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Thread: H335 - "Boomy"?

  1. #1

    H335 - "Boomy"?

    Hello chaps,

    It's a long time since I've been here lately - should have posted this question in September but I've been so busy I've not had a chance. That's a way of saying that I hope my memory of what happened / was said is correct.

    I was at a BDS range day at the start of Sept. I was testing another of my .308 reloads - a 110gr SP on top of H335. I've shot lots of these rounds previously during load development and I'm currently trying to refine them further for accuracy. Certainly on that day in September, it was going well - three rounds through the same ragged hole at 100m was one of the targets I produced on the day in question.

    Unfortunately, what should have been a successful day worthy of celebration was interrupted by the RCO saying that he wasn't happy with the amount of muzzle blast the rounds were producing. He feared a safety issue and asked me to stop using them and I did. Although I wasn't convinced that his assertion that a split barrel could result was correct, it would have been disrespectful to argue with him and one can of course never be certain that something untoward isn't happening, so erring on the side of caution, I stopped.

    However, my doubt at his diagnosis was partly based on the fact that I've shot around 80 of these rounds previously without incident and partly because the behaviour of the rounds (i.e. excellent accuracy) didn't fit with his explanation of what he thought was wrong.

    To wit:

    The rounds, propelling a very small bullet for .308, are short, loaded to a 2.580" OAL. The RCO feared that they were in fact so short, that they were allowing combustion gas to pass the bullet before it engaged the lands and exit the barrel in front of the bullet, which was causing substantial muzzle blast - more than one would normally expect. An alternative theory centred on worn out brass failing to expand to fit the chamber properly, allowing the same effect to occur.

    In the event, I didn't want to argue with the RCO because I wanted to keep shooting using my other rounds. However, it was generally agreed during discussions after the event that if gas were passing in front of the bullet, several other signs ought to have shown that - notably, the rounds would exhibit "random" groupings due to interference with the gas cloud and noticeably lower power and recoil because the gas in front of the bullet would not be used to propel the bullet.

    As I said above, the groupings these rounds showed were probably the best I have ever achieved with a reload and the recoil / behaviour felt exactly like any other full-power round. The brass was either on it's third or fourth firing. If the cases had failed to expand, I would have expected to see combustion residue on the outside of the case - these were not present.

    I am therefore left to conclude that the substantial muzzle blast is simply a feature of the H335 powder and the fact that some quantity of it remains un-burnt as the bullet leaves the barrel. It is probably a little on the slow side for a 110gr bullet, but not substantially so. Conversation with trusted friends and some research online certainly supports this theory, but I am the only one of my acquaintance who uses H335, so I have no direct, corroborating evidence.

    I am posting this in the hope that someone can either corroborate, or refute the idea that H335 is simply "a bit boomy" and either
    a) reassure me that I need not worry about this particular situation, or
    b) warn me about some effect and consequence I have not yet considered.

    I would very much like to continue using this round now I've found it to be accurate, but I need to reassure myself and be able to reassure the RCO that whilst the muzzle blast is undesirable, it is not unsafe, if that is indeed the case.

    With many thanks for any input you can give,

    Last edited by neutron619; 28-10-2015 at 22:09.

  2. #2
    Ignore that range officer. A split barrel?? Good grief. If you are using a listed load from Hodgdon then it is perfectly safe. Top loads for H335 and a 110 grain only generate in the low 50K for pressures. His assessment is like a motor cop handing you a ticket because your parked auto 'looks' fast. Stupidity.

    It's Ok to be disrespectful to idiots.~Muir

  3. #3
    Flashy isn't necessarily a sign something is amiss, if you've ever seen a Moisin Nagant being fired you'll know what I mean.

    H335 is about right for that weight but it could be slow which is a factor.
    If it works, smile.

    Is it by any chance a short barrel without a mod?
    If so it'll scare the BDS RCO's.

  4. #4
    Quote Originally Posted by Milligan View Post
    Is it by any chance a short barrel without a mod?
    If so it'll scare the BDS RCO's.
    The barrel is 24" and yes, I was shooting it without a mod. In the past, I've used one, which I suspect has hidden the effect previously. Completely unrelated to the above, I believe I had a baffle strike at some point a few months back as my groups suddenly expanded when the mod was on. Took it off, re-zeroed and they went back to normal - improved, even.

  5. #5
    Sounds like your RCO needs to gen up on his interior and exterior ballistics. Or indeed what would constitute an unsafe load enough to split a barrel

    muzzle blast comes with every shot
    muzzle "flash" or "flame" comes from unburnt powder exiting the muzzle as it burns.
    what exactly is he talking about?

    if the latter, his thoughts are unfounded

    i have an extremely accurate .270 round that spits flames at the muzzle and is a joy to watch in a tunnel range.

    couldn't give a toss I may be wasting a grain or two of powder or it may be less efficient

    several hundred rounds and no split barrel!

  6. #6
    Run the load / barrel length data through Quickload & it will indicate velocity, pressures, % burn & efficiency. The muzzle flash is just powder burning outside the barrel. Shoot some of the rounds over a chrono to cross check the velocity of real life against the Quickload calculation. Pull a bullet & check your powder load value just to be reassured that you hadn't cocked up. Examine fired cases & look for pressure signs.
    When you have the results laid out - pass them on to the RCO concerned & tell him the error of his ways & to go back to ballistics school.

    Don't you just love over zealous officialdom!

    Last edited by Yorric; 29-10-2015 at 13:09.

  7. #7
    Hello again chaps - thanks for the further replies - much appreciated.

    QuickLoad data is good pressure- and velocity-wise and (from memory) indicated 98.1-99.1% burn depending on the exact load I used. Would be nice if that was 99.9%, but I don't particularly mind a 3' fireball either (and someone just mentioned tunnels which is rapidly turning into a plan to go to a tunnel range, just because it sounds fun).

    I haven't put the round over a chrono, but on paper it's supposed to be around 3350fps. Experience with this gun, these cases and QuickLoad suggests it'll probably be in the 3250fps area, since my QL numbers are usually optimistic compared with the reality.

    When I get out next with the appropriate people (still saving for my own chronograph) I'll measure the MV and get the actual figure.

    I'm pretty certain that the loads are good as I pulled a few of them when I came home to check, but it's been a while so I'll pick another couple at random this evening and check.

    Thank you again for your thoughts.

  8. #8
    quickload and MV (within reason) says nothing about the actual pressure

    some rifles will show pressure with odd component choices
    some have slack chambers, bigger bores, smaller bores, tight muzzles...etc etc

    either way your RCO should not be concerned

  9. #9
    Muzzle flash and excessive blast with traditional 'ball' powders is a sign of a low load, sometimes excessively so. These powders need to be up at or close to full working pressures, in 308 Win say 55,000 or 57,000 psi PMax to perform optimally. Many handloaders take fright at the symptom and reduce loads believing it to be a sign of excessive pressure - quite the wrong response.

    So, whilst a bit disconcerting, if the load combination is working, there is nothing to worry about provided pressures and velocities are within a reasonable variation. (It's not unusual for such powders to produce considerable MV variations until the magic level is achieved whereupon MV takes a hike and the velocity spread drops. Some of the older ball types such as H335 are also primer sensitive and experimentation can pay off. Modern recently introduced types seem less prone to many of these characteristics, although I've obtained some weird results from Hodgdon CFE223 in .308 Lapua Palma (small primer / flash-hole) brass in recent weeks almost certainly an ignition / lower temperatures issue.

  10. #10
    Tell the RCO to put fresh batteries in his muffs!, Seriously though, If the RCO makes a request (in effect an order), you need to comply as he /she is in charge of your detail, and also the range.
    (The Unspeakable In Pursuit Of The Uneatable.) " If I can help, I will help!." Former S.A.C.S. member!

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