Is there any loss of accuracy if you shoot 55 grainers out of a 1/7 twist barrel?
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Is there any loss of accuracy if you shoot 55 grainers out of a 1/7 twist barrel?
I've never noticed a difference in group size when shooting M193 through a 1:7, 1:9, OR 1:12 barrels. However, none of these barrels would be considered match-grade...just plain-jane gov't profile units.
Typically, 1/7 barrels shoot 55gr VERY well out to about 100-110yds. After that accuracy tends to degrade somewhat.
C4
Grant,
Can you define "somewhat" (ie. degrades by a couple inches, a couple feet, ???).
I shoot 1/7 barrels using 55gr ammo (XM193, Q3131A, Black Hills Blue Box, IMI, etc) on a very regular basis out to 425 yards shooting 12 - 24" steel gongs, steel poppers, LaRue's, etc. and have no problem hitting the target when I do my part.
Semper Fi,
Jeff
We shoot Federal TRU 55gr SP from our duty rifles & AE 55gr FMJBT for training. Twist rates vary from 1/9 on our issue entry guns & 1/12 on our issue patrol rifles. I use 1/7 CMMG medcon on my own entry/patrol rifle with no accuracy issues at 100yds. Beyond that I cannot advise since I've not yet shot that far with the CMMG using the TRU 55grs. All twists have shot very well using the 55grs. All bores & chambers mentioned are chrome lined. There are several individual officers that have a mixture of CL & non CL on their own rifles.
I have shot plenty of 55gr, XM-193 out of my 1-7 barrels and I have no problems getting COM hits on a IDPA target at 300 yards.
Average accuracy is about 1.5-2.5 MOA at 100 yards if you do your part. Since, XM-193 is not loaded to match ammo specs I'm very satified with those results.
Yes. It looks somewhat like a pattern to me instead of a group. I have only run this test using one type of ammo (might have had a bad lot). Generally a 1/7 twist barrel will over stabilize a 55gr bullet.
I will try and shoot some other 55gr ammo at 100yds and 300yds to see how the groups open up.
C4
Thanks Grant.
I already have a Super Match Stainless Steel Pac-Nor 1/12 3-groove barrelled .22-250 that I use for varmint work, but it would be nice to at least have a chance up to 300 yards using my 1/7 twist AR-15 using factory ammo like Hornady 55gr V-MAX. Quick follow up shots with little to no recoil sounds like fun.
I'm no rifleman, but can hit steel plates (about chest-sized) consistently at 100 and 300 yards with 55 grain Winchester .223 (white box), American Eagle .223 and Winchester USA 5.56 (also in a white box, but different markings). No idea on group size, but it's close enough for government work.
As an aside, is there a problem with an agency that fields 64 and 77 grain loads but quals and trains with 55? I want to say no, but would be interested in opinions.
I think it depends on the ammo. My LWRC has a 1-7 twist tube. When loaded with 55gr. UMC remington it groups around two-two and a half at 100 yards. If I switch over to 55gr. TAP, I have a hard time telling how many rounds are in one hole. It does well with most bullet weights 55 and up. I havent fire much light stuff through it. I fired Mil frangible through it a bit indoors, not sure of weight but I think it's in the 40s, wasnt long shots but it did stay right together. No FTF, FTE, or anything common to frangible.
The U.S. Military considers M193 as an acceptable substitute when M855 is not available for use in 1-7 twist barrels.
The reverse isn't true for 1-12 barrels.
I have found most 52 to 55 grain bullets to be fairly accurate out to 300 meters in my own 1-7 twist rifles.
General rule of thumb for optimum accuracy at ranges to 500 meters;
1-12=45-55 grain bullets
1-10=50-60 grain bullets
1-9=52-68 grain bullets
1-8/1-7.7/1-7=60 to 80 grain bullets
I shot my 16" 1/7 at 200 yards the other week. I have an Aimpoint on the upper - so obviously no magnification.
I used a big Shoot-N-See target which I estimate to be 8x8 or so. At 200, the dot covers the entire target. Shooting off of a sandbag, I kept all rounds on the target, but it did not resemble anything like a grouping.
Ammo was XM193. Honestly, with an Aimpoint, I don't shoot any better than that at 200 with 55's with my 1/9 twist or 1/12 twist barrels.
I need do a comparision with some better ammo and with my Meopta 1-4x.
I have fired several types (including Wolf) of 55 grain ammo thought a 1/7 barrel (Colt 6920) with an eotech sight and bipod. I regularly shot 1 1/2 inch groups at 100yards, but have found to maintain consistent groups, you must fine tune/re-zero your weapon, depending on the type of ammo being used. I got surprisingly good accuracy from Fed xm193, Wolf military classic, Wolf Black box, PMC Bronze, Winchester Q3131, and American Eagle. All 1 1/2 groups, but I did have to fine tune. YMMV.
Once a bullet is adequately stabilized, the riflings' rate of twist has no further influence on bullet accuracy.
Light .224" bullets suck for accuracy at longer distances merely because they drift more in the wind.
The dimensional consistency of your bore and chamber have a hell of a lot more to do with accuracy than twist rate ever will.
"We all have our idea of what is acceptable".
In my opinion minute of angle is acceptable to 400 meters and most high quality 55 grain ammunition will do that in any decent AR15 1-7 twist rifle.
4" groups at 400 meters is plenty acceptable to me and that is what I can wring out of my 1-7 rifles using 55 grain bullets.
My Government profile and heavy barrel 1-9 twist rifles won't do much better, my Match guns will.
62 grain M855 is even worse than 55 grain M193 in the accuracy department in my opinion.
I always notice that 1x12 does very well with 55gr.
Noticeably more accurate than in 1x9 or 1x7 (for me). The difference in 55gr in 1x7 and 1x9 is hard for me to see unless I'm using really high powered scopes even then it's pretty nill.
There is only a "loss of accuracy" with that configuration (leaving out problems with the nut behind the trigger:p ) if
A. your BBl just doesn't like the ammo(which can be a problem no matter what BBl twist bullet combo you try) or
B. over rotation is a problem with the particlular bullet you are shooting. ie you might a shoot v-max bullet and have it fly apart due to over rotation but a Barnes bullet of the same weight may hold up better and shoot fine. Its a funny thing how one 1-7 twist BBL might shoot 55 grns just fine and the next won't shoot them worth a darn, but it is true. When you get on the edge of the Bullet weights (high or low) your twist rate was designed for, you just need to shoot N See...there is no other way to know. It's a far better practice to simply stay in the middle of the road so to speak with BBL Twist and Bullet weight. ie a 1-12 twist with those 50-55gr etc.
"Typically if I am getting half inch groups at 100yds, I will see groups open up by about .25 around the 110-130yd mark."????
Pardon me, but that doesn't compute in my mind.:confused: :confused:
I believe the only way you get a 50% increase in group size within 10-30 yds is lucky/ misleading groups at 100 yds or poor shooting at 110 yds. That is not an ammo problem. If the bullet survived the first 100 yds in tact, the centrifigal forces acting upon it have decreased greatly and have less negative effect not more at longer ranges.???
Thats just me tho. Shrug?
The only main time you should get issues in a few yards/meters is when the bullet is going from sonic to transonic fligth -as its not affected buy its own wind forces.
I've shot 55gr out of 1:7's (only twist I own) out to 500m with decent results (it does seem to get a lot worse between 300 and 500 though)
Off topic I guess but...
I have a 1 in 9 twist 16 inch barrel...Whats the heaviest bullet that commonly works well with that twist?
I'm looking for the heaviest, ACCURATE round...I intend to deer hunt with my AR (its legal here, and I'm a good shot)...I was thinking 68 - 70 grains...specifically the Barnes Triple Shock (62 or 70 gr.) or possibly the Federal factory load using the 60 grain Nosler Partition bullet. Than You.:)
your 1-9 twist should shoot any of the bullets you listed just fine.
Ricky
At our shop, we are one of the rare CATM ranges staffed by reservists rather than active duty personnel. Of course some students that come to our range feel offended that they are being taught by reservists (matter of fact, one of our instructors was critiqued that "they couldn't belive that they had to be taught by reservists"..freakin' bigot! :mad: ) so we come up with a challenge for them. We are currently using M-193 out of rack grade M-16A2s at 25 meter targets. Air Force ranges aren't exaclty known for long range due mainly to available real estate. Well, if somebody has a problem with us teaching them, we'll take them out to the firing line with one of our instructors, each getting 20 rounds. We use 10 rounds for zeroing then we begin our competition. We set up 10 casings at the 25 meter line and you have 1 minute to see how many casings they can shoot. We haven't had an active duty shooter beat our guys yet!:D All-in-all, you do loose a little accuracy using the lighter 55 grain bullets but nothing that significant that it really matters. You'll be just fine shooting 55 grain bullets through a 1:7 barrel.
I have...its a S&W M&P 15...last year I used a commander length 1911 45 acp to fill my freezer (3 deer)...all were clean 1 shot kills...it's legal and I'm more than capable...nuff said.
EDIT:...Having said that...I have a few rifles to choose from....ranging from 22lr (I've used that one too....also 1 shot kills...but not legal) up to 300 Win Mag.
I have 7 rifles that I have used for deer hunting...25-06, 270, 280, 30-06, 7mm Rem Mag, 350 Rem Mag, and of course the good ole 30-30. You are entitled to your opinion...but the 223 is a more capable deer killer than the 30-30 ever was...and in an accurate gun (like my AR) will do fine on deer within 200 yards (same effective range as the 30-30) with the right type of bullet.
The 70 grain Barnes requires a 1 in 8" twist or faster. That doesn't surprise me since 100% copper bullets are always longer than their jacketed lead counterparts (copper isn't as dense as lead). So while 1 in 9" works fine for conventional bullets weighing 68/69 grains, that Barnes 70 grainer is probably as long as as 75/77 grain conventional bullet.
I'm not aware of anyone that commercially loads these, this is probably a handloading proposition. Also, from bolt gun users, I've heard some guys say these are accurate, others have difficulty getting them to shoot. Assuming you limit your ranges to 150-200 yards max, I would guess you could get a load developed where accuracy was good enough for that application.
Link
I think the 62 grain version would work fine, it's just the 70 grain version I'd be cautious about.
Nosler is a good load. Trophy Bonded also makes a 62 grain bear Claw load (I think is LEO-only), Winchester makes a 64 grain Power Point and Sierra came out with 65 grain Game King if I'm not mistaken. All would be suitable candidates for your application.
One lone example of a 1/7 twist Noveske that loves to shoot AE 55gr ball. 200 yard 3 round group at 3/8". I have a picture but don't have an online posting service.
I just purchaed a CMMG 16" 1/7 twist and plan to shoot a bunch of Wolf Gold 55grain FMJ, and I have several boxes of 60 grain tap, I expect 1 or 2 inch groups out of the tap out to 200 yds, we shall see......