Trail Boss, Cast and Varget 303B 6.5X55 Final Load Proofing

Proofing your loaded ammuntion.
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Macd
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Trail Boss, Cast and Varget 303B 6.5X55 Final Load Proofing

Post by Macd »

So I finally got out to the range today. Results with Trail Boss in the PH 303B at both 10.5 and 15 were disappointing. Velocities were very consistent with 10.5 running from 1143 fps to 1147. At 15 grains they ran from 1219 to 1237. This is significantly below predicted by Quickload. It was hovering around freezing and TB is temperature sensitive. Accuracy at 50 meters was 2 to 2.5 inch groups. I then moved up to Varget at mid jacketed levels 38 - 38.5 grains. Velocity spread was over 100 fps for each loading and accuracy about the same as the Trail Boss. I had some 39 grain loads with me but the top 38.5 shot was just over 2200 fps. My experience is that definitely is pushing the envelope for gas checked cast. I suspected the bullet was the problem but when I got home and was cleaning the rifle I discovered the butt stock screw has loosened so I am not so sure now. I am having some seating issues with the bullet however. If I seat it too deep it just falls into the case. I think my next try I will just seat it enough to be straight then allow it to be finally seated by the rifle. I have found this sometime works.

I also learned that I need to move to a longer eye relief scope and add some length to the length of pull. Got some nasty abrasions on my nose from the scope cover when shooting semi-prone.

The day wasn't a complete loss however. I finished load development for my 6.5x55 Swedish M96 Mauser. It put five 139 grain PRVI FMJBT bullets into a dime sized cloverleaf, again at 50 meters. That is off of a shooting bag, 2x7x40 long eye relief scope. Powder was 43.2 grains of HV100, Norma neck sized brass with bullets seated well off the lands. My previous best was with 43.0 (second picture) so that little bit of extra powder found the sweet spot. Highest velocity was 2653 fps. Incredible for a military rifle made in 1905.

I edited this when I took the picture and discovered it was a dime sized group. +guns
HV100 6.5X55 43.2.jpg
HV100 6.5x55.jpg
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Last edited by Macd on 08 Feb 2018 22:47, edited 2 times in total.
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Re: Trail Boss, Cast and Varget 303B 6.5X55 Final Load Proof

Post by RBHarter »

Awesome shooting !
I do love it when a load comes together .
Just a Red neck,White boy, Blue blood American.....
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Re: Trail Boss, Cast and Varget 303B 6.5X55 Final Load Proof

Post by Ranch Dog »

Macd wrote:I am having some seating issues with the bullet however. If I seat it too deep it just falls into the case. I think my next try I will just seat it enough to be straight then allow it to be finally seated by the rifle. I have found this sometime works.
What bullet are you using? It sounds as though the bullet is seated to the point that the case mouth is forward of the bullet's ogive.

I have found the 303 British tough to find a bullet that fits; tougher than the 308 Win or 300 Savage. The latter two have a similar short case neck but the 303 British has a long throat made up of freebore & leade. That makes it very tough to find a bullet that fills those features with a bullet body that doesn't extend into the case. The case neck protects the bullet body from the initial combustion gases just like the gas check protects the bullet base. My experience is that if the bullet extends into the case beyond the neck, you are going to lose acceptable accuracy.
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Re: Trail Boss, Cast and Varget 303B 6.5X55 Final Load Proof

Post by Macd »

Ranch Dog wrote: What bullet are you using? It sounds as though the bullet is seated to the point that the case mouth is forward of the bullet's ogive.

I have found the 303 British tough to find a bullet that fits; tougher than the 308 Win or 300 Savage. The latter two have a similar short case neck but the 303 British has a long throat made up of freebore & leade. That makes it very tough to find a bullet that fills those features with a bullet body that doesn't extend into the case. The case neck protects the bullet body from the initial combustion gases just like the gas check protects the bullet base. My experience is that if the bullet extends into the case beyond the neck, you are going to lose acceptable accuracy.
Here is the bullet with some measurements. I don't think it is suitable for the .303B. My case necks after sizing and trimming run around .340 deep. That is below the top lube groove The combination of oversize gas check and small diameter bands seem to be the problem but I am definitely no expert in this regard, just guessing. Wonder if these will work okay in some other calibre or are they only fit for the pot?
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Re: Trail Boss, Cast and Varget 303B 6.5X55 Final Load Proof

Post by Ranch Dog »

Yeah, I would say that the bullet is designed for the long case neck of the 30-06. The tapered bands are not appropriate for the short neck of the 303 British. I'm going to call it a night will check in tomorrow.
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Re: Trail Boss, Cast and Varget 303B 6.5X55 Final Load Proof

Post by Ranch Dog »

Thank is some great load work with the 6.5x55![hr]
What I wanted to get back to you with on your Parker Hale 303 British sporter is concerning that forward stock. I converse with a professional hunter in South Africa that has taught me many things about my two SMLEs. The most significant "improvement" that I made with my No. 5 Sporter was installing three small cork pads between the stock and barrel. The PH insisted that this was a must and it cut my MOA in half.

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Re: Trail Boss, Cast and Varget 303B 6.5X55 Final Load Proof

Post by Macd »

Going to try that. I was looking at bedding to free float. I free floated my PH 98 action in 30-06 and it improved accuracy about the same 50%
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Re: Trail Boss, Cast and Varget 303B 6.5X55 Final Load Proof

Post by Macd »

This morning I finished my evaluation of the .303B brass from this range trip. The brass was FL sized and trimmed to 2.222. At mid-point of case the diameter was .425. After firing the brass expanded to a very consistent .429 (+/- .0005). (I use a flat surface to raise the calipers to get a measurement on each case at the same location.) The case length on all fired cases regardless of powder or charge shrunk by up to .006. Since I intend to neck size these cases, it will be interesting to see what happens lengthwise next firing. I will be using Varget again but at jacketed loads and Speer Hot Core SPRN 180's.
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Re: Trail Boss, Cast and Varget 303B 6.5X55 Final Load Proof

Post by Ranch Dog »

I think our cases are identical. Average midpoint dimension of mine, .429". With such a change in the shoulder, the brass is going to shrink as it fills the huge difference between case and chamber. Now with each firing cycle, the brass will start flowing forward. There has been a mix of different shot pressures with my brass, and as I went through the third cycle, I was trimming some at 2.222". Now moving into the fifth, all of the cases are being trimmed.

I've been thinking about a question Johnny Enfield asked concerning annealing. I'm going to go ahead and anneal all the cartridges on this fifth cycle. With the need to trim, that tells me the shoulder is well defined and might be at the point that they will become tough to cycle. With annealing, I probably can get a few more cycles with more pliable brass, before I need to start the sizing cycle over with the full-length sizer. I honestly think that might be the death knell for any lot of brass in that the change is so dramatic.
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Re: Trail Boss, Cast and Varget 303B 6.5X55 Final Load Proof

Post by Ohio3Wheels »

With moving that much brass around my concern would be case head separations. I have a 6.5-06 that I have to keep careful watch on. With it I get the best case life by just barely kissing the shoulder and sticking to Winchester or Federal brass. I do plan to try some PPU brass for the next cases I make up.

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Curt.......makin' smoke and raising my carbon foot print one cartridge at a time +guns +guns
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