Suddenly my m-305's groups got twice as wide. please help!

axxxel

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The rifle is an m-305 with a shimmed gas system and a basset mount that used to hold a Nikon Monarch in Weaver rings. The ammo was handloaded with once fired brass. During the selection of the handloading recipe I got 1.5" groups consistently at a range of 90 yards. After finding this recipe I made a large batch of hunting ammunition using a Hornady 168 grain bullet. It sure was nice to have a lot of well shooting, well tested hunting ammo at hand!

Then I dropped the rifle from shoulder height while standing on a chair placed on concrete floor. One of the sling attachments got loose and dropped my rifle. The rifle fell on the scope and dinged it (the scope) up pretty bad but I shot some groups under un-scientific circumstances and it seemed ok.

A few months later I wanted to test the rifle before a hunt so I went to the firing range with twenty or so of my handloads. The best five shot group was more than three inches across. The hunt was for roe deer, which is a very small and skittish deer.. Needless to say I had to use another gun.

The first thing I did was to thouroughly clean the barrel with both copper-solvent and normal gunpowder/gunk solvent using experienced help, a nylon brush, a bronze brush and a zillion linen patches. Then I shot the rifle again and got pretty much the same result as before.

I've tried firing it from the bench, from prone, prone with sling, prone without sling. I shoot whith 10-20% air left in my lungs, being wary of high pulse or strained eyes. I've got a home made cheek rest that is so good I could fall asleep on it and wake up with my eye in the right spot. It doesn't matter, the groups vary in the 3-6" range.

I know I used to do <1.5" groups, I had a witness and I wrote all the group sizes down so that I could pick just the right amount of gunpowder. The best 4 shot group was closer to 1.3" than 1.5"

So I bought 100 rounds Norma FMJ factory loaded ammunition and went to the range today.

1. Five shots without changing anything (using my 1.5-6x Nikon Monarch with scrathes from the fall). 3" group at 90 yards
2. Five shots after disassembling the scope rings and removing the bases from the bassett mount (have tried remounting the bassett previously without any change), then reassembling the whole thing. 3" group at 90 yards
3. Two shots after removing the Nikon and installing an old 3-9x Weaver scope. 1.25" group at 90 yards
4. Five more shots with the weaver. 2.5" group
5. Four more shots with the weaver. 3.3" group
6. four more shots with the weaver. 2.5 " group

When I got home I used a pencil to look at how the groups would have been if I had shot them all at the same target. With the Nikon I put eight shots within four inches. With the Weaver I put eleven shots within five inches.

I wasn't shooting perfectly at the beginning of the session, or at the end of it for that matter. I was thirsty and there were mosquitoes, but I wasn't having the best day of my life when I made the handloads either, and those targets looked so very much better. Removing two flyers the weaver put nine shots within 2.1". THat's a good group, but it's not as good as the gun used to shoot, and I had to remove a couple of shots from the equation.

I have a Mauser to hunt with but I REALLY want to use this as a hunting rifle. It's just such a lovely design! I'm puzzled by this, and I don't want my dad to win.

"that semi-automatic cold war gun will never be good enough to be your hunting rifle"
"Son, buy that rifle now, but know that it's just a toy".

He was with me when I shot the handloads, his eyes were filled with awe and he admitted that I was right when he saw the target. I might have been wrong before, the day shooting those handloads just might have been the best day I've ever had :D.

Anyway, I'm gonna do some reloading tonight (using my good old recipe) ad I'm testing those shots tomorrow. Any help on what to do after that is appreciated.
 
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Yeah, I did, see report in the first post.

Basically it might have helped, but I don't really know because I wasn't using the ammo that previously got such great results in this rifle. New test tomorrow. I have a feeling it won't work though :(. What else to do? THe rifle doesn't seem to sit sloppily in the stock either, although I'm suspicious toward the stock.
 
http://www.bassettmachine.com/

I don't think so. At this moment I can't remember if it's stainless steel or anodized aluminum but it is one hefty piece of equipment. I'd be disappointed and surprised if it turns out that the mount got permanently damaged because of the fall.

thank you for the replies.
 
Went to the range today. Previously I did very fine with 44.0 grains of a swedish brand of gunpowder that supposedly is very similar to RL-15.

I had 12 rounds of 43.8, 12 rounds of 44.0 and 12 rounds of 44.3, because I found the 44.0 load using 0.5 grain increments, and I've changed the primer since.

I didn't even shot all of he handloaded ammo. THe 43.8 grain batch was visibly worse than the heavier loads, but it was all worse than the commercial ammo that I brought. I could see the crappy groups through the scope. Three inch groups at 90 yards does not a worthless rifle make, but I was using all kinds of support and "cheating" that's not availible in the field. This means that that the rifle isn't good enough for a hunt with a possibility of a roe deer@ >150 yards.

The commercial ammo shot just as bad as it did yesterday (that's the brand that I listed above). This rifle used to shoot 2" groups with the commercial ammo and <1.5" with not-so-finely-made handloads with a good recipe.

I've noticed a couple of possible reasons for my issues

1. My gas lock is loose, one of the shims have probably fallen out of the rifle during cleaning.
2. The necks of the once-fired cases had an increased diameter from the shoulder up to about half the neck. Why?
3. I have never checked head space for this rifle, but it used to be fine, why is this happening?
4. I did use the cleaning rod that came with the rifle a couple of times before buying myself a Dewey rod. Could I have badly damaged the end of the barrel?

As I said before, all input is appreciated!
 
I didn't realize until just now: the gas plug is getting loose while firing. I've noticed that it's loose before, but I've always assumed that I just didn't assemble it properly after cleaning. Then I've finger-tightened it and let it be. Today at the range I tried using the gas plug tool that comes with the rifle and actually tightening it well.

Do you think it's propable that the loose plug opens the groups like this?
 
I didn't realize until just now: the gas plug is getting loose while firing. I've noticed that it's loose before, but I've always assumed that I just didn't assemble it properly after cleaning. Then I've finger-tightened it and let it be. Today at the range I tried using the gas plug tool that comes with the rifle and actually tightening it well.

Do you think it's propable that the loose plug opens the groups like this?

It's possible, but I'm suspecting your scope isn't holding zero properly. You did say that you dropped the rifle on the scope, so your scope mounts might have come loose or shifted a bit.

Have you tried to re-zero your scope and see what happens then?

I'm sure Hungry or M14Doctor will chime in shortly (unless they're out shooting on Canada Day!!:D)
 
I've changed the scope completely! As I said in the OP, I started off using my Nikon Monarch, now I've mounted a Weaver, specifically for the purpose of seeing if the scope got messed up.

I've tightened the plug up really well now, and I've made a fine adjustment to my shims using a piece of paper (yah, I know, it's just for 10-20 rounds).

Leaving for the range with some ammo in ten minutes. Back again within 60.

I won't have another chance to go to the range for at least four weeks. I'd rather NOT be worrying about why my rifle suddenly is only good for fireworks and instead be daydreaming of all the deer I'm going to take with it.
 
No luck, the range closes at 17:00 (or 5pm).

How the hell am I supposed to last a freakin' month without knowing?!?!??!
 
Have you removed and re-installed the scope mount?

From the looks of the mount that could be your issue with it landing on the scope.

Shawn
 
Yes I have, several times. I've tried tightening it both with the recommended torque and with more than the recommended torque. Didn't seem to matter one bit, unfortunately.
 
I use a torque wrench to tighten the gas plug to what the experts (Gus Fischer et al) on M14forums suggest, 120inch/lbs. A loose gas lock/gas plug could be the culprit
 
What can kill a scope on this type rifle is not the recoil generated energy, its the recoil energy in the forward direction, when the recoil spring slams the bolt into battery. I thinking it's like how powerful air rifles(with only forward acting recoil from spring) can damage good quality scopes, that are tested with .375H&H recoil in the normal rearward direction only.

I'm not planning on scoping because only real men shoot iron sights right.:pJK

If I were to scope, there has to be lots of history on particular models that hold up well in this type of backward forward recoil environment.
Good luck in sorting this out.:)
 
Have you tried removing the scope completely and shooting Irons? Isolate the issue to either rifle or scope.


As I said in the first and third post, I have tried more than one scope snd gotten exactly the same results. This does not rule out the mount, but it does rule out the scope. I am not capable of beating 2.5" @90 yards with the stock sights. My best group with irons and that rifle is 4" or something like that. I've got good eyes and all, I' m just not very experienced with iron sights rifle shootong.

Rememberthesomme's theory is valud but I donot think that the rifle managed to beat my 30 year old steel tubed Weaver to death in the first 20 rounds.

Thank you for your input.
 
I didn't realize until just now: the gas plug is getting loose while firing. I've noticed that it's loose before, but I've always assumed that I just didn't assemble it properly after cleaning. Then I've finger-tightened it and let it be. Today at the range I tried using the gas plug tool that comes with the rifle and actually tightening it well.

Do you think it's propable that the loose plug opens the groups like this?

The gas plug coming loose suggests to me that your gas cylinder is loose and needs to be re-shimmed.
 
I did a reshimming and I torqued the gas plug much harder using a bathroom scale and the m14 tool.

Today at the range was great. I did some shooting with the factory fmj ammo that I use and noticed an improvement. Then I switched back from the 3-9x weaver to my 1.5-6x nikon and shot three rounds with my handloads.

Three holes touching.

I did two more 3 shot groups for zeroing. One of them was easily sub-moa, the other had a flyer because I squeezed the trigger too tight and the gun went off two inches to the right. I usually shoot five to ten shots for accuracy but today I was just shooting to see if the gun was functionally accurate or not. Boy am I pleased! I've spent a lot of time and ammo on this issue and now I'm coming out of it a lot wiser. By the middle of august Miranda and I will be out hunting and it feels great knowing the rifle (Mindy) is plenty accurate for the job.

A great big thank you to all who helped me!
 
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