Hybrid 100V and .257 Roberts

Discussion in 'Handloading and Reloading' started by gdcpony, Sep 5, 2017.

  1. gdcpony

    gdcpony Member

    Aug 28, 2008
    Sherrodsville, OH
    CAUTION: The following post includes loading data beyond currently published maximums for this cartridge. USE AT YOUR OWN RISK. Neither the writer, The High Road, nor the staff of THR assume any liability for any damage or injury resulting from use of this information.

    I source loading data from Hodgdon reloading site easily reached to confirm my information at: http://www.hodgdonreloading.com/data/rifle

    I went out today to check this powder out in my old 1943 98 Mauser sporterized by Johnson Automatics in 1954 with a 25" .257 Roberts sporter weight barrel. I give that so you know what rifle is being used. The history behind this piece is actually pretty good. It was the first ever centerfire I shot back in the early 90's and I found it later at auction in 2005. I paid more than I should have for it, but it was nice to have. Since then it has been my go to deer rifle and has even seen some matches when it had its old Lyman receiver sight on it. It now wears a Boyds Thumbhole stock and a scope. The barrel is about gone after thousands of rounds through my hands and who knows how many through the hand of others.

    It's favorite bullet has always been either a 90gr or a 100gr GameKing from Sierra. The 100gr (https://www.sierrabullets.com/store/product.cfm/sn/1625/257-dia-100-gr-SBT) is a much better deer round while still leaving enough expansion to drop a 'yote in its tracks. It is also a few bucks cheaper a box so I go with it. It is a Spitzer Boat Tail design with a BC of .355. Not the best I have used, but with this old gun being a 300yd piece 98% of the time, it works well. I have used this bullet out further on occasion when the barrel was in better shape, but not anymore until I get ER Shaw on the job.

    I have been using H414 in it to bring velocities to around 3200fps with a listed max load of 45gr. It lists a max velocity of around 3100fps, but the rifle spits them out a little faster than that. Hybrid 100V advertises to accomplish the same speed with its max load which means I could expect to see a touch higher out of my rifle. So out to the range I go with a selection of loads from 44gr to 48.2gr. Why over max? Well, the original data is written for rifles of... questionable strength ie. the 95 Mauser. With mine having been inspected and cleared for modern pressures, I went for a slight +P loading. Hence the disclaimer at the top.

    I as usual started with the min listed load of 44gr and went up in .5gr increments. This rifle won't notice finer so I figured until I approached max it wasn't worth it. I used standard CCI LR primers and Winchester +P Brass trimmed to min and necksized.

    So how did the powder perform? Five shot groups at 100yds are rounded nearest .1, average velocity is rounded nearest 10fps, and yes, I checked a couple shots of the second string over another chronograph to make sure my old beat up one wasn't being funky. I had a 25fps extreme spread so pretty reliable for data.

    Charge Group Speed
    44.0 1.8 3210
    44.5 1.5 3230
    45.0 2.1 3260 (pic)
    45.5 1.6 3310
    46.0 1.2 3340
    46.5 1.1 3350
    47.0 1.3 3410
    47.5 1.5 3440
    48.0 2.1 3450

    Please don't judge the groups. The rifle will get rebarreled after it brings home a couple deer this year. I am thinking an Ackley version simply to keep brass longer.

    The speed is the big surprise. I stopped without going any further because I had more than I expected. No need to push it. I was looking for pressure signs as soon as I read the Chrony the first time. I saw none. Even at max load the primers were a little flat, but no cratering, no flowing, no marks at all on the case head. I was seeking less pressure without compromising speed and it seems I got it. I will measure case head expansion in a bit and post that separately.

    One oddity I did notice was that the site lists this as a compressed max load. I got nothing of the sort. Maybe it is the slight difference between the Speer SPBT bullet and the Sierra equivalent but I doubt it. The 100V only filled to about halfway up the shoulder at 48gr. Seating the bullet should only have brought it to just barely out of the neck and not compressed the powder at all. Oh well, minor thing.

    Hope you enjoy the review. This powder has already proven its accuracy in my .260 Remington AR10 build where it strikes 1000yds with precision enough to out perform me. There it also exceeds book speed. For once a company seems to be under rating its product rather than giving results you can't duplicate. Too many times I have seen reports that no one can reach the speeds listed in a manual.

    Now for a quick disclaimer. Remember I said the barrel was worn out? After I have personally thrown 8k rounds through it over the years, it has lost a ton of its precision. It used to easily be a sub MOA rifle. Now, to get that I have to load very long rounds. I left them at 2.80 for this test. I will try working on OAL later.

    Now I am going to pull the remainder, measure some case heads, and load some of the best loading for some OAL testing.
    horsey300 likes this.
  2. Stevenvalleyky

    Stevenvalleyky Member

    Jan 5, 2017
    Is setting the barrel back an option?
  3. GooseGestapo

    GooseGestapo Member

    Jan 6, 2003
    Sounds like you got the same lot # I had.
    I got cratered primers and primers practically fell out of the ruined cases.
    STARTING load, 44.0gr. 3,200fps from a 22" E.R.Shaw barrel. 3" chamber/throat.
    100gr Hornady PtdSpt.

    I used it to fertilize the azaleas. Scariest powder I'd run across since some deteriorated H450 caused my .30/06 to make belted cases! Tossed it too!

    Be sure to get that action to them shortly after the first of the year. Last I heard, they were 9-10 months back logged.
    Last edited: Sep 8, 2017
  4. Patocazador

    Patocazador Member

    Jul 8, 2012
    Central Florida
    I have a .257 Roberts AI in a Winchester model 70 featherweight. Using IMR 4350 with 100 grain Nosler Partitions gives me very good groups of 3/4" (3 shots) @ 100yds. However, every now and then the groups get erratic. I tried all combos and switched to IMR4064 with good but not great results.

    It may be the featherweight barrel but I don't think I would have it rechambered to AI if I had to do it again. My 7x57 AI was always spot on.
  5. Orcon

    Orcon Member

    Aug 25, 2015
    Sidney, MT
    Holy hand grenades, that Bob is cooking!
  6. gdcpony

    gdcpony Member

    Aug 28, 2008
    Sherrodsville, OH
    Tell me about it. I have since found that 46.2 is the high group performer at an average of 1.1". Speed is steady at an average of 3340 over 20 shots so far. Some porr deer is going to regret passing by me this year.

    With me wanting to go the Ackley route mostly to save brass life, I don't think it would be worth it. But I will look into it with a local smith.

    Thanks. I will get it to them soon. I switched lots by picking up another can. Same results.

    I had a 7x57 AI before. Damn that thing would hit! I think there are only 5 of us in the world that even know that round. lol
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