1888 TD groove diameter

[varsity07840]

I've had my TD for about 15 years. It's been my plinker in my BPCR inventory. I always shot .459 dia Lee 405s and Saeco Government 500s in it, 20/1 even though I had a suspicion that the groove dia. was over .458. To that end, I followed Wolf's advise on using the .459 with a tight crimp. On a whim, I finally slugged the bore and sent it to Matt Dardas to be measured. Turns out it's .4574. He suggested MINIMUM size of .459. I'm thinking backing off on the crimp and maybe trying the 405 as cast, around .462.

Feedback would be appreciated.

Duane

[skeettx]

Hello
Do you mean Winchester/Browning 1886 TD in 45-70?

Are you dissatisfied with your current ammo and accuracy?

On low pressure loads in strong rifles, I suggest the largest
diameter in which the cartridge will chamber.
So if the 462 will chamber, then try it.

BUT I said LOW pressure loads and you have not mentioned the load
you wish to try.

Mike

[varsity07840]

Hello
Do you mean Winchester/Browning 1886 in 45-70?

Are you dissatisfied with your current ammo and accuracy?

On low pressure loads in strong rifles, I suggest the largest
diameter in which the cartridge will chamber.
So if the 462 will chamber, then try it.

BUT I said LOW pressure loads and you have not mentioned the load
you wish to try.

Mike

It's an 1888 Springfield Trapdoor .45-70
Current load(s):
70 gr Swiss 1.5F
.459 405 gr Lee HB no wad
.459 Saeco 500 gr with .030 wad
WW Brass
Fed. 215 primer
Accuracy is ok but given the very good bore condition I thought it could do better. I don't get to shoot it enough to really develop a load, but retirement looms so I thought I'd give it some more time.

Duane

[skeettx]

He he he
OK Trapdoor and not Take Down, my bad
I would not consider the Trapdoor to be a strong rifle

http://castboolits.gunloads.com/show...reloading-data
Mike

[fouronesix]

An original M1888 TD with a groove diameter of .4574! That's the tightest I've ever heard of. They usually run well over 460. If it is indeed .4574, I'd consider that a very good thing as it opens all kinds of possibilities. TDs can be made to shoot really good. Of course good accuracy is a "floating" concept depending on who you talk to. Any number of ways to get there including both BP and smokeless.

With an excellent bore and unless the barrel is warped, it should do and inch or better @ 50 yards. I use the peep in the Buffington and a taller front blade for best sight combination for target work.

[texasmac]

An original M1888 TD with a groove diameter of .4574! That's the tightest I've ever heard of. They usually run well over 460.

Duane, I agree with fouronesix. Although it's possible to have a 0.4575 groove diameter it's not likely. You might consider having another slug measured by someone else with a v-anvil micrometer. I'm certainly not offering a service to anyone else, but I'm curious and since I have a v-anvil micrometer I'll be glad to measure a slug for you as a one-time only service if you include funds ($6.00) for USPS Priority mail shipping back to you. I'll be out of touch for about a week but send me a PM if you'd like to take me up on my offer.

Regards,
Wayne

[Tom Trevor]

Answered you on the other site you posted this on.

[varsity07840]

Duane, I agree with fouronesix. Although it's possible to have a 0.4575 groove diameter it's not likely. You might consider having another slug measured by someone else with a v-anvil micrometer. I'm certainly not offering a service to anyone else, but I'm curious and since I have a v-anvil micrometer I'll be glad to measure a slug for you as a one-time only service if you include funds ($6.00) for USPS Priority mail shipping back to you. I'll be out of touch for about a week but send me a PM if you'd like to take me up on my offer.

Regards,
Wayne

PM sent.

Thanks,

Duane

[John Boy]

Daune - your posted reloads are perfect using 459 diameter bullets. You might want to back down 68gr for the 405's - but not a must

[texasmac]

Hey guys,

I need to “man up” and confess I screwed up big time. I posted earlier, and just deleted the post, that indicated I disagreed with Tom Trevor's comment that measuring across the corners or edges of the lands works as well as using a v-anvil micrometer. The bottom line is Tom is correct. But the technique only works because the odd numbered lands and grooves in a TD are the exact same width.

Posting that the land and grooves in my carbine are close but not the same width resulted in additional thoughts on the subject and subsequently researching my TD files. I currently have a couple of TD’s and the chamber cast I grabbed to make the recent measurements was from a TD carbine that was relined some time ago by Bobby Hoyt. Bobby makes his own liners, cutting the lands and grooves himself. Hence the reasons the width of the lands and grooves are close but not exact.

What I found in researching my files is I exchanged comments with Dick Hosmer (the “resident ex-spurt” on TD’s that Tom referred to earlier) around 4 years ago on the subject of measuring groove and bore diameters. At the time I measured slugs from the original carbine barrel and found that carefully measuring across the edges of the lands was the same as the measurements using a v-anvil micrometer. So I stand corrected and, if you read my earlier (now deleted post), I apologize for unintentionally leading anyone astray.

Wayne

[varsity07840]

Found this today.

Duane

http://www.sodcity.com/gallery2/view_photo.php?set_albumName=US-rifles%2C-Ammunition-Accessories&id=trapdoor_bores_1

[texasmac]

Guys,

After checking the calibration of my v-anvil micrometer, which was right on, I gently measured a soft lead bore slug I just received from a TD owner. The groove diameter was measured 3 times (once using each of the three grooves). Then, using a standard micrometer I made 3 measurements across each land and opposite groove. Finally I measured across opposite land edges with a vernier caliper and standard micrometer to see if it agreed with the groove diameters. Here's the data:

Groove diameters: 0.4638", 0.4638", 0.4637" (average of 0.4638")
Across land and opposite grooves: 0.4575" (average of 3 measurements)
Across opposite land edges: 0.4615" (average of 3 measurements)

The bottom line is the groove diameter is 0.4638" and bore diameter (land diameter) is 0.4512". The land heights (groove depths) are 0.0063".

BTW, I also measured another soft slug and a Cerrosafe cast made from two other TDs to determine/check if measuring across opposite land edges will provide the same measurement as using a v-anvil micrometer. As noted above, using the technique the measurement was off by 0.0023”. The slug I had from another TD was also off a little over 0.002". But measuring across opposite land edges on the much harder Cerrosafe cast was very close (within 0.0005”) to the same measurement when using a v-anvil micrometer. It was obvious the soft land edges of the slug will not stand up to even gentle measurements using a vernier caliper of standard micrometer.

So the the “resident ex-spurt” on TD’s premise/assumption that measuring across the corners or edges of the lands works as well as using a v-anvil micrometer which I agreed with 4 years ago is technically correct but the technique of measuring across opposite land edges does not work very well if the medium used is pure lead or a real soft alloy. BTW, I just checked my collection of casts and slugs. When initially exchanged emails on this subject with the “resident ex-spurt” 4 years ago, I mentioned “slugging the bore”. I’m now sure that was a misnomer and I actually used a Cerrosafe cast, not a slug, made from the original bore of the 1877 carbine I later had relined. Hence the reason that at the time I agreed the premise was valid.

Wayne

[varsity07840]

As the TD owner Wayne referred to, I'd like to publicly thank him for taking the time to help me.

Duane

[texasmac]

Duane,

You are very welcome. I also learned something in the process. Interesting exercise.

Wayne

[John in PA]

My technique for measuring odd-number groove diameters is to turn the slug very gently in the jaws of a vernier caliper, allowing the high spots to just brush the jaws. Take a few measurements to see if I agree with myself, and call it good. I'm dubious as to the benefit of knowing groove diameter to greater precision than half a thousandth anyhow when you're going to hammer a tin/lead alloy bullet with a full blackpowder load, which will INSTANTLY swage it to full throat diameter, to then be squeezed down to fit the rifling anyhow. It would be different with hard-cast, non-deforming bullets and mild smokeless loads, though.

Also. if you're using Swiss powder, most N-SSA shooters I know find Swiss to be 10-15% hotter that GOEX, which is the powder that Spence Wolf used to develop his trapdoor loads (Spence's book is a fantastic piece of investigative work, BTW, and his methods really do work. I use the compressed black loads with the 1881 bullet in all my 45-70's when I want to use fixed BP ammo.) Anyhow, the Swiss may be exceeding the performance you were looking for if you were wanting to duplicate arsenal loads.