What have I done wrong now?

[MistWolf]

rojodiablo, thanks for defining what you mean by "dwell time". Your definition doesn't match what is generally meant on other sites. (Of course, I realize that dwell time can apply to many situations.)

I'm coming at this from the perspective of the small AR so please bear with me. I've heard many times about bolts out running mags but have seen no hard data to support the claims. In the past, with the little ARs, the bolt overs have been solved by eliminating short stroking. Not saying this to disccredit your experience, far from it. Making this statement to let you know what my experience has been and that it's not been much with the Big Smith. I figured being the same basic system, the same basic troubleshooting was a good place to start. In fact, this is the first place I've heard of the M&P-10s having problems.

I'm not surprised to learn gas port diameters are varying. I know from first hand experience that hole diameters can vary with something as simple as a change in drill pressure. Sometimes the flutes will collapse with too much feed & speed, especially with reamers and the holes come out smaller. We also found out that reamers will open up their holes too big when they heat up due to stresses in the metal from cutting the flutes. When trying to eliminate hole quality problems at McDonnell-Douglas/Boeing, we made a few discoveries about bits and hole quality.

I'll search your posts and read them

 

[rojodiablo]

MistWolf; the rifles are... the same.

Or- in THEORY, they are the same!! But in reality, the 308 platform is not just a larger brother. It's a bit different.
Weak ammo can affect the 15 platform because their is a lot of interchangeability with buffers, springs, gas lengths. A rifle of mixed parts very well might run fine with strong ammo, yet malfunction on weaker ammo ruthlessly. Usually it's tied to a mismatch of parts; a mid length buffer on a rifle spring, or a carbine with a lighter BCG, and it is then sensitive to ammo. So many people, sub-contracted out parts supplied to manufacturers that things get mixed up easily. Weird thing is, many times, they will still work.

On the 308 platform, no 2 manufacturers are alike. Too many proprietary platforms, and it makes customizing more of a challenge in some ways. The problem is, with proprietary stuff, the spring, muzzle break, gas block that works perfectly well on brand A makes brand B act up and it suddenly will not function as well as brand A, or as it did before it was modified.

AR15's are much better in this respect. Spikes barrel on a Colt rifle with a DPMS trigger works just fine if that it how it gets set up.

 

[rojodiablo]

I'm not surprised to learn gas port diameters are varying. I know from first hand experience that hole diameters can vary with something as simple as a change in drill pressure. Sometimes the flutes will collapse with too much feed & speed, especially with reamers and the holes come out smaller. We also found out that reamers will open up their holes too big when they heat up due to stresses in the metal from cutting the flutes. When trying to eliminate hole quality problems at McDonnell-Douglas/Boeing, we made a few discoveries about bits and hole quality.
I'll search your posts and read them

You will be the first guy I call when I have the itch to make a titanium barrel........ (Never. EVER going to happen. Not by me. And I'll let you explain to the folks why a Ti barrel would not be an easy thing to create!!)

 

[copemech]

You will be the first guy I call when I have the itch to make a titanium barrel........ (Never. EVER going to happen. Not by me. And I'll let you explain to the folks why a Ti barrel would not be an easy thing to create!!)

There must be a good reason or it would be done by now!

I did speak with S&W tech rep today just to ask if there was anything new as far as updates or changes with these issues, he said no, but if it will not run after further testing with standard factory ammo and reinstall of flash hider, send it in!

Reviewing the muzz brake install in my head, I cannot quite get my head around a major change in dynamics here, as X pressures and Y lengths would be unchanged.

I did review some buffer options today, they all make great claims, and the weights seem all over the board to me, then you get into springs!

All this is fun and all that, but I shall not be spending tons on experimental combinations to find a working solution to cover a broad range of ammo. All within reason, cause cheap **** is still get what you pay for to a given extent. It may work fine in a bolt gun.

 

[MistWolf]

Not to step on the toes of the Red Devil, but I suggest returning everything back to stock and seeing how the rifle works with factory ammo. It doesn't have to be anything special, just ammo loaded to normal pressure. I'm pretty sure Winchester white box would be good to start. If you still have short stroking, then you know it's not ammo. You have to establish a baseline of performance to troubleshoot your problem.

The truth about any self loading rifle is that you have a narrower range of ammo that it will function with reliably than with a manually operated repeater.

Rojo, deep boring drilling is beyond me. We were just trying to figure out how to drill holes clean & round in the aluminum and aluminum & titanium stack up of the structure of the then new MD-11. One type of fastener required an interference fit and had to be driven in with a rivit gun. Hole tolerence was .185"-.187" and had to be drilled with a pneumatic hand drill

 

[copemech]

Okay, I can give hints and helps!
1. The rifle will ALWAYS jump off the sight picture, unless you weigh it down a metric ton or so. The AR recoils in BOTH directions, every shot. A kick back, followed by a slam forward. Much more noticeable on the 308 than the 223, especially with a carbine style rifle weighing in under 9lb.
We have a 24" barreled rifle (Tims', not mine) and it weighs in at a svelte 14.5lb. Barrel is 1" diameter, fore grip is extra heavy, the A2 stock has weight in it, and the bipod is very heavy for what it is. This one hardly moves when you shoot it. The gas block is adjustable, and the recoil spring was chosen for the softest one that would function the rifle. His wife likes to shoot it because it does not get 'upset' as she put it.

When the rifle is operating- it moves about 4 times as fast as you can humanly pull the trigger a second time. If the 308AR were a full auto rifle, it would easily cycle in the 400-500 rounds/ minute range without breaking a sweat. No human outruns the bullet, on either side of the bullet!!

Yes indeed, when the bolt is moving that fast, it can easily blow right past the magazine follower and not stop on the last round hold open. That is in fact a good indicator that the bolt is moving very fast, and more importantly, there is not enough DWELL TIME. Dwell time is where the bolt is basically stopped for a nanosecond at the peak of the recoil before it starts pushing forward.
Your gas block is set correctly..... the rifle was functioning well. That tells you the story. An easy way to see if the block is offset is to take an air nozzle and a cotton ball.
Open the rifle up.
Lightly oil the cotton ball and stuff it into the chamber.
Air nozzle goes onto the gas tube. Lightly blow air into the tube, no need to blast it. 5-10psi is plenty. Feel the air at the front of the barrel. If you have very, very little air? The gas block might be offset, or the gas port might have a blockage. If so...... crank the air up to 60 and see what you get. You will not hurt the rifle.
An easy way to tell if the gas block is leaking and letting out excessive pressure (venting) is to spray soapy water on the gas block while doing the air nozzle job with relatively low pressure. Should not see much in the way of bubbles, at 60psi. If the leakage is really bad, you will see powder dust all over the gas block and the port where the gas tube enters the gas block.
It should be noted that a little gas venting is not bad. The rifle will expand and seal things as the barrel gets heated up and the gas tube will seal with the pressures created from firing. 60psi is nothing compared to the pressure developed by the powder being burned in the chamber.

Rifle is clean, I believe you. Saying 'Filthy rifle' is only a reference point. People seem to like to shoot 10K rounds thru their rifle without cleaning..... just to prove it can get dirty. Some relish in dusting them out, or dropping them in mud, etc.

If the rifle performs well with the brake removed still, then the easy and cheap modification is to start by adding weight into the buffer tube and try the rifle with the brake installed. The buffer has weights inside it. Add some more weight, and keep track of what you have added, so you can always go right back to stock as a reference point.

Range update. So I took it out today with the factory Rem 150, Monarch 150, and Tul 150, later two being steel.

Gun ran ok, ran 3-4 rd groups, had last round lockback issues with both steel(cheap)rounds while Rem worked well, and a soft point it was. Made no difference switching between brake and stock flash hider.

Still pitches cases a long way, and I did notice a couple things today, as the brass ammo did have a couple sharp edge scratches on the neck from the ramps, but also a nick or sharp edge mark in the bottom apparently from the ejector hitting.
Not sure if this is any indication? As I think it is still a bit "on the edge" and perhaps the heavier buffer is the key?

Brakdown after revealed a 2.96oz buffer weight(say 3 oz). It rattles a bit so I decided to take it down to see what is in there or if weight could be added. Well, I had a time getting the plug out, found three steel weights with pads with no room to add more it seems. Possibly remove steel for lead it it were the correct size, or just fill with shot or something? Totally unsure here.

Did see brass mark on the ejection port hump today, yet no case dings, once again, not sure about indications here.

So as things go, gun is working, and now down for trigger work as well. That creep just creeps me out! We shall see if we can go from a long 5 to a short 3.0 or so!

 

[copemech]

Rojodiablo,

I have found and read a few of your comments on similar threads, and we kinda think alike it seems.

I have still seen no specific recommendations for the M&P from you.

So based upon what I have read, this 3.0 oz buffer would be like standard AR carbine issue, and an H or H2 buffer at 3.8 or 4.6 oz may be called for.

Having read some reports on the standard 223 gun, even them guys often say the H2 is the way to go, and as I have no tungsten nuggets in my pocket, I will likely have to buy something as I am totally out of depleted uranium at the moment.

Suggestions?

 

[rojodiablo]

Rojodiablo,

I have found and read a few of your comments on similar threads, and we kinda think alike it seems.

I have still seen no specific recommendations for the M&P from you.

So based upon what I have read, this 3.0 oz buffer would be like standard AR carbine issue, and an H or H2 buffer at 3.8 or 4.6 oz may be called for.

Having read some reports on the standard 223 gun, even them guys often say the H2 is the way to go, and as I have no tungsten nuggets in my pocket, I will likely have to buy something as I am totally out of depleted uranium at the moment.

Suggestions?

Trade the steel ball out for a round lead fishing weight of the same diameter. It's a little bit heavier, and often the difference can be less than a half ounce when the rifle is close to ideal. If they rattle, you can add cotton ball material to fill the voids. If you want a bit more weight, #8 or 9 shot from a shotgun shell and that makes a great buffer material that adds weight. I have found in general that adding around 1/4-3/8oz. tends to be the little bit that takes the speed down just enough.

On the brass dragging; A good little trick to see just where the brass is getting scratched is to do THIS:

Insert a round into the chamber with the bolt open, and directly on the side facing you right where the extractor will grab the brass, take a sharpie pen and put a mark on the brass.
This will tell you exactly how the brass sits, and by simply looking at the brass after firing, you will know what is scratching your brass, as well as see what if any mark is made by the extractor.
or, load a magazine with the rounds, and on each round put a mark which will be on top. The bullets do not rotate much at all when being fed into battery, and you can wail away on a mag and then investigate and compare brass.
This can be really helpful when you find one mfg. has an ammo which gives you a different looking scratch, or feeds a little different, etc.

If you feel the ammo is scratching from the feed, it's pretty easy to figure out: Load a mag, with the top round marked as described. Pull the charging handle back all the way, and let it fly closed.
Now, do not fire the gun, just extract it ssllowwly. This will keep you from scratching on the extraction.
If the brass comes out clean, then you might be scraping on the extraction and not the feed. Remember, the feed speed IS the same when you drop the charging handle if you are full back and you truly just let it go as when a round is fired.

Extraction...... there is no way we can extract a round quick enough to emulate the rifle functioning a firing cycle. So this is how you can find that particular difference.

If the round IS indeed scraping the brass on the feed ramp, then it's kind of a witch doctor thing to start playing with it. Anything you take off..... can not be put back on.
Polishing the feed ramps was a very common thing years ago before M4 feed ramps were the norm. I am impartial to rubberized wheels which polish and take very minimal material off. Second choice is cotton buff wheels and rubbing compound or black beauty polishing compound. Last choice ever is files and sand paper. On the old rifles, we used to use silica wheels and would real carefully polish the transition from aluminum to steel, and widen the bottoms of the feed ramps. (I'd get all anal-retentive and make them tapered and BS.... but the factory version we have today is just as good, if not even better.)
Feed ramps will smooth out and self polish..... after lots of cycles of ammo thru them.
A dremel and small cotton wheels and polishing compound/ automotive rubbing compound can make a ramp edge slick in a few seconds time. TREAD CAREFULLY. A little can be a LOT. A pinky finger feeling for a hanging edge should be enough to feel the difference. A TINY improvement in felt smoothness will translate into a MUCH better feed, similar to how a little elbow grease and love can transform a trigger in a matter of 5 seconds on each contact face.

But yeah, it can make a magazine which feeds so-so become a Lancer plated in gold, if that was a problem for the rifle.

 

[rojodiablo]

Rojo, deep boring drilling is beyond me. We were just trying to figure out how to drill holes clean & round in the aluminum and aluminum & titanium stack up of the structure of the then new MD-11. One type of fastener required an interference fit and had to be driven in with a rivit gun. Hole tolerence was .185"-.187" and had to be drilled with a pneumatic hand drill

You indeed hit the nail on the head. A machinist friend of mine makes a lot of car parts from Ti. I asked him if he could actually make a barrel out of Ti. He laughed at me, and told me to hand drill a chunk with a 1/4" bit a distance of 2". Welllll........ I hung that bit 4 out of 4 tries. In a drill press, I hung 2 out of 4 tries. The only Ti I had ever drilled previous was maybe 1/8" -1/4" thick. I had no idea how bad it grabbed on drill bits. He said a 20" barrel run would be one VERY complicated task, and the sheer cost of the experiment of getting it right would run several thousand in mistakes. (Maybe he tried it and was just letting me know how bad it was...??!!)

He then told me "If you want a really nice barrel, just buy one."

I would suppose your .02 tolerance was enough to make one or two of your crew VERY particular and VERY GOOD hole drillers!!

 

[apiccola]

Copemech, I have a spare 4.5ish oz carbine buffer I will mail to you to see if it works as a solution. If interested, shoot me a shipping address through private messenging.

 

[copemech]

Copemech, I have a spare 4.5ish oz carbine buffer I will mail to you to see if it works as a solution. If interested, shoot me a shipping address through private messenging.

Thanks for the offer, however in the past week or so and the absence of further comments from others here, I did order an H2 buffer which should be 4.5 ish to try. And if for some reason too much I can now swap out tungsten for steel to take it down to an H 3.8 or so.

In other AR threads I have read that the H2 does help with felt recoil(which I have a lot), so we shall see.

Rojo, thanks for the long reply. At least I am now fairly sure the gun will run as of the last tests using even the steel case 150. Last round lockback with it not withstanding.

I can live with the two scratches from sharp feed ramp edges on the necks, minnow and I would not condemn the cases as unusable because of it, however I hope they wear in.

It still kicks like a mule and spits brass like watermelon seeds, so all good. I did pick up another box of the cheap 145 Monarch just for testing again with heavy buffer.

In the eventuality of things I may need to settle things with some 168gr decent ammo, but that does not mean I do not want it to feed whatever I put into it within limits.

Thus far I have not impressed myself with accuracy, and even though I have not taken it beyond 50yds, the combo of cheap ammo and me flinching has been an issue. 1.5 - 2.0 or so groups, not great at that range. My 10/22 will beat that, but it is easier to shoot!

Trigger on its way, so hope to re-test soon!

Thanks all!

 

[apiccola]

Good luck sir. There are a good number of folks on the board watching and rooting for your solution.


AP


License to kill gophers by the government of the United Nations. Man, free to kill gophers at will. To kill, you must know your enemy, and in this case my enemy is a varmint. And a varmint will never quit - ever. They're like the Viet Cong - Varmint Cong. So you have to fall back on superior intelligence and superior ... M&P 10 ... firepower. And that's all she wrote. -- Carl Spackler

 

[rojodiablo]

Copemech, I am curious about your feeling that the 308AR has a lot of recoil. A couple questions:

Do you have/ shoot any other equal or heavier calibers; ie 30-06 or 7mm mag, etc?

Do you feel the rifle's recoil is bringing on a flinch due to a trigger issue- like say it's grabby, or feels sloppy, or it feels like you need to hit it with a truck to get the trigger to move?

And, does the recoil bother you due to the kick, or is it the rifle bucking back and forth from the bolt movement?

I ask because the 308 is a fairly mild round to shoot. And in a semi, the recoil is usually buffered a bit and lessened. The one difference I see is the bolt assembly and action; a shooter with even an ultralight SOCOM 308 will not feel the bolt's action upsets the shooting, while many feel the 308AR jolts around a lot. A lot more forward reaction from the bolt assembly.
You'd not be the first with that complaint; it's one of the things guys sometimes ask me to help eliminate. (About doubling the rifles' weight tends to do the job..... but kiss goodbye any thoughts of mobility once it starts weighing in at 12-14lb......) The new trigger might make you happier with the rifle and help tighten up your groups.

 

[copemech]

Copemech, I am curious about your feeling that the 308AR has a lot of recoil. A couple questions:

Do you have/ shoot any other equal or heavier calibers; ie 30-06 or 7mm mag, etc?

Do you feel the rifle's recoil is bringing on a flinch due to a trigger issue- like say it's grabby, or feels sloppy, or it feels like you need to hit it with a truck to get the trigger to move?

And, does the recoil bother you due to the kick, or is it the rifle bucking back and forth from the bolt movement?

I ask because the 308 is a fairly mild round to shoot. And in a semi, the recoil is usually buffered a bit and lessened. The one difference I see is the bolt assembly and action; a shooter with even an ultralight SOCOM 308 will not feel the bolt's action upsets the shooting, while many feel the 308AR jolts around a lot. A lot more forward reaction from the bolt assembly.
You'd not be the first with that complaint; it's one of the things guys sometimes ask me to help eliminate. (About doubling the rifles' weight tends to do the job..... but kiss goodbye any thoughts of mobility once it starts weighing in at 12-14lb......) The new trigger might make you happier with the rifle and help tighten up your groups.

Rojo,
It has been many years since I have shot .308 and -06 in bolt guns. I originally figured the 10 would be a bit more than my old 15, and dampened a bit by the action, but combo of the larger round and factory hard plastic stock took its toll! Better now with the padded stock, break, and a couple pounds worth of scope and bipod mounted! No bruise!

Friend at work just scoped his big DPMS and took it out last weekend. Said he found himself closing his eyes in anticipation of pain when pulling the long creepy trigger! I just laughed! And he is a big boy!

I bought the Smith because of its light weight and I am no pack mule! Everything is a tradeoff, seems I just need to figure out what it will do, and I still like to keep range ammo on the cheap side, but in the end if I can pound out 6" groups with this thing at around 300 yds, I will be happy and call that a dead hog!

I am spoiled with short sweet triggers so that will help. My test with/without the Tacticool break installed revealed little difference in recoil, I think it may be more a compensator by design, and am still looking at other recoil reduction options like the JP.

 

[rojodiablo]

AR recoil is definitely different than bolt rifle recoil.

I'm pretty used to heavy hitters, so I don't even notice the 308AR, other than it will always bug me that the rifle wants to kick forward as well as backwards............

 

[Lief]

I have had my M&P-10 a couple of months and I did not really like the recoil either.
I bought the THE MAKO GROUP - AR15/M16 RECOIL REDUCING STOCK from Brownells and love it. it was a little stiff at first but has softened up nicely and I can shoot all day with no issue.
I also added the JP silent spring buffer. Be sure to get the one for .308 as the AR-15 one says it works for some AR-10 but it does not. You will need to add a piece of the included spacer material but it is easy to cut with a tubing cutter.
Another thing I did was swap the stock compensator (which worked pretty well in my opinion) for a Battlecomp which is amazingly effective at reducing muzzle rise. I don't think it did anything for the recoil but I couldn't swear to it.
I changed the hand guard for the 9" magpul. This requires the tool for compressing the delta ring (you cannot do it without it) but it went on with no filing, cutting or alteration. I did need to use a plastic hammer to encourage it initially but have since taken it off and put it back on and it went much easier. (Tip; put the rail sections on before you install the hand guard.. DOH).
I have run mil-surp, LAX reloads, GGG, and berdan primed 7.62 through the gun and it loves it all.
I really like this gun.

 

[Sonny Gunny]

Lief,

Congrats, followed your path as well to reduce recoil, follow-up shots were terrible in stock, but after the Battelcomp (it even reduced sound at least to the shooter), heavier handguard, and yet to test the JP captured spring and Magpul UBR.. the Beast is tamed. I had the MAKO stock but frankly did not notice any reduction in recoil and the thing rattled so I was not really impressed, please post pics.

 

[apiccola]

When I put the PRS stock on my M&P10, I also picked up a Zel Custom Tactilite buttstock pad adapter which uses a Pachmayr Premium Large Field Pad. Although the adapter and pad set is very heavy (which isn't a bad thing unless you're toting the rifle several miles on a sling), it adds a surprising level of ergonomics and comfort in shooting the rifle. I have bad arthritis in my shoulders, and after 200 consecutive shots through the rifle within an hour, my shoulder felt like I had been shooting a BB gun the whole hour.

 

[Lief]

Pics as requested, Sonny Gunny.

I forgot about the MOE grip and the 2-7 Redfield in my description. I had that M-223 mount from a previous rifle and it is working very well for me here.

I hadn't really noticed that the Mako rattled and in fact mine rattles less than the stock adjustable. Mine does work as advertised though.

 

[Sonny Gunny]

Lief,

Nice one, I see you live in Commiefornia‎... bullet button bull