An Odd 5.56 Problem

[Safetychain]

I built a 5.56 AR-15 last year, finaly laddered up some loads last month and the results aren't what I expected. I had to use AA-2460 as this all I had. Projectiles were Bullet Heads .224 jacketed boattails with canelure. I know these are not in anyway precision type projectiles but I expected more than I'm getting. I started with 22.6 with .3 grain increments to 24.8 using Federal Cartriges. I loaded 5 shots in each increment. My results were less than impressive. Typical shot groups at 100 yds were 5-6 inches except maybe 4 in groups in the 22.6 and 22.9 loads. The baffling part is that in the last three loads, 24.2, 24.5 & 24.8, I got one or two tumblers in each load group. The barrel has a 1 in 9 twist and is 18 inches long with a mid length gas tube which should provide for stable flight with this bullet. Another observation is that amazingly nearly all ejected shells ended up in just about a 3 ft circle about 12 ft away at about 4 o'clock. Then when my testing was finished, I shot a 20 rnd box of PMC 5.56 XP193 X-TAC 55 gn FMJ BT because it was the cheapest thing I could find in the local LGS at $.37 apiece. These tore a 2 inch hole in my target and the ejection pattern was all over the place. I have successfully laddered up and found accurate loads for a variaty of other rifles, so my reloading techniques (by the book) should be acceptable, right?. Powder should be alright but is it? Bullets are not the best but could they be this bad? except for approximately 15 reloaded rnds fired just prior to the testing, this was the first shots through the rifle. The PMC's shot much better than expected so the rifle...? I was flinching bad at the beginning when I shot the slightly better spreads. Was it just me? I was using a 24 power scope that was showing about a 1 inch heart beat that I was shooting around. Can somebody suggest what might be happening. I have a bit over 8 lbs of this powder bought within the last couple of years and was using it in my 30-30 very successfully.

 

[Ifishsum]

Your rifle just doesn't like those bullets, or something about your loads anyway. I was very frustrated loading for my first AR, it's a 1:9 20" barrel. Nothing would group those 55gr FMJBTs better than about 3 to 4" with 4 different powders and workups. Finally decided to try some different bullets; things got better with some basic soft points, the V-Max also shot much better but then I tried the Sierra 53gr HP and Hello!......10 shots into about an inch and a half group. That bullet will shoot in that rifle, I was able to find a similar result no matter what powder I put behind it. I found others as well (mostly match HPs) but the point is that not all FMJBTs are shaped exactly the same and not many of them will be as consistent as flat base bullets or hollow points. The fact that you had a few tumblers are proof enough that your barrel does not stabilize that particular bullet IMO.

Funny thing is that I had loaded about 300 rounds of the best load I was able to find with those FMJs, which was maybe 3" in my first upper; last week I shot 20 or 30 of those through my new Compass Lake mainly to break it in and liberate the brass for something better. Danged if those things didn't group real nicely in that barrel; good enough in fact that I might even use them up in a short match....

 

[IMtheNRA]

Try a brand name bullet, like the cheap Hornady 55-gr FMJBTWC, for example. The problem with buying mystery bullets or an on-line dealer's house brand bullets is that you never know what you're really getting or why the dealer ended up with bullets without a brand name.

 

[gamestalker]

Since it's a new build, is it possible that the crown may not be square? You might check that out, though it's not terribly common, it wouldn't be the first time I've heard of that happening with a new barrel.

GS

 

[Safetychain]

Thanks a lot friends for comments and the longer I've thought about it, the more I fully agree that it is the bullet. I also have a bunch of Hornady's and RMR's (Federal and Lead free frangible). I'll try the Hornady's next. The rest of the Bullet Heads will go for just letting off steam shooting.

 

[Sunray]

Think paragraphs.
Tumbling is caused by undersized bullets, oversized barrel or excessively low velocity.
What bullet weight? A 55 grain Hornady BT-FMJ's? Your rifling is likely too fast for that weight.
However, the lower velocity due to the short barrel might be part of the issue too. Use a heavier bullet like a 62 grain or more, don't expect target accuracy out of an 18" barrel and forget the cannelure altogether.

 

[Safetychain]

"Tumbling is caused by undersized bullets, oversized barrel or excessively low velocity."

I was thinking along this line too but the bullets tumbled at the higher loads.

"A 55 grain Hornady BT-FMJ's? Your rifling is likely too fast for that weight."

I don't agree with this statement as from what I've been reading, they should do well in a 1 in 9 barrel. I guess time will tell as I've already started the process with them. The only difference will be that I will be using LC brass this time. I will definitely let you know if I'm wrong about this, but it will be several weeks at least before I can finish loading and get back to the range testing due to life happening right now.

I also don't fully agree with the barrel length effecting the accuracy. There are several very informative write ups kind of debunking this as a myth. Surely not saying that you're definitely wrong about the barrel length/accuracy but, there are two (or more) sides to this and until I did a lot of reading on it agreed with you. Now I've kind of switched positions. Velocity, Yes - Accuracy, No. This is a link to one of the articles:

http://www.wideopenspaces.com/the-t...letter_4.1 - wos sup CA, MI, OR/WA, OH, NY/NJ

I'm sure there is a better way of giving you this link but cut and paste is what I do best. As the link indicates it is from www.wideopenspaces.com which is fairly well known and I've found to be a safe link.

 

[rcmodel]

Try better bullets.

FMJ-BT are the least accurate bullets anyone makes.

Just about any type of bullet with the jacket hole in the nose will out-shoot one with the jacket hole in the base.

These two groups were shot with a 16" pencil-barrel Colt carbine with an EOTech sight.

Same exact load, except for the bullets.
Nosler 55 grain Ballistic Tip, and Winchester 55 grain FMJ-BT.



rc

 

[Walkalong]

Yep, all day long.

 

[Safetychain]

My next purchase will be some flat based hollow points and ladder up again, will still continue with the Hornady's. They are no good to use as an anchor because they weigh too little. On another tact, how about casting lead, 18 hardness, gas checks and powder coating using the cheap little Lee mold:

http://www.midsouthshooterssupply.c...der-Mold-C225-55-RF-by-LEE-RELOADING-PRODUCTS

Accuracy? Don't try to talk me out of this as I got it already in one of my SHTF moments of weakness. They are selling for $18 now with the handles.

 

[vongh]

I bought some midway 55 grain bullets and the cannelure was in different places. OAL was inconsistent and the weight varied from 51 grains on the low to 56 grains on the high. Its been mentioned that your projectiles may be low quality but this may be one reason why your groups are so large. I bought some nosler varmigeddons and also some extreme bullets and my accuracy showed a definite improvement.

 

[Safetychain]

vongh, I initially weighed out a dozen+ bullets when I received them in 2012 as I do with any purchases of bullets of any caliber and I found very little variance in weight (less than .5 gr), though just prior to laddering up, I didn't check what I loaded. I will do that tomorrow with another handful of Bullet Heads. I will also check the Hornadys prior to seating them in my newest effort. As for seating depth, I set them at the cannelure which gave me an OAL (all the same) length that just barely fits in the magazines I use. I was taught initially, that for rifle loading, to make the bullet as long/close to the lands as possible and still work in the action. I always set up a group of five dummy loads in any new load/OAL to check that they will at least hand cycle through the gun and to be able to easily setup my seating dies the next time around. I do put a very firm crimp on the dummy loads. Inspection of the last laddering showed that all cases ended in the cannelure. I used a Lee Factory Crimp die to just slightly bend the case into the cannelure and not what I would call a crimp. Should there be anything that could cause a bullet setback, I feel my 'crimp' would stop the bullet from going beyond the crimp groove. I am used to load testing in much larger calibers and their resulting recoil and always used a definite crimp. 5.56 is the first time I haven't used a real crimp in rifle. Will report tomorrow on bullet weights.

 

[Hardtarget]

My AR is from Model1Sales and has a 20", 1/9 twist barrel. I have a Bushnell 1.5-4.5 scope on it.

I tried several different bullets when I first got it and was just trying to learn how to reload for it. I got some Hornady 55gr V-Max and using H-335 (CCI#41 primers) I've shot some three shot "mini groups" of 0.75" with peeps and even one three shot 0.5" group. These were at 100 yds, benched.

This was six weeks ago...maybe eight. I fell and dislocated my left shoulder so I haven't shot much yet.

The surprise about those bullets was...they were pulled bullets. Dents and all, they shot better than the fmj stuff I'd tried! Can't wait to try some new undamaged projectiles.

At first I was much too scattered. I tried too many bullets and weights to keep it all straight. I will go back to retest the Sierra 55 and 65 SBT Gamekings. There are also several others I want to work up when I can find time.

Mark

 

[rcmodel]

You are just wasting powder, primers, and time trying to wring small groups out of FMJ-BT military type bullets.

They are death on beer cans.

But a waste of time & money for accuracy testing.

rc

 

[Catpop]

+1 on what rc said. I've just gone down that road and learned it the hard way.
The trds opinion was stick with flat base at 1-200 yards. And this is what I also found so far----- still testing though. I had good luck with 50 grain fb, but bad results with 55 bt, I'm testing 55 fb now.
Good luck, catpop

 

[W.E.G.]

The best domestic-produced "low cost" bullets are the Hornady 75-grain blems.

Even the non-blem 75's are less-expensive than all other OTM bullets.

My attitude toward the 55-grain FMJ's is that they are excellent for generating once-fired LC brass. I buy 'em already loaded, and I shoot the beer cans (or at least some target larger than the cap on a beer bottle), and I collect the once-fired brass to make my best handloads.

Non-blems @ 16 cents per bullet: http://www.midsouthshooterssupply.com/Item/0000322796?Tk=DFBU

 

[W.E.G.]

The reason for the OP getting absolutely horrible groups with the 55-grain FMJ's was that he was pushing them WAY too slow. I guarantee it is the slow velocity - and not anything to do with barrel twist-rate - that is the cause of the largest component of the problem.

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Far better accuracy results would be obtained if the charge were in the 27.3 grains range.

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laddered up some loads... results aren't what I expected. I had to use AA-2460 as this all I had. Projectiles were Bullet Heads .224 jacketed boattails with canelure.... Typical shot groups at 100 yds were 5-6 inches...last three loads, 24.2, 24.5 & 24.8

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[W.E.G.]

 

[W.E.G.]

You can see that the AA 2460 powder is not very well-suited to this caliber/bullet combo. TOO SLOW.

A full-plus case of 2460 is still running slow by 5.56 55-grain standards.

The FULL case of 2460 is probably way more accurate than the cat-sneeze load that the OP was having the trouble with. But would be much better to use a powder better-suited to the application.

 

[W.E.G.]

As a caveat to the preceding Quickload data, those numbers assumed an OAL of 2.250.

Here is the data for the H335 load when the bullet is seated to the point where the case mouth probably meets the cannelure.

Gains a couple thou in pressure and some extra fps.

 

[iagbarrb]

Twist rate of your ar? Lenght of your barrel?

 

[rcmodel]

You would have to read post #1 to find that information.

He clearly stated the twist & barrel length in the OP.

rc

 

[Safetychain]

W.E.G. - Thanks for the info there. I took nearly 20 minutes trying to digest it all. I know what Quickload is but I've not seen any kind of screen shot to see the info that is provided. Pretty neat. I realize that 2460 is not the ideal powder here but you seem to infer that my load would be more accurate at higher loads when my higher loads were resulting in tumbling. Disregarding that fact that they are tumbling for a reason I don't understand, I do understand what you were saying. Regardless, I won't be expecting accuracy with Bullet Heads, at least with 2460 and in this gun. And RC, as usual, you cut through to the chase quickly with the solution. Gamestalker, the crown looks square and my laser boresighter uses the crown to line up with and it is dead on. You can spin the laser and the dot stays stable so it likely is right.

I measured my other bullets on hand, unfortunately all are boat tails, so I cannot eliminate that feature in the next few weeks. I have on hand:

Hornady 55 gn FMJBT - >54.9 & <55.05
X-treme 55 gn FMJBT - Same, could be same manufacutrer, looked exact same
RMR 50 gn Frangible >49.6 & <50.3 most close to 49.6, bullets are very long, can see probable stabilization problems here with my 1 in 9, but of course will try them
RMR 62 gn Soft Point FMJBT - >61.2 & 62.2 Have a jacket base, which I read usually results in more consistent construction, RMR states that they "may vary up to 64 gn but mostly around 62 gn'

Measured samples consisted of 12 bullets poured from each box/bag.

RMR's present frangible product, 42 gn supposedly has the same OAL as the 55 gn. Though the 50 gn bullet is a different shaped/constructed bullet, the ratio 42/55 would equate my 50 gn to a 65 gn bullet OAL. As I read it, bullet stabilization is directly related to length of bullet and speed of rotation. The longer it is the faster it needs to spin; so, slipping in the lands, too slow of bullet speed or a very long bullet will cause destabilization. The 1 in 9 is supposedly a little iffy at the length of a typical 75 gn bullet. With what happened with my 55's tumbling.... The 50 gn frangible is 1.008" and the 62 gn softpoint is .801". I will be finding out.

 

[rcmodel]

RMR 50 gn Frangible >49.6 & <50.3 most close to 49.6, bullets are very long, can see probable stabilization problems here with my 1 in 9, but of course will try them

I think you are over thinking this.

1/9 will stabilize anything you can get in the magazine.

1/12 is good for up to 60 grain.

1/9 is good for anything else that will fit in the mag.

I also think there is nothing at all to the theory that 1/9 won't stabilize a 55 at 2,900 FPS, because it will.

Low Velocity is not your problem.

rc