stock and barrel block trivia

[dave]

not wishing to infringe on existing threads dealing with these topics.

the following are just some opinions and my experiences in these areas.

barrel blocks.

although, only an opinion, i support alan fraser's and brad y's thoughts on the possible choking of the barrel by clamped barrel blocks.

therefore to avoid this possibility, for all my barrel blocked rifles, efforts have been made to ensure that the barrels are fitted within the blocks in a stress free state.

ie whether using split or one piece blocks (in either steel or aluminium), all blocks were machined with around .002"-.003" clearance over barrel diameter.

barrels were then carefully glued/bedded in position with loctite 620.

regarding the theoretical stiffness/rigidity factors provided by barrel blocks, some may find the following of interest.

according to mr otteson, the following rigidity factors are provided for various actions.

rem 700 - 0.5 units
stolle panda - 3.9 units
rem 40xbr - 2.3 units
stolle polar (all steel approx 2"squarish shape) -28 units
sleeved rem 700 - 3.3 units.

as a comparison, (assuming correct calculations on my part)consider the following rigidity factors.

2 inch square steel block with 1.125" barrel - approx 40 units (used for Heavy Gun)
2 inch square aluminium block with 1.125" barrel - approx 15.4 units (used for 17lb Light Gun)
2 inch round aluminium block with 1.125" barrel - approx 9.7 units (used for 17lb Light Gun)

1.125" parrallel barrel - approx 2.4 units

2 inch wide X 3 inch deep timber section (working on approx youngs modulus being 1/18 of steel) - 9.06 units.

but, while theory is fine, it is important to test the rigidity of stocks.

so with the assistance of students and staff at the narromine shooting institute.

a ninety kg load was applied to the plywood stock.



and then to really test the stock rigidity friendship around a 160 kg load was applied.



BTW -for this rifle the theoretical rigidity of the barrel block (including barrel) is similar to that of the stock at the mid section.

But as mentioned previously, unless the desired accuracy is achieved, it all means nothing.

cheers
dave g

[IanP]

Interesting Dave! Would be nice to know the units for the rigidity of a Barnard Model P and also for the Rem 700 action with a steel picatinny scope ramp mounted across the action.

Laminated stocks are right up there and that stock of yours looks absolutely unbreakable. I notice the diameters of the barrels seem low as Krieger quote 1.250" and TruFlight at 1.20". The diameters you are giving are they turned down to fit the barrel blocks? Never used a block so I guessing that accounts for the difference.

Ian

[Brad Y]

Dave
Fantastic experiment and a great way to practically demonstrate your findings!

If you lived in South Australia you do realise it would be painted and covered in stickers?

[dave]

g'day ian

yes, over the years, the barrels were custom profiled from maddco,tobler and kreiger.
the barrel makers provide a parrallel section to the diameter and length specified.(within the block)

for the light guns the blocks are all solid aluminium (both square and round) at around 8 inches in length.

only my opinion, but the weight of steel (3 times that of aluminium) limits it's aplication for LG blocks unless it is much shorter than 8 inches in length or much less in diameter which both significantly negate the applied rigidity.

i also believe that the blocks act as a "heat sink".

there are many advantages and disadvantages with blocks.

2 piece blocks can be reasonably easily removed from barrels.

1 piece blocks cannot be removed without virtually destroying the block or barrel or both.

1 piece blocks are uniform in rigidity throughout their length.

all blocks provide uniform and long term stable bedding.

no need to worry about solvents seeping through action threaded holes to weaken and attack bedding, which WILL HAPPEN in time.

blocks permit the use and application of less expensive and lighter weight actions if desired.

there a many examples of unblocked superbly accurate rifles, here and overseas.

as with stock design, i guess it all depends on personal priorities, experiences and needs etc.

the choice is left to each individual.

cheers
dave g

[dave]

brad

the rifle in the photo in the other thread is the 7mm kreiger which i have mentioned to you previously.

due to it's less than expected accuracy after 500 rounds of wasted time effort, $$ and frustration, it is now a "club gun".

the 6mm kreiger ordered and received at the same time in an identical configuration and stock design, "SHOT FROM THE START" and continues to do so!!! (when i don't interfere).

i suppose it proves that one should not take anything for granted, and really appreciate and take special care of accurate barrels whenever they come along.

cheers
dave

[RDavies]

Good post Dave.
I will soon have a barrel blocked rifle and was wondering about a few things.
Have you (or other barrel block users) found the accuracy nodes are at different speeds? Do you think the nodes are wider, or less critical?
Someone told me that glued in blocks might cause more throat erosion due to the insulating effect keeping heat in the throat are, have you found any evidence of this?

[dave]

rod

the possible insulating characteristics of the bonding medium between the block and barrel with bedded/glued in barrels was a consideration.

i agree that if the bonding gap is thick that it would be a problem, but as i have around .0015" max loctite thickness, i am confident that any heat build up would be insignificant and not worth worrying about.

going by feel and the heat strips on some of my blocks, it is apparent that the blocks quickly absorb heat from the barrels.

pm sent.

cheers

dave