them. home.comcast.net/~gocartmozart/16_hbar_groups1.jpg home.comcast.net/~gocartmozart/16_hbar_groups3.jpg

I can't see your pics

I've always been very skeptical of people that claim sub-MOA accuracy with a stock AR and ammo like XM193 - certainly if they claim it with iron sights.  That's part of the reason for this thread, because I was pretty surprised that I could get groups this small with a pretty basic scoped AR-15 and Xm193.



For what it's worth, I didn't know that 10 shot groups are the norm (although I guess it makes sense).  Often I see people on arfcom post pictures of 3-shot groups, and I personally think that's a little too few - so I thought I'd shoot 5 shots.

When I get the Black Hills I'll definitely shoot 10-shot groups, and try the XM193 again (just to see if I was just incredibly lucky for those groups above).

Btw - I personally don't subscribe to the "flyers" excuse - any bullet that leaves the barrel is part of the group.

"I can't see your pics"

Try now.

Quoted: "I can't see your pics" Try now.

Sorry - still getting the red X.



...but based on your description, we can tell what the grouping was, so please don't spend a lot of time trying to figure it out just for my sake.

Quoted: Quoted: OldPainless did some tests to prove to himself that people claiming 1MOA or better with any military ammo were (at best) deluding themselves. Now that you mention it, I DO remember that.  I wonder if the results are posted on Box O'Truth? His results were as expected - rather large groups. If you are getting 2MOA you are doing really well. Here's what I was getting at 100 yards So I should be pretty happy with that from XM193 - and try something like Black Hills, before I do anything to the rifle?

I'd say you should be dancing with joy at that level of accuracy from military surplus ammo.

I have shot 3/4 in groups with S&B fmj ammo at 100 yards 3 shot groups that is.  I have also shot 2 in groups the smae day with the same ammo from the same box.  alot of stock ARs are capable of very good accuracy.

Try the remanufactured Black Hills ammo. It's good stuff.

My 6724 likes XM193, but I found out yesterday it really likes 69 gr. SMK's with 24 gr. of AA2230 - This group was shot from the bench at 200 yards -

Here is an interesting quote from an article in Rifle magazine #115.

"5.56mm Paramilitary Ammunition" by John Schaefer

"U.S. military specifications for M193.....The accuracy requirement from a test fixture calls for a maxiumum of a two-inch mean radius at 200 yards from ten 10-shot groups (which equates to approximately three MOA.)"

Quoted: Here is an interesting quote from an article in Rifle magazine #115. "5.56mm Paramilitary Ammunition" by John Schaefer "U.S. military specifications for M193.....The accuracy requirement from a test fixture calls for a maxiumum of a two-inch mean radius at 200 yards from ten 10-shot groups (which equates to approximately three MOA.)

In that case, I clearly lucked out with that particular batch, and shouldn't necessarily EXPECT that kind of consistency from XM193 in general.

Three shot group with M193... I can't ask for much more than this.




- BG




(Yes, I know, I need to adjust my irons...)

Quoted: Three shot group with M193... I can't ask for much more than this. www.students.bucknell.edu/clanger/arfcom%5Cmoa.jpg - BG (Yes, I know, I need to adjust my irons...)

3-shots groups are...well...undesireable and potentially misleading. I've had 3 shot groups that had all holes touching. Then in the next 5, 1" @ 100 yards.

But, anyway, M193 should get you about 2-3 MOA. There are variances in rifles.

My particular rifle likes 52gr Black Hills and I would estimate it's 0.5MOA in my rifle. It's just that the shooter behind it adds 1MOA.

Basically, I'll put a 20 round mag in a 1" hole. or I'll do about 4-5" at 300 yards.

Even 5-shot groups can be misleading.  Look at the first target below. It was fired from 100 yards from a stainless steal Krieger barrel using handloaded 55 grain Sierra BlitzKings.  At first glance it looks like a pretty outstanding 5-shot group.  (the solid blue lines form one inch squares)



Now, when I move the dime, you can see that it was actually part of a larger 10-shot group that gives you a truer indication of the rifle/ammunition accuracy dispersion. (.740")



Here is another group from the same barrel from 100 yards.  It just happens to show in one 10-shot group the complete radial dispersion for this rifle/ammunition combination.  (.677")

Quoted: Quoted: OldPainless did some tests to prove to himself that people claiming 1MOA or better with any military ammo were (at best) deluding themselves. Now that you mention it, I DO remember that.  I wonder if the results are posted on Box O'Truth? His results were as expected - rather large groups. If you are getting 2MOA you are doing really well. Here's what I was getting at 100 yards photos.ar15.com/ImageGallery/Attachments/DownloadAttach.asp?iImageUnq=44514 photos.ar15.com/ImageGallery/Attachments/DownloadAttach.asp?iImageUnq=44513 So I should be pretty happy with that from XM193 - and try something like Black Hills, before I do anything to the rifle?

Yes, or hornady match, or federal match or handloads.  XM193 is not match ammo.  You probably figured that out already.  That said, those groups aint bad for XM193.  Shoot, 1 moa is good for any kind of shooting unless you're talking super good hipower shooters and varmint hunting.  

Quoted: Quoted: Have you ever noticed that when someone tells you that they are getting minute of angle accuracy with XM193 they usually fail to mention: a) the distance the groups were fired from b) how many shots were in the group c) whether or not they discounted "flyers". U.S. military specifications for M193 require 10-shot groups for accuracy testing. Below are two 10-shot groups fired from a Colt 16" HBAR at 100 yards using handloaded 55 grain Sierra BlitzKings.  All ten shots were counted when measuring the groups.  Group one measures .948" and group two measures .969".   Now, the third group shown below is the best 10-shot group from 100 yards that I have obtained using XM193 fired from the same Colt barrel.  It measures 2.32".  XM193 has many positive attributes but minute of angle accuracy is not one of them. home.comcast.net/~gocartmozart/16_hbar_groups1.jpg home.comcast.net/~gocartmozart/16_hbar_groups3.jpg I can't see your pics I've always been very skeptical of people that claim sub-MOA accuracy with a stock AR and ammo like XM193 - certainly if they claim it with iron sights.  That's part of the reason for this thread, because I was pretty surprised that I could get groups this small with a pretty basic scoped AR-15 and Xm193. For what it's worth, I didn't know that 10 shot groups are the norm (although I guess it makes sense).  Often I see people on arfcom post pictures of 3-shot groups, and I personally think that's a little too few - so I thought I'd shoot 5 shots. When I get the Black Hills I'll definitely shoot 10-shot groups, and try the XM193 again (just to see if I was just incredibly lucky for those groups above). Btw - I personally don't subscribe to the "flyers" excuse - any bullet that leaves the barrel is part of the group.

From what I understand, 5 is the benchmark for testing MOA.  But 10 would be a better benchmark.  Problem is, when you shoot 10, you have that many more chances of user error.  At least for me.
3 is a few but the hunter types use that alot.

Here's a bit of a fudge, this is IMI M193 ammo at 100 yds, for comparison purposes.

Quoted: From what I understand, 5 is the benchmark for testing MOA.  But 10 would be a better benchmark.  Problem is, when you shoot 10, you have that many more chances of user error.  At least for me. 3 is a few but the hunter types use that alot.

I'm not satisfied with my groups unless I get 10 shots minimum out there. I've also been known to put entire 30 round mags in.

As a personal pet peeve, I also don't believe in shooting with a bench "rest" But for load development, etc. I definitely see their place.

Quoted: Quoted: From what I understand, 5 is the benchmark for testing MOA.  But 10 would be a better benchmark.  Problem is, when you shoot 10, you have that many more chances of user error.  At least for me. 3 is a few but the hunter types use that alot. I'm not satisfied with my groups unless I get 10 shots minimum out there. I've also been known to put entire 30 round mags in. As a personal pet peeve, I also don't believe in shooting with a bench "rest" But for load development, etc. I definitely see their place.

If you want to be really anal, you SHOULD use 30 rounds - since a sample size of 30 usually allows for a nice normal distribution to control for various errors that might affect accuracy.  (Of course, if you or your eyes start to get tired or fatigued after 20 rounds, then you are just introducing different error).

In retrospect, I'll probably shoot 10 rounds in a group (when I get those Black Hills boxes I ordered).  I definitely think 3 is too little.

Quoted: If you want to be really anal, you SHOULD use 30 rounds - since a sample size of 30 usually allows for a nice normal distribution to control for various errors that might affect accuracy.  (Of course, if you or your eyes start to get tired or fatigued after 20 rounds, then you are just introducing different error). In retrospect, I'll probably shoot 10 rounds in a group (when I get those Black Hills boxes I ordered).  I definitely think 3 is too little.

You are certainly correct.

Larger group numbers will give a "truer" picture of "average" accuracy.

But, the more shots fired, the larger the average will usually be.

Be ready to feel inadequate when you report (honestly) that your rifle shoots a 3 to 4 inch group at 100 yards, and then have to read the posts of a bunch of guys that say, "I always get less than 1 inch".

Of course, they are doing one of three things:

1.  Shooting 3 rounds and culling "bad" groups

2.  Shooting 5 round groups and culling a lot of "bad" groups

3. Lying.

Quoted: Quoted: If you want to be really anal, you SHOULD use 30 rounds - since a sample size of 30 usually allows for a nice normal distribution to control for various errors that might affect accuracy.  (Of course, if you or your eyes start to get tired or fatigued after 20 rounds, then you are just introducing different error). In retrospect, I'll probably shoot 10 rounds in a group (when I get those Black Hills boxes I ordered).  I definitely think 3 is too little. You are certainly correct. Larger group numbers will give a "truer" picture of "average" accuracy. But, the more shots fired, the larger the average will usually be. Be ready to feel inadequate when you report (honestly) that your rifle shoots a 3 to 4 inch group at 100 yards, and then have to read the posts of a bunch of guys that say, "I always get less than 1 inch". Of course, they are doing one of three things: 1.  Shooting 3 rounds and culling "bad" groups 2.  Shooting 5 round groups and culling a lot of "bad" groups 3. Lying.

That is the truth!

Quoted: When I get the Black Hills I'll definitely shoot 10-shot groups, and try the XM193 again (just to see if I was just incredibly lucky for those groups above).

Be sure to post your results.  It will be interesting to see the comparision.

Quoted: Here's a bit of a fudge, this is IMI M193 ammo at 100 yds, for comparison purposes. www.pbase.com/wingman26/image/49351972.jpg

Nice shooting.  I have a stash of the IMI M193 and it always seems to shoot more accurately than XM193.

Quoted: Quoted: When I get the Black Hills I'll definitely shoot 10-shot groups, and try the XM193 again (just to see if I was just incredibly lucky for those groups above). Be sure to post your results.  It will be interesting to see the comparision.

Got the ammo yesterday, but it'll probably be a week before I can get to the range.  I"ll definitely dig this thread back up and post new results.

Quoted: Quoted: Quoted: When I get the Black Hills I'll definitely shoot 10-shot groups, and try the XM193 again (just to see if I was just incredibly lucky for those groups above). Be sure to post your results.  It will be interesting to see the comparision. Got the ammo yesterday, but it'll probably be a week before I can get to the range.  I"ll definitely dig this thread back up and post new results.

Sounds good.

Quoted: Quoted: Quoted: When I get the Black Hills I'll definitely shoot 10-shot groups, and try the XM193 again (just to see if I was just incredibly lucky for those groups above). Be sure to post your results.  It will be interesting to see the comparision. Got the ammo yesterday, but it'll probably be a week before I can get to the range.  I"ll definitely dig this thread back up and post new results.

Any new results yet?

Quoted: Any new results yet?

I wish !!  

Sorry it's taking me so long.  I have WANTED to go to the range for weeks now, and have the ammo ready - I just keep getting totally bogged down with work.  I've been working on the same project for the last three weeks (usually staying up until 2 - 3 in the morning working), and I hope to be done with it in another week.  If I get a lot done in any one day, I might take a couple of hours to relax at the range - but I keep planning to, and then never quite find the time.

Don't worry - I definitely WILL get it done.  I am DYING to try the Black Hills, and it's frustrating as hell to not be able to go shoot it.  

Quoted: Sorry it's taking me so long.  I have WANTED to go to the range for weeks now, and have the ammo ready - I just keep getting totally bogged down with work.

Yeah.  Right.

You're a University Professor.  They don't do any real work.

Product Specification Sheet
Centerfire Rifle
LOAD NUMBER: XM193
CALIBER: 5.56 mm
CASE: Brass (Copper Alloy No. 260)
BULLET: 55 Gr. FMJ Boat-Tail
PRIMER: M41
Operating Range (-40 degrees to +125 degrees Fahrenheit).
PRIMER SEALANT: Water Resistant Lacquer
CASE MOUTH SEALANT: Yes
CASE KNURL: No
HEADSTAMP: Each loaded cartridge shall be headstamped with the manufacturer’s symbol and year of manufacture
Revised 1-24-05
Federal Cartridge Company
900 Ehlen Drive
Anoka, MN 55303
(800)322-2342, ext. 3822 or 2370
ACCURACY: Three 10-round groups not to exceed 4.00” mean radius maximum average at 200 yards
INSTRUMENTAL VELOCITY: 3165 +/- 50 FPS using a 5.56 test barrel (78 feet from muzzle)
MUZZLE ENERGY: 1225 Ft-Lbs. at 78’
CHAMBER PRESSURE: Piezotronic maximum average per 10 rounds – 55,000 PSI in 5.56 test barrel (case mouth location)
BULLET PULL: Minimum individual 35 Lbs.
PROPELLANT DETECTION: 100% mechanical and/or electrical detection of propellant levels within the cartridge
VISUAL INSPECTION: 100% visual inspection of finished cartridges prior to packaging
WARNING: For use in standard 5.56 mm chambers. Do not use in non-standard 5.56 chambers

I shot 5, 10 shot groups with my Bushy Varminter and got between 1.2 to 2.6 inch groups with a variable left to right breeze of 5 to 10 mph.

Quoted: Quoted: Sorry it's taking me so long.  I have WANTED to go to the range for weeks now, and have the ammo ready - I just keep getting totally bogged down with work.   Yeah.  Right. You're a University Professor.  They don't do any real work.

You're thinking of TENURED university professors  


My "vacation" (i.e. the three months out of the year I teach) is over, and I've been working like a hyperactive ant since the new year started.

Quoted: Product Specification Sheet Centerfire Rifle LOAD NUMBER: XM193 CALIBER: 5.56 mm CASE: Brass (Copper Alloy No. 260) BULLET: 55 Gr. FMJ Boat-Tail PRIMER: M41 Operating Range (-40 degrees to +125 degrees Fahrenheit). PRIMER SEALANT: Water Resistant Lacquer CASE MOUTH SEALANT: Yes CASE KNURL: No HEADSTAMP: Each loaded cartridge shall be headstamped with the manufacturer’s symbol and year of manufacture Revised 1-24-05 Federal Cartridge Company 900 Ehlen Drive Anoka, MN 55303 (800)322-2342, ext. 3822 or 2370 ACCURACY: Three 10-round groups not to exceed 4.00” mean radius maximum average at 200 yards INSTRUMENTAL VELOCITY: 3165 +/- 50 FPS using a 5.56 test barrel (78 feet from muzzle) MUZZLE ENERGY: 1225 Ft-Lbs. at 78’ CHAMBER PRESSURE: Piezotronic maximum average per 10 rounds – 55,000 PSI in 5.56 test barrel (case mouth location) BULLET PULL: Minimum individual 35 Lbs. PROPELLANT DETECTION: 100% mechanical and/or electrical detection of propellant levels within the cartridge VISUAL INSPECTION: 100% visual inspection of finished cartridges prior to packaging WARNING: For use in standard 5.56 mm chambers. Do not use in non-standard 5.56 chambers I shot 5, 10 shot groups with my Bushy Varminter and got between 1.2 to 2.6 inch groups with a variable left to right breeze of 5 to 10 mph.

Ch0wd3r, you have posted some interesting product information.  Let's look at it closely.

The part in red says that they are loading the ammo to meet 4 MOA at 200 yards or 2 MOA requirements (at 100 yards).

You noted that you shot groups from 1.2 to 2.6 inches at 100 yards?

I don't know how many of each you had, but if we average those numbers we get approximately 2 MOA.

Now the problem we often see is that someone (not you) will post that they did what you did and say, "I shoot 1.2 inch groups with XM-193".

No, they don't.  They shoot a rare 1.2 inch group, but their average group size is 2".

This is what I find so frustrating about discussions about ammo accuracy.

And secondly, you note that with your rifle you shot 2 inch groups (average).  That means that your rifle was able to wring all the accuracy out of the XM-193 that is possible.

No matter how good the rifle, it cannot shoot that ammo into better groups than a 2 inch average.  That is the limitations of that ammo, as manufactured.

A poor shooting rifle will shoot larger groups, but no rifle can shoot smaller average groups than 2 inches with that ammo, if that ammo is manufactured to shoot into 2 MOA.

An interesting subject, especially if everyone would tell the truth about their groups.

Everyone can have freak occurences of superb accuracy with any ammo, regardless as to what it's ratings are.

But, generally I get 2-3" with XM193 and I hate it for accuracy. For blasting away or self defense within 50 yards it is fine, but for accuracy I go with something else.



- rem

Quoted: Quoted: Product Specification Sheet Centerfire Rifle LOAD NUMBER: XM193 CALIBER: 5.56 mm CASE: Brass (Copper Alloy No. 260) BULLET: 55 Gr. FMJ Boat-Tail PRIMER: M41 Operating Range (-40 degrees to +125 degrees Fahrenheit). PRIMER SEALANT: Water Resistant Lacquer CASE MOUTH SEALANT: Yes CASE KNURL: No HEADSTAMP: Each loaded cartridge shall be headstamped with the manufacturer’s symbol and year of manufacture Revised 1-24-05 Federal Cartridge Company 900 Ehlen Drive Anoka, MN 55303 (800)322-2342, ext. 3822 or 2370 ACCURACY: Three 10-round groups not to exceed 4.00” mean radius maximum average at 200 yards INSTRUMENTAL VELOCITY: 3165 +/- 50 FPS using a 5.56 test barrel (78 feet from muzzle) MUZZLE ENERGY: 1225 Ft-Lbs. at 78’ CHAMBER PRESSURE: Piezotronic maximum average per 10 rounds – 55,000 PSI in 5.56 test barrel (case mouth location) BULLET PULL: Minimum individual 35 Lbs. PROPELLANT DETECTION: 100% mechanical and/or electrical detection of propellant levels within the cartridge VISUAL INSPECTION: 100% visual inspection of finished cartridges prior to packaging WARNING: For use in standard 5.56 mm chambers. Do not use in non-standard 5.56 chambers I shot 5, 10 shot groups with my Bushy Varminter and got between 1.2 to 2.6 inch groups with a variable left to right breeze of 5 to 10 mph. Ch0wd3r, you have posted some interesting product information.  Let's look at it closely. The part in red says that they are loading the ammo to meet 4 MOA at 200 yards or 2 MOA requirements (at 100 yards). You noted that you shot groups from 1.2 to 2.6 inches at 100 yards? I don't know how many of each you had, but if we average those numbers we get approximately 2 MOA. Now the problem we often see is that someone (not you) will post that they did what you did and say, "I shoot 1.2 inch groups with XM-193". No, they don't.  They shoot a rare 1.2 inch group, but their average group size is 2". This is what I find so frustrating about discussions about ammo accuracy. And secondly, you note that with your rifle you shot 2 inch groups (average).  That means that your rifle was able to wring all the accuracy out of the XM-193 that is possible. No matter how good the rifle, it cannot shoot that ammo into better groups than a 2 inch average.  That is the limitations of that ammo, as manufactured. A poor shooting rifle will shoot larger groups, but no rifle can shoot smaller average groups than 2 inches with that ammo, if that ammo is manufactured to shoot into 2 MOA. An interesting subject, especially if everyone would tell the truth about their groups.

Old_Painless,

If I am reading the part in red correctly, it states they are loading XM193 to meet a maximum of 4" MEAN RADIUS at 200 yards.  This is not the same as Minute of Angle.  Otherwise I agree with you completely, especially the part about telling the truth about reporting groups.

Quoted: Old_Painless, If I am reading the part in red correctly, it states they are loading XM193 to meet a maximum of 4" MEAN RADIUS at 200 yards.  This is not the same as Minute of Angle.  Otherwise I agree with you completely, especially the part about telling the truth about reporting groups.

Upon re-reading, I believe you are correct.

So, a 4" mean radius means an 8 inch circle at 200 yards, or 4 MOA.

Is that how you read it?

Dang it.

So I get a ton of work done last night, so I feel like I can take a couple of hours off today, and decide to head to the range.  My new Black Hills ammo is all loaded in mags, and I pack everything in the car and go ...

... just to discover the rifle range is closed today (some special event I guess), so no shooting for me!!

This is going to be rather long but hopefully I can keep it rather painless. (sorry, I couldn't resist the pun)  U.S. military specifications for M193 (MIL-C-9963) call for an accuracy requirement of a two-inch mean radius at 200 yards (using 10-shot groups).  Now the red highlighted requirement stated above for Federal XM193 calls for a four-inch mean radius at 200 yards.  Right from the start we can see that Federal XM193 is only required to group half as accurately as U.S. M193.

To understand the actual size of the groups we are talking about we need to understand the difference between group size as measured in extreme spread versus groups measured using the mean radius.  Below is a picture of a 10-shot group of Federal XM193 fired at 100 yards.  The group size or extreme spread measures 2.34" or 2.34 minutes of angle.*  The mean radius of this same group is only 0.72"!




Mean radius as defined in Hatcher's Notebook   "is the average distance of all the shots from the center of the group.  It is usually about one third the group diameter" (extreme spread).

"To obtain the mean radius of a shot group, measure the heights of all shots above an arbitrarily chosen horizontal line.  Average these measurements.  The result is the height of the center of the group above the chosen line.  Then in the same way get the horizontal distance of the center from some vertical line, such as for instance, the left edge of the target.  These two measurements will locate the group center.

"Now measure the distance of each shot from this center.  The average of these measures is the mean radius."

Once you get the hang of measuring groups using the mean radius it becomes very simple to do.  While being very simple to do, it is also very time consuming.  Modern software programs such as RSI Shooting Lab make determining the mean radius a snap.

The picture below is a screen snapshot from RSI Shooting Lab using the group from the above target.  The red cross is the center of the group (a little high and right of the aiming point).  The long red line shows the two shots forming the extreme spread or group size.  The yellow line from the red cross to one of the shots is a radius.  Measure all the radii and take the average to obtain the mean radius.




Using Hatcher's one-third rule   and applying it to my group above you can see that while not exact it is close enough for "government work."
2.34" (extreme spread) divided by 3 equals 0.78" (mean radius).  Actual mean radius being 0.72".

Finally, applying Hatcher's one-third rule to Federal's requirement for XM193 of a 4" mean radius at 200 yards for three, 10-shot groups, we see that it only needs to group into a 12" average group for three 10-shot groups at 200 yards!  

4" (mean radius ) times 3 equals 12" (extreme spread).  12" at 200 yards is 6 minutes of angle.

Old_Painless I totally agree with your reply to my post. To further clarify my groups I actually shot 6, (miscounted the targets yesterday) at 100 yards.

The first group I shot 2 foulers then grouped 8 in 1.2 inches,
2nd group, 1.8
3rd 1.7
4th 2.0
5th 2.6
6th 2.2
add together=11.5 divide by 6=1.916
Throw out the first group (since it's not a true 10 shot group) it equals 2.06

I agree with your point on lack of complete honesty when reporting groups sizes and that averages are a true measure of accuracy.

Now Molons post is very interesting.

Finally, applying Hatcher's one-third rule to Federal's requirement for XM193 of a 4" mean radius at 200 yards for three, 10-shot groups, we see that it only needs to group into a 12" average group for three 10-shot groups at 200 yards!
Which would be 6" at 100 yards.
Some would say that is close enough for government work!