M&P 45 last round in mag FTF

[mtnsmithguy]

The first time I shot my new M&P .45 full size it Failed to Feed the last round in the mag, a factory Federal Hi Shok JHP. It occurred a couple of more times in the 5 mags I shot that day. I chalked it up to needing break-in. About 200 rounds later, today, it FTF the last round in 2 mags out of 5. My magazines have the black follower. Both mags that came with the pistol do it. It handles RN ball ammo fine.

Does it seem like a weak spring or bad follower? It only happens on the last round in the mag, others feed, chamber, fire, eject fine. Any similar experiences?

For now I'll keep a FMJ RN as number 10.

 

[Fastbolt]

Did you clean the magazines before using them? I've had to remove some heavy oil & sometimes a thickened brown goo from new mags.

Last round feeding issues can sometimes be caused by weakened springs, or dirty mags which allow dirt & fouling to create drag in the mag body when the spring tension is at its weakest (about the last round or two).

Of course, depending on what you mean by failure-to-feed, it might also be influenced by a dirty chamber.

An occasional ammunition related issue isn't impossible, either. By Hi-Shok, I take it you mean the low cost 'Classic' line? I actually had a box of another brand's budget LE line in .40 S&W which contained two rounds with improperly trimmed cases. Both were just barely too long to permit the rounds to completely chamber in my duty gun when I was shooting for practice one day. What were the odds?

Naturally, it's also possible that what I like to call a grip-stability issue ... (what other folks like to call 'limp wristing') ... can result in feeding issues. While it can happen when some folks shoot metal-framed pistols, it's more commonly reported being observed when folks are shooting lighter weight plastic-framed guns. I've seen my fair share of it while working with folks. I remember one time when a couple of smaller statured folks were taking turns shooting & evaluating a G21 with factory 230gr JHP loads. One of them was able to get the G21 to repeatedly have the same feeding problem, shooting ammunition out of the same case as the other person, while the other person had no problems whatsoever. Nobody else, including me, experienced that issue when shooting that gun with that ammunition that day.

The current M&P 45 mag springs have purple paint on the upper coils, replacing the earlier ones with orange paint. I believe there may also have been a revision to the .45 follower (I can't remember from an earlier parts order).

My earlier M&P 45 10-round mags (orange spring paint) all worked fine with an assortment of different hollow point loads, although I did have one spring which took on a bizarre bend for some unknown reason. I didn't notice it for any functioning problem, but discovered it when I removed it from the mag for normal cleaning and saw that it was oddly bent at one coil at an acute angle. Weird.

Dunno what happened in your case, and it's not really possible to diagnose gun, ammo or shooter problems via the internet. S&W is going to be closing for the holidays (Wed or Thurs this week?) until the first week in Jan, I think? Can't remember. You might call them tomorrow and ask them what they think.

 

[M29since14]

I have this same problem, but since I shoot mostly handloads, I have a hard time diagnosing. My gun does seem to feed 100% with either JRN or LRN ammo, whether factory or my handloads. A little disappointing.

I have a couple of the newer M&P45 mags that are a dull gray, rather than black finish, but I have not had time to test them. Anyone care to comment about the differences in the magazines: old/black finish vs. newer/gray finish?

I would like to hear more about this from others.

 

[Fastbolt]

The newer gray finish (contains Teflon) was the result of complaints by users that the original blued mag bodies could rust. (Remember when we carried blued revolvers and pistols and used blued mags in Colt Government Models?)

 

[Dan Cash]

mtmsmith,
You don't fully describe the FTF. Does the slide over ride the last cartridge or is the round getting partially out of the mag before the slide over rides it?

I have had similar problems with alloy framed 1911 pistols combined with magazines designed for wad cutter bullets (read all current non mil spec magazines except for Wilson). On these magazines, the lips are cut back to allow the cartridge to angle up sooner than the magazines of orriginal design. Recoil allows the last and even the next to last round to move forward in the magazine and stand up as the slide moves rearward. The cartridge is then positioned so that the slide over rides the rim partially or fully and the gun hangs up.

I suspect that this is what is happening with your Smith. Since you can't use a "mil spec" magazine in your gun, Try a longer bullet. You have noted that ball ammo does not cause the problem. If you hand load and your bullet/chamber combination will permit, try seating the bullet out a bit and see if the problem persists. New spprings and clean magazines will help but I think the fault lies in the magazine lip profile combined with the type of bullet you are using. If the gun does not fail with ball ammo, use ball ammo. I guarantee you it will get the job done.

 

[mtnsmithguy]

mtmsmith,
You don't fully describe the FTF. Does the slide over ride the last cartridge or is the round getting partially out of the mag before the slide over rides it?

What happens is that the round takes a sharp climb upward and seems to get stuck just inside the chamber. It comes out of the magazine fully. The slide then jams against the round with about 2/3 of the round showing from the top.

Doubt if its limpwristing. I shot my old Colt 1911 .45 (which fed the JHPs fine) and a Glock 36 .45 during this session, both fed the same rounds fine. Another thing that doesn't seem right with the M&P is when I put 10 rounds in the mag, it won't go into the pistol, without a lot of force, then you can't pull the slide back. Soooo, I have 8 JHPs and the last one, a FMJ RN in the mag for now. I'll call Smith after the holidays for their ideas. Thanks for your responses.

 

[Fastbolt]

What happens is that the round takes a sharp climb upward and seems to get stuck just inside the chamber. It comes out of the magazine fully. The slide then jams against the round with about 2/3 of the round showing from the top.

Doubt if its limpwristing. I shot my old Colt 1911 .45 (which fed the JHPs fine) and a Glock 36 .45 during this session, both fed the same rounds fine. Another thing that doesn't seem right with the M&P is when I put 10 rounds in the mag, it won't go into the pistol, without a lot of force, then you can't pull the slide back. Soooo, I have 8 JHPs and the last one, a FMJ RN in the mag for now. I'll call Smith after the holidays for their ideas. Thanks for your responses.

BTW, I can barely get the 10th round in a brand new 10-rd M&P 45 mag, and when I do it still takes some real effort to get the full mag securely seated. A bit of a smart whack with the palm of my hand. Retracting the slide when it's closed, and tension is being exerted on it by a full mag, with a new spring, is going to be less easy than later on as the spring relaxes a bit.

Repeated loading and shooting over a few range sessions generally allows the springs to relax enough for me to load the 10th round reasonably easily, as well as for easier insertion/seating in the mag well when the slide is still forward in battery (think tac load). That being the case, however, when using a brand new mag I usually load my M&P 45 with the slide locked back so the mag goes into the mag well without effort, and then I release the slide stop lever (or retract & briskly release the slide, depending) to load/chamber a round.

That's just me, though.

It's even harder with some Glock models when the mag springs are new, but that's probably due to the angle used in the front of their stripper rails, which can make retracting the slide on a full mag load even harder until the springs relax a bit and don't resist the rail's front end pushing downward on the full mag load quite as much.

 

[Matt Dillon]

The first time I shot my new M&P .45 full size it Failed to Feed the last round in the mag, a factory Federal Hi Shok JHP....... It handles RN ball ammo fine.

mtnsmith, could the bullet tips be dragging on the feed ramp
(because of a slightly different angle on the last round)?

If the pistol has machining marks going across the feed ramp, maybe it would help to smooth them out with sandpaper or emory cloth...?

I polished out the ramp on a Colt recently, and it was
amazing how much smoother it fed the ammo.

 

[sipowicz]

I had this problem with my P7 using 147 grain rounds....an expert on P7's over at HK seemed to have the solution...not sure how much of it is relevant here (gas piston tolerances and all that) but I thought I would share as it's good to have as much info as possible...

Any last round or 2nd last round "nosing up" (live projectile pointing out of the ejection port) is classic overfunction. My bet is that your piston/cylinder tolerance is on the loose side (excessive) reducing the amount of gas system "braking". That causes the slide to strike the frame harder (due to increased slide velocity) upon full recoil which dislodges the last round forward from the magazine versus a controlled feed into the chamber. When the slide finally catches up to the back of the round not fully under the feed lips the round jumps out from under the lips and most often is caught in the ejection port by the slide. I have reported on this before here. It is caused by over function, gas system tolerance (due to wear), short mag lips on old-style P7 magazines and often a weak/worn mag spring - or sometimes a combo of all. The easiest fix is to switch ammo from that hot +P+ round that that is not a true fix as the gun should run fine with it. Get some new or stronger mag springs as mentioned. Gauging the gas piston should be done at HK which means sending it in to Repair.

 

[Spotteddog]

All of that was a beautifully constructed and an accurate treatise on a gas operated gun. I'll be saving it due to it's high level of informational value! Thanks Sip!
But the M&P's a recoil operated gun you'd say?
Which naturally would make someone believe that the info had little or no bearing on the recoil operated M&P? Au Contraire mon amie!
Slide velocity, magazine spring pre-load, and time in cycle (especially at the end of travel/frame contact point) apply to all auto loaders. Regardless of the operating system used.
Once again, always a pleasure reading anything the gent writes!

 

[Matt Dillon]

But would this theory (of inertia loosening the round
in the magazine) explain why ball ammo will feed but
hollow points will not....?

Mntsmith, examine the chamber area with a magnifying
glass, looking for brass residue in one particular spot.
That might give a clue as to where the problem lies.....

 

[mtnsmithguy]

Hey guys, good info posted. Update to today, Dec. 24th. My wife and I went to our shooting spot and I brought new Federal Hi Shok, 230 grn, JHP, and 185 grn ball ammo (new but bought from a dealer that packages their own from bulk, a very reputable ammo distributor in GA). I also stripped and cleaned the magazine. It jammed the other day with the other mag.

I loaded the first mag with 6 JHPs, no problem. Second mag with the JHPs, the last one jammed. I looked at it closely, wish I brought a camera, but the round's nose was up and at a slight angle to the right side, and jammed the slide into the rear of the case, with the head of the case below the firing pin.

Next mag, I loaded 5 JHPS and the last a FMJ RN. That last round jammed also, which surprised me since I thought it would feed them okay. So, after two jams out of three mags, I quit, resigned to call LSG Monday. Then I took out my AR-15 .223 and had a jam free blast! At least the day wasn't a total loss.

Almost forgot: From looking at the position of the slide/firing pin area and the cartridge, it looks like the round started to come out of the mag but went up and right, instead of up and straight into the chamber. Then the slide continued like it should, pressing up against the crooked round. Just to note, the gun was field stripped and thoroughly cleaned before going to shoot, and only the last round in the mag causes a problem.

 

[Fastbolt]

It's often helpful to begin diagnosing a suspected pistol problem by eliminating any potential contributing (or causal) factors ... like ammunition.

Personally, as an armorer I wouldn't ever try to trouble-shoot a pistol using anything other than new ammunition made by one of the major manufacturers. By that I mean I wouldn't rely on using re-manufactured, or even 'new manufactured', ammunition from a company that wasn't one of the big names.

Ammunition component consistency and power level variations can sometimes be an influence in functioning 'problems'.

Even the lesser cost/budget offerings from the major makers may sometimes contribute to what might sometimes be charitably called 'less consistent feeding & functioning' than their more expensive offerings.

Sometimes you only get what you pay for, you know.