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6mmtcu

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Reply with quote  #1 
Ok Mongoose shooters, my son and I took the Mongoose out Saturday to fireform some more brass. I took a hundred of my usual ff load of 26.5 bl-c2 under 80 grn sp (which shoots awesome ) & a hundred 25.0 h-335,80 grn sp ,both loads using cci 450's. The 335 loads seemed to be short stroking ,but I would have bolt lock on last shot . Where could I start to look ? I also had this problem when using benchmark , thanks
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Reply with quote  #2 
Quote:
Originally Posted by 6mmtcu
Ok Mongoose shooters, my son and I took the Mongoose out Saturday to fireform some more brass. I took a hundred of my usual ff load of 26.5 bl-c2 under 80 grn sp (which shoots awesome ) & a hundred 25.0 h-335,80 grn sp ,both loads using cci 450's. The 335 loads seemed to be short stroking ,but I would have bolt lock on last shot . Where could I start to look ? I also had this problem when using benchmark , thanks


Where was both sets of brass landing?

I'm not savvy on bl & h to know if you just didn't have enough smash to cycle the bcg .. so I ask the above question.

Without an adjustable gas block you could be short stroking .. or the bcg could be cycling so fast (i.e. not enough mass or spring in the buffer) that you are not catching the next round after it has risen to the top of the mag (i.e. the bcg is beating the round to the top of the mag).

Do you have pic's of the condition (re: what appeared to be short stroking)?

Anyway check your brass patterns .. then adjust you gas block if you have an adjustable one .. then change your buffer & spring weights as necessary .. based on your brass patterns.

My AR 308 would cycle fine without a suppressor. Add a suppressor and it would cycle so fast (because it was now over-gassed) that it would strike the brass well forward of the headstamp & end up as a ftf problem .. drop mag & repeat (sigh) .. but would lock open at the end of a mag.

The problem was fixed with a (super) heavy buffer & spring set-up from heavybuffers(.com). I don't have an adjustable gas-block on my AR308.

Without pic's & pattern dispersion info .. I'm guessing (e.g. I don't know about those powders).

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FWIW ..

When trouble shooting (heh) .. always adjust 1 thing at a time and start well left, right, over or under the problem .. if you don't then you are left wondering which adjustment to make next .. it's called walking it in or bracketing the problem.


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Edit
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https://faq.nosler.com/images/22-Nosler.jpg

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6mmtcu

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Reply with quote  #3 
I was shooting prone off of bags , every piece of fired brass landed in a nice little pile at 3:30 . The 335 loads would fire, eject and miss next round ... Rack bolt ,repeat lol. I didn't have another mag with me to try . I think you're on to something with the bolt going by next round... I did get bolt hold open after every shot .thanks for the help...I'm learning lol . after looking at the link you posted ,brass seems to landing where it shoul be .
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Reply with quote  #4 
Quote:
Originally Posted by 6mmtcu
I was shooting prone off of bags , every piece of fired brass landed in a nice little pile at 3:30 . The 335 loads would fire, eject and miss next round ... Rack bolt ,repeat lol. I didn't have another mag with me to try . I think you're on to something with the bolt going by next round... I did get bolt hold open after every shot .thanks for the help...I'm learning lol


It could be a mag .. (it could also be the bcg or something else) .. I'd start with the mag .. even if it's a new one.

Then try a heavier buffer or spring if you have one .. then start walking it in from there .. especially if you don't have an agb.

Make it over or under buffered .. I prefer to start with over .. then walk it back the other direction. For me it's easier to over buffer it when I can't change the gas .. it's safer too .. if you're under buffered & then go even more under buffered it might do some bad things to you equipment.

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That pic above is by no means an exact rem-eye-dee .. it's just a good place to start if you don't have a good starting point already in mind.

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You may very well be under gassed with that one load. (My above technique is still vaild .. it just might take a lot more shooting to get the final solution.)

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6mmtcu

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Reply with quote  #5 
Thanks , I' just got her tore down for a scrubbing. Probably won't get to shoot again until the weekend . I appreciate your help.
Phil

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6mmtcu

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Reply with quote  #6 
Ok guys I need to pick your brains ...I am still having issues with my Mongoose refusing to feed any bullet / powder combos other than the BL-C2 / 80 grn loads . It will cycle all the loads I've tried with the BL-C2 ....26.5 up to 28.5 . 335,benchark ,322 all refuse to pick up next round . All loads with with these powders gave bolt hold open when firing one round .All spent cases land at 3:30 - 4-00 . Any ideas ??? When I went this weekend ,rifle was fresh cleaned and lubed . All brass was once fired . All loads shot well 1/2-3/4 ...I'm missing something . Help is greatly appreciated .thanks
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Reply with quote  #7 
Quote:
Originally Posted by 6mmtcu
Ok guys I need to pick your brains ...I am still having issues with my Mongoose refusing to feed any bullet / powder combos other than the BL-C2 / 80 grn loads . It will cycle all the loads I've tried with the BL-C2 ....26.5 up to 28.5 . 335,benchark ,322 all refuse to pick up next round . All loads with with these powders gave bolt hold open when firing one round .All spent cases land at 3:30 - 4-00 . Any ideas ??? When I went this weekend ,rifle was fresh cleaned and lubed . All brass was once fired . All loads shot well 1/2-3/4 ...I'm missing something . Help is greatly appreciated .thanks


When it locks back, is it on the bot face or on the carrier just behind the bolt? Curious because mine did the same thing, I have had to open the port on mine and a buddy's rifle to get to run correcly, I had just enough gas to work with a few combo's but not everything. Only went up one port size (20") but now cycles everything.

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6mmtcu

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Reply with quote  #8 
Honestly,I didn't notice . I am kind of new to msr weapons ,so I'm just now learning what to look for lol. I was kind of thinking I might need to open the port up . I'm running carbine buffer/spring ,22" 1-8" 4groove ,rifle gas . You know what ,now that I think about it ,I did notice that after firing the last shot I would lay the rifle down to go mark my targets and the light jar would send the bolt to battery ! So ,I actually wasn't getting bho ! I didn't really think about that until you mentioned that .
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6mmtcu

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Reply with quote  #9 
Next question would be ,what size are the barrels ported to AT MDWS ? What size should I go to ? This rifle shoots amazing ,I really would like to shoot it as a semi lol Right now I have a heavy version of my T/C 6mm tcu 😂
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6mmtcu

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Reply with quote  #10 
Thanks for the info W !
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Reply with quote  #11 
No problem, just trying to help. I'm not sure what the 22" is ported at, I have a set of drill bit (numbered) from harbor freight. Just find which one fits through tight and pick the next one up. Then shoot, it takes very little to fix the gas issue sometimes. I had to do the same thing to my 6x45 as well. Rather to be small ported vs. large though, can find top end then adjust to operation, done! lol
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6mmtcu

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Reply with quote  #12 
I appreciate your help Wikster ! We have a good machine shop here at work , hopefully one of them will have a set I can borrow .
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Reply with quote  #13 
Quote:
Originally Posted by 6mmtcu
Honestly,I didn't notice . I am kind of new to msr weapons ,so I'm just now learning what to look for lol. I was kind of thinking I might need to open the port up . I'm running carbine buffer/spring ,22" 1-8" 4groove ,rifle gas . You know what ,now that I think about it ,I did notice that after firing the last shot I would lay the rifle down to go mark my targets and the light jar would send the bolt to battery ! So ,I actually wasn't getting bho ! I didn't really think about that until you mentioned that .



If you are running rifle gas (as opposed to carbine or mid-gas) then you are probably not getting enough gas into the system to cycle things properly except for that one load.  I would open the gas port one step to see if things improve. 

The type of powder has a lot to do with it as well.  Some powders generate a lot more gas than others and are more suitable for use in an AR.  That's why I prefer mid-gas over the other types.  It is much easier to tune and far more forgiving when you're on either end of the optimum window.  For carbine gas it is very easy to over gas things to the point of breaking parts, so you need an adjustable gas block to tune it, and often have to tinker with buffer weights.  Rifle gas often requires opening up the gas port several steps to provide good gas flow, and you may need an adjustable gas block with certain powders as a result.  What it boils down to is that at either end of the spectrum, things are more finicky.  In your case, with rifle gas, you need to open up the port to make sure you have enough gas, and may need an adjustable block to fine tune things with certain powders.  I wouldn't mess with the buffers at all except as a last resort.  Also keep an eye on dwell time.  Ejection should be at 4 o'clock, indicating the gas system is good and dwell time is correct.

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6mmtcu

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Reply with quote  #14 
Thanks Rifter ! I have a adjustable gb on it right now,wide open lol Everything is starting to click with me and this style weapon. The insight I've gottenon this forum is invaluable! I appreciate it guys ! I guess I need to get a few more powders that are more AR friendly 😁
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Reply with quote  #15 
Quote:
Originally Posted by 6mmtcu
I did notice that after firing the last shot I would lay the rifle down to go mark my targets and the light jar would send the bolt to battery !

That could also be because the bolt release paddle is on the left side of the rifle.  Setting it down on that side could easily be enough to hit the paddle and release the bolt catch.

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6mmtcu

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Reply with quote  #16 
True it could have,but I laid the rifle on ejection port side . Thanks
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Reply with quote  #17 
to your question a 22 should have an .086 port. i would open to .088-.089  that is a #43 drill   and you should be good to go.  i had to open mine also on my 10 twist.
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6mmtcu

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Reply with quote  #18 
Just what I was looking for ! Thank you ! I had grabbed up a hand full of plug gauges here from a machinist here at work to see exactly what size it was before I opened it up lol . Thank you everyone who has offered up info/ advice ! This is a great place 😁
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Reply with quote  #19 
Quote:
Originally Posted by 6mmtcu
Thanks Rifter ! I have a adjustable gb on it right now,wide open lol Everything is starting to click with me and this style weapon. The insight I've gottenon this forum is invaluable! I appreciate it guys ! I guess I need to get a few more powders that are more AR friendly 😁

As a rule of thumb, you want the gas block at about the mid point in the adjustment range when the port size is correct.  So, if you're running the block wide open and still having problems with lock back, and timing, the port needs opening up.  Even if you change to a gassier powder, you want to be able to close down the port to the mid point area to have the most leaway in adjustment.

Sounds like you're on the way to getting it dialed in though.

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6mmtcu

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Reply with quote  #20 
Thanks for that info ! That makes sense to allow the most leadway for tuning .
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6mmtcu

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Reply with quote  #21 
So, opened the port up ,adjusted my Superlative Arms 3 full turns open ,and there she is ....cycling the 335 loads great ! 4o' clock ejection & full lock back 😁 . I'm going to load up some of the 322 loads that shot so well tonight & hopefully get to the range this weekend and see if they're going to cycle . I was getting right at 3400 with 322 under the 65 grain OTM bullets with <1/2" groups at 100 .thanks for all of the help & info guys !
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