I wanted to post a question to see if anyone else has experienced this issue. Let me first say that I don't believe the issue with with the rifle as I think it's the ammo.

I have notice a few times that I will get a weak round (Federal bulk pack) and my bolt will not lock open on the last round. The reason I noticed it on the last round is that I have a range that is great for sighting in, but it only allows one round at a time in semi auto's.

Has anyone else experienced this with this ammo?

One round at a time in semi autos? That's no fun at all...

Could be the rifle is short stroking slightly, meaning the bolt isn't coming back far enough to catch. Could also be a problem with the bolt latch or magazines. Make sure the rifle is clean, check to make sure the bolt catch can move freely, and make sure your magazine springs have good tension and present the follower up sharply after they are compressed and let go.

A weak round could also cause this if everything else is fine in the firearm. Do you get the issue with any other ammo? Fed bulk pack is usually pretty good from all reports.

Hi,

So I am about 99.99% sure it's the ammo. I can tell when it happens because the shot seems to be under powered and I get a little smoke that comes out. All in all the Federal is great for the price, I just notice this every now and then.

I have not had this issue with CCI min mags, but I think they have a little more kick to them.

This issue has been discussed here Last shot hold open pretty well. Try the fix and let us know how it works for you.

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Go to page 3 (last shot hold open) and do tacticool22 fix, very simple to do. It fixed mine, I love shooting this gun when every feature works !!!!!

Dunno, sounds like a problem with the range. I think these guns thrive on repete shooshting. My range won't allow rapid fire, but I'm going to one this week that does...so happy. I've noticed that "dead" feeling on the Fedrial ammo as well, every once in a while it just kinda puffs the shot out, it is very noticable when your pluckin thru 25 rounds at a time. That has got to take a long time to finish off 550 rounds one at a time.

It could be the magazine. I had one that randomly did not hold open with cci. I rotated the spring and it has been perfect since.

Just a re-post of my theory.
I think the bolt hold open feature has more to do with the high spring tension of the bolt catch spring and low spring tension of the magazine.
Here's my theory.
When the bolt goes all the way back, there is a limited amount of time for the bolt catch to pop up in front of the bolt. If there is too much spring pressure for the magazine spring to overcome then it takes too long for the bolt catch action to work. When you pull the charging handle back the mechanism works, because of the huge amount of time. You can't pull the charging handle and release it as fast as a gun can.
You would think the lower powered ammo would allow more time for everything to work, as the bolt would be traveling slower. But more force back means the recoil spring has to work harder overcoming that force equaling more time.
Try the spring mod (remove 1 1/2 coils) and the cheap ammo and let us know how it works.
Plus, there seems to be 4 things that prevent the bolt from staying back after the last round.
1) Holding the mag well and your hand touching the bolt release.
2) Holding the magazine.
3) Using the magazine as a rest.
4) Lots of grit in the bolt catch area.
So I guess we need to not touch the magazine area at all and everything should be fine.

Attached Images

	Clipped Bolt Hold Spring 1.jpg (38.9 KB, 141 views)
	Clipped Bolt Hold Spring 2.jpg (49.4 KB, 151 views)

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My bolt has stayed open after the last shot since I did Tacticool22 mod. I am up to 4000 rds since I did the mod. My 15-22 has run flawlessly, I am so pleased with this gun.

Sounds like you need a new range.

I have noticed the issue you describe on my 15-22. I never thought of it as a problem until you mentioned it here. Once in a while if I have a single bullet left over, I'll just pop it in the chamber and fire it. I noticed that the bolt doesn't lock open after such shots. I never gave it much thought.

I have an M&P 15-22 that is about a year old. I usually shoot it with an AAC Element. Ammunition is always CCI Subsonic. My version has the Magpul furniture.

I have only experienced feed problems when the rifle has seen a lot of range time without being cleaned. Other than that, it runs like a gem with no remarkable issues.

After cleaning the gun post the last range session, I noticed that the bolt would slam shut if I pulled out the stock to the full length position hard. Apparently the backward jolt of the stock disengaged the bolt from the stop long enough to allow the stop to lower and the bolt to move forward.

I sent it to S&W for repair and it was returned with the same issue.

Anyone experienced this anomaly? Any ideas on how I might address a fix?

Thanks for any help.

Don't open the stock so forcefully.
You can close the bolt on a 15-22 and the M&P15 by bumping the butt against the floor or hitting it with your palm.
With an empty mag in, it should never close accidentally, only when you press the bolt release.

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Thank you very much for the information. I feel more comfortable knowing it is just the nature of the system and not a problem. The hold open with an empty mag is solid.

I also had this happen after over 2,000 rounds thru the rifle. I cut my spring (one and a half cirlces) and it solved the issue. I had this issue with all three of the magazines I use. That for your help.
Mike Bauer
Harry Five Pins w Lay Down - YouTube