Stuck with my ar15, IMR4198, and 55 grain varmageddons....

[Garyson1311]

Hey guys so I have a brand new AR (about 100 rounds through it) that I built and the bolt is pretty tight, which I believe has been causing some short stroking with some of my lighter 223 like PMC bronze, etc. All the different kinds of 5.56 i've fed it have cycled great. Anyhow, I picked up some 55 grain Nosler Varmageddon's and I have a few kinds of powder but one in particular is imr 4198. While I know its not ideal for 223 because its pretty fast, 223 is the only caliber that I shoot that is at least semi applicable to the imr 4198 so I was hoping to use it with my ar15 until its done and then switch to something a little more suited for the 223 rem. I used Noslers Flat Base Ballistic tip data as I saw on a forum (possibly this one) that a guy put a call in to Nosler and was told to use the Ballistic Tip data so here's what I got from loaddata.com which is sourced from Nosler #6:

19.5gn
20gn
20.5gn
21gn
21.5gn MAX

All COAL's are 2.260 as specified in the Nosler #6 data, along with federal primers and mixed brass (mostly lake city once fired by me)

All 5 batches shot the first one after manually charging the gun, ejected the spent cartridge, and closed the bolt without chambering a new round. I had no jams or anything, it just simply did not pick up a new round. I am quite sure this is the very definition of a short stroke. I've checked the gas tube a few times and it looks straight and I see now signs of leakage out of the gas block. Anyhow, I now have about 50 rounds (made 5 batches of 10) sitting here and I have a question; 21.5gn is listed as the max load but is there anything I can do to get this load to work? Chamber is 5.56 but I am somewhat worried about increasing the charge much further, or maybe changing the seating depth slightly to get a little more pressure to hopefully cycle the round? I would like to be able to use this powder up as opposed to selling it or letting it sit but not at the expense of doing something hazardous to myself or my new rig. What say the gun nuts at thefiringline.com??

Thanks guys!

[steve4102]

IMR 4198 is on the fast side for the 223/5.56. Fast burning powders often times do not produce enough port pressure(gas) to cycle the action of an AR. Adding more powder will certainly increase "chamber" pressure, but it probably will not increase "port" pressure (gas) enough to cycle your action.

You can switch to a slower powder, install a lighter recoil spring, install an adjustable gas block or maybe even a lighter buffer, but do not just keep adding powder, it will not solve your problem, only create new ones.

BTW, you are not alone here, there are many an AR handloader that are experiencing the same as you with IMR 4198.

[Garyson1311]

Thanks for the info. I was afraid that the imr 4198 was too fast but I wanted to try it. I picked up some alliant Reloader 7 recently and am wondering if that may work a little better? I have some imr 3031 as well but I am hoping to use that solely for my 30-06 since I have Rl-7.

[steve4102]

According to Hodgdon R-7 burns faster than 4198, might work, might not. Alliant has 223 load data fro R-7 with 40,45 and 50gr bullets.

[Garyson1311]

Crap. Okay I guess I wasted some money on the RL-7. Powder is hard to come by around here so I saw a powder that said "great for small rifle calibers" so I grabbed it. Won't be doing that again lol

[243winxb]

brand new AR that I built. I see now signs of leakage out of the gas block.

May not be the powder.

[Garyson1311]

Sorry I meant that I see no* signs of leakage at the block.

[Swampman1]

IMR 4198 working flawlessly with my Hornady XTP 55 gr FMJ and Everglades 55 gr FMJ

[JimDandy]

I've been using RL-15 under 69 and 77 grain Nosler Custom Competitions and love it.