BP Compression... What is too Much?

[Prs61109]

I'm new to BP cartridge loading for a 45/70 using RCBS 500 grain BPS bullets in Starline cases. Using .10 to .15 inch compression, I can get 57 grains of FFg in the case with a .125 inch grease cookie (SPG) plus a .030 veggie wad under the bullet. This give me a COL of 2.860 inches with finger seating. The bullet's top grease groove is exposed. This is about the maximum COL I can chamber in my Pedersoli.

Are there any guidelines or recommendations for how much compression I should use? My BP rifle range goes to 500 yards so this will be my maximum distance. I know I can get more powder in the case with the 405 grain bullet but the 500 bullet appealed to me. What are your thoughts and experiences? Thank you.

[country gent]

When working a load up here is what I do. I start with no compression/no air space just a full case of powder. Now work up in 2 grn increments 10 rounds of each works for me. to where you believe compression is getting heavy. ( I normally stop around .200 unless groups show diffrently). Fire these and see what groups best then retest the performer and 1 grn either side. Leave the compresion die set at no air space and just add the 2 grains powder it changes powder charge and compression both. This will help you find the best load quickly. A few other pointers a wad between powder and grease cookie to keep from contaminating powder and a wad over grease cookie to keep it from sticking to bullet. Not sure if you need the grease cookie with a grease groove bullet. Maybe try with the lube the bullet carries and see 1) if you get a lube star at muzzle 2) fouling stays soft and managable. In hot dry weather a blow tube can be a big plus. I would make a good chamber cast of the rifle to check throat dia and length also check twist rate that will determine bullet length or wieght needed. In my pendersoli (45-70) and Hepburn (45-90) iuse the 535 grn lymann postell or a 500 grn Paper Patched money style from a brooks mould. The postell carries enough lube in my 34" barrels. The paper patch requires a grease cookie but is bore riding so only .250 or so is in the case.

[nhrifle]

Good explanation above. Fine tuning will yield excellent results with the Holy Black. As to your question, how much is too much? If the brass will chamber freely you are good. If the compression level expands the brass enough that it no longer fits the chamber, you have gone too far and need to back off.

[Prs61109]

Thank you for the information. I placed a wax paper wad between the BP and grease cookie. I used a compression die after loading the case with a drop tube. I took careful measurements with my dial caliper during my loading steps for accuracy and repeatability. I'll load up some rounds without the grease cookie. Is it important to use a wad to protect the bullet base? From my research, it seems most people do so followed this practice.

I determined my initial charge by filling the case via drop tube to a calculated depth that would produce the desired COL with .10 inch compression, grease cookie and wad. I then weighed this charge (55 grains). When the round was assembled, I found I could increase the COL slightly and still chamber the round and this became my new, adjusted COL. The bullet is a few thousands of an inch short of contacting the throat or rifling. I was able to add 2 additional grains so 57 grains of FFg is my starting load, with compression, grease cookie and wad. I'm hoping to get to the range next week to shoot these. Then I'll have a better idea of how to proceed.

I've installed a set of Lee Shaver sights since my last range trip so I'm looking forward to trying them out. I could not get a good sight picture with the Pedersoli open sights with my old eyes.

[25ring]

nhrifle is correct. When I was using Goex some of the best loads had compression of over .3 to .4 of an inch. FWIW

[montana_charlie]

Are there any guidelines or recommendations for how much compression I should use?

For 'guidelines' most of us depend upon the experience of others for getting started, then analysing our own experience to see how much it agrees with the former.

I have no experience with the 45/70 case, so I won't give you any personal 'advice' of my own. What I will do is pass on some advice from others who are well-known ... or respected ... or both.

Spence Wolfe wrote a book on shooting the 45/70 in trapdoor rifles. I think it's formally named "The Book".
Anyway, on the subject of powder charges (which directly relates to compression) he said ...

500+ gr bullets can employ powder up to 5.3 gr per .1" of case interior length. Example: Interior length = 1.92", subtract the bullet seating depth of .55" gives 1.37" of interior powder space. 5.3 gr x 13.7= 72.6gr max for a 45-70 with a typical Postel bullet.

If you are able to get 72 grains in a 45/70 case, you may need something over .400" of compression to seat your bullet. That is not a dangerous practice, but is probably overkill.
Some feel they have reached the maximum practical level of compression when they have to run the charged case through a resizing die to squeeze it down enough to chamber.

Looking at 'compression' from a different starting point, one very well-known shooter swears that .385" of compression is the perfect amount.
However, he shoots a Sharps 2 7/8" (45/110) so I have my doubts that the same .385" will work identically in a 2.1 inch case.

But, using 'ratio' rather than exact match, something between .250" and .280" of compression should get similar 'density' in a 45/70 charge.
You have the cases, so you get to figure out how much powder it takes to achieve that amount of compression.

From the experience that I HAVE gained, .250 to .280 sounds pretty likely, to me.

CM

[oldracer]

A few years ago when I got my first BPCR 45-70, Doug Knoell told me how he did a work up and I followed his advice even though it finally took me 6 months to get a load I was happy with. Here is what he said to do:
1. Get the OAL of your seated bullet by filling a case with rigid type foam, putting in a bullet finger tight and seating it so the bullet hit the lands.
2. Measure the OAL and take off 2 to 3 thousands for a starter dimension.
3. Prime the fire formed cases and load somewhere around 64 to 68 grains of FFG and a milk carton and news paper wad on top. You can use what type of wad you like as the OAL of the bullet in the case in relation to the chamber is what is important.
4. Compress the powder with a compression die NOT the bullet to get the measured OAL. If you use the bullet it will swell and cause possible leading.
5. Seat the bullet with finger pressure and in all my guns (Rolling Block and 2 Sharps), a 540 grain bullets had no grooves showing.
6. Load at least 10 of each powder load and adjust compression to same OAL with no touching of the lands by the bullet.

As you can see as powder load goes up there is more compression to get the same OAL of the loaded bullet, less compression if less powder.

[Prs61109]

Thanks! This is great information that will really help me get started. As a smokeless powder shooter for most of my life, powder compression seems strange, maybe a bit dangerous but this is the nature of BP. I have lots to learn and I appreciate all of your comments and tips. Benefitting from the knowledge of your experiences is why I joined this forum.

[oldracer]

I forgot to mention, write down exactly what you are doing for each load you do and when you go to the range use something like a Lead Sled with some extra foam at the butt so the gun is sitting very solid. That takes YOU pretty much out of the equation and lets the gun do it's work. If possible try to get the same weather each time and if your range is like mine, early morning or late afternoon are the only times with no wind.

[TRX]

> powder compression seems strange

(Some?) factory loadings in .458 Winchester Magnum use compressed charges of smokeless.

[Prs61109]

I used the above information and loaded up some 45/70 without the grease cookie but used the .030 inch wad under the bullet base. I found I had a little more COL when testing loaded cartridges (2.880 inches). After carefully checking all my measurements, I found I could get 65 grains of BP into the case with about .11 inch compression and 70 grains with .22 inch. It remains to be seen how these will shoot. I may be able to find out later this week (hopefully). I made a blow-tube so this might work for those rounds without the grease cookie. The atmosphere here in the Midwest is more humid than the West or Southwest.

BP cartridge shooters will be at a nearby rifle range in a couple weeks. I'm planning on attending as a guest, watch, ask questions and get more information. I really appreciate all the help I'm getting from you fine gentlemen!

[Toymaker]

I really don't think you need that grease cookie with a bullet grease that really works. I just use a cardboard disk, like posterboard, and a disk of newspaper to keep it from sticking to the bullet. With a round nose 500 grain (521 grains actual) I can compress 70 grains of Goex FFg 0.26 inch. That gives me an OAL of 2.904 inches which just engages the rifling. I've found that Goex FFg likes to be compressed about a quarter inch. Swiss does not like that much compression.

When I first started shooting muzzle loaders I read several articles that stated black powder ignites most efficiently when compressed 65 lbs. I spent a lot of time with the bathroom scale getting the feel for 65 lbs downward pressure with my ram rod. It really worked with the front stuffers, so I guess a quarter inch compression must be about 65 lbs of pressure.

[dlbarr]

That is the approach I've taken in my short experience with reloading BP. Although I like Country Gent's detailed methodology.

Good explanation above. Fine tuning will yield excellent results with the Holy Black. As to your question, how much is too much? If the brass will chamber freely you are good. If the compression level expands the brass enough that it no longer fits the chamber, you have gone too far and need to back off.

[Prs61109]

I shot 17 rounds yesterday - my first BP loads in my 1874 Pedersoli Quigley 45/70. These rounds had 57 grains compressed about .10 inch and with a grease cookie. I used a blow tube between shots and had no hard fouling. I ran a snug, dry patch through the barrel when I finished shooting. The fouling on the patch was soft and showed no slivers of lead. There was a small ring of lube on the muzzle crown so I think I had no lube difficulties in the 34 inch barrel.

My friend's bench rest/sand bag arrangement did not permit me to shoulder the butt properly so after these, I decided to call it a day with a tender shoulder. I did not shoot my 65 and 70 grain loads without the grease cookies.

This is was my first trip using the Lee Shaver sights. I like them very much but have many more questions than answers about which aperture I should select and why. I'm right handed but left eye dominate which is no big problem with handguns but I realized afterwards, I was not seeing the target as clearly as I need to. The sights were clear. I guess I need a tune-up at my eye doctor.

I did not achieve the results I had hoped for but the experience was fun and important. Matthew Quigley made it look so easy! It's NOT and I have barely scratched the surface of what you experienced shooters know and practice. Sunday I'm attending a BP Cartridge shoot where I hope to get acquainted and asks some questions. I may join this club next year.

[country gent]

I too am attending a match sunday where is yours at? You look thru the rear appeture not at it ,keep the front in focus lettingthe rear and target blur or become fuzzy. The eye naturally centers in the rear. Appeture size depends on eye sight, light for a given day and distance. Front appeture is again eye sight and target size. You want a solid ring of white around the target with the front appeture. For shilouettes some use a post as wide as the target appears to them. Most benchrest front rests are to low for these rifles You want a much more upright position with these rifles to help handle recoil and keep from stressing the firearm on the bags. A set of bench sticks are a big plus Mine are normally set to have the rifle 8-10" above the bench depending on rifle and range Im at.

[JSnover]

This is was my first trip using the Lee Shaver sights. I like them very much but have many more questions than answers about which aperture I should select and why. I'm right handed but left eye dominate which is no big problem with handguns but I realized afterwards, I was not seeing the target as clearly as I need to. The sights were clear. I guess I need a tune-up at my eye doctor.

You only need the one that works best for you. Try them one at a time, you'll notice the sight picture changes with each one and it will depend on the condition of your dominant eye and the ambient light on any given day. It's one more thing you'll have to work out at the range.

[Prs61109]

CountryGent - the black powder shoot I'm attending is at the Beloit Rifle Club in Beloit, WI, about an hour's drive north of my home. I am not a member (yet) and I think this is just a monthly shoot. I doubt it is a formal competitive event. They just opened a 500 yard range this summer.

My shoulder and right bicep have some nice bruises showing. Us old guys are pretty delicate sometimes. I've added a recoil shield to my MidwayUSA wish list. Any recommendations? It sure was fun shooting the Sharps and I'm certainly looking forward to my next trip.

[JSnover]

I added a LimbSaver to my Enfield (45-70 conversion). Love it!

[country gent]

Im attending a local match at Defiance Ohio sunday Its a shillouette match. I put a leather declerator removeable pad on my Hepburn ( 45-90 ) and wear a shoulder pad I got from buffalo arms with it. The CPA 40- 65 Im shooting Sunday will be just the shoulder pad. If your not shooting long distances lighter bullets may be an option to help reduce recoil. Alot shoot 405-450 grn bullets at the local matches here. The shotgun style butt stocks help with recoil a lot over the cresents. In 45 cal I normally shoot 500-550 grn bullets ( I did open up the brooks mould all the way today and cast 60 575 grainers to be paper patched and Im thinking about lapping a .001-.002 from it to get a better fit in the bore. If your shooting 100-200 yds load down to around 1000 fps to help lower recoil. A taller position more upright hold rifle into shoulder firm and relax rolling with the recoil helps also. Trying to lock these rifles in tight and not letting them move is asking for bruising. Wish you a great day Sunday hold hard and have fun. Also watch and see what other competitors are doing and using, ask alot of questions.

[John Boy]

prs, actually the amount of compression is powder dependent for good accuracy. Give this a read:

the Black Powder Cartridge News -2009 Fall - "Some Black Powder Compression Data" article by Bob Woodfill:
Caliber - 45-70
Lyman 457124
Constant volume of FFg powder used
Compression tested: 0" - 1/8" - 1/4" - 3/8" and 1/2"
Best 3 Shot Groups 100yds ... 5 shot groups were tested also, with the same compression values except for Goex (1/4") and Schuetzen (1/2")
Goex - 0.62" with 1/8" compression
Goex Express - 0.26" with 1/4" compression
Schuetzen - 0.61" with 1/4" compression
Swiss - 0.56" with 1/2" compression
KIK - 0.65" with 0" compression