300 blackout pistol question

I have a 300 and just once in a while it will try and double load. not ejecting the fired case and trying to load the new one. not sure what the fix will be, maybe a h1 buffer weight, clip a coil off the spring or open the gas post(currently .089).
when fired the cases are not hot when you pick them up, just luke warm at best.
tia for any help
bob
 
what ammo are you using?
have you tried other mags, or does it happen with multiples?
have you tried a different lower?
or even just a different bolt/bcg from another upper? (any standard 223 bolt/bcg will work, although a full auto/m16 style bcg is recommended due to the bit of extra weight)






generally with a pistol configuration you need a H2 buffer to cycle properly with the 300 blk.

modifying things so that the bolt travels faster is not going to be helpful.

a h1 & carbine buffer are both too light and clipping any coils off the standard spring is only going to make things worse.

since its not kicking the shell out, as noted above checking the ejector is going to be a solid place to start. i would also suggest looking for any burrs on the extractor and check the spring there. you'd see nice big ugly claw marks on the case rims if the extractor is marred up.

modifying the gas port should be an absolute last ditch effort if *NOTHING* else solves the issue. rarely - if ever - is this necessary on a pistol gas configured barrel these days. peel the clock back 5-7 years and it was more common, but most manufacturer's have solved it and your 0.086 0.089 (sorry typo, corrected) seems about right, if not a bit on the large side.




general rule of thumb for blackout (with adjustable stock) to operate in all 4 configurations (suppressed subsonic, suppressed supersonic, unsuppressed subsonic, unsuppressed supersonic)

rifle barrel, carbine gas = carbine buffer and standard carbine spring
pistol barrel, pistol gas = h2 buffer and standard carbine spring


if you have a pistol gas setup on a 16" rifle barrel you'll probably need to go to a h2 AND an adjustable gas block, especially if shooting suppressed supersonic loads. that configuration with supers tends to be reeeeeeeeeely over gassed due to dwell time and the port being (relatively) far from the muzzle.


hth
 
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Originally Posted By: Plant.Onewhat ammo are you using?
have you tried other mags, or does it happen with multiples?
have you tried a different lower?
or even just a different bolt/bcg from another upper? (any standard 223 bolt/bcg will work, although a full auto/m16 style bcg is recommended due to the bit of extra weight)






generally with a pistol configuration you need a H2 buffer to cycle properly with the 300 blk.

modifying things so that the bolt travels faster is not going to be helpful.

a h1 & carbine buffer are both too light and clipping any coils off the standard spring is only going to make things worse.

since its not kicking the shell out, as noted above checking the ejector is going to be a solid place to start. i would also suggest looking for any burrs on the extractor and check the spring there. you'd see nice big ugly claw marks on the case rims if the extractor is marred up.

modifying the gas port should be an absolute last ditch effort if *NOTHING* else solves the issue. rarely - if ever - is this necessary on a pistol gas configured barrel these days. peel the clock back 5-7 years and it was more common, but most manufacturer's have solved it and your 0.086 seems about right, if not a bit on the large side.




general rule of thumb for blackout (with adjustable stock) to operate in all 4 configurations (suppressed subsonic, suppressed supersonic, unsuppressed subsonic, unsuppressed supersonic)

rifle barrel, carbine gas = carbine buffer and standard carbine spring
pistol barrel, pistol gas = h2 buffer and standard carbine spring


if you have a pistol gas setup on a 16" rifle barrel you'll probably need to go to a h2 AND an adjustable gas block, especially if shooting suppressed supersonic loads. that configuration with supers tends to be reeeeeeeeeely over gassed due to dwell time and the port being (relatively) far from the muzzle.


hth

THANKS X2

 
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Originally Posted By: Plant.Onewhat ammo are you using?
have you tried other mags, or does it happen with multiples?
have you tried a different lower?
or even just a different bolt/bcg from another upper? (any standard 223 bolt/bcg will work, although a full auto/m16 style bcg is recommended due to the bit of extra weight)




can you give us some input on these questions? this may well help us sort out some of your issues.



additionally, i should have asked initially three more questions

did you assemble this or was the upper purchased complete?

what brand barrel is it?

is this a known good lower?
 
Originally Posted By: Plant.OneOriginally Posted By: Plant.Onewhat ammo are you using? [color:#FF0000]federal 120 hp and handloads with barnes 110 blk [/color]
have you tried other mags, or does it happen with multiples? only have one magpul magazine but it worked flawlessly as a 223.
have you tried a different lower? No it's the only pistol lower I have
or even just a different bolt/bcg from another upper? Haven't tried a different bcg but I can. (any standard 223 bolt/bcg will work, although a full auto/m16 style bcg is recommended due to the bit of extra weight)




can you give us some input on these questions? this may well help us sort out some of your issues.



additionally, i should have asked initially three more questions

did you assemble this or was the upper purchased complete? bought it used as a 223 with an extra 300 barrel, lower is an aero ar. shot lights out as a .223

what brand barrel is it? N/a

is this a known good lower? yes
shot lights out as a 223, .50 at 100
thanks for the help.
bob
 
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ok... i suggest u head to walmart and pickup a box of the remington 120gr stuff.

use that as your benchmark ammo - its pretty much the gold standard for function testing, without spending on the primo stuff anyway like the barnes blacktips or hornady 110 vmax.

not that the federal are bad, nor are handloads.. but you should use a known good factory load for this kinda thing just for consistency & benchmark purposes.


look forward to following this forward as you figure it out.
 
changed the buffer weight to h2 and now the carrier won't stay open on last shot with p-mag magazine but will with metal magazine. your thoughts? pistol did stop stove piping and trying to double feed.
if you pull the charging handle back to where the carrier locks and tap the side of the receiver the bolt will drop on the pmags, all 3 I have..
 
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glad we got the double feed / fte issues out of the way.


sounds to me like the bolt stop isnt getting pushed up far enough with the pmags.


re: the pmags,are they gen1, gen2 or gen3 pmags?
 
I had some issues with gen3 pmags but metal mags would function fine. Turns out the mag catch spring was a full coil shorter than it should have been. The mag would not stay up as far as it needed to feed reliably. The metal mags have a sharper catch tab on them so they stayed where they should but pmags would wiggle enough to cause issues.
 
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all there mags are generation 3 and I understand from my research this is a common problem.
was thinking of going to a magpul B.A.D. ext bolt release but need to fix the mag problem first.
 
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have you tested those pmags in another lower? im not suggesting that you DONT have a mag problem, but i would want to do some more testing before you come to that conclusion.

the bolt catch isnt terribly uncommon to be out of spec, or have a burr on it, etc. does NOT take a whole ton to get it to malfunction. ive gotten a bad one myself from a generic LPK. doesnt need to be off by much to be an issue. i'd be checking the lower before you start abandoning one of the better poly mags available.

*most* of the problems with pmags were based on older load data - if you loaded certain bullets too long (especailly some of the heavies used for subs) their meplat would be too far forward and bind up on the rib designed to ride the shoulder of a 5.56 round. the OAL data for most projectiles was modified and updated a while back (~5 years or so? maybe more) to mitigate that issue, although some folks used to take a file to the rib to remove it themselves to make them more universal. as i understand it, thats the primary change (internally) with the new 300blk specific pmag - removal of said rib inside the body.

i run g2 and g3 pmags regularly in both of my blackouts - pistol and rifle. this is for everything from 110-208gr loads. they're my goto mags in fact... i keep the metal GI mags for my 204 ruger (the shoulder is just a smidge to far forward to work in pmags, and the case rubs on said same internal rib).
 
switched the pmags to another ar and they work fine, just like when I put the metal mag in the 300 aac. I think I have a bolt release problem.
the back of the release is shiny and looks rounded off. brownells sells a slightly better release for the colt. may have to try one.
 
i would get ahold of whoever you got your LPK from - if you bought it new anyway... i know you said you picked up the upper used as a 223... but i dont recall seeing if you mentioned wher the lower was from.


as i'm sure you've seen - that bolt catch isnt very expensive part. swap it out, make sure you lube it before you reinstall it, etc.

should only be a few mins swap thing.

might even be worth calling around to some of the local shops to see if they have one on hand. save ya a few days shipping time, etc.




please keep us in the loop as you tweak this out. i cant wait to hear you say "yay its working great!"
smile.gif
 
If you plan on ordering a catch I would order a colt mag release spring also. When you take the bolt catch out you can take the mag catch out and check the spring. For $5 its cheap insurance. My mags are now held solid. I learned my lesson with lower quality LPK.
 
replaced the latch and the spring and the rifle is working fine so far. the back of the latch was worn and had a pretty good diagonal gouge in it.
 
I put it together for pistol deer season here in Missouri. should work great with the 110 Barnes at 2270 fps. not bad for a 10.5" barrel.
 
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