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View Full Version : Why is there a difference in AR-15 & bolt action load charts?



brown3345
01-22-09, 18:37
I was just thinking of reloading a few hundered rounds of .223/5.56 tonight so I opened up the Sierra reloading manual and saw that there are 2 different charts for this caliber. Taking a closer look at the charts they have heavier loads for the Bolt Guns and lighter loads for the AR platform.

Now this really blows my mind because I thought that the AR Weapons are made to handle hot military loads!

Here is an example for max loads:

Bolt Gun;
55gr FMJ Powder H335 @ 27.5 grains 3,300 FPS

AR-15;
55gr FMJ Powder H335 @ 25.7 grains 3,000 FPS

What am I missing here guys?

Ttwwaack
01-22-09, 22:28
I'll take a stab at this.

1. The barrel for the rifle is probably listed as 24" The barrel for the AR-15A2 is 20". At a conservative loss of 30 FPS per inch to 50 FPS that would knock the difference down to 3100-3180 FPS

2. No two barrel are alike. You can get two barrels off of the production line chambered with the same reamer and one will be show higher pressure before the other with the same load (faster barrel).

If you are all that worried about it, Look in the back of the book under pistol loads for 223 shot out of a 14 or 16" contender. You will notice that the higher velocities in the pistol section are the faster burning powders, 4198, 3031 ect..... If you are so inclined to really push it, I'd recommend a Rem 7.5 or possibly a sml Rfl Mag primer working it up carefully. I'm comfortable with the forum load or AA 2230 with a 55gr FMJBT.

brown3345
01-23-09, 08:00
Yes, I can see that but it wouldn't explain the heavier powder charge they allow for the bolt gun.

Ttwwaack
01-23-09, 16:48
'I was just thinking of reloading a few hundered rounds of .223/5.56 tonight '


'Now this really blows my mind because I thought that the AR Weapons are made to handle hot military loads!'


Well, which is it, 223 Remington or 5.56 X 45mm. The SAAMI max for the 223 Remington is 52-55K PSI which the above and below loads are published for. 5.56 x 45mm US and NATO is loaded to a higher pressure in the 60-63K neighborhood. There is a source for this data at a nominal cost (assumed) posted on TOS I believe. I don't think you are going to get there with H335 but I have not seen 5.45 X 45mm data. Powders more suited for this is AA 2230, Varget, and BL-C (2) and possibly Win 748.

These 'recommended' maximum loadings are from various manufactures here in the U.S. As you case see, they use a smorgashboard of various components to arrive at these maximum recommended loads in various barrels from 18.5 - 26" in length from 1-7 to 1-14 twists. When compared to one another, one sometimes doesn't look like the other. Life is grand with only one load manual. Add 2-3 and Uh.... These are '[B]LOAD GUIDES[B] 'The loads published within the confines of this and only this manual were safe within the confines of our test facility in the firearms used to yadda yadda yadda...... Sounds like I'm getting ready to fly someplace, ' In the event of and Emergency kiss your ass yada yada yada.


Sierra (3rd Edition) Colt AR15-A1, 20" Brl, 1-12 twist, Case Remington

Rem 7.5 Primer, Max 25.9gr H335, Vel 3000

Sierra (5th Ed) Colt AR15 A-2, 20' Brl, 1-7 twist, Case Federal

Rem 7.5 Primer, 25.7gr H-335, Vel 3000, [B]* COAL 2.250[B]

Speer (11th Ed) Ruger Mini 14, 18.5" Brl 1-10 twist, Case WW

CCI450 Primer, Max 27.0 gr H335, Vel 3193

Hornady (4th Ed) Rem 700, 24" Brl, 1-12 twist, Case Hornady/Frontier

Rem 7.5 Primer, Max 25.4 gr H335, Vel 3200

Hornady (7th Ed) Rem 700, [B]26"[B]Brl1-12 twist, Case Win

Win Sml Rfl Primer, Max 23.2 gr H335, Vel 3100

Lyman (48th Ed, Copyright 2002) Universal Rcvr, 24" Brl, 1-12 twist, Rem Case

Rem 7.5, [B]Sierra 55gr SPT[B], Max 27.0 gr H335, Vel 3270

The above loading data was extracted from the listed [B]Load Guides[B]. Powders and primers change from lot to lot. I used to shoot alittle skeet and loaded 14.5gr of Grn Dot in my 20ga shells. About 1997, Alliant, in their wisdom changed Grn Dot alittle which pushed the pressures up and over the top and after I finished up the last original 8 lb keg I had, I had to move to Unique

The pressure developed by a cartridge as previously stated is different for each barrel. A tighter bore, rougher finish, tighter chamber/neck, longer -vs- shorter barrel.

I have a factory Colt A2 plane Jane that I used to shoot HP with. I worked up a SMK 69gr load out of the Sierra Ed 5 manual for the rifle. Please bear with me.

LOAD
223 Rem: Test Rifle Colt AR15 A2, 20" Brl, 1-7 twist, Rem Case & 7.5 Primer

24.2-26.8gr Win748 for 25-2900 FPS. Accuracy Load 26.2gr Win748, COAL 2.260

MY LOAD Rem Case, CCI BR4 Primer, 69gr SMK, COAL 2.260


Grains, HV LV AVG ES SD Accuracy

25.7 2930 2818 2857 112 43.3

25.9 2895 2835 2859 60 21.7

26.1 2932 2889 2913 42 17.9 5/8"

26.3 2969 2870 2919 99 31.1

The only component that I changed was the primer from a R7.5 to a BR4 and probably the lot of powder. How come I'm getting 113 FPS more than the book. The book or the rifle must be wrong. The book is published by XXXX so I guess my rifle is bad, any takers?

Actually, the only way to tell is running the above load through a pressure barrel. Damn, I loaned mine to a friend before he move and he never returned it.

Each load combination (Primer, powder and bullet) has a sweet spot in a rifle(s) (*no guarentee) . This sweet spot is were the pressure is just right that the powder burns the most uniformly. At least that is what we try to accomplish. Some loads might be very erratic but still prints one hole on top of another. It is a science, not law.

At 26.1 grains, the load was right. It was the most uniform according to my chronograph and shot well to boot. The primers 'looked' good and could get several loads before I got uncomfortable using the brass. I continued with the testing to the max and the velocity just got more erratic which made the extreme spread and standard deviation even worse. If I recall correctly, the primers at 26.7 were flat. I wish I had the rest of the data on my log sheet to show you the whole picture from starting load to max. As you can see, the optimum charge weight for the 748 was in the area of 25.9 and 26.1. After getting the good results with 26.1 and the velocity, I ran with it without further testing. I tried to duplicate that load last year with a different lot of powder and primers. It looks like I'll have to re-invent the wheel for a 200 and 300yd load if I get back into HP again.

Another good load is Sierra's 52/53gr bullets for reduced course (100 yd) firing. The 53gr FB is good in my rifle at 3100 with AA 2230. It's no a full bore load so it is abit softer on me and the rifle and as far as drift ect, it only needs to go 100m, after that it can do what it wants.

You can experiment for yourself or follow suit. MARKM has been selling the Hornady 55gr FMJBT, WSR primer and 24.5 grains of TAC for a long time. I've tried it, got good results but am kinda stuborn since I'm sitting on 24 lbs of AA2230 that I got for a good price. Once that is gone, I'll probably move over to TAC. I've been putting together a 50lbs powder order the last couple of days and I've got an 8 pounder slot reserved for TAC. Drink the kool aid and be done with it.

THE DISCLAIMER: THE LOADS LISTED IN THE ABOVE RAMBLE WERE SAFE IN THE FIREARMS YADA YADA YADA. Prudence is a survival tool.

brown3345
01-23-09, 17:17
Nicely said Ttwwaack! You know your user name reminds me of the noise my head made when it contacted my wifes shoe after I told her about my last gun purchase. Coincidental?

Thanks,

Bimmer
01-23-09, 21:15
Ttwwaack, this is great, but it still doesn't answer the question.

Why a hotter load in a bolt gun than in an AR?

Is it that .223-chambered (not 5.56) ARs simply aren't designed to handle as much oomph as a typical bolt gun?

Or is it that there isn't time for the extra powder to burn in a 20" barrel, but it will in a 24" barrel?

I made these up, but they make sense to me. I don't know, so I'm asking.

Bimmer

shadowalker
01-23-09, 21:47
I am also curious. Most other load sources don't break it down in AR-15 vs bolt, Speer does indicate which powders work for gas operated semi autos.

One thing that comes to mind is the AR-15 is gas operated and not all powders / charges are suited for the gas system.

Ttwwaack
01-23-09, 23:36
Why a hotter load in a bolt gun than in an AR?

As I stated earlier, barrel length and bore condition. Both are probably stopping in the same neighborhood of pressure 50K. Once a load reaches it's optimal pressure, adding additional powder won't make it go faster reliably sorta like like the fuel air mixture for your vehicle. Accuracy will fall off and pressure spikes will occur ie (from above).


Grains, HV LV AVG ES SD Accuracy

25.7 2930 2818 2857 112 43.3

25.9 2895 2835 2859 60 21.7

26.1 2932 2889 2913 42 17.9 5/8"

26.3 2969 2870 2919 99 31.1

Although the max load data was 26.8, I settled on 26.1. The other two ten shot strings for 26.5 and 26.7 grains were shot but the extreme velocity spread and standard deviation just grew along with the group size. For that barrel (bore and length), 25.9 to 26.1 was optimal. Although 'the guide' stated I could go to 26.8 and stay within the 'SAAMI' pressure limits.

Does that explain it? Look at the Hornady 4th and 7th edition data. Both are for a Rem 700 but one with a 26" and one with a 24".

Hornady (4th Ed) Rem 700, 24" Brl, 1-12 twist, Case Hornady/Frontier

Rem 7.5 Primer, Max 25.4 gr H335, Vel 3200

Hornady (7th Ed) Rem 700, [b]26"[b]Brl1-12 twist, Case Win

Win Sml Rfl Primer, Max 23.2 gr H335, Vel 3100

There is a 2.0gr difference between the loads. The only differences are two different rifles, primers and cases. Confused yet, look at the Speer data for the Mini-14.

Granted, a bolt gun is stronger than an AR-15 but both should be loaded close to SAMMI specs. Sure, you could load it up till the primers fell out and it would hold for awhile. The important question is how long is awhile?????

I haven't tried the questioned [B][U]MAX LOAD[B][U] in a Bolt Action Remington 223. The STARTING LOAD is 23.5 gr of H335 with a Sierra 55gr projo and work it up from there. The 'manual' is a LOAD GUIDE. It tells you where to start and by your careful experimentation and observation where and when to stop. Sierra says to stop at 27.5, Hornady says to stop at 23.2. (7th) and 25.4 (4th).

Based on a comparison of the different load data, I take Sierra's data with a grain of salt and work it up carefully since one manufacturer is calling another manufacturers starting load already over the max. Go figure. Just because it is in black and white does't mean that it is right. Unless the round is shot through a pressure barrel you have no way of knowing for sure.

Bimmer
01-24-09, 00:31
I'm still confused... and I still don't think you're answering the question.

I understand that the "max" charge is NOT the most accurate load.

What I still don't understand is why the max charge for a bolt gun is more than for an AR.

I'm not interested in loading rounds anywhere near the max, but since the "starting" charge is usually 10% less, and the difference between them is 6-7% different, it would seem that it matters...

Bimmer

shadowalker
01-24-09, 11:08
As I stated earlier, barrel length and bore condition. Both are probably stopping in the same neighborhood of pressure 50K. Once a load reaches it's optimal pressure, adding additional powder won't make it go faster reliably

While speculating is fun it is probably a good question just to ask Sierra, they are pretty friendly.

The 223 / 5.56 case is pretty low capacity so I wouldn't expect much wasted powder even with slower powders (though they may not work with the gas system).

What is interesting is Sierra used a 20" AR-15 and a 24 inch bolt action barrel, from what I've seen there isn't much velocity gain in 223 from 20 to 24 inches.

There is a big gain from 16 to 18" and a respectable one from 18 to 20"though.

brown3345
01-24-09, 13:12
That's a great Idea, I will call them Monday and see what they have to say then I will post the answer here.

brown3345
01-26-09, 11:57
That's a great Idea, I will call them Monday and see what they have to say then I will post the answer here.

Just talked to Customer Service over at Sierra Bullets. He said that they have 2 different loadings because they have had many people call them with gun failures when using full house loads which could have been caused by many things like:

Guns not rated for 5.56

Home assembled guns that were put together by people who didn't know what they were doing.

Full power loads made with a combination of commercial and military brass mixed together.

Or a combination of all the above and more.

He further stated that you can use the Bolt Action load data as long as you use your head and load methodicaly like you should be doing anyway. Nice people over there at Sierra!

jstevens
02-16-09, 15:32
a bolt action rifle is stronger than a semi-auto, so will handle a heavier load. Barrel length has no relation to pressure at all.

Bimmer
02-16-09, 15:42
a bolt action rifle is stronger than a semi-auto, so will handle a heavier load.

Huh? What's your basis for saying this?

You can say that a bolt action design is inherently stronger than a typical semi-auto design, but the SAAMI specs for any given cartridge are the same for all actions that chamber that cartridge they all have to have the same "strength" to resist the same pressure.

nemohunter
02-16-09, 18:33
i'm a NOOB to the sight but not to guns or reloading. the big reason is the pressure curve the gun is designed around. it is designed to work on a certain time/pressure curve. start jacking around with it too much and you start battering the gun. you CAN load bolt gun loads you just need to compensate for it somehow. stouter spring and or heavier buffer would be a good place to start. you could also use and adjustable gas block. also shoot some plain jane loads in your stock set up and measure how far the cases are flying. then when you dial up the pressure you will have a reference piont to go buy. for instance my new 6.8 tosses then about 7-8 feet at about 4:30 to 5:00 from my position when standing. now if i go a jack around with loads for hunting season like i know i will have a piont of reference. hope that helps.

shadowalker
02-16-09, 19:44
The OP called Sierra, they said as long as you use proper load development you can use their bolt action loads in semi autos.

The powder you select still has to be suitable for gas operated semi autos though.

jstevens
02-16-09, 22:48
bimmer

My basis for saying this is because it is true, a bolt action is stronger than an AR15. Sure SAAMI specs for a .223 are the same for both, but have you ever sent any ammo to SAAMI and had it checked? The margin of errror is greater with a bolt rifle than a semi-auto. Sierra when printing up a loading manual has no idea what the pressure is in YOUR rifle, just what it is in their test rifle, therefore it is up to you to decide what is maximum. If you have no way of testing but a WAG then it is prudent to use a lighter load than you could in a bolt action Rem 700. Does this make sense? I have a pressure trace strain gage system on some of my bolt rifles to check pressure, but this isn't possible on an AR15 (or at least not practical) since the gage is mounted over the chamber, which would be under the handguard. The logistics would be difficult. If there is no way to really check it, it pays to be cautious. Excess pressure will be a lot tougher on a semi-auto than a bolt. From using my pressure trace, I have found a large increase in pressure when you let a cartridge get hot, such as firing several rounds, getting the barrel hot, then letting a cartridge sit in the chamber for a couple minutes, pressure may increase almost 7-8000 psi. I think everyone will agree that it is easier and more common to get a barrel hot to the touch with an AR15 than a 700 HB varmint rifle. Just another reason why an AR15 should be loaded to a lower level than a bolt gun. This is just another variable that SAAMI specs have absolutely no control over. If you throw some of SAAMI's tested ammo of a known pressure on the dashboard of your truck in the summer, the margin of error may be erased completely.. Reloading is just no place to wing it and push the envelope without really understanding it and thinking it through.

nemohunter
02-17-09, 07:06
Proof loads are used to test all firearms these days. a Proof load is a SAAMI max load heated to 160 degrees for an hour. the only rub is we have such good stable powder anymore that this is hard to do. Hogdon extream propellents typicaly vary no more than few FPS up or down from 32 to 100 deg. this is good for us. nice consistant ammo no matter the temp.