Long Branch 69L Mk 1/3 gets a new Barrel

I`ll second that

The process I use is:

1) Fire one shot and clean, repeat as many times as necessary until copper fouling begins to reduce. Typically 5 to 10 shots. 

2) Fire three shot strings and clean, repeat two or three times until you see more reduction in copper fouling.

3) Fire five shot strings and clean, repeat two or three times until you see little fouling. 

4) Fire 10 shot string and clean. Break in is done. 

I was able to do this today with 40 rounds.  

I cleaned with Bore Tech Eliminator, it is easy to tell if there is significant copper fouling as the patch turns blue. Dark blue is heavy fouling. The first patch comes out black and is the powder fouling, second patch (and third) will be blue.  Once the third patch comes out with only light blue streaking, you know you’re close. 

I’ll need to tighten the barrel another 3 degrees.  The first shot went left approx 7 minutes. This is the first time I’ve had that problem. On the five barrel installations I’ve done, the first shot has always been within a minute or two of center.  Also, the elevation changed considerably, by 9 minutes (low). I don’t have an explanation for this.  I’m going to measure the pressure at the forend barrel bearing (this rifle is center bedded at 5 inches forward of the chamber). 

Once I fiddled with the sights, it started to put rounds in the x ring (200 yards), so I think this barrel is going to shoot.  This was the first 9 rounds, which I cleaned the bore between each shot with Eliminator. 

Then with a close fitting drill bit thru the rear sight axis pin ears the barrel was indeed under torqued, by about 2 to 3 degrees. Just one degree of under turn results in a 2 MOA lateral shift (to the left) in the MPI. 

Nipped up the action body a small amount at a time until the barrel and body were level. 

Now to test for groups…

Skies were clear.  This range faces south, which is the worst direction for this time of year on a clear day. The sun shines right on the firing point, and in the winter, the sun is more to the south so shines in your face. The targets are in the shade. I’m finding these lighting conditions harder every year to get a good sight picture. I far prefer to shoot on a cloudy day. 

Tweaking the barrel indexing helped, but it still shoots a bit to the left.  First five shots with the front sight centered.  200 yards prone in the sling. Held good waterline, about 1 MOA vertical spread. 

Adjusting the front sight and shot 10 rounds. I’ve zoomed into the 9 ring here for this photo. I called shot #5 to the right, that was all on me. Shot 8 and 9 was my attempt to hold slightly low as the previous 7 shots were grouping a bit high, over corrected. 

It looks like this barrel is going to shoot, five of these 10 shots are within 1/2 MOA. 

I’m going to widen the front sight by fixing .020 inch thick sheet brass to each side of the front sight blade with epoxy. I need all the help I can get, my vision is deteriorating. I found it nearly impossible to get a clear sight picture today. 

I now have 225 rounds thru the new Criterion barrel.  It’s not settling down, groups have been opening up. It will shoot perhaps 5 rounds just over 1 MOA, then throws fliers.  Many times, the first shots out of a cold bore land 3 MOA high and left. 

Some groups are terrible, over 4 MOA. It’s not good enough for shooting the 200 yd vintage matches.

 Looking thru the 18 target plot sheets of ten shot groups, the best was 2.1 MOA. That is respectable shooting prone with the Mk 1 service sight, but not 4 to 5 MOA. It’s just inconsistent and not what I expect from a new barrel. It seems to “want to shoot” but something is just on the edge regarding bullet stability. 

I don’t know what the problem is. I suspect it might have been the chamber finish reamer. This extended the throat considerably resulting in a bullet jump to the lands of 0.305 inches (174 gr SMK seated to 3.05 inches OAL). 

The first thing I noticed with the barrel was the significant change in POI on the target. About 8 MOA low and 7 MOA left. I reindexed the barrel past vertical and still a lot of left drift on the foresight blade. Never had this kind of issue before with barrel replacement. 

Thinking the worst, that I had somehow distorted the action body removing the BSA barrel, I decided to remove the Criterion barrel and reinstall the old BSA barrel I had removed. This barrel has upwards of 10,000 rounds thru it and the borescope pictures look like it does.  Indexing this barrel back to where it was by using a spirit level on the foresight block band and rear sight axis pin holes, my first shots on target were right where they should be. And it shot well for the first 5 shots. Groups did open up as expected, but it was nowhere near as bad as the new Criterion barrel, 2 to 3 MOA. 

First 5 shots just over 1 MOA. 

Three ten shot groups fired for score were 98-2x, 99-1X and 100-3x. About what it was shooting before I removed it, probably a bit better.  Not what it once was, but after 10,000 rounds, that’s still pretty decent. 

I talked to Criterion about this and they sent me a new barrel free of charge. I’m impressed with their customer service. So, this next barrel will not get touched by the chamber reamer. It is supposed to be short chambered by 0.01 inches, but SAAMI specs for .303 British chamber are likely similar to military specs and these chambers are typically reamed long to account for wide dimensional tolerance in ammunition and mud/dirt in the battlefield. Well, I don’t intend to shoot this in the trenches nor load old military ammo that may be a bit long. 

I did check several Canadian Mk 7z rounds, and they drop freely into the chamber right to the base of the rim. I also checked the throat length with my Hornady OAL gage, a 174 gr SMK touches the lands at 3.098 inches (giving a jump of 0.048 inches when seated to 3.05 inches). A 2.225 inch long case drops into the rim freely, so the chamber is long enough “as is”. 

Borescope reveals nicely cut lands in the throat area, much nicer than what they looked like on the first Criterion barrel after finish reaming.

So, I can’t see any reason to put a reamer in this barrel. I’ll install it as is, headspace it by picking an appropriate bolt head, and break this barrel in.  Hoping for a much better result. 

The barrel did headspace perfectly, 0.0640+ inches using the same bolt head. If it was too short even with a #0 bolt head, then I would have to ream it, but hopefully not necessary with this second CBI barrel (which I already have now). 

I have rebarreled two M1’s and windage was dead on center using a spirit level to index the barrel and front and rear sights set to mechanical zero. Not on this first CBI barrel…foresight blade was all the way to the left such that the right side of the base of the blade was flush with the front sight block band. Not a good sight picture.