m-305 accuracy and POI greatly deteriorated. Help me troubleshoot please

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axxxel

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Hello everyone!

Yesterday I went to the range to try some prone shooting off a backpack. Usually my hunting keeps ranges at less than 100 yards but this weekend I'll be looking at ranges closer to 200 yards.

Instead of the usual 2" 5 shot groups my groups opened up to 4". I tried five shot groups with the forestock resting on my backpack and supporting the butt with my left hand, I also tried five shot groups from the bench using the sling for support. I used an elevated cheek rest to minimize neck tension and I paid attention to my breathing. When I dry-fired everything looked good through the scope. I also tried a three shot group from a sitting-on-my-butt-resting-my-elbows-on-my-knees-position, and it was at least as tight as the 5-shot groups.

Also, the center of the 4" groups were about 2" higher than my usual 2" groups are.

The rifle:

m-305 w original 22" barrel, stock except for:
shimmed gas (did it about six months ago and have shot 200+ rounds since, it seemed to help).
Bassett mount
weaver 30mm rings
Nikon Monarch E 1.5-6x42

The scope took a beating in march ( I think), but since then I've fired hundreds of rounds and the groups have been in the 2" range, so I don't think it was hurt other than cosmetically.

The ammo:
Handloaded hunting ammunition that usually enables me to shoot 2 MOA groups. 44gr Norma 203-b (which I think is similar to RL-15) pushing a 168gr hornady SPBT interlock.

The techniques tried yesterday:

1. Shooting from the prone position without using the sling. Stock resting on backpack stuffed with clothes, buttstock held with non-firing hand. Head resting on cheek rest.

2. The above, but waiting just over 1 minute between each shot

3. Shooting off a bench with rifle supported front and back, using sling with non-firing hand. ( the way I usually shoot when shooting for accuracy)

4. Shooting sitting on my butt.

All techniques led to the same 3-4.5" groups. POI moved 2-3" higher than what I set it to last time on the range.


What is wrong?:confused:

The stock hasn't been treated since I bought it. Is it possible that it warped due to humidity or something?

I haven't had time to go through the rifle yet. I'm going to check the mount and rings of course, what else do you recommend?

ALL HELP APPRECIATED, PENDING HUMILIATION DUE TO USING BORROWED RIFLE FOR WEEKEND HUNT!!!:eek:
 
Make sure your scope and mount are rock solid, check the stickies, do a search on scope mounting. Cheap scope mounts are often a culprit.

Second, unless you have a very rigid stock, sling tension on the fore end will make your POI change alot because you really can't get the tension the exact same every time.

Good luck.
 
giwolf said:
Make sure your scope and mount are rock solid, check the stickies, do a search on scope mounting. Cheap scope mounts are often a culprit.

Second, unless you have a very rigid stock, sling tension on the fore end will make your POI change alot because you really can't get the tension the exact same every time.

Good luck.
Click to expand...
:agree:
Plus did you take note on the change in weather (Summer weather will resualt in different group size & POI than in Winter weather), load (different powder, primer, round, O.V.L.)
Also did you clean the gun? Some times after so many rounds the same ammo will produce different resualts.
Finnaly also check your gas lock. If you are doing cold bore shots you want a tight fitting gas lock. Now if your athe the range blasting off 50 or more rounds you might want to flip your gas lock over so it's a little loose. This will resualt in the first couple of groups to be larger than normal but once the rifle warms up the groups will start to shrink again.
 
Use J-B weld or some other type of epoxy, instead. I would be concerned about damaging the barrel with welding.
 
The part of the op rod guide that is the furthest away from the barrel (i.e. 6 o' clock when rifle is horizontal and magwell down) moves less than 2 mm when I'm pushing it left/right. I'd say it's less than 1.5mm.

I read the scope mounting sticky and I didn't really find anything that I could have done wrong. The scope and mount combo has been great so far. I use the bassett mount, and it's installed according to their instructions. The screws for the rings are not dinosaur tight but they're tight.

As I said, I tried using the sling for a group or two and it shrunk the groups, but not radically. If all of this is caused by sling pressure then I need to remedy that somehow. The POI changed by several inches and the group size doubled. To me it's not feasible to have a "hunting rifle" that has a POI that varies with more than an inch and that sometimes shoots 4MOA groups when I'm getting great support. Imagine the risk of wounding a roe deer if I'm taking a 150 yard shot...

Last time I shot the rifle it was a little hotter and dryer than yesterday, but not radically.

It seems that both hypothesis one (sling) and two (stock change due to weather) imply that I should get a stiffer stock. Do you think that's a decent way to handle this?
 
Banana Wood

a###el said:
Hello everyone!

Yesterday I went to the range to try some prone shooting off a backpack. Usually my hunting keeps ranges at less than 100 yards but this weekend I'll be looking at ranges closer to 200 yards.

Instead of the usual 2" 5 shot groups my groups opened up to 4". I tried five shot groups with the forestock resting on my backpack and supporting the butt with my left hand, I also tried five shot groups from the bench using the sling for support. I used an elevated cheek rest to minimize neck tension and I paid attention to my breathing. When I dry-fired everything looked good through the scope. I also tried a three shot group from a sitting-on-my-butt-resting-my-elbows-on-my-knees-position, and it was at least as tight as the 5-shot groups.

Also, the center of the 4" groups were about 2" higher than my usual 2" groups are.

The rifle:

m-305 w original 22" barrel, stock except for:
shimmed gas (did it about six months ago and have shot 200+ rounds since, it seemed to help).
Bassett mount
weaver 30mm rings
Nikon Monarch E 1.5-6x42

The scope took a beating in march ( I think), but since then I've fired hundreds of rounds and the groups have been in the 2" range, so I don't think it was hurt other than cosmetically.

The ammo:
Handloaded hunting ammunition that usually enables me to shoot 2 MOA groups. 44gr Norma 203-b (which I think is similar to RL-15) pushing a 168gr hornady SPBT interlock.

The techniques tried yesterday:

1. Shooting from the prone position without using the sling. Stock resting on backpack stuffed with clothes, buttstock held with non-firing hand. Head resting on cheek rest.

2. The above, but waiting just over 1 minute between each shot

3. Shooting off a bench with rifle supported front and back, using sling with non-firing hand. ( the way I usually shoot when shooting for accuracy)

4. Shooting sitting on my butt.

All techniques led to the same 3-4.5" groups. POI moved 2-3" higher than what I set it to last time on the range.


What is wrong?:confused:

The stock hasn't been treated since I bought it. Is it possible that it warped due to humidity or something?

I haven't had time to go through the rifle yet. I'm going to check the mount and rings of course, what else do you recommend?

ALL HELP APPRECIATED, PENDING HUMILIATION DUE TO USING BORROWED RIFLE FOR WEEKEND HUNT!!!:eek:
Click to expand...

If it is a chu wood norinco stock, they are soft and eventually spring loose around the action causing groups to open and wander.

If synthetic, try removing the copper from your bore with an EFFECTIVE copper remover like KG-12 or J.B. paste.

:ar15:
swingerlh.gif
 
tjhaile said:
Use J-B weld or some other type of epoxy, instead. I would be concerned about damaging the barrel with welding.
Click to expand...

Thanks, never thought of that. Is that from person experience or just a guess?

Yes, I am also concerned about damaging the barrel which is why I haven't done it. Although the barrel is much thicker at that part. Either way, it's not something I would do without at least hearing from someone who's had good results.

Perhaps the OP can benefit from this as well. 1.5-2.0 mm of play is alot in my opinion, although I readily admit I am not an expert on the subject.
 
RockyMountain said:
Thanks, never thought of that. Is that from person experience or just a guess?

Yes, I am also concerned about damaging the barrel which is why I haven't done it. Although the barrel is much thicker at that part. Either way, it's not something I would do without at least hearing from someone who's had good results.

Perhaps the OP can benefit from this as well. 1.5-2.0 mm of play is alot in my opinion, although I readily admit I am not an expert on the subject.
Click to expand...

I have successfully used J-B Weld to secure the guide on my M14. Red Loctite is sometimes recommended, but I found that it would not keep the guide properly centred; it would tend to "walk" over to the left side (from the shooter's point of view), resulting in the operating rod being excessively tight against the receiver.
 
a###el said:
It's a Chu stock. Do you guys think a Boyd's laminate or perhaps a custom stock would be a good idea?
Click to expand...

Well...it would be stronger, higher quality, tighter tolerances, and look like a million dollars for $100...yea, it would be a good idea!

That said, your issues with group size MAY not be because of the stock. If you aren't super tight on cash, then absolutely get a better stock than the Chu.
 
Replacing the factory (thin walled and prone to break) op rod guide pin is easy. Replacements are easy to find at different hardware shops. In Sweden, that might be easier said than done. I can always mail you a few of them.

We take a 1/8" diameter pin that's 3/4" long. Shove it inside and hammer another 1/16" pin into the middle of the 1/8" pin (you must flare this one open with a broken pin punch- easy to find because we have broken so many at my clinics).

Does this help much?

Cheers,
Barney
 
a###el said:
It's a Chu stock. Do you guys think a Boyd's laminate or perhaps a custom stock would be a good idea?
Click to expand...

Yes, the Chu stock is probably your problem, if your M14 to be consistent then you need to use a laminate, or synthetic stock. Boyds laminates are excellent. Bedding in the boyds stock will make it even better.
 
I study mechanical engineering and I have access to an awesome workshop. As long as I take the time to think through what I'm doing (we study mostly math - not lathe manuals) I think I could do anything.

I might start a new thread in a few weeks or months asking for criticism on the stock drawings - or I'll just get a Boyd's and work with that.

I'm going to try and make an op rod guide by myself though.

Thank you all for your input.
 
+1 on the op guide rod and the synthetic stock. Just the general rule of keeping everything tight and mechanically consistent should reduce the variables of wandering accuracy. This applies on your hold and follow through with shooting. Be aware of your positions and it's effects.
 
Some great advice being shared here.
A few things I've noticed that affect accuracy.
-poorly fitted chinese stock liners, often not sitting true and often one receiver lug recess tighter on one side than other.
-Handguards touching stock with tension
-stock too long and making contact with inner face of gas band plate
-loose oprod guide- play of less than an 1/8 inch rotation either way is acceptable any looser and problems arise. If you have a shop, get a knurling tool and knurl the barrels oprod guide location. Apply red loctite or steel epoxy and drive the guide back on. Before it sets, position guide so as to match the oprod center to center with the piston itself.

And I could go on, but the above are common issues I deal with on a regular basis.

A stiff, correctly fitted/bedded stock in quality wood or laminate or a laminated composite are the ticket.
And an NM oprod spring guide rod is a must addition for the accuracy seekers
 
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