Short-barreled 30-06 with muzzle break

A

aletheuo

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Cranbrook, BC
My dad has been frustrated with his BSA featherweight in 30-06. It's got a 20 inch barrel with 2" factory muzzle break on the end (ie/ 22" of steel). He's been shooting IMR4350 for years but never been able to get very good accuracy out of it - plus the muzzle blast is enough to knock a mule down. One point is that it's pretty light to hold on target but I think there's something else going on here.

Today we took it to the range with his 165 ballistic tips loaded variously...
imr4350
54 grains (was his go-to load for a few years, too slow IMHO)
56.5 grains
57 grains
57.5 grains

Groups were around 2.5" (horizontally strung mostly) with all of these loads except they started opening up at 57.5 to 3"...

Then for variety I made some IMR4895 loads:
50 grains --> groups dropped to 1.5" with more clover leaf patterns

The 4895 loads were quicker in recoil and far less muzzle blast. What's going on here? I have a theory but I'd love to hear your thoughts since I'm not a seasoned reloading vet yet...
 
Muzzle blast comes part and parcel with a muzzle break, so does loud report. Vertical stinging can be due to barrel heating among other things. Have you fooled around with seating length?
 
762nato said:
Muzzle blast comes part and parcel with a muzzle break, so does loud report. Vertical stinging can be due to barrel heating among other things. Have you fooled around with seating length?
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Not vertical, horizontal so I don't know about that. No vertical stringing at all which is nice to know. Barrel is free floating.

OAL was my ultimate fixation - went 0.020 from lands (3.42" oal) but got chamber feeding problems from magazine but fine single feed so went back to 3.3 oal since it's a hunting rifle and he doesn't want a single shot rifle for some reason. So, in a nutshell, no I didn't mess with seating depth because it can't feed them reliably much longer than 3.3.
 
A short-barreled .30-06 has a lot of muzzle blast. A short-barreled .30-06 with a muzzle break will have even more - wow!

Your 4895 loads had less muzzle blast because the muzzle exit pressure was lower (longer explanation - they had ~50 grains of powder, vs. the 4350's 10%-15% more. If both charges reached full pressure and the powder was fully burnt (which for these loads you mention, is most likely), then the larger amount of gas in the 4350 loads (57.5 grains of gun gas) would be at a higher pressure in the same volume (chamber plus bore) as the 4895's 50 grains of gun gas).

As to why the 4895 loads felt "quicker" in recoil, I don't know, nor do I know why they were more accurate for you.

Chrono numbers might be interesting (I am guessing that the 4895 loads might be giving higher velocity than the 4350 ones)
 
Here are my suspicions...

The factory muzzle break on BSA rifles include left-right baffles, nothing top or bottom. So what I think it happening is all the excess muzzle pressure in 4350 loads is causing turbulance left to right and so the round is stringing horizontally. When I switched to a faster burning powder (with less muzzle pressure as noticed my less blast) the side-to-side turbulance was reduced. Yes, no? What say you? I'm only putting forward a possible explanation.
 
aletheuo, could be. Or, perhaps the factory muzzle brake is not installed perfectly symmetrical, or perhaps it is not manufactured perfectly symmetrical; either of these could have an effect similar to a bad muzzle crown.

If your muzzle brake is "at fault", you might notice that flat-base bullets tend to shoot better, and that bullets with a boattail shallower than the Ballistic Tips' relatively steep boattail, will shoot worse.

Have you tried shooting the rifle without the muzzle brake? Is it shootable? Is it accurate? (I would expect that there is so much blast from the brake that it would be inadvisable to hunt with it without ear protection...?)
 
the break is actually machined right into the barrel so no telling what is going on. It would be a one-time removal. Who knows how perfect it is - there's no telling. At this point I found a load that works and have some sort of theory that may be plausible.
 
I have yet to find any of my guns that actually like IMR4350. They all shoot 2.5" groups or larger with 4350. I keep trying because I have a few pounds of it but no success yet. I'll just have to keep buying guns until I find one, as a CGNr somehow that makes sense. ;)

Varget, IMR4831, Re19&22 are all great in my various rifles.
 
Why not? said:
Aletheou,

I had one of those same rifles with the integral muzzle brake. IMR 4320 was THE powder. Best accuracy and highest velocity with 180s.

Ted
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Ted - thank you for your advice. Doesn't surprise me that 4320, being part way between 4350 and 4895 might be a good call.

Out of curiousity, why didn't you keep yours? Aleth
 
With shorter barrel, I always use faster burning powders than average powder used for the caliber (for the 'ol'06, say, W760/H414/IMR-H-4350). This lowers the muzzle blast quite a lot.
I do that in my GF 30-06 HVA 1600 Std (20.47" barrel) and the rifle is much more fun to shoot. I use RL15 in that case (better velocity than H4895 for the same pressure).
When a powder burns faster there is less residual muzzle pressure (hence to less blast).
 
aletheuo said:
Ted - thank you for your advice. Doesn't surprise me that 4320, being part way between 4350 and 4895 might be a good call.

Out of curiousity, why didn't you keep yours? Aleth
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That is quite a story. I'll give you the Readers' Digest version.

Friend of mine up here who is a biologist borrowed it for a sheep hunt he was going on with another guy. They shot two rams that were together, and while they were caping the first ram, a grizzly charged them. Busy with the work, they were not aware of the charge until they actually heard the bear running towards them. The other guy's rifle was beside his sheep, so he was totally helpless! :eek:

My friend killed the charging grizzly at less than twenty feet. He kept the rifle, and has it to this day. :)

Ted
 
Thanx for PM...

Just got home and read your query about the BSA FW in 30-06; I have 2, but have not got around to wrking them up!

Your 4198 load should achieve full combustion in 20", the 4350 load will likely be marginal, meaning that you are wasting powder as well as spewing burning grains, which well migh affext the bullet as it exits the muzzle.

The calculated velocity from the 4198 is a tidge LOWER than the full boat load of 4350.

OAL is just a rough indicator of the critical length; what you need to compare is length to ogive. All OAL really tells you is if the loaded round will pass through the feed system!
 
Your 4198 load should achieve full combustion in 20", the 4350 load will likely be marginal, meaning that you are wasting powder as well as spewing burning grains, which well migh affext the bullet as it exits the muzzle.
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Almost all loads will achieve full combustion within the first couple of inches of bullet travel. (and most centrefire loads will achieve maximum pressure at the point where the bullet has travelled an inch to an inch and a half)

A load that doesn't reach "all burnt" within the first two inches, is unlikely to reach "all burnt" before bullet exit (these loads are typically less-than max loads of particularly slow-burning powders, which don't reach anywhere near max safe pressures). Such loads are not only inefficient, they usually aren't particularly accurate either.
 
If it was me I'd loose the break, blast is worse than recoil and with a good quality pad recoil a .30/06 is manageable for most. A 20" .30/06 is likely to be a tad on the noisy side anyway, but nothing compared with that break pushing the sound back at you. Once the break is gone you may find that the accuracy with any given load changes dramatically due to the different barrel harmonics, but velocity should be unchanged as the break does nothing to increase velocity as would a couple extra inches of barrel. Your 4895 load may very well prove to be the most accurate out of that rifle.
 
Yeah - we're talking 4895 (which I'm sure you meant) and thank you for the input. Yes - I was working with length to ogive with 165 ballistic tips and if I recall it was 3.475. I loaded them to 3.425 oal but they don't feed. The mag is long enough but point gets stuck in the top of the chamber.
 
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