Bad impacts on target

[DWalt]

It's not the bullet's weight so much as it's the bullet's length which requires a tighter rifling twist to stabilize it. I won't get into the details, but once I was evaluating .223 frangible bullets which were jacketed around a copper/polymer composite core. They weighed around 45 grains and were fairly long, longer than the 62 grain M855. I was using a 1:12 twist rifle, and I experienced many keyholed bullet holes at 100 yards - and grouping was poor. They performed much better in an M16A2 with a 1:7 twist barrel, no keyholes. Also worked fine in an M249, same twist as the M16 as I remember.

 

[S&WIowegan]

It's not the bullet's weight so much as it's the bullet's length which requires a tighter rifling twist to stabilize it. I won't get into the details, but once I was evaluating .223 frangible bullets which were jacketed around a copper/polymer composite core. They weighed around 45 grains and were fairly long, longer than the 62 grain M855. I was using a 1:12 twist rifle, and I experienced many keyholed bullet holes at 100 yards - and grouping was poor. They performed much better in an M16A2 with a 1:7 twist barrel, no keyholes. Also worked fine in an M249, same twist as the M16 as I remember.

I was Army 1965-67 and never got my hands on an M16 because they went straight to Nam. One buddy went through OCS and artillery school with M14s. When he got to Nam he was handed an M16 and one mag full to qualify. The early M16s did not stabilize the bullets. The Army said that was OK because the bullet made bigger holes. That works if the guy is close enough be get hit. Secretary McNamara may have been in error, but never in doubt.

 

[DWalt]

The earliest M16s had 1-14" twist barrels. While those worked OK to stabilize the 55 grain bullet of the M193 round, in cold weather, it would not stabilize the companion M196 tracer round bullet, which was somewhat longer. So the M16's rifling twist was speeded up to 1-12". Later, when the M249 was adopted, which was intended to use the M855 round (green tip with heavier 62 grain and longer bullet) and had a 1-7" barrel, for the sake of ammunition commonality, the M16 was changed to use the same 1-7" rifling twist of the M249. Actually, the M855 round is not that terrible when used in a 1-12" barrel, it produces good enough grouping to do an effective job on a human-sized target at 100 yards but you won't win any matches with it. It is incorrect that the early M16s would not stabilize the M193's 55 grain bullet.

 

[loc n load]

Fuch,
As mentioned in previous posts, the classic keyhole profile on paper tells the tale. Also you have a couple other oval holes that testify to the bullet starting to yaw and destabilize.
223’s with the slower rate twists will not stabilize the longer/heavier bullets, which is why there was a move to 1/7 & 1.8 twist barrels.
As I understand your post # , you are shooting 55 grain bullets.
Those certainly should be stable in your Ruger. I would try shooting another 55 grain bullet, and or have your gunsmith scope that barrel and see of you have issues internally.

 

[Fuch]

bad impacts on target: the guilty is found

I come back from the shooting range and I believe I have found the source of the problem of bad impacts in the target: it is the magazine which is in question, during the transfer of the bullet from the magazine to the chamber the edge of the magazine deforms the cartridge , I took pictures of the deformed cartridges that I removed manually after chambering, I then made about twenty shots per shot by loading the mini 14 manually without a magazine and no more bad impacts, I am reassured because the barrel is intact, now I just have to buy new chargers !!

 

[loc n load]

Wow! I am surprised the round would even chamber and allow the bolt to go into battery with the round in that condition. I have been shooting Mini 14’s since the 80’s and the only magazines I have found to function reliably are the Ruger factory magazines. They cost more than the after market mag’s, but function well.
Don”t know if those are available at your location.
Glad you found out what the issue was.

 

[Fuch]

Wow! I am surprised the round would even chamber and allow the bolt to go into battery with the round in that condition. I have been shooting Mini 14’s since the 80’s and the only magazines I have found to function reliably are the Ruger factory magazines. They cost more than the after market mag’s, but function well.
Don”t know if those are available at your location.
Glad you found out what the issue was.

thank you for your answer yes your remark is relevant, I am also amazed that the cartridge can enter the chamber in this state may be the force of the breech spring straightens the bullet a little, that leaves me in doubt, but in any case this does not come from the ammunition or the barrel because as I specified I fired by reloading manually shot by shot and the problem disappeared

 

[DWalt]

That was my first thought - how could those rounds even chamber? But beyond that, I can't imagine how than much case bending even happened. I've not seen anything like that before.

 

[Mike SC Hunter]

All I’ll say is had an early mini-14, would only shoot “ barn door” MOA, hard to believe but traded it straight for a M-1 Garand which I gave to my son.

My early one was the same way. Gone and replaced with a much more accurate AR.

 

[Fuch]

My early one was the same way. Gone and replaced with a much more accurate AR.

that's for sure yesterday at the shooting range I took my mini14 and my AR15 ruger, the AR is much more precise, but despite that I still adore my mini14 which is superb !!

 

[Cdog]

My first experience with Keyholing was when I owned two Bisley model Rugers.

One a Blackhawk chambered in .45 Colt, the other a Super Blackhawk .44 Mag.

I was shooting 240 grain cast .44's at 25 yds and noticed some holes that just didn't look right. Before I even looked at the revolver, I knew exactly what I had done. Luckily the .45 Colt didn't so much as hiccup from the undersized rounds.

Youthful haste lead to carelessness.


I've seen keyholing few times since, but not because I picked up the wrong ammo or firearm!

 

[WR Moore]

OK, we used early Minis in industrial quantities. While not varmint guns, they generally shot acceptably* and were extremely reliable. The twist rate in the early (180-18? series) guns was 1-10 which would stabilize up to and including the 69 gr SMK. I have no idea what the OAL of the 62 gr slug is, but if longer, could possibly cause issues.

Ruger refused to sell 20 and 30 round magazines to the general public for quite some time. This resulted in a lot of companies getting into the magazine business and the quality ranged from decent to awful. It would appear you got one of the awful quality. Pick up some Ruger magazines if you can find them. John Masen also makes some very good magazines.

*Due to what I think is the design of the gas system, if you rest the forend on something hard or mount a bipod there, strange things happen to your point of impact. Usually by hitting really, really low. It may or may not affect groups.