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I purchased a used Springfield M1A last year. The previous owner modified the stock ferrule so the front band does not hook over it. Is this a common modification? If so, why?
Next question, lyman 311299 will reliably cycle at 32gr of H4895. If I go to the noe 30-165, should I expect the min charge weight for reliable operating to go up, down, or remain the same? I probably won't have a chance to experiment until next spring, but need to stary to make plans.
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The change to the stock ferrule was a common mod. It keeps the gas system vibrations from playing odd games with the barrel harmonics, or that was the theory. I can't speak about cast loads as I haven't tried any yet. You would need x psi at the gas port for the system to cycle. If quickload will give you pressures at different points of the barrel find the pressure at the gas port with the 311299 load then see what the pressure is with the 30-165 and go up or down as needed and check again.
Actually, conventional wisdom states that the front band lip MUST contact the stock ferrule, and create a 'draw' (pressure) for the rifle to group consistently. Typically the bottom of the ferrule and the top of the front band lip are polished, then lightly greased to eliminate friction and binding. A very, very few gunsmiths set up M1As and M14s with a free-floating barrel as you describe. There is a lot of voodoo involved with the front band, stock ferrule, and gas cylinder on these rifles.
Yes there is some National Match mods concerning gas cylinder and joining the ferrule. Marine Corps has there way and the Army has another, look into the M14 forum. When I acquired my M14, I joined it and was enlightened by the following there. Many guys get those things shooting some impressive groups, very few specialize in making them accurate, Jon Wolfe in North Carolina and another named Tony and some guy in Texas think he is Warbird Custom.
Also, by design those guns are over gassed. Had some 110 grn light loads that cycled the thing to my amazement.
I shoot a 190 and a 170RN in my rack grade Springfield, and it likes them.
I bought it new in the 80s, and it has no modifications.
For accuracy, I ended up a little higher than the middle of charge weights for best accuracy at one Minute Of Turtle and Soda Can.
Then it also cycled, and would lock the bolt to the rear on a empty magazine.
I have seen them set up both ways Mine are set up with the ferrule and lip polished together. They are easier to bed with the lip I think. There were two mods to that plate to the gas system, one marine and one army, one file 2 small notches in the plate and tig welded it to the gas system the other annealed the shut off drilled and tapped it for 2 number 6 or 8 flat heads. both worked well but the welded still allowed the shut off to function. There were 2 different "gages" for bedding with the lip. one for the heavy barrels and one for the pencil barrels.
I've seen several double lugged receiver M1As with the barrel/gas cylinder free floated. Never shot them so I've no experience on their worth.
Bruce B Did a bunch of work on Shooting Cast in M1A
More information than 1 Person can remember
https://castboolits.gunloads.com/sho...pringfield-M1A
I once experimented with a friend to get a M1A to shoot subsonic. We went quite a bit below minimum charges, before it stopped cycling. Never got it to shoot subsonic without the bullets tumbling. We figured it was because it didn’t have the right rifling.
It has been about a year since I've had my hands on my M1A. I almost forgot I had it. I sent mine to Ted Brown, who was the most knowledgeable M14 gunsmith that I could find. I knew from research that I preferred the stock ferrule unitized with the glue and screw method, which Ted Brown also prefers. I basically told him I wanted him to make my rifle consistently 1.5 MOA accurate. Keep in mind my rifle is still in a Fedex warp hole, but the spec sheet I got says he did the following.
Inspection N/C
Adjust barrel index $60
Install new front sight $35 (this sight is .611" tall which will lower the POI)
Glass bedding $210
Unitize gas cylinder $95
NM stock ferrule $30
NM spring guide $40
He asked me if it was ok to adjust the barrel indexing. While I had 400 rounds through the rifle, I did not have a single fail to feed. He said it was more or less for sight alignment, and overall getting things in proper order.
With the taller front sight I didn't have the heart to tell him I mainly shoot cast. I did think a thinner sight might be useful though, so I'll file it down if I have to.
Bedding is the big one. I have two stocks for mine, and both stocks the action is a loose fit. The design of these rifles is such that the trigger group holds it in tight to the bottom, but also the stock needs to be tight to keep the whole action from shifting side to side. I could move the action inside the stock with my thumb, not good for accuracy. My shifting groups showed that.
Unitize gas cylinder, which mainly pertains to your question is just like stock fit. While the stock and trigger group hold the rear end of the rifle, the ferrule holds the front end. By unitizing them with the gas cylinder, they can not shift on the barrel. Without it, the ferrule is a stamped steel plate, loosely fitting on your barrel, and is only held by the pressure from the gas system nut. In your case, something else must have been done. If you took the ferrule completely out with no other modifications, I don't understand how it could be accurate. The only way I can imagine it possible, is some kind of stock bedding block was added to secure the action bolt action style.
I have no idea how the NM stock ferrule is different. The one on the stock I had polished with steel wool, and had a dab of grease. The reason for this is every shot you want that curved ferrule to return to the same point every shot. I assume that is also why you want a little draw pressure there at the front of the stock. I have heard it is a good idea to epoxy/bed that stock ferrule to the stock to guarantee it never moves. Maybe that is what he did.
I do not know what the NM spring guide is, or why it effects accuracy.
Also to answer your question about cycling, your powder charge weight will have a bigger impact than small changes in the bullet. Mine would cycle and lock back the bolt with as low as 28 gr IMR 3031 from what I remember.