Short cycling resolved

[MistWolf]

Steel cased ammo is loaded to lower pressure because it's steel cased. If loaded to full pressure, the cases would stick in the chamber. Try the rifle with good commercial ammo.

The gas block may be misaligned. Most gas blocks are made to align to the gas port With the hand guard cap in place. If the block is pushed back against the shoulder, the port will be partially blocked

 

[copemech]

Hahaha....why do you think I took it to my friend with the tools and the workshop.

I'll try some other ammo and see what that does.

As for another question about the ejection pattern and if it locks back. With the open day it was too busy to really look at ejection patterns and it doesn't consistently lock back after the last shot.

As for how it worked with the factory setup. I never shot it in factory configuration. Yes, in hind sight that was a bad idea but time wasn't on my side. We needed the rifle Saturday.

I'll have to go to the gun shop and see what 308 ammo they have in stock. At the moment I have 1050 of the Norinco ammo and 200 rounds of PMC ammo. Would the PMC ammo be considered good ammo to test the rifle with?

The fact it did not lock back is another sign of weak gas due to low pressure rounds. Not really sure the PMC would be better, possibly so, but the stock gun is gassed for US ammo like Rem, Fed or Win, 150 gr or better, pref 168 gr, as they do not seem to like the 150 for accuracy.

It seems to me that most gas blocks will accept the slight offset of the removal of the front plate, due to the fact that the hole in the block is larger than the gas port in the barrel. Add the fact the hole is many times chamfered a bit. But to align one really nice, one would need a dimpling jig to dimple the set screw opposite the port and lock it in to position. This puts the block back about .030-.035 or so as I recall from the machined step on the barrel. No guesswork!

 

[yqtszhj]

Hahaha....why do you think I took it to my friend with the tools and the workshop.

I'll try some other ammo and see what that does.

As for another question about the ejection pattern and if it locks back. With the open day it was too busy to really look at ejection patterns and it doesn't consistently lock back after the last shot.

As for how it worked with the factory setup. I never shot it in factory configuration. Yes, in hind sight that was a bad idea but time wasn't on my side. We needed the rifle Saturday.

I'll have to go to the gun shop and see what 308 ammo they have in stock. At the moment I have 1050 of the Norinco ammo and 200 rounds of PMC ammo. Would the PMC ammo be considered good ammo to test the rifle with?

PMC worked ok in mine. It didn't group that well (about 2 1/2 in. groups) but no malfunctions in the one box I shot. ZQ1 malfunctions at least once per box, it short cycles.

Like Cope said try some Federal if you can find it.

 

[Tbat]

My MP10 is in stock form and has ran ZQ1 ammo reliably so far.

I guess I jinxed myself. I can no longer say that ZQ1 has been trouble free in my MP10. I had about 10 rounds of it today that were not powerful enough to send the bolt carrier back far enough to either pick up the next round, or even lock the bolt back on an empty mag. I tried different mags just to eliminate the possibility of a defective Pmag.

So I stand corrected, now ZQ1 is the only ammo that I have tried so far that has given me issues with the MP10. Looks like I will be sticking with Federal, Remington, Hornady, PMC, Monarch and Perfecta.

 

[yqtszhj]

I guess I jinxed myself. I can no longer say that ZQ1 has been trouble free in my MP10. I had about 10 rounds of it today that were not powerful enough to send the bolt carrier back far enough to either pick up the next round, or even lock the bolt back on an empty mag. I tried different mags just to eliminate the possibility of a defective Pmag.

So I stand corrected, now ZQ1 is the only ammo that I have tried so far that has given me issues with the MP10. Looks like I will be sticking with Federal, Remington, Hornady, PMC, Monarch and Perfecta.

Sorry man, didn't mean to do that to you. It's still good party ammo when you have visiting shooters that don't know the difference anyway.

 

[Tbat]

Sorry man, didn't mean to do that to you. It's still good party ammo when you have visiting shooters that don't know the difference anyway.

LOL, true! It will slow them down and keep them from shooting up the good stuff.

 

[copemech]

Although my gun does seem to run cheap **** fine now with the minor gas port mod(Tula steel, Wolf steel, and the others) the accuracy of the ZQI was **** as well.

Seems I was getting 6-7 inch groups with it, the others a bit better, and the latest M80 us made mil surp seemed to run about 3in. All 150 gr ammo.

With the 168 gr stuff I have tried thus far, down to about two in. or better running the Amax or the Sierra HP or OTM match bullet.

Best thus far has been with the Australian Outback 165 gr soft point at around 1.5 which is a Hornady bullet I think.

I am now looking to refine a bit with some handloads to see how that works out.

 

[potentpoefie]

Hmmm....thing is in SA good old Federal etc. is not always available and if it is, it's at a premium price.

I've not had a chance to go shoot the rifle this week as I planned to do but this coming weekend is a 3 day weekend so I'm sure I'll have a gap to go shoot it with some other ammo. Also got some good tips to try out and make sure the gas block is aligned properly from another forum.

I'll just be happy when this rifle is functioning like its little brother. I've been more than happy with my M&P15. So I'm sure we'll get this sorted out.

If it's just the ammo I'll have to start handloading in bulk then. 3GN eats a lot of ammo.

I was looking at running 168 grainers or heavier seeing this rifle has a 1 in 10" twist rate. Should do fine with heavier bullets.

I've not shot the rifle for groups yet but at our club's open day this past weekend it hit all the steel I could put the sights on and steel and I have a hate hate relationship.

 

[yqtszhj]

Although my gun does seem to run cheap **** fine now with the minor gas port mod(Tula steel, Wolf steel, and the others) the accuracy of the ZQI was **** as well.

Seems I was getting 6-7 inch groups with it, the others a bit better, and the latest M80 us made mil surp seemed to run about 3in. All 150 gr ammo.

With the 168 gr stuff I have tried thus far, down to about two in. or better running the Amax or the Sierra HP or OTM match bullet.

Best thus far has been with the Australian Outback 165 gr soft point at around 1.5 which is a Hornady bullet I think.

I am now looking to refine a bit with some handloads to see how that works out.

I agree 100% on ZQ1. Also 100% on the 165gr. Australian Outback. This pic is of shots playing around with different types of ammo. I pulled one of the shots at 50 yds. and called it when I pulled the trigger. The 100 yard group was what the Outback 165gr. will do in mine. I bought a bunch of it when I saw how it shoots.

 

[copemech]

I wish I had the charts and graphs to post to you so you could make more sense out of this, but I do not.

Long story short, the 7.62 and some lesser .308 rounds may not cycle correctly in the gun due to fast burning powders.

The MP10 gas port is set for US hunting ammo with slower burn and higher pressure at the gas port for a full push in a long rifle(bolt gun). At .068 in.

By the time the bullet has travelled past the gas port, the quick powders have lost their pressure level, requiring more gas at the lower pressure to work the action because it is highly restricted.

In my tests, and where mine is still, the change in gas port size from .068 to .073 has thus far allowed proper cycling with all ammo I have tried or had problems with. I have since been recommended the .075 size for somewhat ultimate reliability by other pros in the field. I know I am close.

Excess gas can cause unnecessary harshness in the cycling operation, but that is where adjustable gas blocks come in. My little DPMS AR carbine was this way, eat anything but harsh!

Really, it is a 10 min. fix on the 10! Pull handguard, remove gas block, enlarge port using #49 drill to go .073. Use quality drill and it goes like butter!

The jump to .075 requires a 1.9mm drill, and I do not have one on hand, but a quick lookup online indicates they are a whopping two bucks or so!

Put a stop on it so you don't nick the other side of the rifling. Then reassemble, blow out the barrel and swab it.. Done.

Accuracy loads, that is another issue! 150 gr seems out of the picture at this point. I am wondering about 175's but have no feedback at this time. Bet reports have been in 165-168 range thus far.

 

[Drag]

Hey copemech -

Thanks for that. Is there a method to remove the possible burr in the bore from the drilling operation? An additional challenge I have is that I used Rocksett for the set screws on my low profile gas block. Uggh.

Anyway, I may have an opportunity to go to the range this week and will try some 168 and 175 grain 308 win match ammo.

 

[copemech]

Hey copemech -

Thanks for that. Is there a method to remove the possible burr in the bore from the drilling operation? An additional challenge I have is that I used Rocksett for the set screws on my low profile gas block. Uggh.

Anyway, I may have an opportunity to go to the range this week and will try some 168 and 175 grain 308 win match ammo.

Obviously one would want to blow out the bore and run a patch or boresnake through it before fireing, but that is all that is necessary.

With red locktite or similar products, heat is the answer. Typically up to around 250F, which may require a small torch if things don't move. Heat is your friend here and I doubt there is anything you will damage with a propane torch.


I have no reports on 175, but would like some! I am handloading some 168 Amax at the moment, trying the 175 range could happen later, wish we had others input here.

 

[MistWolf]

Soak Rockset in water to soften it

 

[Drag]

Here's my latest range report with my M&P10. I had reinserted the spacer as wisely advised. My experience is that my rifle simply just doesnt like 147/149gr 7.62NATO. I tried Federal, ZQI, Winchester, as well as mil surplus ball - all no go. It just short cycles which parallels others' experiences. However, it clearly loves the heavier PPU 168gr Match! That stuff is definitely hotter and the rifle cycled through 40 rounds with no hiccups. So I'm sticking with 168gr 308Win if not heavier for now, which is what I should be shooting anyway with the rifle's 1:10 5R barrel.

 

[yqtszhj]

I like your setup. What kind of group could you get using PPU?

 

[potentpoefie]

Hmmm....thing is in SA good old Federal etc. is not always available and if it is, it's at a premium price.

I've not had a chance to go shoot the rifle this week as I planned to do but this coming weekend is a 3 day weekend so I'm sure I'll have a gap to go shoot it with some other ammo. Also got some good tips to try out and make sure the gas block is aligned properly from another forum.

I'll just be happy when this rifle is functioning like its little brother. I've been more than happy with my M&P15. So I'm sure we'll get this sorted out.

If it's just the ammo I'll have to start handloading in bulk then. 3GN eats a lot of ammo.

I was looking at running 168 grainers or heavier seeing this rifle has a 1 in 10" twist rate. Should do fine with heavier bullets.

I've not shot the rifle for groups yet but at our club's open day this past weekend it hit all the steel I could put the sights on and steel and I have a hate hate relationship.

Update:

The rifle has not been touched since it last gave issues. That includes no lube, no cleaning.
I got to the range with some PMC Bulk Ammo. Loaded up the first mag. Shot it slowly and no issues.

Wondering if maybe some people "limp wristed" (or whatever you will call it for a rifle) I gave it to my friend to shoot. This would be his second time shooting a firearm and figured if a noob error would be induced he would be the man for the job. Functioned just fine.

Then I ran the gun fast and hard. Still no issues. The PMC bulk ammo isn't exactly top quality ammo but it still worked. So conclusion is that the fault was definitely ammo related. So the M&P 10 issue needing to be run in for a couple of hundred rounds with full power loads seems to have been my issue.

Now that that is sorted out I figure I have enough PMC ammo left to just run our first ever 3 Gun Nation South Africa nationals with Heavy Optics division (only because I don't feel like putting down my Versamax for a 870). Happiness is a functioning gun.

P.S. Of course the guy that worked on the gun originally was on hand and ready with an "I told you so". He was always sure he did a good job on the alignment. For him it was a matter of pride.

 

[Drag]

I like your setup. What kind of group could you get using PPU?

Too early to tell. I was really more focused on function than outright accuracy this past time out. At my next session, I will shoot for groups. Im just heavily relieved to have observed that the rifle works as intended.

 

[copemech]

Too early to tell. I was really more focused on function than outright accuracy this past time out. At my next session, I will shoot for groups. Im just heavily relieved to have observed that the rifle works as intended.

Just a note for your consideration, Freedom Munitions sells reman using the premium 168 Hornady A-max bullet for aroun $17 a box as I recall.

Works well and free shipping for first time buyers.

Shipping is slow, but!

 

[Rjin316]

Want to add my own experience....my rifle short stroked like crazy. I first shot maybe 50 rounds completely stock to check function and it short stroked maybe 5 times with 145 gr ppu. Didnt short stroke with ppu 168 gr bthp. I thought it was just break-in, so i called it good and installed luth-ar stock with dpms rifle length buffer tube and s&w supplied spacer. Shot over 250 rds after install and it was short stroking pretty much everything i put in it. Some ammo will short stroke more than others it seems. It short stroked a lot with 145 gr ppu which i thought was normal during break-in, but it would still short stroke occasionally with black hills 168 and federal 168, even after 200 rds shot. After i cleaned and re-lubed, i took it out again with freedom 168gr a-max and bthp and it started off short stroking every 5 rds or so but it got progressively worse as the bcg soaked that lube up. When i got to the a-max rds, it literally short stroked every round. Also i can hear and feel the bcg cycling when shooting as it was slightly delayed. Also, i always thought the action on this gun was pretty stiff since day one, but it was somewhat noticeably stiffer when i went with the rifle length stock. So obviously i was pretty frustrated that after 300 plus rds, it was still short stroking. So i decided to remove the spacer to see what would happen. INSTANT FIX. None of the rds including the 145gr ppu were short stroking. I didnt feel the bcg cycling slightly after the round goes off like before, but now it feels like the gun is firing and cycling at the same time. Charging the gun doesnt take much effort as it used to. It still takes a little more effort than a standard ar15, but it doesnt feel like i need to work out to charge the gun anymore.
Im gonna call sw to see what the deal is here...

Recap:
Installed spacer for rifle length stock, still short stroking after 300 plus rds of all types, i could feel and hear the bcg being slightly delayed after round goes off, removed spacer and gun functions perfectly. Who knew....

 

[copemech]

Want to add my own experience....my rifle short stroked like crazy. I first shot maybe 50 rounds completely stock to check function and it short stroked maybe 5 times with 145 gr ppu. Didnt short stroke with ppu 168 gr bthp. I thought it was just break-in, so i called it good and installed luth-ar stock with dpms rifle length buffer tube and s&w supplied spacer. Shot over 250 rds after install and it was short stroking pretty much everything i put in it. Some ammo will short stroke more than others it seems. It short stroked a lot with 145 gr ppu which i thought was normal during break-in, but it would still short stroke occasionally with black hills 168 and federal 168, even after 200 rds shot. After i cleaned and re-lubed, i took it out again with freedom 168gr a-max and bthp and it started off short stroking every 5 rds or so but it got progressively worse as the bcg soaked that lube up. When i got to the a-max rds, it literally short stroked every round. Also i can hear and feel the bcg cycling when shooting as it was slightly delayed. Also, i always thought the action on this gun was pretty stiff since day one, but it was somewhat noticeably stiffer when i went with the rifle length stock. So obviously i was pretty frustrated that after 300 plus rds, it was still short stroking. So i decided to remove the spacer to see what would happen. INSTANT FIX. None of the rds including the 145gr ppu were short stroking. I didnt feel the bcg cycling slightly after the round goes off like before, but now it feels like the gun is firing and cycling at the same time. Charging the gun doesnt take much effort as it used to. It still takes a little more effort than a standard ar15, but it doesnt feel like i need to work out to charge the gun anymore.
Im gonna call sw to see what the deal is here...

Recap:
Installed spacer for rifle length stock, still short stroking after 300 plus rds of all types, i could feel and hear the bcg being slightly delayed after round goes off, removed spacer and gun functions perfectly. Who knew....

You need to ck some lengths on components. That spacer is there for a reason. It is a mechanical stop for bolt travel. Just sayin,