After shot bolt cycle stiffness

[Freethinker]

I have been experiencing an issue with my MPA Matrix Pro 6GT towards the end of matches. The bolt becomes more difficult to cycle towards the later stages, after I have put 75-80 rounds through it. It is difficult to even raise the bolt to cycle it. I'm not sure if this is chamber pressure, expansion of the bolt from heat or something else. I have tried putting some grease on the bolt contact points, but has not helped. I am running factory Hornady ELD-M 109. MV is 2953fps. Bolt is an Impact 737. Primers and cases don't look abnormal after shot. Any ideas or confirmation of what I've already listed? Thanks

 

[Supersubes]

Show detailed pictures of your case heads. More than likely just too much pressure in a dirty hot barrel.

 

[spife7980]

What do you do to it that’s different from the end of that match to the beginning of the next where it’s not difficult?

Is it difficult if you start in the afternoon vs all day extending into the afternoon?

 

[FisherT&C]

Could be a lot of powder that burns dirty.
Are you using a suppressor?
Does the problem go away after cleaning?

 

[Freethinker]

What do you do to it that’s different from the end of that match to the beginning of the next where it’s not difficult?

Is it difficult if you start in the afternoon vs all day extending into the afternoon?

It is difficult after I have been shooting several stages. By the time I get to stage 7 out of 10 it is difficult to cycle.

 

[Freethinker]

Could be a lot of powder that burns dirty.
Are you using a suppressor?
Does the problem go away after cleaning?

No suppressor and cleaning doesn't make a difference. It's factory Hornady ammo. I've shot different lots and same result.

 

[spife7980]

It is difficult after I have been shooting several stages. By the time I get to stage 7 out of 10 it is difficult to cycle.

Yeah… you’ve said that. I’ll repeat the questions.
It’s not at the start of the next days shooting?
And if you start in the afternoon when it’s hot vs in the morning when it is not.
Ie is it air temp or barrel temp related? What changes between when it’s difficult va when it becomes not difficult.

 

[Freethinker]

Yeah… you’ve said that. I’ll repeat the questions.
It’s not at the start of the next days shooting?
And if you start in the afternoon when it’s hot vs in the morning when it is not.
Ie is it air temp or barrel temp related? What changes between when it’s difficult va when it becomes not difficult.

Not at start of shooting, ever. I can start when it's hot and not have any issues until later into the match, it just might happen sooner, I don't recall that detail to say for sure. I don't think it's barrel temp related. I have a temp gauge sticker on the barrel and it doesn't get blistering hot. I'm sure it does get a bit hotter when the air temp has climbed from 75 in the morning to 95 in the afternoon like it does in middle Georgia this time of year. However, I do remember it doing this after I got the rifle in March when it was still pretty cool air temps. I was taking it to the range to test and sight it in and noticed it was hard to cycle after putting 40-50 rounds through it.

 

[spife7980]

And cleaning doesn’t affect it… You’ve got a metallurgical marvel lol

If you lube the bolt up after stage 6?
What lube do you use? Heat changes it’s behavior for some.

Do you notice that your cases are tacky feeling? Sometimes fouling and humidity mix poorly.

 

[FisherT&C]

Well, what a bummer.
Check for galling on the bolt lugs and the cocking ramp on the bolt body. Also remove the firing pin assembly and see if there is any indication the mainspring is binding in the bolt body. Those three things can affect opening the bolt.