AR Sponsor
Posted: 10/13/2009 7:47:30 AM EDT
|
So I took my AR-15 out to really sight it in this weekend and am having some accuracy issues. Both me and my dad were shooting a mix of Federal and PMC 55gr FMJ rounds. His rifle is a Smith and Wesson M&P with a 1/9 twist. Mine is a Spikes Tactical with a 1/7 twist DD barrel. We were shooting from a lead sled to try to maximize accuracy testing. He was getting 1 MOA groups while I was getting a little under 3 MOA. Could shooting 55 grain rounds though a 1/7 barrel be hurting my accuracy?
At the moment, I'm planning on picking up some 65-75 grain rounds to throw down range and see if my gun likes them. Does that sound like a good course of action? My goal is to find a load that can get sub MOA for me to start handloading. |
|
Quoted:
So I took my AR-15 out to really sight it in this weekend and am having some accuracy issues. Both me and my dad were shooting a mix of Federal and PMC 55gr FMJ rounds. His rifle is a Smith and Wesson M&P with a 1/9 twist. Mine is a Spikes Tactical with a 1/7 twist DD barrel. We were shooting from a lead sled to try to maximize accuracy testing. He was getting 1 MOA groups while I was getting a little under 3 MOA. Could shooting 55 grain rounds though a 1/7 barrel be hurting my accuracy? At the moment, I'm planning on picking up some 65-75 grain rounds to throw down range and see if my gun likes them. Does that sound like a good course of action? My goal is to find a load that can get sub MOA for me to start handloading. Did your dad get the same size groups as you with your rifle and the same ammo? |
|
First of all...
At what range were you sighting in? My recommendation would be to sight in with some good quality ammo like Hornady. And yes a heavier weight would be better for your 1/7 twist barrel as its better at stabilizing heavier projectiles. But shooting 55gr out of a 1/7 is still good to go. 
|
|
Thanks for the input. We both fired the rifles. Part of it could be me, as we rigged a normal rifle lead sled for our AR's and there could be a little human error. But we both tried switching ammo and shooter. We were shooting at 100 yards. The accuracy as is is acceptable for its purpose (SHTF rifle) but for kicks, I'm trying to get as precision as possible.
Thanks again everyone. |
|
It's pretty popular on the board here to state that 55 gr FMJ shoots just great out of a 1-7 twist barrel as a means to defend choosing a mil spec 1-7 twist barrel. The degree to which that is true depends to some extent on the velocity (faster = worse) and to a large extent what you define as "acceptable" accuracy.
I'm one of minority of people here who thinks 1-7 is a poor choice, particularly if you plan to shoot 55 gr bullets as they will not shoot nearly as well as the rifle and barrel are capable of shooting, and that 1-9 or 1-8 provides a lot more flexibility overall. Besides, accuracy aside, the faster the rifling rate, the more velocity and the shorter the range at which the bullet will still fragment and or tumble on impact, so faster rioling rates tend to have a negative impact on terminal ballistics and the 5.56mm has very little it can afford to lose in that department. If both of you shot both rifles and got better acuracy with one than with the other, it is a rifle issue, but there are still a lot of varaibles. Shooting different ammunition with heavier bullet weights through both rifles will help you narrow the bullet weight variable and shed some light on what might be happening. |
|
Myths never die.
Neither federal nor pmc's 55-grain fmj ammo is 'match' ammo by any stretch of the imagination. 3 MOA isn't out of line at all. http://www.ar15.com/forums/topic.html?b=3&f=118&t=436376 |
|
I bought the upper completed from Spike's. It's the Operator upper. I built the lower myself. I may take my lower to my gunsmith and see if he can smooth the pull some, because it's rough right now.
On examining the federal and PMC ammo, the bullet seating is very inconsistent. Anyways, when I put together my rifle, I did so with the intention of storing 55 grain as plinking ammo, and handloading heavy grain ammo for tight groups or defense. It may be unrelated, when I first took my rifle to shoot, I shot some 55 grain Centerion bulk and a few 65 grain vmax rounds from Georgia Arms out. The vmax seemed more accurate from what I shot. |
|
Quoted:
It's pretty popular on the board here to state that 55 gr FMJ shoots just great out of a 1-7 twist barrel as a means to defend choosing a mil spec 1-7 twist barrel. The degree to which that is true depends to some extent on the velocity (faster = worse) and to a large extent what you define as "acceptable" accuracy. I'm one of minority of people here who thinks 1-7 is a poor choice, particularly if you plan to shoot 55 gr bullets as they will not shoot nearly as well as the rifle and barrel are capable of shooting, and that 1-9 or 1-8 provides a lot more flexibility overall. Besides, accuracy aside, the faster the rifling rate, the more velocity and the shorter the range at which the bullet will still fragment and or tumble on impact, so faster rioling rates tend to have a negative impact on terminal ballistics and the 5.56mm has very little it can afford to lose in that department. If both of you shot both rifles and got better acuracy with one than with the other, it is a rifle issue, but there are still a lot of varaibles. Shooting different ammunition with heavier bullet weights through both rifles will help you narrow the bullet weight variable and shed some light on what might be happening. It has nothing to do with being popular. It's just a given that 55gr can & will shoot very well out of a 1/7 twist barrel. I for one prefer 1/7 & not because it's "popular" or because it's what the mil uses. I shoot 55gr exclusively. |
|
Quoted:
First of all... At what range were you sighting in? My recommendation would be to sight in with some good quality ammo like Hornady. And yes a heavier weight would be better for your 1/7 twist barrel as its better at stabilizing heavier projectiles. But shooting 55gr out of a 1/7 is still good to go. The part in red is stupid. Sight the rifle in with whatever ammo you are going to use the most. Sighting in with some high grade varmint rounds and then switching back to your "normal" loads wouldn't make much sense. You may find out that the rifle can shoot MOA but all the "real" shooting you do could be off by several inches. |
AR Sponsor