Odd failure mode.

[andyo5]

I have several times experienced a failure mode which seems to occur only when I shoot handloads using W748 powder. My main load with W748 is 55g Hornaday FMJ over 27.9g of W748 and a CCI magnum primer.
The failure is like this: Pull trigger, hammer falls but round does not fire. I try to retract the handle in order to eject the round and reset the trigger, but I cannot pull it back. Instead, I must open the action at the rear, reset the hammer by hand, close it back up and fire the round. It always fires after this.
I have not had this happen with the gun when I shoot commercial ammo or my same reloads with 27.5g of Varget.
Can anyone provide some insight on what is happening?

 

[LVSteve]

Sounds like the case is tight in the chamber and the gun is not going into battery when the gun is first loaded. Are you using new cases or reloaded ones? If the latter, it suggests to me (as a total non-reloader) that the resizing has not gone well.

 

[rockquarry]

A compressed charge may be causing the problem. When you seat the bullet, the compressed powder can actually force the bullet up, increasing overall length and hinder chambering. Perhaps the bullet is jammed into the throat area, preventing proper functioning.

I'd have to check some manuals to be sure, but that looks like a heavier than maximum powder charge, though maybe it isn't. Some .223 cases hold more powder than others.

 

[andyo5]

My Varget load is compressed. My 748 charge is not. Overall length is controlled, measured, and does not change as far as I know. But I'd expect the Varget charge to be worse if compression is an issue.
These are all published loads for .223.

 

[sgtsandman]

Is there a dimple in the primer from the first strike? Does it look like a light strike? Are your primers seated to past flush of the case head? I'm wondering if the primers aren't seated deep enough to set the primer off. Too many questions and things to check but this is some that come to mind off the bat.

 

[andyo5]

Well, the failure to fire is one issue. If I could extract the round I would examine it. Trouble is, I can't eject it. And that is the reason for my post. I cannot pull the charging handle back. I can only open the action, recock the hammer, close the weapon again, and then it will fire.

 

[rockquarry]

My Varget load is compressed. My 748 charge is not. Overall length is controlled, measured, and does not change as far as I know. But I'd expect the Varget charge to be worse if compression is an issue.
These are all published loads for .223.

I'm not being critical, those were just some quick thoughts as to the problem. I realize you measure the OAL, but load just a couple using the same brass you were having problems with and seat the same bullet to the same OAL. Set these aside and measure the OAL again after a couple of hours, then measure again after twenty-four hours. If there is no change, that will completely eliminate the "growing" possibility.

 

[Mike SC Hunter]

I believe you may be bumping back the shoulders on your brass causing the round to not initially fully chamber. Even though your OAL is good your case diameter isn't. My pet AR load is 26 grs of 748 behind a 55 gr bullet. I have no problems with this combo. See if your "sized" case will fully chamber before loading the round.

 

[Moe Mentum]

I use 25 grains of w748 and never experienced any problems. If your getting a fail to fire, and the round gets stuck, I would look into the resizing of the case. The fail to fire may be caused by the round not going into battery, because the case is not sized correctly.

 

[MichiganScott]

There is no way that the bullet is jamming into the lands if the cartridge fits the magazine. The M&P-15 has a NATO chamber with a long throat.

The problem is with the resizing of the cases. It's possible that the shoulder needs to be set back a bit, or the body needs to be sized more, or both. I've given up with partial sizing for AR's because it causes more problems than it solves, particularly if you own more than one.

Although the procedure seems to be disliked on this forum, if the OP learned how to safely mortar the rifle he could get the cartridge out and examine it.

 

[andyo5]

Although the procedure seems to be disliked on this forum, if the OP learned how to safely mortar the rifle he could get the cartridge out and examine it.

This may be so, but mortaring at my shooting range would get me kicked out and losing my membership. They have made this clear.
And I wouldn't want my neighbors to see me doing it in my yard.
I plan to carry a wooden dowel rod next time I go to the range, so I can remove the upper and then push the unfired round back out of the chamber so I can examine it.

 

[Ackley1952]

You didn't mention what type gun. Is it by chance a Thompson Contender?

 

[Ackley1952]

Ok just realized it's an ar . Resize all brass with small base die. Gun not going into battery.

 

[MichiganScott]

This may be so, but mortaring at my shooting range would get me kicked out and losing my membership. They have made this clear.
And I wouldn't want my neighbors to see me doing it in my yard.
I plan to carry a wooden dowel rod next time I go to the range, so I can remove the upper and then push the unfired round back out of the chamber so I can examine it.

I read reply's like andy's and get very grateful that I belong to the gun club where I currently have life member status.

Be careful. There's been more than one instance of the stuck cartridge going off when someone sticks something down the bore to pound out the round. Often you can get a dull, flat faced screwdriver in front of the carrier and break it loose with just a little bit of leverage.

 

[WR Moore]

Looking in my Hornaday manuals, your load is more than a full grain over maximum for .223 and that bullet. Looking at 5.56 x 45 mm load data, the only 55 gr bullet shown is the GMax all copper bullet and again, you're more than a grain over max. Magnum primers don't help and really aren't needed in that small case.

So, starting at the beginning:

1. You measure OAL, do you check the length of sized cases to make sure they haven't grown too long? If your cases are too long, they'll reach the crimp feature of the die too soon and cause the case shoulder to be forced back and out. This will result in the issues you note. Buying a case gauge to make sure your finished rounds are within spec is a good investment.

1A. Make sure your sizing die is snug in the press. It doesn't take much movement to change the case head to shoulder datum line dimension to cause an over length cartrige. Again, the case gauge is your friend here.

2. Your over pressure loads may be expanding the case heads, causing the issue. SMALL BASE DIES ARE NOT THE CORRECT SOLUTION! Reducing your loads to get back into the proper pressure envelope is. That your other reloads and factory ammo chamber properly is what is called a clue. Never rely on only one source for load data. Any source produces the velocities and pressures with any given load in that test barrel/firearm. It's not a warranty that you'll get the same results.

 

[andyo5]

Looking in my Hornaday manuals, your load is more than a full grain over maximum for .223 and that bullet. Looking at 5.56 x 45 mm load data, the only 55 gr bullet shown is the GMax all copper bullet and again, you're more than a grain over max. Magnum primers don't help and really aren't needed in that small case.

Speer #12 and the current Lyman manual both show my load as within SAAMI specs. Speer says 28g, Lyman 27.9g. I don't wish to be argumentative but I am not a careless or ignorant reloader.
But I do appreciate your comments. Cases are not swollen. All fired cases still fit the case gauge, even before resizing. Necks are actually a bit below the minimum. No overpressure signs. Primers look the same as any military primer or those with lower loads.
My current theory is that like the early AR15s, my gun has neither chromed barrel nor chamber. And I am using a fairly sooty burning ball powder. I think that chamber fouling is my problem. This never happens with high loads of Varget, which is even more compressed than W748.

 

[andyo5]

Ok just realized it's an ar . Resize all brass with small base die. Gun not going into battery.

So maybe I should try using the forward assist before pulling the handle?

 

[WR Moore]

Appreciate the additional information, I was working from your OP, which lacked some information. Sorry if I came off overbearing. Not my intent.

When the bullet makers publish load data it's with their bullets. The Speer bullets may differ in bearing length, core alloy, jacket thickness and other parameters from a similar Hornaday product. Any/all can affect pressures. Unless Lyman specifies the bullet, their data may also be suspect, and again, those were their results in the particular barrel/firearm in question. YMMV.

Working off additional information you provided, try the 748 loads in a clean gun and see if that's the issue. I've never been a real fan of 748, although I do use it in a load for bolt guns-largely to burn off a stock I got when I used it in a target load. I'd back off the loads a wee bit, the guys I knew back in the day who used 748 ran 26.5 gr for their ball duplication loads. I generally use IMR/H 4198 for ball duplication. The Hogdon stuff generally runs smaller SDs.

BTW, using the forward assist may just get you a more stuck cartridge. If you do try it, use thumb pressure, not a heel of the hand strike.

 

[andyo5]

WR Moore, I have shot 26.5g of W748 and it does print decentr groups at lower velocities. I am using heavier charges in an attempt to get the bullet drop compensator on my optic to match my load. It is designed for military ball, so that's the benchmark (no pun intended) that I m trying to achieve in terms of velocity and trajectory. My W748 load is a good match, aside from the issues with jams.
I have heard that H335 is the same as the powder that is used in military ball. I have considered buying a pound of that and trying it.
My best results in terms of accuracy have been with Varget. No contest. It is a stick powder and a bit more fiddly to load, but I can live with that if need be.

 

[Westie1]

Gonna put my $0.02 in. More than likely what is happening is a soft carbon ring building up with the 748. I wouldn't be surprised that if you cleaned the chamber as soon as you had the issue, the gun would work normally.

Just out of curiosity-Have you chrono'ed those 748 loads? And as far as the BDC in your scope; What bullet/velocity is it spec'd for?