Bore diameter and groove diameter.

[Pat73]

Hi folks, hope you are doing all right.

I am currently reloading for my Henry Big Boy 44 magnum. The Henry riffle technician send me these infos about my riffle:
*****************
Thanks for the image Patrice.
It's clear enough for me to confirm you have a 1:20 ROT bbl.
The bore in that case is 12 groove, with a .423(+2/-0) bore diameter and .430(+2) groove diameter. I can say that our bore specs are set with the goal of optimizing jacketed bullet performance.
*********************
Considering the informations received, should i load jacketed bullets like XTP and Winchester? If i use cast bullets, should i size them .432"

Since i a not a seasoned reloader, i am seeking your adives.

Thank you.

 

[AJC1]

.431 is a good place to start.

 

[Bearded Phil]

.430(+2) groove diameter.

This is the key part. They're saying their groove diameter is shooting for .430 with a tolerance of .002" over. So the grooves could actually be as big as .432".

Like AJC said .431" is a good place to start with cast and if it's not going well you want to try to a larger diameter.

I've shot plenty of cast & coated bullets in my Henry .357 Mag with 158gr bullets sized to .358 with decent results. I've also shot some 180gr heavies (actually closer to 190gr) from Missouri Cast that were supposed to be sized .358" but were actually closer to .359". The larger diameter shot as decent as some other 180gr from the same sample pack that were .358" and better in some regards and definitely didn't make groups worse.

Long story short, you can get cast & coated plain base bullets to shoot well out of Henry rifles but it may take some experimenting, whether with commercially bought bullets or ones you cast your self.

Remember for cast bullets the general rule of thumb is to shoot bullets sized .001" over groove diameter.

So if you got some cast bullets sized .431" and you're getting poor groups and leading that would be an indication that you could benefit from a larger diameter cast bullet. Undersized for groove diameter bullets can sometimes be shot well but the velocity often has to be reduced to produce groups.

Also my general advice is to buy sample packs of commercial cast bullets when you can before you commit to a lot of 500ct or more.

 

[AJC1]

If your looking for a sample pack noe sells them and if you find one you like they sell the mold

 

[Pat73]

This is the key part. They're saying their groove diameter is shooting for .430 with a tolerance of .002" over. So the grooves could actually be as big as .432".

Like AJC said .431" is a good place to start with cast and if it's not going well you want to try to a larger diameter.

I've shot plenty of cast & coated bullets in my Henry .357 Mag with 158gr bullets sized to .358 with decent results. I've also shot some 180gr heavies (actually closer to 190gr) from Missouri Cast that were supposed to be sized .358" but were actually closer to .359". The larger diameter shot as decent as some other 180gr from the same sample pack that were .358" and better in some regards and definitely didn't make groups worse.

Long story short, you can get cast & coated plain base bullets to shoot well out of Henry rifles but it may take some experimenting, whether with commercially bought bullets or ones you cast your self.

Remember for cast bullets the general rule of thumb is to shoot bullets sized .001" over groove diameter.

So if you got some cast bullets sized .431" and you're getting poor groups and leading that would be an indication that you could benefit from a larger diameter cast bullet. Undersized for groove diameter bullets can sometimes be shot well but the velocity often has to be reduced to produce groups.

Also my general advice is to buy sample packs of commercial cast bullets when you can before you commit to a lot of 500ct or more.

I should have mentiioned that i live in Canada. I am limited to 5 000 ammo. There's some casting cie here and i will ask them for samples. Thank's for the advice.

 

[Swampman]

I'd recommend slugging your bore before purchasing any cast bullets or casting equipment.

 

[mdi]

I would. Since I started allowing 44 cal. jacketed bullets in my shop, XTPs have worked fine (I didn't use jacketed bullets for any 38 Spec., 357 Magnum, 44 Spec, 44 Magnum, 45 ACP or 45 Colt until about 4 years ago). My 44 Magnum carbine likes .433" cast bullets with a groove diameter is .431"+...

Slugging a barrel is not a difficult task and you will get the true dimensions. Not that the Henry rep is wrong, but you will know, for sure, the barrel's dimensions...

 

[reddog81]

What's the largest diameter that will chamber? .433, .432, .431? Go with whatever that is.

 

[AJC1]

What's the largest diameter that will chamber? .433, .432, .431? Go with whatever that is.

That will work in conjunction with what brass is used. I find Remington and blazer to both be thin walled in 38/357 allowing the largest bullets to still chamber.

 

[RowdyReid]

Slugging the bore will save a lot of guess work. Starting with .431 can get you some information if you have a chronograph. I found velocities to be very low when shooting undersized cast bullets, and the grouping was wide. Without the chronograph, I was having trouble figuring out if it was the load or the bullet.

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I have been using cast bullets from Montana Bullet Works. They are pricey, but really good quality. They will also size and lube the bullets for you. I was told that .001 over size for cast is pretty standard, and it has been rocking and rolling for me so far.

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[Pat73]

I'd recommend slugging your bore before purchasing any cast bullets or casting equipment.

Considering the information provided by the technician, should i choose a soft round ball 44 caliber .433 or smaller?

 

[Pat73]

That will work in conjunction with what brass is used. I find Remington and blazer to both be thin walled in 38/357 allowing the largest bullets to still chamber.

I use Starline brass.

 

[AJC1]

I use Starline brass.

Those may be thicker. A pin Guage would tell you max size and then measure the loaded round and bullet giving you clearance and max size bullet you could use.

 

[larry7293]

I use .431 boolits from MBC in my Henry. They work well.

 

[tightgroup tiger]

For some un-Godly reason some of the rifle manufacturers are using .430-.431" bore barrels for the rifles they make instead of .429" like the revolvers have.
So you may have to deal with that also and use a .432 lead bullet to get good accuracy and velocity.
It won't hurt shooting .432" lead bullets out of a revolver in case you have a 44 revolver to go with your rifle.

 

[AJC1]

For some un-Godly reason some of the rifle manufacturers are using .430-.431" bore barrels for the rifles they make instead of .429" like the revolvers have.
So you may have to deal with that also and use a .432 lead bullet to get good accuracy and velocity.
It won't hurt shooting .432" lead bullets out of a revolver in case you have a 44 revolver to go with your rifle.

I never understood why they did that, makes me want to skip that pair of rifle and pistol. If marlin comes back it would be a big win for them to fix it.

 

[Mycin]

I never understood why they did that, makes me want to skip that pair of rifle and pistol. If marlin comes back it would be a big win for them to fix it.

Blame SAAMI.

The SAAMI pistol specs for 44 Mag say .429" groove diameter. VELOCITY AND PRESSURE DATA (saami.org) (page 54)
The SAAMI rifle specs for 44 Mag say .431" groove diameter. VELOCITY AND PRESSURE DATA (saami.org) (page 143).

I've never seen a good explanation for the difference, but don't blame they rifle makers. They're just building to spec.

 

[AJC1]

Blame SAAMI.

The SAAMI pistol specs for 44 Mag say .429" groove diameter. VELOCITY AND PRESSURE DATA (saami.org) (page 54)
The SAAMI rifle specs for 44 Mag say .431" groove diameter. VELOCITY AND PRESSURE DATA (saami.org) (page 143).

I've never seen a good explanation for the difference, but don't blame they rifle makers. They're just building to spec.

A good company would go on the tighter side of the tolerance and make them as close as possible. There would be zero upset customers I promise.

 

[Mycin]

Blame SAAMI.

The SAAMI pistol specs for 44 Mag say .429" groove diameter. VELOCITY AND PRESSURE DATA (saami.org) (page 54)
The SAAMI rifle specs for 44 Mag say .431" groove diameter. VELOCITY AND PRESSURE DATA (saami.org) (page 143).

I've never seen a good explanation for the difference, but don't blame they rifle makers. They're just building to spec.

Interestingly, I see that the 444 Marlin spec calls for .430" groove diameter. At least they're consistently inconsistent.

I remember reading about this discrepancy between 44 revolvers and rifles back in the '80s in gun mags. It's nothing new.

 

[Mycin]

A good company would go on the tighter side of the tolerance and make them as close as possible. There would be zero upset customers I promise.

I agree, but there'd be lots of upset lawyers.

 

[AJC1]

I agree, but there'd be lots of upset lawyers.

I haven't looked but as long as the spec is followed there is nothing to say. I guess I'll check out the spec before I say more.

 

[AJC1]

There not even close

 

[Swampman]

I'm going from ancient memories here, but my understanding is that when Marlin submitted the .44 Magnum rifle specs to SAAMI, they were geared towards Micro Groove rifling.

 

[Mycin]

I'm going from ancient memories here, but my understanding is that when Marlin submitted the .44 Magnum rifle specs to SAAMI, they were geared towards Micro Groove rifling.

I think you may be right. Notice in the pics that @AJC1 posted that the rifle spec (top) says 12 grooves, whereas the pistol spec says 6 grooves.

So, I guess Marlin deserves some of the blame.

 

[mdi]

I've been reloading 44 Magnum or revolvers, single shot handguns and a levergun carbine for about 34 years. The .431" spec. for my carbine doesn't bother me one bit. (and I don't see any reason or a lawsuit against an industry standard). But the .431" groovve diameter is a spec for all 44 Magnum rifles. What would bother me is a manufacturer that would cut their rifle barrels undersize to .429". For me it's a moot point anyway as I slug the barrels of every gun that comes into my posession, along with a thourouh cleaning. For me it's no big deal to size some of my cast bullet to .432"/433", and some to .431".

I also have three riles that the groove dimeter is large than it's "supposed to be", an SKS, a Mosin Nagant and a Lee Enfield #4 mk II. Each one has barrel dimensions up to .004/.005" larger than "spec.". I guess I could complain, but I'm fine with customizing some Lee sizing dies an sizing bullet for each gun...