IMR4198 AR problem

[imarangemaster]

Well, DANG! I have about 400+ rounds of my pet 223 load loaded: 21.5 grains IMR4198, CCI #41 primer, and A 55 grain FMJBT bullet. I had used this load since the 80s with a SP1 AR15 16" Carbine. More recently, I had been using it in a 16" barrel M4gery. Accurate and reliable load, with same POI as M193 from the 16" barrel.

The problem is that I switched to a 20" barreled platform with a rifle length gas system. Guess what? It apparently 4198 is too quick a burn for the 20". It will not lock the bolt to rear after the last round, and about 1 out of 3 times, it won't cycle far enough to pick up the next round. In a 16" system, you can't tell the difference between M193 and this load as far as noise and recoil. In the 20" system, the reload is definitely not as hot.

I don't want to pull 400 bullets of plinking ammo, so I picked up a spare rifle length buffer spring for $10. I thought I would clip about 10% off the spring, and just use it with the plinking ammo.

Information

Warning: This is a relatively older thread This discussion is older than 360 days. Some information contained in it may no longer be current.

[browningautorifle]

That should do it. Or...what about a carbine buffer of standard carbine weight?

[jmoore]

I've been running a 55gr hunting load using IMR4320 that very nearly fills the case to overflowing for some time, not that it sorts your current drama. But it chronos right at 3200fps (which is surprisingly just what the Sierra manual states that it should do) out of a 20" barrel 1-12" twist barrel and is happily accurate. Works on both fixed and retracting stock lowers.

[imarangemaster]

I still have another 600 55 grin FMJBT bullets to load up. In looking around, H335 is the best, but no one has had any for a year. I also looked up some IMR 4064, and read good reviews. Much like H335, it can be used for effective loads for 55 to 77 grains. The local gun shop had some IMR 4064, so I picked up a couple jugs for $30 a pound (cheap for around here).

I looked up loads, and 25.6 grains fills the case and gives between 3200 and 3300 fps. That gives 52,000 CUP (5.56 is 55,000 max SAAMI specs) It is a long stick powder, so I have to give a slight rap on the dump when filling cases to feed evenly. I tried 10 test dumps in the case, and all came out at 25.5 grains.

I counted up the 4198 loads, and I have 400 (actually 397). I also have about 500 rounds of factory M193 that I am saving for "serious" work. I may take a rainy afternoon, and actually pull the bullets on the 4198 loads, and reload with 4064.

I had worked up a 160 grain 7.62x39 cast bullet plinking load that uses 16 grains Alliant 2400 powder. I still have 3 pounds of 4198, and found I can use 18 grains of 4198 instead of the 2400 for those. that leaves the 2400 for my cast bullet 30 carbine loads.

[imarangemaster]

Interesting.... I found that IMR 4064 is also an excellent powder for 308 Winchester. I plan on loading for my PTR-91 also, so this might be a better choice than I thought.

[browningautorifle]

I've taken my medicine before and pulled several hundred bullets...my choice at the time was that or toss them into the ocean. Save the powder and pull the bullets...

[vintage hunter]

I found that IMR 4064 is also an excellent powder for 308 Winchester

It is indeed. Don't know what bullet weight you plan to load but FWIW 43.0 gr pushing a 168GR SMK is a very accurate load and it duplicates Federal GMM.
I've also used IMR 3031 in the 5.56/223 with good results and it's also the choice powder for my 6.8 AR with 110gr Sierra Pro Hunters.

[imarangemaster]

Ugh! Been busy pulling bullets since i got home at 3:30. Still have 175 to go, but more than half of the 400 done. I had to knok off, as I have a blister on my palm now, and the collect that holds the base in my kinetic puller needs reworked. Why in the heck do they make it out of aluminum??????

The good news is two fold: One, these will be easy to reload, as they are primed already. Second I will have a pound of 4198 powder for my 160 grain cast 7.62x39 loads!

[browningautorifle]

Have strength my brother, where you go we have been...

[imarangemaster]

Argh! My powder measure does not like 4064! It meters worse than IMR 3031! Hmmmmm. The good news is that a LEE 1.9cc dipper throws 25.4 to 25.5 grains of 4064 every time (at least the first 20 tries). Average was 25.45 grains. The max load listed is 25.7 (52,000 CUP) to 26 (54,000 CUP) for 5.56 with a 55 grain bullet. I had the measure set for 25.5, but the dipper works better with less frustration! Close enough for plinking ammo. It should be hot enough to cycle the 20" AR-15!