Ignition issue...

[cwlongshot]

Morning guys Happy New Year all!

Hoping maybe someone has seen this. I know changing powders might likely change things. But this powder is most accurate. Vel is not as important to me.

Question for you.

I've been having a bit of a problem with an AR in 450 bushmaster.
At first it was cycling and then feeding, I got that worked out. I had a bad follower and then I had a foul up with powder charge. I'm using AA 9 and one manual has a maximum load that's below the starting load for the same powder!!!! So Im now using the manufacturers data. Once I use the manufactures data, it's cycling,locking the and shooting perfect. Clovers @ 50 all day.

Now... with these heavier loads. 38.3 & 38.7g #9. Zero pressures seen and cycling is great, as I said. But so so slight, even an infinitesimal delay in ignition. Im using a CCI mag primer. Maybe its nothing, but it bothers me...

BTW, I saw this exact with lil gun too. (Part of what made me stop using that powder too.)

I have opinions asking to see if others agree.

Any ideas?

CW

[Al in Mi]

Might try some 7 1/2 remmys if you can find them.

Maybe get some more tension on the bullet, try a tighter crimp, skip the expander ??

[plant_one]

have you checked for primer pocket blockages - wondering if some of yours still have the flash hole punch on them and its partly blocking the hole?

[Hoot]

...and / or...
How are you seating your primers? If they don't bottom out in the pockets, that can lead to erratic timing. I use a hand seater so that I can feel when they bottom out. A weak hammer spring, while more delightful to shoot, may not be getting the job reliably done. Ditto on lock time as a function of lubrication of the fire control group moving parts. Some folk prefer their rigs bone dry down in the FCG so as not to accumulate dust and debris but it only takes a second to clean out and relubricate. I'm a fool for experimenting with lubricants and have finally settled on Sprinco's MGL (Machine Gunner Lube) wherever one surface rubs against another in the FCG. I didn't notice what bullet you were having trouble with. I had a little bit of hang fire with lightweight jacketed projectiles that didn't have adequate neck tension once and once with Berry's 230 TMJ's which I never tried again. They were too soft for adequate neck tension. Made greay slingshot projectiles. Do you trim your brass and if so, to what length? Just throwing some ideas against the wall to see if they stick.

Hoot

[Texas Sheepdawg]

Hoot pretty much covered it. I do believe that a firm crimp is key to getting good ignition. I also had some delayed fires using 38 and 39 grains of Lil Gun. Tightening up the cramp and even going with the LeGendre side crimp really helped me. Also I went back with the mill spec hammer spring to make sure I had good hard strikes on the primer.

[cwlongshot]

OK!! Thanks guys!!

This was brand new brass.

Yes fully prepped. Deburred and uniformed flash holes cked for uniform length

Powder is AA9

Primer is CCI 450

Gun is a MSR brand new bcg disassembled oiled and re assembled 60-80 rounds ago. (Will tear down and ck)

Bullet is 200g FTX. ( Crazy accurate!!)

Taper Crimped. I can fiddle a bit here.

I have Rem primers match & reg SR.

I was gonna try diff prim & Add grex to make 100% density load.

CW

[cwlongshot]

Well... That didnt do it???

NEW BRASS. Resized primed CCI 400 - 38g #9 - 200g FTX - Taper crimped firmly.


I loaded five... FOUR shot perfectly one hang fired.


Now I say hang fire. But it is the absolutely slightest hesitation in ignition.


Next is lil heavier taper crimp and a Rem Match SR primer.

Along with that. Used annealed brass loaded same same.

Cycling was 100% and cases ALL CASES could go into a 5gal pail behind and 7-8' to my right.

CW

[Al in Mi]

grabbing at a straw here, but AA #9 is a slower powder I believe, just might be to slow to get a good light on that lighter 200gr bullet with out some compaction or a heavy crimp. Maybe the ole Legnder side crimp would help here.

If you have some Lilgun, you might try that just to see if you feel that hangfire.

[Hoot]

grabbing at a straw here, but AA #9 is a slower powder I believe, just might be to slow to get a good light on that lighter 200gr bullet with out some compaction or a heavy crimp. Maybe the ole Legnder side crimp would help here.

If you have some Lilgun, you might try that just to see if you feel that hangfire.

According to QuickLoad, Lil Gun is slower burning but it is predicted to give more velocity for the same pressure than AA9.

IE Per QuickLoad using 1.695 brass:

42gr Lil Gun (93% fill), 200 FTX, 2.19 COL, Rem 7 1/2, .474 Taper crimp = 2510fps @ 37.8k psi
34gr AA9 (74% fill) *, 200 FTX, 2.19 COL, Rem 7 1/2, .474 Taper crimp = 2338 fps @ 38.1k psi

While I can speak to the behavior of Lil Gun with the 200 FTX, I have never tried AA9, so we're at the mercy of QuickLoad's accuracy in predicting its behavior and I've seen QuickLoad over-predict some powders. IE W296, which I've used a lot with 300gr bullets, produced significantly lower velocities than QuickLoad predicted for a given charge.
I always had to put a strong taper crimp down into the cannelure, to hold back lighter bullets like the 200 FTX and 200 XPB. Both achieved their best accuracy with Lil Gun from my 20" barrel. Interestingly, I tried Alliant 2400 once, which has a burn rate more like AA9, with the 200 FTX and experienced some hangfires. You'd think that the faster powders would be easier to light off. I reiterate the importance of having your primers, regardless of brand, seated down in the pocket to where they bottom out, for consistent ignition.

Hoot

[Texas Sheepdawg]

CCI 400 is not a hot primer. CCI 450 is hotter.
The only other powder for me, other than Lil Gun, is one that
I use for 275-300 grain bullets and probably wouldn’t
be ideal for light bullets. (A1680). However, I’ve heard good
Things about 296.
Also you might want to de-burr your flash holes in the brass.