.308 1st time fail...help please

[Fyathyrio]

I recently loaded my first ever batch of .308 to fire from my 20" AR-10 style rifle. The rifle reliably feeds and fires WWB 7.62 147 gr FMJ with decent accuracy from Magpul PMags, but I had many FTF problems with these rounds in the past with metal C Mags. Once fired brass from my rifle was carefully fully sized, trimmed and checked with calipers, a Hornady headspace gauge and a Dillon case gauge. Each powder charge was measured by hand with a Hornady powder drop, trickled up to correct amount, and verified with a Dillon beam scale. Bullets were seated and crimped using Dillon dies in an RCBS Rockchucker Supreme. The rounds OAL were all within a couple thousands of an inch using Hornady bullet comparator, with a little more variance in COAL due to bullet shape. The rounds reliably loaded into a magazine. I'm reasonably positive that all steps were performed correctly and these are good rounds as far as that goes. The only QA check I did not do at home was to chamber a round as I didn't think an ND slam fire would be a good thing inside my garage should that occur, but they did fit the chamber when dropped into the disassembled rifle.

Components...
WCC 09 w/ NATO cross once fired brass
Hornady 168 gr BTHP
OAL 2.81" (Max IAW Hornady 7th)
Varget 43gr to 45gr in .5gr steps (Source: Hornady 7th & Lyman 49th.)
Wolf LRP

Unfortunately the one check I couldn't do at home is the one I needed...they do not chamber. I purposefully chose to load them at max length to get a little closer to the lands and to minimize possible pressure issues with new loads. Lesson learned...make a few dummy rounds and verify they will reliably feed from the mag prior to making a batch!

Upon my return home and reviewing my process, I compared 10 random WWB rounds with 10 random home rolled. Avg OAL using Hornady comparator is WWB is 0.0193" shorter.

So, on to my questions...first, can a seat lightly crimped rifle rounds a little deeper to match recommended OAL of 2.80 and try again? I did pull one during the loading process to ensure the crimp was not marking the bullet with a ring. Second, any input on the above process?

Thanks,
Mark

[bruceflinch]

Could these be former machine gun rounds?
If so, I believe you have to F/L w/ a U-Die.

[nmerced]

A picture of your handload beside a factory ammo would help.

I have a suspicion something went wrong in the bullet seating step. I've experienced the same thing and it was due to the bullet seating process. Instead of seating the bullet, it first shoved the neck down creating a small bulge on the side before seating the bullet. OAL would come out the same but it would not chamber.

[joefreas]

My AR-10 won't chamber a round with an OAL of over 2.8". I load 2.75+ depending on projectile and get pretty good accuracy with great reliability. There is a trade off with the semis that do not have a match chamber, basically it puts your bullet further from the lands. The distance off the lands can be beneficial especially with match grade solid copper projectiles.

Research will dictate which rounds shoot best in your rifle. I recommend keeping detailed notes on everything OAL, distance off lands, as well as the usual.

When you say "fully sized" do you men full length sized? Or fully neck sized?

and Are you trimming your brass?

[huckberry668]

1 thing jumped out at me from your description. You crimped the round. I suspect you buckled the shoulder area a little.

Load a few more rounds w/o crimp & try. You can remove the firing pin from the bolt to be safe.

Another possibility is you're not bumping the shoulder down enough during resizing. You need s comparator set for that.

[Fyathyrio]

Thanks for the fast responses!

jowfreas...Brass was trimmed to 2.005, every case was measured and good, and sorry, I did mean to say they were full length sized.

nmerced...Photo below of the three rounds I tried to chamber next to the known good WWB stuff I use. If it helps there was very little resistance in seating, and just a touch more at the top of crimp step stroke. The three rounds I tried to chamber at the range still fit in the case gauge smoothly now, but there's a scratch on each bullet from the FTF event. Left of each pair is WWB, right is mine.



Bruceflinch...these were once fired Win brass in the same rifle, and were full length resized with Dillon dies.

[SixPointEight]

Have u measured if you're setting the shoulder back enough? It...doesnt quite look like it. But it could be the pic.

[Fyathyrio]

Huck, when looking at the photo it shows a noticeable crimp on the factory round compared to mine, so I think I might be OK.

I did use a comparator to measure the once fired brass from my chamber before setting the sizing die...but I still may not have bumped it back enough. I initially checked five pieces of brass, they ranged from 1.630" to 1.6315", so I set die to get 1.627", or 3/1000" set back from shortest. I just re-measured three pieces I prepped in this same batch (made some extra in case of mistake during loading) and they all are at 1.626" but it's now 25* colder in my garage so I suspect they shrunk a bit.

Thanks for the tip on removing the firing pin...hadn't thought of that!

[Fyathyrio]

OK, I just measured the shoulder spec on the factory WWB vs mine, it's at 1.623, or another 4/1000" shorter.

[rsrocket1]

Another trick is to paint the entire case and bullet with a magic marker, chamber it and see where the marker rubs off. Look carefully at the base, shoulder and bullet.

[Thatguy80]

I would remove the firing pin and try and chamber a round without the projectile and powder.

If the casing doesnt chamber its a headspace issue and if it does its a COAL issue.

But thats my .2

Good Luck!!!

PS: Id also not run a crimp as your pressures might jump if your nearing max loads. I use varget in my pet loads and have never gone over 43.5 gr in commercial casings.

[Fyathyrio]

Thanks again for all the tips and assistance! OK, to remove one variable, the OAL, can I safely seat these a little deeper considering they were crimped or will I likely damage the bullet or maybe even the brass?

[kurac]

+1 on the magic marker trick, this is the poor mans way of finding the lands and then seating a few thousands deeper.

[Fyathyrio]

My lands are 0.147 past my current OAL (and max mag length) of 2.810, so they're pretty much out of the equation.

[mudshark]

Looks like you need to bump the shoulder back a bit. Do you have a drop in case gauge?