To Stretch or Not

[ColColt]

Trying to fore go using Cerrosafe, I found an article about a simple way to check the length of your chamber and gave it a try. I have a Browning 1885 BPCR in 45-70 and wanted to determine how short my brass may be decided to try this method. I used a full length sized 45-90 case to check...


"Quick Method 2
The following technique also requires a case longer than the chamber. As in the
“Quick Method 1” above, a full length resized .45-90 case was used for a .40-65
chamber. Expand and then flare the mouth of the case so the flared portion can
be felt dragging on the inside of the chamber wall when it’s being pushed in.
Continue to push until it comes to a hard stop, indicating the mouth or lip of the
case has hit the start of the chamber transition. Using the rear end of vernier
calipers as a depth gauge, measure the amount of the case that’s sticking out of
the chamber. Subtract the amount from the length of the extended case. Adding
head clearance results is a very close approximation of the maximum case
length. I found this technique to be faster and slightly more accurate than “Quick
Method 1”.



Having done this I found the chamber is 2.155" long. With standard Starline or Winchester that puts the brass considerably shorter than the chamber by .055" or more. I did all this to determine if I needed some form of case stretcher before purchasing one and it appears it would be appropriate. Thoughts?


http://www.texas-mac.com/Determining_Case_Lengths.html

[Gunlaker]

Mine is on the long side too. I just use .45-90 brass trimmed to the correct length.

Chris.

[country gent]

Remeber when streching cases longer that the amount of brass is fixed so making a case longer thins it .050 would move alot of brass around, Forming and firing also hardens brass meaning cases stretched may need annealed and be harder than normal towards the head. I would rather cut down 45-90 to length and Then anneal to be sure necks are good. Are you getting lead rings or having issues with the short cases?

[ColColt]

No issues with leading of any sort from what I can discern. The long chamber and short cases are conducive to potential problems and that's why I thought a little stretching may be beneficial.

[Gunlaker]

My Browning BPCR shoots more accurately with the longer cases. I think it's all about reducing bullet distortion as the bullet moves from the case and through the chamber.

I do own two case stretchers. I've used the Checker one from Buffalo Arms to experiment with stretching. I was able to stretch the brass nicely but stopped when the case mouths reached a thickness of 0.010". If I remember correctly it would have been a length gain of 0.020 or 0.030. The one benefit of stretching it that it seems to make the case thickness at mouth much more uniform in diameter.

I also have one of the KalMax stretchers, designed by Montana Charlie on this forum. I haven't used it as I never got around to buying the hydraulic ram for it. I believe that it would be able to stretch the cases longer. It seems like a really nice design.

Chris.

[montana_charlie]

My Browning BPCR shoots more accurately with the longer cases. I think it's all about reducing bullet distortion as the bullet moves from the case and through the chamber.

I do own two case stretchers. I've used the Checker one from Buffalo Arms to experiment with stretching. I was able to stretch the brass nicely but stopped when the case mouths reached a thickness of 0.010". If I remember correctly it would have been a length gain of 0.020 or 0.030. The one benefit of stretching it that it seems to make the case thickness at mouth much more uniform in diameter.

I also have one of the KalMax stretchers, designed by Montana Charlie on this forum. I haven't used it as I never got around to buying the hydraulic ram for it. I believe that it would be able to stretch the cases longer. It seems like a really nice design.

Chris.
If there you can't find one at a tool rental place, Home Depot has the lowest price around ... and free shipping.
http://www.homedepot.com/p/Big-Red-4-Ton-Porta-Power-with-Carry-Case-T70401S/100595209

CM

[Gunlaker]

Thank you.

Chis.

[Lead pot]

For the cost of buying equipment for stretching cases one could buy longer cases and cut them down to the proper size and add to your supply of cases.
Stretching a case long enough to fill the gap to the 45 degree transition at the chamber end will not completely stop lead or paper rings. They are still there and you can find them if you took the time to find out. Yes a proper fitting case will help but if that case is to long where it comes in contact where the 45 degree starts that case gets pulled forward by the friction of the compressed powder in the case or tight neck tension that holds the bullet and this will pull the case up into the lead a little and a lot if your rifle has to much head space and this does bad things to the bullet and contributes smearing lead up into the bore.
This is one of the problems with the chambers are now cut for these lead bullet rifles. That 45 degree chamber end came about the time the smokeless powder and gilded bullets came about. I think it was designed to hold the bullet back to build up pressure to get the cordite or smokeless powder burn more efficiently, but it sure raises hell with the lead bullets.
Below are two .44-90 bn chamber casts made from my two rifles. The top cast has the now common 45 degree chamber and the second has a chamber end closer to what was used before the smokeless powder and jacketed bullets came around. Even the 5 degree chamber end I have in that chamber is not as flat as what was common in most rifles. The difference between those two types of chambers is very noticeable with lead fouling and what the results are down range.
I don't have a problem if the brass is short 1/10" it makes no difference in performance shooting PP or GG bullets.
Check out a .22 rim fire chamber once. It is still the same as it was back in the 1800'rds.
Yes the 45 degree chamber end shoots well but so do my 4 degree/1.5 degree throats or I wouldn't have changed out the 45's in my rifles.
I have 7 degree, 5 degree, and 4 degrees and the flatter out shoots them all with less problems.

http://i704.photobucket.com/albums/ww43/Kurtalt/IMG_0254.jpg (http://s704.photobucket.com/user/Kurtalt/media/IMG_0254.jpg.html)

[ColColt]

That being the case then why don't manufacturers of BPCR's cut the chambers in accordance with what it's use is-black powder?

[Lead pot]

Don't know Col.
The Browning BPCR is the closest to the old ways that the chamber is cut. I think they use around a 12 degree???

[ColColt]

That's good to know. I just happen to have one...may be on the lookout for another since it shoots so well and to date, zero leading.

[montana_charlie]

Check out a .22 rim fire chamber once. It is still the same as it was back in the 1800'rds.
That argument doesn't really apply to BPCR calibers because none of them use rebated bullets, sized to 'chamber diameter', with no step of any kind at the end of the chamber.

The .22 rimfire 'chamber' is nothing more that an area of groove diameter freebore which extends back to the breech face.
The bullet is groove diameter, but the brass case is also at groove diameter. That's why it can end in a 'flat' path.


Don't know Col.
The Browning BPCR is the closest to the old ways that the chamber is cut. I think they use around a 12 degree???
I'm not pushing Pedersoli products here, but saying this strictly as information ...
The transition step in the 45/70 chamber for the Pedersoli Sharps has an angle of only 10° 12' 14".

CM

[ColColt]

Funny you should mention Pedersoli. I've been looking at their Rollers for the past four days. No Lone Star but look pretty good to me and I hear they're very accurate.

[montana_charlie]

Funny you should mention Pedersoli. I've been looking at their Rollers for the past four days. No Lone Star but look pretty good to me and I hear they're very accurate.
It's logical to assume that Pedersoli copied an actual Sharps rifle when they set out to build their Sharps replicas, so that would presumably be the inspiration for that 10 degree chamber end.
However, I have no clue about what thinking went into the specifications for their rolling block rifles. I wouldn't even go so far as to 'assume' that the Sharps chambers and rolling block chambers are cut with the same reamer.


Returning the the 'stretching question', this comes from my 'notes' on BPCR info.
While it provides a link to the source of the quote, everyone knows that Theodore has gone through all of his stuff and replaced his comments with Greek gibberish.

CM



A post by Dan Theodore which confirms that 'stretched' cases are beneficial.
http://bpcr.net/forum/viewtopic.php?t=2982

"Make sure your brass is 2.1250" long as the Browning chamber is on the long side. Remington 45-70 brass is a good way to go. Just size the brass in the 40-65 FL sizer until it will just chamber and extract with ease, then trim to 2.1250". There's no reason to over-size the brass when first making it as that could necessitate fire-forming before load development. If the brass is made correctly one can do their load-testing without fire-forming, a time-saving technique that makes a lot of sense to me. If one is looking for top accuracy, using brass that is as long as the chamber is important. Too much of a gap between the case mouth and the end of the chamber will cause accuracy loss due to the bullet bumping-up in the gap. That section of the bullet that bumps-up in the gap will distort when it is forced to be "sized" back down as the bullet enters the rifling. I've seen recovered bullets that had the section of the bullet between case mouth and freebore distorted due to the above problem. The problem is further compounded by the excess finning from the base-band bumping-up the gap. It will also cause the base to be cupped."

[ColColt]

Dan was right. I cut back a few 45-90 cases and they just fell in the chamber at 2.150" but in closing the breech block it pinched in the mouth of the case. I cut back to 2.125" and no more pinching. I decided the best way out and cheapest was to order some 45-90 cases and do this.

[Gunlaker]

That's also very close to the brass length use in my Browning BPCR.

Chris.

[montana_charlie]

Dan was right. I cut back a few 45-90 cases and they just fell in the chamber at 2.150" but in closing the breech block it pinched in the mouth of the case. I cut back to 2.125" and no more pinching. I decided the best way out and cheapest was to order some 45-90 cases and do this.
I have some new Bell 45/90 that I will probably not use.
How many do you plan on buying?

CM

[ColColt]

I bought 40 already from good ol' Larry Potterfield. I've got maybe that amount of the same Bell brass but it's in rough shape. Got it from a guy for free and it looked like it went through several buffalo hunts in 1870 so, I don't use it. Some look a bit green inside.

It sort of chaps me that I've got 100 new Starline cases that are too short.

[Lead pot]

That's good to know. I just happen to have one...may be on the lookout for another since it shoots so well and to date, zero leading.


That argument doesn't really apply to BPCR calibers because none of them use rebated bullets, sized to 'chamber diameter', with no step of any kind at the end of the chamber.

The .22 rimfire 'chamber' is nothing more that an area of groove diameter freebore which extends back to the breech face.
The bullet is groove diameter, but the brass case is also at groove diameter. That's why it can end in a 'flat' path.


CM

Charlie I don't know if you have ever made a chamber cast of a .22 rim fire chamber of just looked down the barrel and assume that is a free bore instead of a long funnel type of lead. There is a difference between the two chambers.
Here are two casts I made this morning to illustrate the chamber leads. These are high resolution so you can expand them quite a bit to get a close look.
The chamber measures .2268" then with a long tapered lead down to .2228". I don't have enough magnification to measure the length of the taper, or the degree.

http://i704.photobucket.com/albums/ww43/Kurtalt/th_IMG_2159_zpsaf59e8b5.jpg (http://s704.photobucket.com/user/Kurtalt/media/IMG_2159_zpsaf59e8b5.jpg.html)

[EDG]

The ding dong post translates as follows

Έχετε μια υπέροχη ζωή. >>>>>> Have a wonderful life.

[sthwestvictoria]

Trying to fore go using Cerrosafe,


If it is more that you don't have or don't want to buy Cerrosafe, a sulphur/graphite chamber cast gives an excellent impression and the ingredients are available from the hardware store or chemist.

[ColColt]

Well, I'm not sure I did the right thing by cutting those 45-90 cases or not. Now, of course, I have about .025" longer cases, which I wanted, which means the bullet will be seated out further than before with the Winchester cases. Most of the Winchester and Starline 45-70 cases ran 2.092-2.097" but this chamber is 2.125". I cut the 45-90 cases to 2.122". I seated several to the same place on the bullet I did for the Winchester cases which is just under the front drive band on this particular bullet, chambered it and found the front drive band was engraved by the lands. Don't know if that's a plus or not as before that bullet gave excellent accuracy somewhat away from the lands.

[Gunlaker]

Why don't you just load the cartridges to the same OAL as your existing load?

Regardless, I'm sure you'll have no problems working up a good load with that longer brass. I've had good results with multiple bullet styles and powder granulations in the Browning BPCR. It shoots well with powders as fast as FFFg Express and as slow as plain Goex Fg.

Chris.

[ColColt]

That would push the bullet further down the case but in retrospect, I've read many times to seat the bullet where it just engraves the rifling. That may work with some rifles and bullets but I experimented with OAL and was getting good 1-1/2" groups. Perhaps the somewhat longer length may even make it better. I'll find out next Tuesday.

This rifle seems to do best with Swiss 1.5. I've tried KIK and Goex 2F and they just won't give the same groups as Swiss.

[texasmac]

After reading this thread I thought I'd comment on the Browning chamber lengths and overall case lengths. Keep in mind that Dan Theodore's comment about trimming the brass to 2.125" length is for the Browning .40-65, not the Browning .45-70, although the Browning .45-70 needs brass almost as long. In researching and writing my book on the rifles I made a bunch of chamber casts of all the Browning BPCRs. The average inside the rim chamber length + Headspace is as follows: .40-65: 2.125", .45-70: 2.118", .45-90: 2.424". Also, for what it's worth, the chamber to bore transition step angle for all three is 12.75 degrees. BTW, the longest overall case length for a Browning .45-70 I measured was 2.121" and the shortest was 2.117".

Finally, using the quick method posted on my website to determine overall case length works to get close but is not as accurate as taking measurements from a chamber cast. I would expect the quick method to yield slightly longer results (in the range of 0.005" to maybe 0.010" at most) as a result of where the case lip hits the angled transition step and the thumb pressure applied to the case.

Wayne

[ColColt]

When I cut those 45-90 cases back to 2.125" they would fall in the chamber but after closing the breech block I found the case mouth pinched. I cut it back to 2.121-2.122" and the pinching stopped and case fell right in. I cut 20 cases to that length and of course, being longer than the average Winchester/Starline case at 2.095" I seated the three different bullets I use to the same place as when using the other shorter cases and each of those three bullets had engraving marks on the front drive band...not a bad thing but it could change the accuracy I've developed with the shorter cases. I'll know by Tuesday or Wednesday next range visit.

[Gunlaker]

Thanks for that Wayne. On most of my rifles I do chamber cast but on the Browning I didn't want to pull the breech block and extractor. It sounds like my brass might be just a smidgen too long.

Chris.

[montana_charlie]

I'll know by Tuesday or Wednesday next range visit.
You'll also know how much shorter they get when fired.
If that is a lot, you'll be wanting to figure out how to fireform cases to your chamber before you cut them to final length.

CM

[texasmac]

You'll also know how much shorter they get when fired.
If that is a lot, you'll be wanting to figure out how to fireform cases to your chamber before you cut them to final length.
CM

CM brings up an excellent point and I should point out that the .40-65 case length determined by Dan Theodore and the ones I posted earlier are for fireformed cases. A full length resized case will shorten around 0.008" or so when fired.

Wayne

[texasmac]

Thanks for that Wayne. On most of my rifles I do chamber cast but on the Browning I didn't want to pull the breech block and extractor. It sounds like my brass might be just a smidgen too long.
Chris.

Chris,

Since I offer a chamber cast with each Browning I sell, I have made dozens of Browning BPCR chamber casts without pulling the breechblock and extractor. I do pull off the forearm and clamp the rifle vertically in a vice with a towel wrapped around the barrel for protection. Open the action and plug (push) a Q-tip into the extractor slot. After heating the chamber area with a hot air gun the melted Cerrosafe is slowly poured in using a bent tuna fish can, which is held with a gloved hand. For more details go the the following link on my website and page down to the section titled, Making a Fusible Alloy Chamber Cast.

http://www.texas-mac.com/Chamber_Casts_and_Impact_Impression.html

Wayne

[Gunlaker]

Wayne I use pretty much the exact same technique but I use a coke can instead. The q-tip is a really nice idea.

Chris.

[ColColt]

Just getting back from the range and I can't say I was happy with the groups with the new trimmed 45-90 cases. the two bullets that always give me under 2 inches, the Postell and 457125, were strung vertically and at a slight angle and groups ran about 2 3/4"- 3 inches. It could be a combination of these being new cases and the possibility this rifle just doesn't like the bullet being engraved by the rifling. I won't pass judgement, since they are now fire formed, until next time. I'm going to load the same rounds and see what happens. If I get the same scenario I guess it's back to the shorter WW cases so I can seat those bullets a short distance from the lands.

I did find the new cases shrunk .010" upon firing.

[country gent]

Keep in mind with those bullets at the longer seating / overall length you also changed the amount of powder compression, unless you compensated for it with another wad or slightly more powder.

[ColColt]

I used a .030" was in all cases but the compression was, in most cases, a little more. I had expected less since the case is longer but the Starline cases in 45-90 must be a little thicker.

[montana_charlie]

I used a .030" was in all cases but the compression was, in most cases, a little more. I had expected less since the case is longer but the Starline cases in 45-90 must be a little thicker.
Starline brass (in 45/'bpcr') is substantially thicker than Winchester down in the body.
Did you anneal the Starline cases before loading them?

CM

[ColColt]

That explains why I had to compress a bit more and why my decapper was tighter pulling the cases off the shaft whereas the WW cases slid right off. I have read many places about annealing Starline brass when new and it got the full treatment prior to loading.

[country gent]

Try adusting the powder charge a little to get the same compression as before and see what happens.

[Lead pot]

I'm more concerned with the case length in front of the rim then the back of the rim (head stamp side) There is just to much rim thickness variances that effect head space. The thought with most shooters is to get the case right up to the end of the chamber. Say if the case has a rim thickness of .069" and you trim that case so it is tight right up to the 45 degree chamber end what most chambers now days have. Then you get a case that has a rim thickness of .063", something not uncommon with some brass I have measured, now this case is the same total length as the one with the thicker rim and both cases get came in so they are in contact with the breach block there is a gap between the front of the rim and the beginning of the chamber. It now has .006" that this case can be pushed ahead by the firing pin plus the friction of the powder and the bullet pulling it ahead up into the lead and this extra friction release of the bullet will throw your accuracy off by the rise of chamber pressure increasing velocity. And also will stretch the case. I have had case necks get separated having brass right up to the chamber end and when the case gets pulled forward this crimps the case mouth tight to the bullet shank when it gets pulled past the 45 degree chamber end. Look at your fired cases that fit the chamber tight and see if the case mouth looks like it has a slight crimp after it was fired.

[ColColt]

I went from getting groups like this last week and the week before with this bullet...

http://i180.photobucket.com/albums/x220/ColColt/Targets/_1DF3098a_zps12b58c88.jpg (http://s180.photobucket.com/user/ColColt/media/Targets/_1DF3098a_zps12b58c88.jpg.html)

...to this today, same bullet and charge...

http://i180.photobucket.com/albums/x220/ColColt/Targets/92adac97-4bf5-4249-9c95-6d0a232734c5_zps3fdacf12.jpg (http://s180.photobucket.com/user/ColColt/media/Targets/92adac97-4bf5-4249-9c95-6d0a232734c5_zps3fdacf12.jpg.html)

I wouldn't think there should be that much difference because brass hasn't been fire formed yet and/or cases are thicker. Those bullets were weighed within .3 grain.

[Lead pot]

:D Col when you shoot these Powder rifles for a while you will this happen on and off. More on then off. :D

Just like these groups shot from the same rifle. I shot these 10 shot groups with a MVA scope on my Shiloh at 200 yards.

http://i22.photobucket.com/albums/b302/940Leadpot/IMG_1178.jpg (http://s22.photobucket.com/user/940Leadpot/media/IMG_1178.jpg.html)

Went back a few days later and it turned out like this [smilie=f:

http://i704.photobucket.com/albums/ww43/Kurtalt/th_IMG_1140.jpg (http://s704.photobucket.com/user/Kurtalt/media/IMG_1140.jpg.html)

It could be the light, climate who knows. Maybe even Henry the gremlin :D

[ColColt]

I think today Henry was alive and well! I was all down in the mouth when I came home.

[Gunlaker]

Have you tried loading to your original OAL? Also, if the cases are crimping even a little bit like what Kurt describes it can hurt accuracy quite a lot. I don't mind a tiny bit of crimping during the first two times the case is used. After that they'll be pretty well expanded and you can trim them to the correct length.

I think you do have to sort the cases by rim thickness. My Starline .45-90 cases have the worst rim thickness inconsistency of any of the cases I use.

Chris.

[ColColt]

To load to my original OAL I'd have to compress the powder more, quite a bit more with one of the bullets. The case mouth is not crimped. It did originally when I first cut back the 45-90 cases but trimming an additional .004" fixed that. That made the cases 2.122" with no crimp. As I mentioned ater the first firing today the cases are now 2.114" so, an .008" loss. I don't crimp after seating the bullet. Only run it up in the size die far enough to eliminate the flare.

I never considered rim thickness as a problem.

[UberDuper]

Any updates?

[ColColt]

Not yet. I'm going back to the range tomorrow with the same loads and try again. Due to the extra length they are going to lightly engrave the rifling but that should be a plus. Maybe I just had a bad day last time. Tomorrow I'll know if it was me or not.