M1 Carbine blowback again

[nwellons]

I posted my M1 Carbine problem (gas in the face) here earlier and the consensus was probably too weak loads allowing gas to escape around the cartridge.

Here is an update. While firing about 30 rounds of M1 Carbine at the range yesterday, I had one blow back with stinging powder/gas in the face. It was in the middle of the string.

I had loaded with 11.1g of 2400 and got a velocity of 1740 on the Chrony. It seemed plenty powerful so I loaded a small batch and took it to the range.

Could the problem be with brass that needs annealing, the chamber/headspace or? No matter what the load, the vast majority of times it shoots fine but every so often, you get the gas in the face.

Maybe the photo will help.

[Larry Gibson]

If you are FL sizing the cases with the shell holder to the bottom of the FL die you might back off the FL die to partial size. You only need size enough to put .003" tension on the bullet. If you can see the base of the bullet bulged out of the case below it after seating then you are sizing too much. The more the case is sized the more psi it takes to obturate it to seal the chamber.

Larry Gibson

[flounderman]

if you have headspace problems, you could see the primers protruding from fired cases. You probably need to full length resize so it chambers reliably. any chanch it is fireing without the bolt fully closed? too light a recoil spring allowing it to cycle too soon? since they all are not doing it something has to be causing it. clean and oil everything. clean the recesses where the lugs lock up, clean and oil the gas piston. are all the cases the same and are the ones that blowback the same as the rest? If the cases are alike and the loads are alike, the problem is likely in the rifle. if the cases are mixed and one brand is doing it, could be hard brass. if you are using cases that have been used a lot, maybe some of them have hardened and annealing would solve the problem

[TommyT]

I had this same problem using 2400. I switched to H110 and the problem went away. YMMV.

[nwellons]

Thanks to all for the great ideas. I will be working on them in the next couple of weeks and will report on any success.

[Grapeshot]

Check your primers to insure you do not have pierced primers letting gas escape rearward. Also, do not oil the gas piston. Clean it well, but make sure it's dry when you put it back together. Any oil on the gas piston will be transformed into an tar like cement you will have to scrub withbrake cleaning fluid to get off.

Having had experience with the M1 Carbine, M14, and the M-60 GPMG while in the Army as a Small Arms Repairman I saw some gas pistons that were a pain in the posterior to remove because some poor private thought it would make his Rifle or Machine Gun shoot quicker and more reliable.

[waksupi]

Do you have ALL lube and oil off of the loaded cartridges before shooting?

[WILCO]

I had this same problem using 2400. I switched to H110 and the problem went away. YMMV.

That was my first thought.
Nwellons, where are you getting your load data from?

[nwellons]

Thanks again for more good ideas.

I really cleaned my carbine (and oiled the gas piston - I will remedy that tomorrow.) I bought a lb of H110 and set up a Lee starting load for the nearest weight (11.5g) I'm using 103 g cast and I think the nearest Lee cast is 115g. Anyway, I loaded 10 and chrony'd them at an average of 1614fps. There was no gas blow back and I was using chemical splash goggles for protection. All primers were normal with this batch and I will definitely check if I get another blow back.

I loaded 50 for my next range trip and put them with the goggles for a reminder.

I will check for residual lube when I go down to clean the gas piston again.

It may be a few weeks but I will post results when I get to the range. I hate to shoot too much in the yard because of my good neighbors.

[barkerwc4362]

I am using a mid 12ish 2400 load with the SAECO #302 120gr gas checked bullet with no problem what so ever. The load you are using on 11.1gr is a little low, that is more than likely your problem. My data comes from one of the Lyman handbooks.

Bill

[Reg]

The soot you are showing on the mouth of the cases generally shows lack of sealing at the case mouth. Up the load or perhaps the H-110 will raise the pressure just a bit and seal that mouth for you.

[nwellons]

Got to the range with 50 rounds of H110 at 11.5 grains.

No blowback; all the cases looked normal.

I'll stick with H110 for now and later may up the load a bit on the 2400 and see if that works.

Thanks again for all the help.