Accuracy issues with warm barrel.

[wadcutter]

I am after some advice on a rifle that shoots completely different with a cold barrel to a warm barrel. The rifle in question is bedded under the barrel for about 2".

After some load develpoement work it now shoots about 10mm to 18mm three shot groups with a cold barrel only. However if I start the group with a warm barrel, and fire it over a short period of time without waiting for the barrel to cool, then the groups are 40mm to 50mm is size.

As the barrel heats up it throws the bullets a bit higher and way out to the right hand side. If I wait 10 minutes for the barrel to cool and fire another shot then this bullet will be back onto the point of aim where it should be. This is very predictable.

Now this barrel is not a light sporter barrel! It is a 30" heavy, custom, hand lapped Lilja barrel. Fitted by Shane Clancy, so I am thinking that the bedding under the barrel might be causing this? Any ideas?

[Curtley78]

G'day Norm,

Generally most rifles upon taking a cold barrel shot will strike substantially lower then those following, however other factors do come into effect such as humidity, barometric air pressure and wind. I experience this frequently in Small Bore.

But in saying this every animal is different.

I am guessing that the rifle in question is your .338 Lapua Magnum?

I have incurred the same heat related issues with my 338 Winchester Magnum, I doubt that it is a bedding related issue.

90 grains of powder will certainly generate enough heat to ensure that the tube expands, by allowing it to cool, you are in effect allowing the tube to contract in size thus placing it back to its initial POI. A hot barrel will generally string shots in the 12 O'clock region and then once they become too hot they will begin to drift substantially.

The fairies could place these anywhere.

I found whilst trialling my 338WM that even with the wind that I experienced had very little effect, I also realised that a I could only manage a three shot group and then would need allow the barrel to cool as the last two shots would just not hit paper.

Having allowed the barrel to cool on the second card, I then found that the first three shots were once again dead on.

I also found that the ADI powders such as 2213 and (I think from memory) 2209 generated too much heat and pressure in my 338WM.

If you want 'bang for buck' I would be inclined to trial a different breed of powder, perhaps N 560 manufactured by Vihta Vuori, I have found that it is the superior powder in two of my rifles (.308 and 338WM) and have almost tailored a load for the 6mm 284.

My 338WM is still running the factory tent peg, accuracy has improved dramatically and heat related issues reduced substantially. It's good stuff.

Hope this helps.

Regards

Sean

[chris.tyne]

Wadcutter what does Shane reckon the problem is ,you have discussed this with him ......havent you




Regards Chris.

[frakka]

Wadcutter what does Shane reckon the problem is ,you have discussed this with him ......havent you

That’s right, he obviously advocates the bedding method.

Cold barrel accuracy is king in sporter weight, three tight shots in the field is plenty adequate.

Where's Macca when you need him......large cartridges, tiny groups and long distance is his forte`

[macca]

Hi wadcutter.
Is this the 338 edge?
I have had various magnums that climb when they heat up.
A 300 win mag would put four into a cloverleaf then gradually climb up and away to the right for the ten shot group.It was very consistant in this regard and I had to aim lower each shot after the fourth.My current heavy barrel 7mm mag is also a climber but it mostly goes straight up.
Trying different powders may help but in the two rifles I mentioned it didn't.
If you don't plan on shooting more then three shots it won't be an issue.
Some more questions,(I'm guessing you would have checked all the usual things scope etc)
Is this an action glued in or with action screws?I have had to fiddle with the poundage on some rifles to get them to gather in their groups.
I doubt it is a bedding issue if the groups return to small when the barrel cools.Bad bedding usually is more unpredictable in its effects.
I'd speak to Shane as he'll probably have a better idea.
Keep us posted.
cheers,
Macca

[wadcutter]

Yeh,
Its the .338 Edge.
I finnaly got hold of Shane......hard man to catch.
He sugested removing material from under barrel and see how it goes. Can always put it back.

Just bought a new Dremel tool for the job, so a hacking I will go.

Let you'all know how it goes...............Thanks

[wadcutter]

Well I tried it out today, with the bedding removed from under the barrel.
Hot or cold barrel. Now makes no difference. Shoots into a single ragged hole at 100 yards.
Very happy with the results.

I wasted a lot of time and ammo to get to this point, but I now have a rifle that shoots like a long range custom rifle should.

[macca]

Well that's good news.Glad it worked.
cheers,
Macca

[wadcutter]

Went out and stretched its legs this morning.
With about a 10km/hr cross wind, I put two shots into a cardboard box at 610 yards and three shots into a ply target at 1000 yards.

On the 610 yard target with a 12 MOA dial for elevation, the bullets were dead centre three inches apart with a 1 MOA dial for wind.
At 1000 yards with a 25.25 MOA dial for elevation, I got a three shot group that was 3" high and 7" wide. The centre of the group was about six inches left of dead centre with a 2 MOA dial for wind.

Next I plan to do some more shooting at different distances out to 1500 yards and validate my chart. Maybe even to 2K if the scope elevation adjustment range will let me.
Should be fun.

[macca]

Way to go wadcutter.Sounds like it will be everything they say they are.
cheers,
Macca

[Predator]

could the bedding material have heated up from the hot barrel and expanded? or is it not affected by heat?

sounds like its shooting really well now, good work.

[wadcutter]

could the bedding material have heated up from the hot barrel and expanded? or is it not affected by heat?

No.

I would say It had uneven pressure from a missalignment of the barrel and the bedding material. This pressure must have increased as the barrel heated up causing the point of impact to move.

[Stonewall]

When you bed this way put a strip of 1/4 or 3/8 tape on the top edge of the bedding area on barrel first.
Then when a few rounds are fired the bedding is stable much like a v-block -not tight at the top.
This gets rid of the p.o.i. changes usually I find.
I bedded a LOT of guns in one 12 year period using many gallons of Brownells compound mostly.
I also shot more than a few to check results.

Glenn

[wadcutter]

When you bed this way put a strip of 1/4 or 3/8 tape on the top edge of the bedding area on barrel first.
Then when a few rounds are fired the bedding is stable much like a v-block -not tight at the top.
This gets rid of the p.o.i. changes usually I find.
I bedded a LOT of guns in one 12 year period using many gallons of Brownells compound mostly.
I also shot more than a few to check results.

Glenn

Glenn,
Where exactly do you place the tape? in front of the bedding or on the sides of the barrel and bed under the barrel only, not the sides?