Last Round in Magazine Off Target

[Historian]

Has anyone else experienced this? No matter what capacity magazine I use on my Bushmaster Varminter, the last round is always drops about an inch below the rest of the group. Have tried different ammo and seems to make no difference. Is this operator error or am I just crazy?

Historian

"Those who do not know history are doomed to repeat it."

 

[kBob]

Historian,

First and last rounds from a magazine of a semi auto magazine fed rifle( or pistol) both tend to have a slightly different striking point on the target.

I was taking a class with Major EJ Land and he watched as I continued to put the first round of a group from a fresh magazine and ambient temperature barrel slightly high and left in my case. At the beginning of the next mornings class he grinned at me (as much as he does) while explaining that the first round form the magazine which is fed "manualy" does not feed quite the same way as a round seated from the action of the rifle mecahanism. He also explained that the last round suffers from ridding on the magazine follower rather than another cartridge. The angle it hits the feed ramp may not be the same and the speed at which it is seated may be different.

IF you are just shooting for group size then I suggest loading two more rounds in the magazine than you intend to shoot for "score". Use the first as a "fouler" and shoot it ito the berm rather than the target and use the last round as a means of feeding the last round of your group. Rember to clear your rifle to remove the magazine AND that last unfired round.

As for regular shooting for say a match where you may not be allowed a fouler or extra ammo in your magazine.....you just have to learn where those two wandering rounds go (and they generally go to different places) and acount for it when shooting.

As my class was originally planned as a short range Law enforcement precission rifle course, we spent more time learning to shoot that first round from a magazine through a cold (back ground temp) barrel rather than groups than most classes might. Knowing where that first and perhaps only round went was more important than cranking out groups. Groups show rifle and ammunition consistancy as well as shooter skill. If you can shoot the smallest group in the world with a warm rifle from a proved shooting position it won't do you a bit of good if you do not know how to correct for that first cold round if an inch and a half might make the difference between a dead right there bad guy and a Dead a second later bad guy that shot a hostage or fellow officer.

For the Designated Marksman in theater today making that max 600 meter shot with his scoped and tricked out AR, that little cold barrel error of 40mm at 100 meters means an error of 240mm (9 and a half inches) at 600 meters. Think you could miss a head and shoulders target partially obscured by an "SVD", RPG or PKM at that range if you did not know to account for it? What can happen during the time you are setting up for you next shot?

It's great that you noticed this characteristic of you rifle. now deal with it.

-Bob Hollingsworth

 

[Historian]

Thanks Bob. That explains a lot. I have always thought that my first round from a cold barrel was just my not getting comfortable with the rifle before I fired. Now I understand and have a greater appreciation for those marksmen who use these weapons to keep us free...from crime or aggression.

Historian

 

[Historian]

Bob,

I've been thinking about the problem with the first round out of the magazine being off target. If I understand you correctly, this problem is caused by the act of manually drawing back the bolt carrier in order to chamber the first round. If I were to insert the magazine into the receiver with the bolt open and then close the bolt using the release wouldn't that cause the first round to chamber in a fairly similar manner to those that follow and thus give it the same consistency of performance as a round out of the middle of the magazine?

Historian

 

[kBob]

First ,let me splain " I am not an LEO, but I also do not play one on TV" and Since I got out of the army last time I could have served enough to retire at 50+ percent today not counting the prior time active and reserve.

I am meerly a gun nut

Second HEY GUYS THIS AINT A PRIVATE CONVERSATION! Let's have some other input.

Third to answer you question,

Nope.

During that class I was loading by drawing back the charging handle and engaging the bolt stopinserting a mag and then relasing the bolt and checking safe. Generaly we left the actions locked open anyway to help show safe in addition to a flag and the mag well empty with the rifles right side up when not in use.

How much further will the bolt go back after you pull the charging handle fully to the rear?

Loading the rifle consistantly WILL tend to make that first strike from a cold barrel group better with other such shots.

Many Gun Rag writers (Hello, My name is Bob and I am a gun rag writer. I have not published gun trash in 14 years (waits for greeting and applaudes))
have been aware of the first round migration for many moons. WHen you see those groups posted on what this or that semi auto groups like be advised that some do "waste" the first round in the magazine before shooting for group. Even with bolt actions that allow one to load the first round directly into the chamber by hand some rifles tend to place the first shot some place away from the others. Frequently when you see that one hole group the furtherest rounds out were firired with the first and last rounds if there were only five round in the magazine. Some have even applied it to revolvers in a since as they might take a six shot ( or seven or eight) and actually figure out which chamber in the cylinder (s) most expands an otherwise great group. Want to have fun with revovler groups? Find the chamber that most consitantly puts bullets in the tightes group on the paper. You likely never knew the old gal was so accurate before. Some hunters do that with revolvers to make that first shot count as well.

No doubt I will be visited tonight by hooded members of the Gun Writer's Protection Guild that will assault me with huge volumes of dictionaries, thesaurouses and spelling guides......especially spelling guides.

Yep, I now know that with that partricular load under those particular weather conditions and direction that My first shot from that particular HBAR-15 will be about one and a half inches away from my group center at 10:30. Might not be there under cold conditions. Or any thing at all changed, but I know what happeded then and can plan for that under similar conditions.

This is why serious competitors and marksmen keep log books and number their hits on every target and record wind direction temperature direction of the sun and other notable conditions along with what rifle and sighting system and ammunition to include lot number or designated hand load is in use.

You start to see trends like cold barrel and first round effects, magazine count verses where a round hits.

This is the way you can detect trends in your rifle and account for them.

This is the sort of thing that can help you win your relay and go on the the last relay.

This is the kind of thing that lets you make a telling shot on the range or in the field.

Sounds like work instead of a fun day at the range? Yep. And that is why I am guilty of not doing it for very long despite several starts and promises.

Having some one else that DOES log every shot tells me what to look for helped me notice and learn to account for those things I meantioned and so I do look for and account for my first cold shot using "Kentucky windage".

Want to see what your rifle and you can do with the first shot? Shoot every first shot from the cold gun made with out sight changes on a same "Fouling Target" after you have five shots from the cold barrel (just let it sit until the barrel is the same temperature as everything else in the shade as though you had been toteing it around) Compare this group with a five warm barrel groups you fired. Find the average center point for your 25 shot group and compare that to the center of your single cold barrel group.

Or keep a log and number each shot and how you called (that is where you think the sights indicated the shot would go when you fired each shoot, be honest to yourself) and just shoot a five shot group straight through, but again shoot at leat five to see if the round ones from a cold barrel display a tendency to shoot elsewhere.

You may be able to hit a quarter rolling across your line of sight every time at 100 meters with a warmed up rifle and a few sighting shots, but when it counts, can you hit a stationary quarter at 100 meters with the first shot from a cold barrel EVERY time?

....and then with a hot barrel hit a quarter at 100 meters most of the time?

Yep, you can go crazy with it, you can learn some useful tricks and be better than the guy in the next lane, or you can ignore it and have a good time shooting.

-Bob Hollingsworth

 

[Historian]

I choose the latter

Historian

 

[geronimotwo]

i would think if the bolt locks back on the last round, that it would also change the dynamics.

 

[SDC]

Yes, this is common for both the first and last round in a mag, and is one of the reasons they developed the SLED single-shot "clips" for the M1 Garand in competition.