Krieger Barrels *** - Cut barrels using CNC machinery
These barrels appear to prefer boat-tail bullets set 20 of 30 thou off of the lands.
Bartlein Barrels *** (ex-Krieger guys) - Cut using CNC machinery and are apparently very accurate barrels. Twist-rates can be ordered to four decimal places!! Wow .... this sort of detail is much cleverer than I am !!
Hart Barrels ** - Barrels are button rifled, famous for the three grooves
Possibly the favourite for the traditional flat base bullet set into the lands
Shilen Barrels **
Broughton Rifle Barrels
Barrel Torque for Custom PPC Action
100 to 150 ft/lb is generally regarded as the normal barrel tightness for Custom Benchrest Actions.
I personally think 80ft/lbs is a good compromise if you are constantly changing barrels on an aluminium action.
Many of the top benchrest shooters in the US do not tighten barrels that tightly. I reckon they are only tightening to 50 to 60 ft/lb
Factory barrels are apparently torqued to nearer 250ft/lb though I must admit when I have removed factory fitting Remington barrels they are not torqued to anything like 250ft/lb .
Clean threads and coat with high pressure grease before installation.
Some very informative comments from Greg Walley of Kelblys
Barrel Torque - 100 ft/lbs Minimum
Barrels need to be
tight. Many years ago, when George Kelbly asked Mike Walker (engineer at
Remington, and one of the original founders of benchrest) about how tight
barrels need to be, he didn’t miss a beat….100 ft/lbs minimum. Keep in mind
that Remington back in those days spent lots of money researching what made
guns perform in their indoor shooting range.
You should lube the shoulder and threads with the green grease that came with your action. Apply a liberal amount to the CLEANED threads and shoulder.
If you do not have any of the grease that was sent with the action, go to the auto parts store and obtain Mobil Synthetic bearing grease. It is red in color, and the grease tube is silver with blue end caps. Lucas Products extreme pressure bearing grease also works well. It comes in a white tube with their logo on the front like the rest of their oil additive products.
DO NOT use nickel or copper anti-seize compounds. They are not for this application. The barrels are usually 416 stainless and only 25-28 Rc. Anti-seize is for hardened bolts and sliding latches, lug nuts and studs, etc.
In many cases where I’ve seen anti-seize used, galling was the result. Not in every case, but many. This has not only been with our receivers, but with every custom and factory action that’s been in our shop.
I’ve done extensive tests on galling of the metals used in actions and barrels, and only extreme pressure rated bearing greases stand up to the task.
I also expect that many barrels and guns that aren’t performing are because of insufficiently tightened barrels. I’ve fixed quite a few bummer rifles simply by tightening the barrel. There was a famous gunsmith some years ago that made a lot of money by simply tightening barrels on benchrest rifles.
Stolle Barrel Tenon & Head Spacing
Stolle Panda recommended Tenon length 1.115. Can go longer for precision fit (1.119). Clearance between bolt face and barrel 5 to 8 thou.
Headspacing is not as critical on a precision rifle as the brass will simple expand to the shape of the chamber. The shoulder is then bumped to provide a 1 or 2 thou headspace gap to reflect the shape of this chamber. Brass must be matched to each barrel and not interchanged.
Headspacing is important on a factory rifle using standard SAMMI ammunition. If the barrel is not fitted with the correct tolerances then there could be excessive headspace between the shoulder of the brass and the chamber which could result in rupturing of the cartridge.
A shorter Barrel Tenon will result in the head of the brass protruding from the barrel. If this is excessive then the case will rupture as there is nothing to support the side walls of the cartridge. The Tenon would probably need to be cut back in excess of 100thou before the cartridge would rupture.
Hart (Original) - 1.115, Hart (Ebay) - 1.100
Benchrest - Case reduction sizing usually has a net reduction of
about 0.000.1 to 0.0002” but up to 0.0005”.
Palma, F-class & Precision Rifles - Case reduction anything from 0.001”-0.0015”.
Hunting Rifles - The SAAMI (Small Arms and Ammunition Manufacturers Institute) specs (tolerances) can be as much as 0.008”-0.009” difference between maximum chamber and minimum cartridge. Their loaded brass must be able to fit chambers that vary as much as 0.008-0.009””.
90 deg recessed Crown, 13 deg Crown, 90 deg flush Crown
1 - The muzzle bore should be aligned with a dial indicator, indicating the grooves, till a 0.0001" or less Total Indicator Runout (TIR) is obtained.
2 - Crowning should be done by facing from the bore to the OD with a very sharp, positive rake, tool. The last cut shouldn't be over about 0.002"-0.004" (0.1 mm) depth of cut.
3 - Use a cotton stick swab (Q-Tip) to test for any burr. Should be practically none.
4 - Re-crowning usually needs to remove about 1/16"-1/8" (2-3 mm) or so to get the worn portion removed.
There is an old gunsmiths trick to use a round-head brass
screw and lapping compound to lap the burr off but I don't think this is a good
idea on a benchrest crown since there is not enough control with a hand held
screw to make an accurate bevel, IMO.
1 -Firstly the barrel must be set up running true - end to end IN THE BORE to 0.0002 (two tenths of a thou.)
2 -Crown from the inside - out. This way, you avoid raising a burr on the inside. Check for burrs by stroking with a cotton-bud.
3 -Don't allow any burnishing of the crown - it should be good without touching-up.
6x47 Barrel Twist Comments
Comment 1 - My 6x47 Lapua, which has a 30" Bartlein 8-twist, shoots both the Berger 115 VLD & DTAC 115 very well out to 1000, at avg. vel. of 2995fps, which is only about 50fps faster than they go out of the Dashers. It seems - based on my experience and what I've heard from a few other HP shooters - that while most 8-twist bbls. shoot the 115s very well, there are a few that don't. Krieger offers 7.5-twist 6mm blanks, while Bartlein has sold quite a few 7.8-twist barrels. I've got a couple of each of these faster twist bbls. on hand, but am planning to go with another 8-twist in my next 6x47.
Comment 2 - Initial testing with 6 X 47L showed promise with 115Gr VLD out of 30" MAB 1:8 in the end 2 X barrels had problems stabilising the 115 B would go 1:7.5 to be curtain
Bullet Choice for the 6x47
105 Berger and 107 Sierra probably better with 8 twist. Can still use out to 1000yds
VLD's difficult to tune (108grn Berger traditional boat tail easier to tune).
3150 to 3250 ft/sec bullet speed
115 Berger and 117 DTAC probably better with 7.5 twist (actual design twist 7.776 twist).... some have been using 7.8 twist
115 and 117 grains are more difficult to tune. Can still use 105/107 grain with 7.5 twist if one cannot make the 115/117 grains shoot.