Staying Safe with an AR-15 - Help!

[DogPatch06]

I'm working up a new load for my AR and I think I'm in nearing the dangerzone because the load data for my combo is particularly conflicted. I haven't shot it yet, and my AR is pretty stout, but I'm worried.

Barrel: LMT 16inch chrome lined 1:7 twist
Chamber: NATO
Bullet: 55gr VMAX
Powder: WIN 748
Brass: LC 2011
Primer: CCI 400
OAL: 2.246 inches
Charge: 27.1-3 grains

My concern is nearing the 27gr mark with WIN 748. Some manuals say 27.8 is MAX and others say 26.5 is MAX.
Can anyone share any experiences with this situation or recommendations? Thanks, Alex

 

[MrMajestic]

Recommendation- Start low and work up watching pressure signs and accuracy nodes.
They are all different!

 

[gtl1946]

Totally agree w/ MrMajestic . If you're pushing for velo. there are better powders (XMR2015, X-Term., AA2230, TAC, VN135). Settle for safe accuracy and if you want more velo. go to a different powd.- Don't make 748 do something others do better. WW748 is an excellent 223 powder ,just use it where it should be.

 

[DogPatch06]

Got it thanks. Your post made me realize that I'm looking for a safe, but high velocity load out of my LMT more so than accuracy. I'll be shooting max at 300yrds and holding MOA is enough for me with that rifle just to have fun.
I'll plan to find a safe and accurate node with WIN 748 and check out the other powders out there for velocity.

Is it reasonable to think that one can recreate the velocities produced by XM193 with propellants designed for more speed than WIN748? I understand the safety implications in that question and I currently value my hands, face, and life. Conceptually, however, is that a reasonable pursuit?

regards, Alex

 

[gtl1946]

There's several good reloading manuals out, but I'm partial to Sierra especially on the AR 15. They've given me a lot of help and direction when reloading and their suggestions often are right on for me. They have an excellent AR section.

 

[JaxCatm]

My first concern would be the with the 748. I've experienced shall we say mood swings with that particular powder depending on temp. One thing about the AR platform and temp sensitive powders that is often overlooked is the volume of fire. If you burn off 40-60 fast and then let the next round hang out in a hot chamber then things can go from sane to off the charts pretty quick. My second concern when dealing with a barrel that short is volume of hot gas being cycled through the gun. I work with M4s and M16A2s daily five days a week 365 days a year. The carbine gas system is getting way to much gas most of the time and it really beats the BCG up reduces the service life of those parts. Sounds crazy but when I work a load up for the AR platform the chrono stays at home. Don't worry so much about trying to duplicate XM193 just find a load that cycles the carbine and shoots to your standards. You can and should shoot the rifle at full distance to find the come ups. Stay safe and have fun just remember when loading for an AR goes bad then life gets interesting/expensive very fast. One other bit of advice get a wilson case gauge and run every round through it. Just another simple and effective step that will cut down on jams and other non-sense.

 

[DogPatch06]

Much appreciated JaxCatm. I normally load at 60-75F temp at home and in the summer I shoot those loads in as high as 95F and as low as 37F with Varget in my 308 and it's fine. Should I expect to see 748 become complicated in my AR even at a lower/safer load in those temp change conditions? I didn't think 748 was so temp sensitive, but I'm new to reloading ARs so thank you for sharing. Would you say that the slightly longer 'midlength' carbine gas system on my AR will help mitigate some of the shorter carbine length concerns given your experience? Regards, Alex

 

[JaxCatm]

To be honest I have no way of prediciting what load will be safe at a given temp. That is the unpredictable part of reloading for me this guy (sometimes 2+2 really equals 8). Pair the sensitive powder with the use of military brass which is thicker and has reduced internal powder capacity maybe throw in a round that got overheated and well smart people at powder companies get paid to figure this one out. As for the midlength gas system I've built a couple of SPR type rifles with them. It is less abusive indeed, but I'm still partial to the full length system. Just depends on what your doing with the rifle. If it is a patrol gun that won't see 3-gun volumes of fire chances are you will never notice the added wear and tear of the carbine system. If you are shooting competition then a midlength system would be the shortest I would consider. BTW look into H335 as a good powder.

 

[markm87]

26.5 is as hot as I ever went with 748 and 55 grain bullets. It got me 100 fps slower than M193. I wanted some cushion for the temp sensitivity of 748.

 

[dennisinaz]

Not a lot of experience with .223, but in .222, I found TAC and Benchmark to be the best powders for 50-55 grain bullets in my two barrels. I have loaded a lot of .223 with TAC and Benchmark but mostly 50 grain bullets.

 

[DogPatch06]

Staying Safe with an AR-15 - Results!

I tried out a few loads today and saved the one discussed here for last. I loaded 10, 5 with light crimp and 5 with heavy crimp. Things went well. No flat primers and no ICHS marks. Mild extractor marks similar but not worse than the ones I see on the military first fired brass. After checking the first 2 cases, I fired relatively fast and it cycled great. Temp started at 80 and when I was done shooting it was 91. Velocity is listed below for the 10 shots.

3159
3152
3122
3159
3167
3054
3058
3059
3072
3058

I'm planning on reducing the charge and finding an accuracy node as discussed, but I had to try it out. Thanks for all the help, Alex