Question for number four MkII shooters

[Jack Stanley]

I was loading some two hundred and eight grain bullets in a number four MkII today . Range was thirty-five yards on a B-3 target . Powder charges were eighteen , nineteen and twenty grains of 2400 powder . The eighteen grain charge landed to the right of center the nineteen grain load was almost centered and higher and the twenty grain load was just left and higher still .

So why do the groups move left like that when the charge is increased ?

Thanks , Jack

[Multigunner]

I was loading some two hundred and eight grain bullets in a number four MkII today . Range was thirty-five yards on a B-3 target . Powder charges were eighteen , nineteen and twenty grains of 2400 powder . The eighteen grain charge landed to the right of center the nineteen grain load was almost centered and higher and the twenty grain load was just left and higher still .

So why do the groups move left like that when the charge is increased ?

Thanks , Jack

Lee Enfields are known for action body flexing that throws the bullet to the left. Enfields normally have rifling with a left hand twist at a 1:10" rate of twist.
Both qualities tend to send a bullet to the left of the line of the bore.
The front sight bases are offset to the left to compensate.
The amount of off set is regulated to the throw and drift of the MkVII cartridge.

Some light heavy bullet loads I tried went far to the right of point of aim. I supose because these light loads did not cause any flexing of the action body.
In other cases differences in velocity may result in the bullet leaving the muzzle on the back swing of the vibration.

The heavier the barrel , as in the No.4 and No.1 rifles with the HT barrel, the less the effect of action body flexing.

PS
Un equal bearing of the locking lugs can increase the effect.
You might want to smoke your lugs and check their bear surfaces.

[Jack Stanley]

Thanks , my first thought was to try nineteen and a half grains and see if that puts it on center .

Perhaps I'll check the lugs too .

thanks again , Jack

[303Guy]

Interesting! I haven't found that effect but then I've had free floating barrels with the action and Knox form bedded. Undoubtedly the action flexes sideways (sort of) but it's interesting to hear of these observations. Why are my observations different? I've had vertical stringing from what I believe to be a stressed action from bad bedding. I built an SMLE sporter for a buddy with a new and full length barrel which I free floated and bedded as I've said and while it could only produce 2 MOA 10 shot groups with my hand loads it seemed to print any ammo to the same POI, military, my loads and factory sporting loads. That guy got a bargain, I did the stock making for free! (Fibreglass - it was light and a nice fitting butt-stock! I was proud of that one).

[Multigunner]

Interesting! I haven't found that effect but then I've had free floating barrels with the action and Knox form bedded. Undoubtedly the action flexes sideways (sort of) but it's interesting to hear of these observations. Why are my observations different? I've had vertical stringing from what I believe to be a stressed action from bad bedding. I built an SMLE sporter for a buddy with a new and full length barrel which I free floated and bedded as I've said and while it could only produce 2 MOA 10 shot groups with my hand loads it seemed to print any ammo to the same POI, military, my loads and factory sporting loads. That guy got a bargain, I did the stock making for free! (Fibreglass - it was light and a nice fitting butt-stock! I was proud of that one).

Since the flex results in a swing, of only a few ten thousandths at most, not much more than a vibration with more movement in one direction, its the point of exit from the muzzle during the swing that governs where POI in the horizontal plane would be.
The very light heavy bullet loads I tried might well have printed to the point of aim had I used either a grain more or a grain less of powder.
Then again its just as likely that these loads simply did not exert enough back thrust on the bolt to cause any flexing at all. This would have made the front base offset the factor in POI being far to the right.

The long range compensation factor works in much the same manner, with slower bullets leaving on the upswing while faster bullets leave on the down swing, This would result in increased vertical spread at short range but gravity acting on the bullet brings them back into the group further down range, while horizontal spread will continue its spread as the bullet travels.

The MkVII and MkVI seem to have much the same POI in the horizontal plane relative to the sights, even though theres a broad difference in both bullet weight and velocity.
My loads using 150 gr bullet with aprox 2600 FPS has the same POI in the horizontal plane as milspec 175 gr bullets at 2440. Each is at its sweet spot.
This 150 gr load is one I found in a very old loading manual. The charge weight was given to within .5 gr. I started out a couple of grain below the recommended charge and worked up. I found that the .5 gr made all the difference in both group size and POI.
That load hit the perfect sweet spot for the Enfields.
This load just happens to mimic exactly a load the British had been planning to try for the .303 before WW1 but cordite and available powders were not well suited to the load at the time.
A 150 gr pointed bullet at 2600 FPS had been recommended by ballisticians as the best compromise for an Infantry rifle cartridge. The 7.62 NATO betters that velocity a bit, as did the 150 gr .30-06 and the German 154 gr Spitzer.

[Jack Stanley]

It was years ago that I had this rifle out and running and if I remember right the ammo was HXP surplus . Just recently I got this one out to shoot some very ultra light Bullseye loads with medium weight bullets . I do remember having to bump the sights back to center from the left side as I recall .

I'm in a bit of a fix with this particular rifle , it has the smallest groove diameter of the three 303 rifles I own . As I remember it shot the HXP surplus well and I have a little more to use . Of all the molds I have only one fits it well AND feeds from the magazine , only real downside to me is my eyes have a hard time seeing that skinny front sight . Oddly enough , when using the number one MkIII , I can cee it's front sight better :veryconfu

My lead bullet goals are to make this bullet work as well as I can for shooting inside of a hundred yards . So I guess twenty grains or a little less centered on the target will do nicely . With the differences of groove diameters of the other rifles I don't think there is much chance of a load that all of the rifles like . So chances are good I'll sell the Mk1 and have different loads for the number four MkII and the number one MkIII .

I'll check the lugs on this MkII , all the screws , and see if nineteen and a half grains will center up .

Jack

[Multigunner]

While looking for something else entirely I ran across a section on experimentation on barrel harmonics in Reynolds' Lee Enfield book.
They tested the No.4 barrel profile by fitting one to a P14 action bedded in a stock which had the fore end cut off just ahead of the chamber.
Results of these and other experiments indicated that free floating would greatly reduce the effects of action body flex on the barrel vibrations.

[Jack Stanley]

Perhaps then the next detail cleaning for the rifle I should look to see the barrel isn't rubbing the stock/handguard ?

Jack

[Multigunner]

Perhaps then the next detail cleaning for the rifle I should look to see the barrel isn't rubbing the stock/handguard ?

Jack

Free floating sounds like a good place to start.

The recommended bedding methods, such as those for sniper rifles, were developed with the full power MkVII ammunition in mind, and may not be as well suited to lighter Cast Boolit loads or other handloads.

[303Guy]

Thanks for that Multigunner. That explains my findings. Yet some say they've had better accuracy with full barrel bedding. I'd have thought the compensating effect would be luck of the draw but then I'd be wrong it seems. Something I've never found is a 'sweet spot'. Changing the powder charge hasn't made any difference to group size but POI changes. I've mentioned before how a 'poorly' bedded No4 two-groove was accurate but sensitive to fore-end hold then after 'proper' bedding the POI changed but the rifle seemed less sensitive to hold but not enough shooting was done to say so that's just conjecture at this time. That same rifle had the same POI with two different powders - Varget and H4350. Interesting. The rifle is fitted with a moderator. I wonder how that would influence POI?

[Dan Cash]

I was loading some two hundred and eight grain bullets in a number four MkII today . Range was thirty-five yards on a B-3 target . Powder charges were eighteen , nineteen and twenty grains of 2400 powder . The eighteen grain charge landed to the right of center the nineteen grain load was almost centered and higher and the twenty grain load was just left and higher still .

So why do the groups move left like that when the charge is increased ?

Thanks , Jack

Barrel harmonics most likely followed by bedding then more esoteric causes. It is not uncommon for different loads, especially those with different weight bullets, to shoot to significantly different points of impact.

[Multigunner]

Thanks for that Multigunner. That explains my findings. Yet some say they've had better accuracy with full barrel bedding. I'd have thought the compensating effect would be luck of the draw but then I'd be wrong it seems. Something I've never found is a 'sweet spot'. Changing the powder charge hasn't made any difference to group size but POI changes. I've mentioned before how a 'poorly' bedded No4 two-groove was accurate but sensitive to fore-end hold then after 'proper' bedding the POI changed but the rifle seemed less sensitive to hold but not enough shooting was done to say so that's just conjecture at this time. That same rifle had the same POI with two different powders - Varget and H4350. Interesting. The rifle is fitted with a moderator. I wonder how that would influence POI?

A moderator can make a great deal of difference in barrel harmonics.
That much weight added near the muzzle, or at any point from before mid barrel on, acts to dampen and otherwise alter barrel harmonics, either for good or bad.

The barrel of my two groove Savage No.4 is one of those rush jobs where they skipped the final finish turning of the exterior between a point a couple of inches past the reinforce and the shoulder before the sight lugs.
These barrels have a slightly thicker wall in the mid barrel. Tests on these to determine if accuracy would be affected by this short cut indicated that the rough turned barrels were noticably more accurate than barrels finish turned full length and properly finished.
Aside from the very rough appearance of the exterior (almost threaded appearance) , and rough hand filing done to break the edge where finish turning met rough turning, the difference in profile is something you have to look closely to spot.
After doing some filing and sanding on my barrel due to some deep pitting on the rough tuned section the difference was more noticable.
In profile the barrel has a somewhat bulged appearance at about three inches past the reinforce, but slugging the bore proved there was no bulging.
The profile is not a straight taper, and the final one third or so has a reverse swamp. The area between reinforce and start of the thickened area has a very slight positive swamp.

Theory on these was that the unequal thickened area dampened barrel vibrations. The same principle has been used in different forms on target air rifles and target rifles, and the SFW barrel for AR clones.
Vibration dampers afixed to the mid section of target barrels serve the same purpose.

I've been wondering if the rear sight base of the SMLE has a similar effect, since the slimmer no.1 barrel exhibiterd more consistent long range compensation compared to the No.4 rifle with receiver mounted apeture sight.


PS
Another thing occured to me. The No.4 MkII has the body hung trigger rather than the triggerguard hung trigger.
I had not looked into these much, but remember reading of experiments done on adding a triangular frame work to the action body and socket of the No.5 carbine, with emphasis on bracing the action for use with heavy anti-tank rifle grenades. Not sure if this bolstering frame also held the trigger mechanism as those added to the No.4 MkII.
The bracing should have some beneficial effect on the rigidity of the action body.