Loading the Smaller Bottleneck Cartridges

[fourarmed]

Yesterday, I shot some cast loads from my .270 max pistol. This round is based on the .357 maximum case necked down to .270, which makes it sort of a scaled-down 7mm TC/U. The powders I tried were 4198, Re-7, and H322. Bullet is the SAECO 270 140 grain GC. Velocities ranged from around 1450 to 1700. I would like to end up at around 1600 with this bullet for the standing category of silhouette shooting. The thing I noticed most, other than indifferent accuracy, was large extreme spreads and std. deviations in velocity. The best group (and smallest ES for 10 shots: 100 fps.) came from 4198 at 1700 fps. The bullets were water-dropped WW. I'm wondering if increasing pressures would be likely to tighten groups before exceeding the pressure limits for this alloy, or if I should consider faster burning powders. I have some cast of straight linotype I intend to try, but I'd prefer to stick to WW if possible. They were sized in a .277 die, and the nose is .270, which is a slightly loose slip fit in the barrel, which is 10" long.

Any of you guys working with small bottlenecks bigger than 22 caliber have any suggestions?

[Bass Ackward]

The thing I noticed most, other than indifferent accuracy, was large extreme spreads and std. deviations in velocity. The best group (and smallest ES for 10 shots: 100 fps.) came from 4198 at 1700 fps.

They were sized in a .277 die, and the nose is .270, which is a slightly loose slip fit in the barrel, which is 10" long.

Any of you guys working with small bottlenecks bigger than 22 caliber have any suggestions?


Fourarmed,

Small bottleneck, large bottle neck, or straight case. 100 fps spread is poor ignition. Think about things that you can do to improve this. You know what these steps are: magnum primers, larger diameter, raise velocity range or go to faster powder, crimp, etc, etc.

I would think you could hear that pistol screaming. 2400 / 5744 / 4759!

[35remington]

Dacron.

[fourarmed]

Thanks, Bass, that reinforces the vague notions I was forming. I have to be careful about primers in the Merrill pistol, as its break-open design is prone to having the firing pin tied up and the gun locked up by any sort of primer cratering. RPM recommends only Rem 7 1/2 caps, though I have gotten away with others as long as I keep the pressure low. I have some 1680 powder I may try in addition to the ones you mentioned.

This cartridge was developed specifically for standing silhouette shooting, but it has a reputation for doing its best with a case full of the slower powders and jacketed bullets. I find that much recoil is not conducive to the best scores, so I want to get this boolit out there at not over 1600 if possible.

I have only a .277 die right now, so I guess the first thing I try will be faster powders. I may try some Dacron with them, if there is significant empty space in the case. Anybody care to hazard some estimates on starting loads with the 140 gr. SAECO?

[felix]

Your 680 would be a good one, I bet. The bore might be small enough just to make this one burn correctly. Try 23 grains for a circa point. ... felix

[Leftoverdj]

Add AA-9 or WC 820 to your list. My lot of WC 820 is AA-9 rate and does very well in my .25-20. Does very well with cast bullets in my 7.62x39 also.

[Bret4207]

Just a thought, but why not try some non-quenched boolits and see if they obturate a bit and provide more consistant ignition. Disregard if you already went there.

[Bass Ackward]

I have only a .277 die right now, so I guess the first thing I try will be faster powders. I may try some Dacron with them, if there is significant empty space in the case. Anybody care to hazard some estimates on starting loads with the 140 gr. SAECO?


Fourarmed,

I am starting to play around with shotgun buffers. They can be thrown with Lee dippers or any other measuring device making everything in the case consistent. I have an old Lyman powder thrower set up for this task that makes this step painless. True, "consistent" compression can take place because it is measured. That is something I can't do with anything else.

The shot gun buffer has the added advantage of acting like another gas check and leaving a film that seems to lubricate for the next bullet. So far, I have been able to push pressures with ACWW approaching 40,000 psi. PB bullets to 1800 fps. (ACWW) And I am able to go even slower down the burn rate chart while still getting consistent ignition. I can use less lube, or I can shoot my existing load levels without waiting for the barrel to cool.

Some of these other advantages that go beyond my experiences with other fillers. Especially in hot weather or rapid firing sequences.

[45 2.1]

Be carefull with shotgun buffers in bottleneck cases, you can get too much in the case and cause problems. Loaded to proper levels, they work very well but when too much is put in and compressed heavily the fresh loaded cartridge shoots fine, but after a couple of weeks you can get higher pressure than you want. Why is something I haven't figured out since they ground poly doesn't suck up moisture from the powder.

[Bass Ackward]

Be carefull with shotgun buffers in bottleneck cases, you can get too much in the case and cause problems. Loaded to proper levels, they work very well but when too much is put in and compressed heavily the fresh loaded cartridge shoots fine, but after a couple of weeks you can get higher pressure than you want. Why is something I haven't figured out since they ground poly doesn't suck up moisture from the powder.


Bob,

Thanks. I hadn't considered that my coments might be misunderstood. Filler for me only occupies the neck on bottle neck cases to compress full case loads. It helps maintain seating depth with the goal to improve ignition. Or in straight cases. Sorta like a taylor made wax check or cookie that guarantees compression, instead of a filler.

This sounded like what fourarmed might be trying to achieve with full case loads from his description in his first post.

[fourarmed]

I shot two more loads in the .270 max this weekend. I gazed into my crystal boollit and came up with 16.0/AA-1680 and 15.0/SR-4759. The 1680 load left quite a bit of empty volume in the case, so I wasn't too confident. My lack of confidence was not misplaced, as 10 shots had an extreme spread of 270 fps - the worst I've seen so far. The 4759, on the other hand, was the best: 1600 on the nose, with es=37, sd=11. What I don't understand was why the 4759 group was BIGGER. Actually, I got TWO groups from that load. Six rounds went into 2" and 4 rounds went into 1" with a 1.5" gap between the two. The scope is a Burris 7x that is pushing 20 years old, and was subjected to quite a bit of .41 magnum load testing, as well as a good many rounds on several of these Merrill barrels. This double grouping could just be a happenstance, as I shot only 10 rounds, and I haven't seen it on any of the other loads I've tried, but the specs on this load gave me expectations.

[9.3X62AL]

My sojourn with the 25-20 will get further travel using the WC-820 as stated by DJ. I loaded up 15 of these with #257420 "for the hell of it" at the beginning of the process, and they did pretty well--but three 5-shot groups doesn't "prove" a thing. I finished up 50 of the #257420's with 8.0 grains and 50 #257312's with 7.0 grains. All were sized .260", and given Dacron treatment, in neck-sized and evenly-trimmed cases. In other words, every possible advantage and enough rounds for 10-shot groups, too. So far, the 25-20 has been an exercise in ballistic masochism with the castings--maybe this series will do better than past work.

[fourarmed]

Deputy Al, I am going to take Bass A.'s advice, and try some of the Grex shotgun filler I have around here someplace. He is not the first I've heard suggest that it may do better than dacron in some situations. It is certainly quicker and easier to use than dacron. It can simply be metered into the case.

I may try another scope, too. I don't think that is the problem, but you never do.