9mm luger chamber tolerances

[DUSTY NOGGIN]

the reason for my question is I have a angstant ar9 upper lower.. bought separate .. I can not get it to feed well .. no reliability whatsoever

the barrel chamber opening really doesn't have any sort of feed ramp pretty sharp corner .. basically just a hope the the round comes out of the magazine and noses into the barrel .. about a 5/16" of a gap out of the magazine to the barrel opening ..
fmjs do ok but there is almost 90% failure to chamber with any HP or FN profiles projectiles

if a guy was to round off the corner of the barrel face to try and create a feed ramp how far up the side of the brass would you dare to go ?? imagine glock swell to give a little slack there

ill get a measurement of how far out my cases protrude and some pictures later ..

seems like the fix is chamber deeper to add in that angle . the shave that depth off the bolt

how far away do you think the barrel face should be away from the magazine ?? if the magazine angle looks in line ???

ill get pictures later today

is there a spec that an ar9 platforms upper need to be or should be so they can be compatible with other lowers ???

 

[LoneTraveler]

If the edges of the chamber is rough enough to bind and scar the case or bullet, A little smoothing and polishing of the edge should help.

Also I would check is the lips on the magazines. If there is any rough grabby edges on steel magazines will grab the brass or aluminium cases and tip the bullet up, down or to either side and cause malfunctions.
If the clips have been loaded and dropped on a hard surface it can cause problems also, By bending 1 or both magazine lips.
Smoothing/Polishing the edges of the lips on the magazines will really improve feed.
When I was a police armor, The department replaced our pistols, 21 pistols with 3 magazines each. I had to polish every clips lips to get them to Jive and Shuck properly.
Good Luck finding the problem and cure. bj

 

[GNERGY]

Does it take glock mags. I have an ARQ 9 from Quentin Defense and it was jamming with cheap ammo and Magpul mags. I tried ETS mags and it did the same thing. My friend told me to buy the KnyShot hyd buffer for the 9mm and a Springco spring and now it feeds everything like a charm.
TArey

 

[DUSTY NOGGIN]

Does it take glock mags. I have an ARQ 9 from Quentin Defense and it was jamming with cheap ammo and Magpul mags. I tried ETS mags and it did the same thing. My friend told me to buy the KnyShot hyd buffer for the 9mm and a Springco spring and now it feeds everything like a charm.
TArey

yes glk 33rd's

it does feel to have a very heavy spring is the spring co a lighter spring ??

im thinking its gonna need some type of feed ramp added , I think what it needs is chamber deeper , heavy chamfer , and bolt shaved down to match HS

 

[GNERGY]

The Sprinco.com spring had less coils but felt just as firm. My friend has over 35 ars in every cal. and all feed like fine swiss watches. This is the one he told me to buy (308 carbine DPMS pattern extra power buffer spring) and it solved my feeding problems.
Tarey

 

[DUSTY NOGGIN]

thanks , for the cost of a spring, may as well give it a try