Bullet pushed back into casing

USMC1990

No Diddy Boppers
Belligerents
Nov 13, 2012
104
62
34
49
Houston, TX
I am waiting on scope for new build and was tweaking the mag well adjustment and sear on JAE700 to get everything as smooth as possible. I loaded up a few rounds in AICS mag and chambered a couple times but found that after ejecting, a couple of the bullets were pushed back into the casing a bit. Prime Match 6.5 ammo. Impact action.
Why is this happening?
Thanks
 

BuLLet

Sergeant (Retired)
Belligerents
Minuteman
Apr 6, 2004
398
827
99
NY
No freebore. Chamber improperly cut.

Any marks on the bullets?
 

jcmullis2

Screaming Eagles
Belligerents
Minuteman
May 12, 2020
779
342
69
USA
The nose of the bullet is hitting some place and my guess is the feed ramp. You need mags with the binder plate
 

WildBill3/75

Sergeant
Banned !
Belligerents
May 21, 2012
332
103
49
Virginia
I highly doubt this is an action problem. This is a Legos problem.

When you play with "Legos" minor fitting is required. Something isn't lined up correctly.

Posts #2 and 3 are solid advise. Watch how it chambers a round.

I think your probably hitting steel hard with the bullet forcing it into the case on it's way into the chamber.

If this was a barrel problem you'd likely have a bullet stuck in the lands. Still check for marks on the bullet from engaging the lands.
 

USMC1990

No Diddy Boppers
Belligerents
Nov 13, 2012
104
62
34
49
Houston, TX
Thanks fellas, I will check for markings when I get home today. If not, will ask my smith about binder plate plus...

I am going to be surprised if the chamber is cut improperly, the smith I used is very reputable in Houston area.
 

6brshooter

Sergeant
Belligerents
Oct 2, 2012
2,303
936
219
Illinois
I'm gonna repeat that I think mag is too low and bullets are hitting feed ramp or barrel tenon. Its a pretty standard, albeit precisely machined, m700 pushfeed action. Somewhere in the feed cycle the bullet is impacting something. Usually thats caused by the mag height or feed lip release angle.
 
  • Like
Reactions: Krob95

FALex

Headmaster of Romper Room
Belligerents
Feb 5, 2011
1,700
256
189
USA
Can you measure how far they are going into the case? Can you see it with the naked eye?
 

6brshooter

Sergeant
Belligerents
Oct 2, 2012
2,303
936
219
Illinois
Try this, take a loaded rd and try to push bullet in on edge of workbench. Just to verify nk tension is good. If nk tension is decent, id think you would definitely feel a hang up during cycling.
 
Last edited:
  • Like
Reactions: Nightsniper

USMC1990

No Diddy Boppers
Belligerents
Nov 13, 2012
104
62
34
49
Houston, TX
Try this, take a loaded rd and try to push bullet in on edge of workbench. Just to verify nk tension is good. If nk tension is decent, id think you would definitely feel a hang up during cycling.
Taking it back to the smith tomorrow and letting him look at it. Let you know what he finds. Thanks for all the responses.
 
  • Like
Reactions: 6brshooter

USMC1990

No Diddy Boppers
Belligerents
Nov 13, 2012
104
62
34
49
Houston, TX
Just got back from my gunsmith and figured out the issue. Two-fold actually. First thing is he checked the headspace and it was perfect. Not sure if this is an old gunsmith’s trick or not but he put spacer in, closed the bolt and it dropped in perfect...he then put a piece of scotch tape on front of bolt, trimmed it so nothing hanging over edges and ran bolt back through, only this time it would not close. Not sure what that tolerance is but seems pretty damn close if the thickness of a piece of tape is all there is. With that out of the way, he checked mags to see how they were feeding. With a small adjustment (widening the lips of the mag with a very small flare at the front), they fed like butter and no longer got caught on the ramp. I also think I received some bad ammo which was a little surprising but I will be reaching out to them. Was actually able to pull the bullet from the casing of one by hand so the neck tension is definitely bad on some.
Anyway, thought I would let you know what we found. Thanks again for all the help.
 

WildBill3/75

Sergeant
Banned !
Belligerents
May 21, 2012
332
103
49
Virginia
Just got back from my gunsmith and figured out the issue. Two-fold actually. First thing is he checked the headspace and it was perfect. Not sure if this is an old gunsmith’s trick or not but he put spacer in, closed the bolt and it dropped in perfect...he then put a piece of scotch tape on front of bolt, trimmed it so nothing hanging over edges and ran bolt back through, only this time it would not close. Not sure what that tolerance is but seems pretty damn close if the thickness of a piece of tape is all there is. With that out of the way, he checked mags to see how they were feeding. With a small adjustment (widening the lips of the mag with a very small flare at the front), they fed like butter and no longer got caught on the ramp. I also think I received some bad ammo which was a little surprising but I will be reaching out to them. Was actually able to pull the bullet from the casing of one by hand so the neck tension is definitely bad on some.
Anyway, thought I would let you know what we found. Thanks again for all the help.
Glad you got it all sorted out. Sounds like you got a good Smith.
 
  • Like
Reactions: USMC1990