Reading my M305's groupings

W

WHOPPER_JR

Member
Rating - 0%
0   0   0
Location
Saskatchewan
My M305 is nothing special, just a wood stock and a match spring guide rod that I added. Earlier this month I decided to put a scope on it using the CASM scope mount and bushnell/ring combo that Frontier Firearms offered. I used 150gr American Eagle to get it on paper at 100m.
I got a Cabelas gift card for my birthday and decided to use some of it on a box of 168gr BTHP Federal gold medal match ammo. I took it shooting last week at 100m and here are the results.

The right target was two groupings of 150gr Federal Eagle for a warm up. A minute of pie plate. I was about to go home and make sure I have the mount on right, but I decided to see what difference five rounds of match grade ammo did.
http://i.imgur.com/5RE553A.jpg

Here is another five rounds of the 168gr. A similar grouping.
http://i.imgur.com/LigObVk.jpg


In both groupings of match ammo, the first shot or two would land 2" above the point of aim. The rest of the shots would form a grouping another 1" high and 2" to the right. What would have caused this? My theory is that I didn't let my barrel cool down between shots. I know there are some faults to my rifle such as the hand guard fitting at an angle and touching the left side of the stock. I also need the shim the gas system. I think the gas ports line up though, I was able to push a toothpick down both holes.

Any feedback is appreciated, thanks.

YTkeaTG.jpg
 
Trigger guard lockup is important as is draw pressure. Shimming the gas system will most likely make the biggest difference. If your gas cylinder slides on very easy or if it rattles around when you slide it on, then peening the barrel so that it's tight will also help. First shot flyer's can also be caused by bolt thrust (how the bolt interfaces with the barrel when a full magazine is inserted) as well as the action settling into the stock. Many variables here. Take care of all the little things first, then see how it shoots and go from there.

Tony.
 
The first thing to keep in mind when dealing with M14-type rifles are reasonable expectations. In terms of pure accuracy, an M14 is not going to be competitive with a bolt action or even one of the .308 AR rifles. The two groups with match ammunition are actually not bad for an essentially unmodified M305.

I concur that shimming the gas system will likely make the biggest difference. Also, the Chinese wood stocks are very soft and definitely not conducive to accuracy or retaining zero.
 
I'm not ####ting you when I say this but Barnual 7.62x51 steel cased shoots the best out of my M305. Norinco 7.62x51 is second best. Eveything else is garbage in comparison. I'm getting ready to start handloading for it though.

Do you have a flat recoil spring guide or a round one? My M305 went from 4" down to 3" with just that drop in replacement.
 
Your rifle clearly isn't impressed with the AE and likes the higher price match ammo better. Sort of typical of any rifle, even those with match grade barrels.
The Federal stuff uses a 168 grain Sierra Matchking at 2650 fps. The 150 is just an FMJ at 2820 fps. If you get into reloading(and you should. Tailoring the ammo to your rifle makes a huge difference.), what you plan on doing with the rifle will matter.
Minute of pie plate is good if you shoot off hand. Not so much from a bench. In any case, if you're not reloading, you have to try a box of as many brands as you can to find the ammo your rifle shoots best.
 
When I switched for the black feather op rod spring guide I barely gained any accuracy but my groupings became more consistent. No more flyer.
The best improvement I gained was from shimming the gas system. I went from 8 MOA (lol) to a constant 3.5 MOA with norc surplus ammo. It's super cheap (Tacticalteacher has them for $5) and you will get a lot more out of your rifle.
 
Quick fixes for you to try. New Op rod spring guide (Round) Check out Tactical Teachers advert, Armtac, or Treeline out of the U.S. Shim the gas system up for a better lock up if the 180 trick doesn't work. while your at it see that the gas system is snug when you are sliding it back on after shimming. If it is not, then Peen the splines on the barrel to get the gas system to fit tighter. Do the same to the flash hider splines. The only thing in these fixes that will cost you anything is the spring guide and spring if you replace it (I would). Good luck with your rifle, they are a blast! On the ammo front try, the good old Federal Blue box 150 grains. They usually shoot awesome out of these rifles. Avery one I have had seems to love that for factory fodder!!
 
Thanks for the info guys.

I already have the shims; I ordered them with my round spring guide rod. I haven't gotten around to putting them on as my 2007 production M305 may have the flash suppressor spot welded on. If that's the case could I get away with snipping one of the shims and fitting it over the barrel that way? My gas lock snugs up at around the 7 to 8 o'clock position and my gas ports line up, so I'd hate to go through all that work of ripping off my flash suppressor if I only get minor improvements.

BTW TonyBen your youtube videos are great. Helped me get acquainted with my new M14.
 
WHOPPER_JR said:
Thanks for the info guys.

I already have the shims; I ordered them with my round spring guide rod. I haven't gotten around to putting them on as my 2007 production M305 may have the flash suppressor spot welded on. If that's the case could I get away with snipping one of the shims and fitting it over the barrel that way? My gas lock snugs up at around the 7 to 8 o'clock position and my gas ports line up, so I'd hate to go through all that work of ripping off my flash suppressor if I only get minor improvements.

BTW TonyBen your youtube videos are great. Helped me get acquainted with my new M14.
Click to expand...

Don't snip the shims, they will not last. Removing the flash hider is not that hard! Tighten up the gun in a vise, take out the flash hider Allen key and back the castle nut off. Give it a whack and then loosen off the castle nut a bit a bit more. The only tool you need are castle nut pliers. If you don't have some you can order online, or depending on where you are myself or another nutter can give you a hand with it. My 22'' was shooting 2-2.5" iron sight groups after the few basic mods and I can hardly see the target at 100 yards with my SH!TTY eyes. Thats why both my Norc and my Springer got their scopes mounted tonight !
 
Yes M14 lovers! :)

Swapping or replacing out the factory flat op rod spring guide (hey, it's a battle rifle) with a round NM style op rod spring guide found at dealers on here like Magwedge, SFRC, SJHardware, and many more others. That's the first thing I did whenever I received a NEW-to-me USGI M14. :)

Then the next thing I needed was a set of castle nut pliers to access that flash suppressor and gas cylinder and then the op rod guide (gotta ensure that there is a snug fit on the barrel.


The very next thing I would do was to tighten up the gas cylinder fit with a gas cylinder lockup that was super tight either by swapping/trading and 180'ing other gas locks. We traded amongst ourselves back in Sharon Gun Club, North of the GTA back in the day (1986). Yes we shimmed our gas systems as a last resort.

Once that gas cylinder fit was nice and tight, we would reassemble after peening our splines and obtaining a super tight fit...no more lateral or side to side woble of the gas cylinder. :cool:



Then I would (iron sight competitor here) replace the front sight with an NM unit (0.062") thick/thin. If I could not afford that front sight (I had 2 kids in diapers) then I would file down the front sight to the NM spec. If I could afford a set of rear NM sights, I would buy and then install them. If I could not, I just purchased the hooded rear aperture and competed with the standard USGI 1 MOA sights.

Tighter groups? I handloaded my own match ammo using the Sierra MK 168 gr booolit and often I would find the Hornady 168 gr Match boolit. In the past I even used Speer 168 Match booolits, too.

Back then the USGI M14 rifles all arrived from Israel (for the most part) were supplied with USGI brown glass stocks. Perfect for glass bedding. That was the next step because we did not have a source of after market match barrels like the Kriegers being inventoried from CGN dealers like Jerry Tao (Mystic Precision) and Peter Dobson (Hirsch Precision). Today, I would rebarrel with a match barrel first, then glass bed!

Oh yah, back up a few steps, did I mention greasing that rifle? For the newbies showing up with recent M14 purchases, have a read here....

https://www.full30.com/video/c3e9b71faaf24cdf7a3369aa1bbf0876

Now get yourself a good and reliable and solid sling ; that's if you shoot with a sling. Remember, I'm coming from the competitive shooting stream, no bench rest for me. And that's why my bench rest shooting sucks big time. :evil:

Enjoy the tweaking process! :wave:

Barney
 
WHOPPER_JR said:
My M305 is nothing special, just a wood stock and a match spring guide rod that I added. Earlier this month I decided to put a scope on it using the CASM scope mount and bushnell/ring combo that Frontier Firearms offered. I used 150gr American Eagle to get it on paper at 100m.
I got a Cabelas gift card for my birthday and decided to use some of it on a box of 168gr BTHP Federal gold medal match ammo. I took it shooting last week at 100m and here are the results.

The right target was two groupings of 150gr Federal Eagle for a warm up. A minute of pie plate. I was about to go home and make sure I have the mount on right, but I decided to see what difference five rounds of match grade ammo did.
http://i.imgur.com/5RE553A.jpg

Here is another five rounds of the 168gr. A similar grouping.
http://i.imgur.com/LigObVk.jpg


In both groupings of match ammo, the first shot or two would land 2" above the point of aim. The rest of the shots would form a grouping another 1" high and 2" to the right. What would have caused this? My theory is that I didn't let my barrel cool down between shots. I know there are some faults to my rifle such as the hand guard fitting at an angle and touching the left side of the stock. I also need the shim the gas system. I think the gas ports line up though, I was able to push a toothpick down both holes.

Any feedback is appreciated, thanks.

YTkeaTG.jpg
Click to expand...

Whopper it looks to me you have windage disperion in your decent groups. On all groups your vertical dispersion was only 1-1.5" so you're doing MOA with that big glass on there. Windage wise you were 2.5-4". I can't say for sure, but it took me a long time with a lot of determined belly shooting unsupported to control the M-14's trigger and not put excessive windage into my groups. I feel the control is in how you grip the pistol grip and trigger finger tip pressure.
Maybe there's an inherent M-14 gremlin that gives wider groups than height due to bedding/action tightness issues, but I'm thinking its can be just as much trigger control practice with this type trigger and stock shape. I found I produced more circular and tighter groups when I would control the pistol grip with right thumb pressing into centerline of stock, lower three pressing back towards thumb to counter(old school weaver pistol stance grip technique:cool:) and trigger finger pressing at the tip imagining it going straight through the centerline of stock. The support hand just doing that,.. supporting,..... and not trying to control the whole operation. Try it out it works for me.:canadaFlag:
 
RememberTheSomme said:
Whopper it looks to me you have windage disperion in your decent groups. On all groups your vertical dispersion was only 1-1.5" so you're doing MOA with that big glass on there. Windage wise you were 2.5-4". I can't say for sure, but it took me a long time with a lot of determined belly shooting unsupported to control the M-14's trigger and not put excessive windage into my groups. I feel the control is in how you grip the pistol grip and trigger finger tip pressure.
Maybe there's an inherent M-14 gremlin that gives wider groups than height due to bedding/action tightness issues, but I'm thinking its can be just as much trigger control practice with this type trigger and stock shape. I found I produced more circular and tighter groups when I would control the pistol grip with right thumb pressing into centerline of stock, lower three pressing back towards thumb to counter(old school weaver pistol stance grip technique:cool:) and trigger finger pressing at the tip imagining it going straight through the centerline of stock. The support hand just doing that,.. supporting,..... and not trying to control the whole operation. Try it out it works for me.:canadaFlag:
Click to expand...

Horizontal dispersion can also be attributed to the fact that he's got no cheek riser. Proper cheek weld is critical when shooting both with scope and irons. It's more obvious when using scopes though.

Tony.
 
TonyBen said:
Horizontal dispersion can also be attributed to the fact that he's got no cheek riser. Proper cheek weld is critical when shooting both with scope and irons. It's more obvious when using scopes though.

Tony.
Click to expand...

Good point Tony, that scope is quite a bit above the irons height over bore distance. Maybe it's my cheek weld more than my trigger control. I'll work harder on both, I never duplicate the horizontal dispersion with any other type I shoot over irons like the M-14 though. In fact my groups tend to be getting more vertical with years from not controlling(seeing, or going blind lol) the vertical aim point. All good on silhouette type targets that are forgiving to vertical more than horizontal, and rightly so.;)
 
Alright, time for an update. Since my last range session I shimmed the gas system and took some sandpaper to the fiberglass handguard for a temporary fix. I also made a cheekriser out of a couple pads and some residue free self adhesive tape.
This evening was a perfect time to try it out as there was no wind. I also tried maintaining the yoga breathing, smooth trigger pull, all that jazz.

I shot two five shot groups of the 150gr American Eagle and saw immediate improvement. They actually formed groups this time!
http://i.imgur.com/ZhWQudn.jpg

I then fired two five shot groups of the 168gr Sierra HPBT Gold Medal Match.
The first four shots made three holes in a 1MOA grouping, and the last shot was a flyer where a mosquito in my ear caused me the jerk the trigger. (excuses, I know)
http://i.imgur.com/N4cylPH.jpg

Then I got a 2 MOA grouping with the second group.
http://i.imgur.com/BJGGjHg.jpg

I also brought a box of 150gr SP Federal Powershock with me. This stuff costs the same as American Eagle, but these groupings surprised me. I took the calipers to that last group and measured 2.2 MOA. I will keep trying different brands of relatively inexpensive ammo, but so far this stuff is my go-to brand.
http://i.imgur.com/vj5paCO.jpg

There is a lot more stuff to do to this rifle such as making sure it is properly bedded and finding a more permanent solution to fitting the handguard. I'm satisfied with the way it is for now, though. I just want to rack up some trigger time with it.
eTQqJ7i.jpg
 
You must log in or register to reply here.
Back
Top Bottom