More than one barrel of same caliber.

[Steve N]

Questions for those of you that have two or three barrels for the one caliber that they swap around on the one action. I am assuming that all were chambered with identical reamers by a competetant gunsmith. Do you generally have keep loads for each barrel separate? I imagine this would be the case because of differences in throat wear and a different bullet seating depth being optimal for each barrel. Are there any other things that have to be considered? (Not all barrels like the same load or projectile)
Has anyone found that the same load can be used in different barrels with good results?
Any information that could be shared on this topic would be greatly appreciated.
Steve.

[ecomeat]

Steve, my experience with 6 different 284Win barrels , in one BAT action, would indicate that it very much depends on the quality of the Gunsmith. The first four were done with a CNC machine, and with the same reamer the closest the "touch" measurement ever got was 0.010".
I used the same custom made FLS die, cut with the same reamer for the first barrel, for all reloading and the headspace had to be fairly close on all four chambers. I bump the shoulders 0.0005 to 0.001" and whilst the resized, reloaded cases will all chamber in any barrel, the critical issue is the freebore.
With greatly varying freebore, you have greatly varying seating depths..........which generally means greatly varying pressures , and so you get greatly varying velocities.

Enter Matt Paroz, who chambered the last two Bartlein barrels for me.
PT & G have supplied both reamers (ie both gunsmiths got their reamers from Dave Kiff)
The "touch" measurement on BOTH barrels is 2.432" with 180 gr Berger VLDs when new.
One does its best with 50.7 gr of AR2209 for 2820 fps
The other one does it's best with 50.8 gr of AR2209 for 2840 fps
I haven't actually fired bullets from one in the other yet, but will try it for you this week. I know they will fit, as I am still doing the same minimum bump with the original custom die, made for 0.313" necks. One uses a 0.005" jump, whilst the newest one likes a 0.010" jam, so accuracy-wise they wouldn't both perform with the same reloaded round.
With a quality gunsmith, it seems that it IS possible to get identical chambers .

When changing barrels, all four by the first gunsmith require minimal scope alterations of 1/2 MOA to 2 MOA. The last two done by Matt are about 1/2 MOA out on each other for elevation, spot on for windage, and both are about 4 MOA different to the average of the first four.
So my experience shows that a top quality gunsmith can get you virtually identical chambers, with virtually identical barrel orientation, but the barrels are likely to perform best with slightly different seating depths and powder charges for the level of accuracy that you are expecting .
Tony

[Steve N]

Thanks Tony. That is about what I was expecting. Sounds from that it would be wise to keep a track of seating depth etc that is required for each barrel and adjust accordingly. Keep one batch of ammo for barrel A and another for barrel B. Would that sum it up?
Steve

[AlanF]

Steve,

Thats good advice from Tony. I have 2 Barnards and about 3 barrels for each, differing brands and profiles, but the same reamer. Because Matt Paroz gets them extremely close with headspace, I can interchange brass between barrels fitted for the same action (the Barnards are many years apart in manufacture and about 0.010" different headspace, so brass not interchangeable). I keep different records for every barrel, and nearly always have a separate set of brass for each barrel, except will often fire-form in an older barrel with identical headspace. Individual barrels, even when the same brand purchased together, prefer different loads, including projectiles, so I tailor loads for each barrel and keep records. Nearly all my records (going back to about 2003) are kept on a single worksheet in Excel. Makes it easy to look back and recognise trends etc.

Hope to see you in the proper part of Australia again soon.

Alan

[Fergus Bailey]

For what its worth, I have 4 BAT actioned 6PPC rifles, and different 25 barrels that I swap across these rifles. The only thing I check when I put on a different barrel is the seating depth as it varies by a few thou on each barrel. Once I confirm the seating depth, I adjust the micrometer seating die to suit, and I am good to shoot. I can swap cases between these different barrels without any issue.

[ecomeat]

Steve,
Keeping track of your throats "touch" measurement is really critical, IMHO.
As Williada often points out, "touch" can be difficult to be accurate with, due to carbon, lint from a patch, ....any number of things.....but it's still the easiest, most accessible way for us to go. You just have to be certain that you are measuring it with an absolutely clean freebore/Leade area.....which you can do now you have that nifty Borescope
I keep a single bullet from each batch number, and always use that bullet when measuring, if that's what I am about to load. It doesn't take long to do 5 or 6 careful measurements each time, then just average them.
The first one that Matt did has eroded from 2.432" touch measurement as new, out to 2.436 after 196 rounds through it. I will quickly check it every 50-100 rounds of its life, and just keep adjusting the seater stem to give me the required jump or jam. It's approx 0.040" per turn of the thread in a Wilson stem, so I just draw a clock face on top, and knowing that a quarter turn is approx 0.010" of adjustment, it's easy to fine tune to the OAL that of are looking for.
I use a Wilson Seating die, and being a numbskull, and probably lazy, I have 5 x different 7mm "drifts" with the VLD seating insert...each one is numbered with a cheap engraver (1-5), so it's a simple matter of just using the right drift for that particular barrel....and life is easy
Tony

[williada]

Steve, I have examined quite a few groups of late with a project with a couple of other shooters and with project Penumbra where switching barrels constantly was par for the course. I endorse Tony’s comments with regard setup. The thing that is imperative is the smith must chamber the barrels so their curvature is in the same plane, so firstly, the scope is in minimised alignment to where the muzzles are pointing; and secondly, because of this alignment the tunes are more likely to be found in similar positions if the barrels are of the same profile and length.

If the tunes are found in similar positions, its more likely you can find a pet load that is suitable for a number of barrels particularly for the OCW style of tune which is neither a nodal tune or a positive compensation tune.

However, very few barrels act in the same way for absolute precision, so the pet load is used as a starting point to find the best tunes for each individual barrel. You just might strike it lucky.

It is absolutely essential that the headspace is the same, as Alan has indicated for all barrels, and that the threads on the barrel shank are of identical dimension because what will vary a tune is the combined pressure when the case is loaded on the headspace and thread contact if they are different.

You have to be acutely aware, for absolute group precision, that you do not wear the threads by constantly swapping barrels. So its a good idea to lubricate the threads. If you do wear the threads and use a tension wrench, you can still screw the headspace. Or if you don’t use a tension wrench but use a reference mark worn threads will screw thread contact tension. Its a catch 22.

People constantly swapping barrels may use 35 ft/pound as a minimum or 70 ft/pound in an effort to reduce the problem. Me, I am old school, I like 120 ft/pound and have already predetermined the crush on chambering so the headspace is identical and I am also familiar with the harmonic patterns these group tensions throw.

The most common fault in machining is that no crest is placed on the thread and on newly installed barrels the peaks of the thread bind in the receiving trough. Sure feels firm on doing up! A big mistake! Because the sides of the V thread bear the load and self centre the barrel to enable the shoulder and action face to draw up like a snap even under hand pressure. If the tension feels spongy or feels it wants to draw further the threads will unload as the barrel heats up screwing your groups. A spirolock thread cut is different but I do not think that thread cut is suitable for switch barrels because of the wear factor. Been there.

If you get a new barrel make sure you wind it in and out many times before you start tuning to make sure the contact surfaces of the threads are smooth. This means your tension wrench will be better utilised.

If you really want to reduce vibrations, the threads need to be lapped smooth with a special tool. Yes, a wooden icy pole stick cut with a 60 degree V on the bottom using suitable grit.

I prefer to have two rifles, just set at 120 ft/pounds and forget it and not have to worry about screwing my tune. Why, don't compete in short range benchrest and I often use positive compensation methods for long range and our barrels are longer, placing more tension and variables on the thread/action joint, and the right tension is critical to harmonics. I don’t want a joint that will unload due to temperature variables with poorly cut threads either. So use someone like Matt or Keith who know what they are doing. I am old school. David.

I just add another comment in relation to tracking wear of the throat. If you want constant pressure on the projectile with a gauge, just use an old case with a split neck to accept the dummy projectile. Pull the round out a bit and close it back into position with the bolt. You can back these measurements up with the Birchwood Casey tool to establish a feel for the use of that tool. Its hard to get constant feel with the rod pushing the projectile through the dummy case with the modern tool especially if its a while between drinks.

[Steve N]

Thanks for the replies.They have answered all of my questions and some I didn't even know about. I have a Sinclair tool for measuring distance to the lands and a tension wrench I got from Aldi a couple of year ago. Barrel vise and action wrench are on the way so all I need now is talk to a gunsmith. Alan and Tony have given me a tip there that I would probably be silly to ignore. This forum is a fantastic place to get advise from some very experienced people hopefully avoiding a lot of trial and error and learning the hard way.
Many thanks
Steve.

[KHGS]

For what its worth, I have 4 BAT actioned 6PPC rifles, and different 25 barrels that I swap across these rifles. The only thing I check when I put on a different barrel is the seating depth as it varies by a few thou on each barrel. Once I confirm the seating depth, I adjust the micrometer seating die to suit, and I am good to shoot. I can swap cases between these different barrels without any issue.

Ditto for me with 2 Barnards, actions are manufactured 10 years apart, same ammo in each with seating depth adjustment only. Both are the same .280 HI chambering, powder charges are the same & both hold the X ring. I can interchange the bolts as well for good measure. A good 'smith should have no trouble keeping headspace to a .002" tolerance or better.
Re throat length variation from barrel to barrel with the same reamer with integral throat, this can vary by .010" due to barrel internal dimension & rifling form & has nothing to do with the skill level of the 'smith.
Keith H,

[Steve N]

Thanks Keith. My aim is to eventually have two complete Barnards with interchangeable everything as you have. I can't see how anything could be better really.
What case is your 280HI based on? Is it a modified 280 Rem similar to a 280 AI? I am currently using a 7-08AI long throated for 180 bergers and am interested in what other options are out there in the larger cases.
Steve

[KHGS]

Thanks Keith. My aim is to eventually have two complete Barnards with interchangeable everything as you have. I can't see how anything could be better really.
What case is your 280HI based on? Is it a modified 280 Rem similar to a 280 AI? I am currently using a 7-08AI long throated for 180 bergers and am interested in what other options are out there in the larger cases.
Steve

Steve, it's based on 30/06 brass with a 40 degree shoulder, it has about the same powder capacity as a 284 Sheehane. It seems to be good on barrels. Both of my barrels have just over 1000 rounds through then now without throat fire cracking. They should make over 2000 rounds with a rechamber, maybe more with luck, time will tell. I do not run them flat out.
Keith H.

[Steve N]

Thanks for the info Keith, sounds like a good thing.
Steve

[williada]

Most land heights are about .004”, and quality manufacturers try to hold these within +- .0005”. So there is usually not a problem with barrels with the same specs. You will get variance in bore size in barrels with more lands and grooves , say a 6 groover compared to 4 groover or the old micro bores which had multiple lands because but there is a general bore land ratio that remains the same. So while the total volume is much the same, the same reamer used on different barrels with a different land height will create a different touch point.

Barrels designed for harder military jackets often had deeper grooves whereas some manufacturers have reduced depth in buttoned barrels compared to cut barrels as German Salazar comments. I remember vividly seeing a couple of carbide buttons going pop during the 1980’s during this process when a reduced land height solved the problem.

As there are tight barrels and looser barrels in .30 cal still commonly used in Australia, such as .3065” to.3085”, so to this end, the reamer must match as the projectile touch location will be different.

This is important for general team shooting specs. It may mean something in the first instance, for comparing barrels but often each barrel work hardens differently. Team shooters shoot at different rates etc. effecting barrel heat or practice more often, so the touch points soon become irrelevant as pressures change through throat wear. Keeping track of the throat is imperative more so than a general team spec given that performance levels with reloading have improved across the board.

Tony’s later Bartleins must have been spot on and the right bloke ensured the quality was maintained putting it together.