Remington 742 accuracy problems and split neck casings

[Salmonhound]

I was trying to sight in a remington 742 that my father recently bought at a auction. I went through the rifle and made sure everything functioned correctly and stripped it down to ensure all the nuts/bolts etc. were tight. After putting a new scope and rings on it i went to the range today. At 50 yards I had it shooting a 1" group after 6 shots. During one of those shots I saw one of the split necks. I moved it out to 100 yards and the group opened right up. Vertical 4" spread between 4 shorts. I even changed ammo and same result. I got another split neck so I stopped shooting it for the day. I got it home and rechecked everything and nothing came loose.
Anybody have experience with this rifle and what is the probable cause of the split necks. They were on the same winchester ammo but I have never experienced this before. I had checked the barrel before and didn't observe any pitting or signs of damage. Could use some advice and curious if this thing is a safety risk.

 

[oldfatguy]

Is the ammo factory or reloads?

OFG

 

[bfoosh006]

Ditto on the ammo used question.

 

[Salmonhound]

Ditto on the ammo used question.

it is factory winchester. 150 grain power point and federal 150 grain soft point. The winchester are the two that split.

 

[Lange Carabine]

They arent known for their accuracy. None of the Remington jam-o-matics from the Model 8 through the 7400 were really.
Zero it at 100 yards firing no more than 2 shots at a time to keep the barrel cool.
After a lengthy cool down check cold bore poa/poi.
Adjust scope if needed without exceeding 2 shots to check correction.
Repeat until satisfied with cold bore poi.
Once you get it shooting to poa it'll shoot the first two fairly tight but usually the third will start to wander.
Handloads in the starting load range will usually improve accuracy some and they'll be much easier on the gun.
Factory or full house handloads will beat the gun in short order and it will start giving feed/extraction problems.
I've had them in 30-06, 280, 270 and 243. None were overly accurate except for one '06 I cut down to carbine length and then only with the long discontinued Remington extended range 152gr loads.
The 760 pump is a much better rifle all round.

 

[Salmonhound]

I was surprised how much it opened up when moving to 100 yards. I let it cool down at least a couple minutes between shots. I worked up some hand loads but I didn't get that far. Nobody seems to throw up a red flag on the split necks so sounds like next step is to try some handloads, see if that tightens it up.

 

[Lange Carabine]

Extraction problems were an issue with this model, it has a DI gas system, was over gassed, and the dwell time wasn't sufficient to let chamber pressures drop to a sensible level before extraction began.
This, combined with even a slightly dirty chamber, would rip the rim right off the case leaving it stuck in the chamber. Sometimes it would shear the rivet and pull the extractor ring out instead.
It was believed at the time that polishing the chamber would solve the problem, but it only made it worse.
Your split necks are quite possibly the result of a sloppy chamber in the neck area due to over polishing by a previous owner or gun plumber.
Look at the case rims and see if its deformed where the extractor was.
The 742 was such a lemon until even Remington stopped repairing them in the early 90's.
For a short while, if you sent your 742 and ,IIRC $175 boot, Remington would send you a brand new 7400 in its place.

 

[Lange Carabine]

Oh BTW, one other bit of interesting history on this rifle that most people dont know....the 742 rifle shares the same basic action as the Model 1100 20ga shotgun......
This is why full power ammunition would beat then to pieces in such short order, the action was never meant to withstand 62k+ psi on a regular basis.

 

[oldiephrt]

Think M1 for pressure.

 

[Lange Carabine]

Think M1 for pressure.

^At the very most.^
This reminds me, it's possible to tell how much a 742 has been fired by removing the trigger group and looking for locking lug indentions in the reciever rails.
The BCG on these are very low mass, and they are way over gassed causing very violent cycling. When BCG reaches the rearward limit of travel it slams the reciever with such force that the bolt rotates and the lugs will peen the rails.
After a while the indentations become deep enough until the bolt will get stuck as the carrier spring tries to push the BCG forward again, jamming the action.
I have been told that this can become a problem after just a few hundred rounds.

 

[Salmonhound]

Sounds like a real gem he picked up. I reloaded some 180 grain Silvertip and will seen how it goes. It seemed to cycle the ammo fine so doesn't appear to be a jam-o-matic. Yet.

 

[1911hombre]

Lange Carabine, I have no doubt you know what you're talking about. My 742 experience saw none of these problems, but maybe they were just a couple of good ones.
My Dad had two of 'em... a .243 and an '06. Both of these shot tight and neither one ever jammed. Neither one was ever taken apart to my knowledge; he sprayed the action with Rem Oil once a year if he thought of it. Bores got cleaned and that was pretty much it. He had a "Colyer Clip" for each one; I think they were 8-rounders. The .243 was his favorite antelope gun on the yearly trek out to Forsyth, MT. I carried the 30-06 for Minnesota deer for a few years. Heavy bastards to haul around, though....

 

[Salmonhound]

Thanks all for the insight. I will keep working on it and let yah know how it goes. Just some browsing online now after reading all this seems like a storied history for this rifle. Luck has it sounds like reloading heavier bullets, read up to 220 grain. Has increased accuracy. So I have plenty of different 180 grain bullets for my 300 win mag and grandpas 200-220 round noses i will see if I can get it shooting straight. Hoping it doesn't care for the 150s and I got some brittle brass. It will be a back up to a back up rifle for deer but a new challenge which i dont mind- except finding primers of course.

 

[Lange Carabine]

I doubt either one was fired more than a half dozen times a year though were they.?
A neighbor bought a 742 in 308 in the mid/late 70s. Around 2000 he brought it to me to clean for him.
Told me that at that time he'd killed 88 deer with it over the years.
The finish was well worn but internally it looked like new, just a hint of rail peening starting to show.
I asked him how much he shot it and his reply was that it took him a half box or so to zero the scope when he bought it and he seldom ever shot it unless he was shooting deer. Based on that I doubt that rifle had much more than 125 rounds through it in 25 years. When bought new or like new condition and only shot during hunting season they'd hold up a long time. But they'd eventually start giving problems.
The "high energy" line of ammo from 30 years ago weren't kind to these rifles at all. Saw one came in the shop that was completely wrecked by less than 40 rounds of the 30-06 Hornady stuff that nearly equaled 300 WM mv with 150 grainers.
Not the best photo but this is the rail damage I mentioned earlier.

 

[6.5SH]

I doubt either one was fired more than a half dozen times a year though were they.?
A neighbor bought a 742 in 308 in the mid/late 70s. Around 2000 he brought it to me to clean for him.
Told me that at that time he'd killed 88 deer with it over the years.
The finish was well worn but internally it looked like new, just a hint of rail peening starting to show.
I asked him how much he shot it and his reply was that it took him a half box or so to zero the scope when he bought it and he seldom ever shot it unless he was shooting deer. Based on that I doubt that rifle had much more than 125 rounds through it in 25 years. When bought new or like new condition and only shot during hunting season they'd hold up a long time. But they'd eventually start giving problems.
The "high energy" line of ammo from 30 years ago weren't kind to these rifles at all. Saw one came in the shop that was completely wrecked by less than 40 rounds of the 30-06 Hornady stuff that nearly equaled 300 WM mv with 150 grainers.
Not the best photo but this is the rail damage I mentioned earlier.View attachment 7590010

The peening in your picture as well as pitting in the chamber was very common in this family of rifles. For the OP if you have a borescope I'd check out the chamber.

 

[Salmonhound]

If you look right behind the back of the bolt to the right of the round drilled indent in the receiver you can see marks that match the bolt carrier pattern. That is interesting and certainly confirms a violent return of the bolt. I am a bolt rifle owner besides a couple 10/22 and the dreaded ar so its interesting to see these comments and results of a semi-auto .06.

 

[68GT]

my 740 also shoots 4"@100, and blows the primers 1/2 way out of factory ammo