AR-10 reloading question

[JohnhenrySTL]

I am reloading some .308s. My loads will have 44.5 grains of IMR4064 stuffed into PPU once fired brass under a Sierra 150 grain BTHP. My brass was all trimmed to 2.005 and chauffered.

As I have loaded mainly 168 grains to OAL of 2.797 I am frustrated with my manual listing a 150 grain soft point to a OAL of 2.735. The 3 rounds I have so far are 2.785 inches long. My concerns with rounds being as short as my manual tells me is that they will cycle funny. Im worried that rounds I have made and would like to make more of will be longer than instructed and will lack chamber pressure to cycle. Before my gun was sent back to the manufactor I had some rounds getting set back about half an inch in the case. These rounds were commercial bought ammo, not my loads.

Think I should go shorter, or would you assume they cycle? Also would you guys crimp .308s for an AR? I always crimp for anything other than my bolt guns, but I would like to find the most pragmatic solution. I am not worried about match stuff at this point. I would like to make some decent planking ar ammo. Thanks in advance.

 

[rcmodel]

2.735" is about standard length for 150 grain bullets with crimp cannelure's.

They won't cycle funny until you try them and find out they don't.

rc

 

[steve4102]

I am reloading some .308s. My loads will have 44.5 grains of IMR4064 stuffed into PPU once fired brass under a Sierra 150 grain BTHP. My brass was all trimmed to 2.005 and chauffered.

As I have loaded mainly 168 grains to OAL of 2.797 I am frustrated with my manual listing a 150 grain soft point to a OAL of 2.735. The 3 rounds I have so far are 2.785 inches long. My concerns with rounds being as short as my manual tells me is that they will cycle funny. Im worried that rounds I have made and would like to make more of will be longer than instructed and will lack chamber pressure to cycle. Before my gun was sent back to the manufactor I had some rounds getting set back about half an inch in the case. These rounds were commercial bought ammo, not my loads.

Think I should go shorter, or would you assume they cycle? Also would you guys crimp .308s for an AR? I always crimp for anything other than my bolt guns, but I would like to find the most pragmatic solution. I am not worried about match stuff at this point. I would like to make some decent planking ar ammo. Thanks in advance.

Couple points,

Chamber pressure is not what cycles the action of and AR. The cycling is done with "port" pressure, which is the amount of gasses created by the burned powder entering the Gas port.

In general, the slower burning the powder the more gasses produced, the higher the port pressure, the faster burning the powder the less the "port" pressure.

As for your OAL, seating the bullet longer, increases chamber pressure in a bottle necked rifle round, but will have little affect on "port" pressure. If your AR will not cycle with the long loads, reducing OAL will not affect "port" pressure and aid in cycle. If they do not cycle it is most likely do to the fact that the round is physically to long or too short and has nothing to do with pressure.

 

[HKGuns]

I load most all of my 7.62 cartridges to 2.800 or magazine length. I don't buy bullets with a cannelure and I don't crimp.

 

[Sunray]

44.5 grains of IMR4064 is a fairly light load, but there shouldn't be any cycling issues caused by that. Have a load for my semi'd Winchester M-14 using 150 Silvertips(my pretend deer load worked up before real M-14's turned evil) that's 1 grain over minimum. Feeds with no fuss.
The OAL might give you grief. OAL for a 150 is 2.800". 2.785" will do though.
No crimping. A crimp is only required for heavy recoiling cartridges and sometimes with a lever action.

 

[FLIGHT762]

I've reloaded for a Knight's SR-25 since 1993 and I have a GAP 10 I bought 18 months ago. Both rifles are in 308 Winchester and cycle well. I do not crimp, never needed to.

Most bullets I shoot through them are the 155, 168 and 175-178 match bullets. My COL for the 155 match bullets is 2.775". For the longer bullets, I load to 2.780" or so to get 100% feeding for magazine length.

The 44.5 load of IMR4064 should work fine for you. I've shot the 155's through both of my rifles with charges of IMR 4064 between 43.8-44.5 grains and they cycled 100%.

You shouldn't have any problem. Shoot them first and see if you have any issues.

 

[Reloadron]

For my AR 10 and M1A I load:

Sierra 150 grain BTHP to 2.775" OAL Sierra 50th Anniversary Edition IMR 4064 MIN: 40.0 MAX: 48.2 grains.

Sierra 168 grain BTHP to 2.800" OAL Sierra 50th Anniversary Edition IMR 4064 MIN: 39.8 MAX: 44.7 grains.

The Hornady 9th Edition runs a little conservative for the 150 & 155 grain bullets with the 155 grain A-MAX loaded to a COL of 2.800" and the 168 grain BTHP loaded to a COL of 2.800" so the Hornady A-Max in 155 and 168 grain are loaded to the same COL of 2.8".

Hornady 155 grain IMR 4064 Min: 38.4 Max: 44.9 Grains.

IMR 4064 is only listed under service rifle loadings for 168 grain!
Hornady 168 grain IMR 4064 Min:36.1 Max: 41.6 grains.

Using the Sierra COLs mentioned I have never had a problem.

Ron

 

[joem1945]

44.5 grains should work and cycle. If they don't Look to the rifel for a problem.

 

[jeffforkliftguy]

I switched.from imr4064 to imr3031 with much better results. Also, do not crimp bottle neck rifle rounds, all it does is decrease your accuracy. Neck tension in a correctly prepped/sized case is more than enough. 4064 is slower, comparable to 4250. If IMR is whats available to you i recommend you try 3031. I reload for my ar10 and have zero issues. Im using 150gr fmjbt. Never a cycling issue and always on the mark.

 

[JohnhenrySTL]

Thanks everybody for the explanations. I am amused how quickly the highroad responds with both facts and tested experience.

I will try not crimping my ar rounds and treat it at first like a hot load, which means I will shoot slowly and check for neck tension.

When I load, I push atleast half of the rounds up against my counter as hard as I can. I measure them before and after, if they dont change length I call it good.

 

[BigBore45]

Here is a thread i'm working on. All these loads cycled my AR-10 just fine and it is new with less than 50 rounds through it when i started.

http://www.thehighroad.org/showthread.php?t=770828

 

[notaglockfanboy]

You should TRY the rounds before you start making assumptions on what will happen. Go out and shoot them and come back with your results. Chamber pressure does not cycle the bolt in that platform anyway, so if it is failing to cycle, there is another problem.

 

[Slamfire]

You should TRY the rounds before you start making assumptions on what will happen. Go out and shoot them and come back with your results. Chamber pressure does not cycle the bolt in that platform anyway, so if it is failing to cycle, there is another problem.

I agree, and I think 44.5 grains IMR 4064 with a 150 is as fast as I would want to go in a gas gun. I tested a number of 150 grain loads in my Ruger M77, my 44.0 grains IMR 4064 pushed them plenty fast, and I use the 155 grain Nosler load in my M1A and it cycles it fine.


Loads lighter than the AA2520 load cycled my PTR 91 perfectly. Just test your current load before bumping it up and creating real function issues with hot loads.

[B][SIZE="3"]
Ruger M77 MKII 	26 " Barrel 1:10 twist[/B]			
								
								
150 gr Hornady FMJBT 43.5 grs AA2520 wtd Lot 9595 Czech Mixed LC WLR		
	 	OAL 2.785 					
30 April 2008 T =  65 °F						
								
Ave Vel =	2756							
Std Dev =	28							
ES =	97							
High =	2806							
Low =	2709							
N =	10							
								
Excellent accuracy							
								
								
150 Sierra SP BT 44.0 grs IMR 4064 IMI brass CCI200 LC90 			
	 	OAL 2.760" 					
30 April 2008 T =  80 °F						
								
Ave Vel =	2749							
Std Dev =	14							
ES =	47							
High =	2777							
Low =	2730							
N =	10							
								
v.good accuracy, no increased effort on bolt lift

155 Nosler Match 42.5 grs IMR 4895  wtd lot L7926 mfgr 2000 TZZ  Brass CC#34  		
	 	OAL 2.750" 					
4 July 2009  T =  86 °F							
								
Ave Vel =	2716							
Std Dev =	33							
ES =	113							
High =	2794							
Low =	2681							
N =	10							
				 Good accuracy			
				[/SIZE]

 

[JohnhenrySTL]

I loaded them up and they shot perfect. I had holes touching holes within 3 shot groups at 25 yards using iron sights. That is great for me. 47 rounds, 20 of which were test loads cycled without misshap.This whole reloading AR deal has been a huge learning experience.

I bought the gun brand new two days before Sandy Hook. Not planning on reloading for it, I could find no ammo anywhere. To shoot I had to make ends meet. I bought a die.The gun never would make it through a full magizine. It was always the same jam. The gun would stop right before battery. I mean barely enough to notice. I kept blaming my reloads. I read every manual I could. I learned quickly about how sensative bottle neck cartridges are rumered to be. I bought a trimmer, a chaumper tool, I tried other brands of dies. I was told I needed Ar powder and a AR sizing die. I was told I was overlubing my brass, I had to remove my first stuck case from my die. I kind of gave up.

I got my hands on a couple varieties of factory loads. When my sig wouldnt cycle factory Fed. 168 bthps with any of my magizines I called them. Within a minute they told me they had emailed me a tag and that it maybe had too tight of a chamber. The rep was understanding. He was calm and asked me about mags and loads. I told him I had tried 3 different factory loads and had the same trouble. I was told 3-4 weeks, well seven days later I got my gun back. It shoots great. I could not be happier with the way Sig handled me. I got a fair deal. So moving along, is it common practice to avoid crimping 40s when charging mild to medium loads with strong "pull" or neck tension?